Physiological adaptations to low-volume, high-intensity interval training in health and disease

Phosphoproteomics Uncovers Exercise Intensity-Specific Skeletal Muscle Signaling Networks Underlying High-Intensity Interval Training in Healthy Male Participants

BACKGROUND

In response to exercise, protein kinases and signaling networks are engaged to blunt homeostatic threats generated by acute contraction-induced increases in skeletal muscle energy and oxygen demand, as well as serving roles in the adaptive response to chronic exercise training to blunt future disruptions to homeostasis. High-intensity interval training (HIIT) is a time-efficient exercise modality that induces superior or similar health-promoting skeletal muscle and whole-body adaptations compared with prolonged, moderate-intensity continuous training (MICT). However, the skeletal muscle signaling pathways underlying HIIT's exercise intensity-specific adaptive responses are unknown.

OBJECTIVE

We mapped human muscle kinases, substrates, and signaling pathways activated/deactivated by an acute bout of HIIT versus work-matched MICT.

METHODS

In a randomized crossover trial design (Australian New Zealand Clinical Trials Registry number ACTRN12619000819123; prospectively registered 6 June 2019), ten healthy male participants (age 25.4 ± 3.2 years; BMI 23.5 ± 1.6 kg/m2;V ˙ O 2 max 37.9 ± 5.2 ml/kg/min, mean values ± SD) completed a single bout of HIIT and MICT cycling separated by ≥ 10 days and matched for total work (67.9 ± 10.2 kJ) and duration (10 min). Mass spectrometry-based phosphoproteomic analysis of muscle biopsy samples collected before, during (5 min), and immediately following (10 min) each exercise bout, to map acute temporal signaling responses to HIIT and MICT, identified and quantified 14,931 total phosphopeptides, corresponding to 8509 phosphorylation sites.

RESULTS

Bioinformatic analyses uncovered exercise intensity-specific signaling networks, including > 1000 differentially phosphorylated sites (± 1.5-fold change; adjusted P < 0.05; ≥ 3 participants) after 5 min and 10 min HIIT and/or MICT relative to rest. After 5 and 10 min, 92 and 348 sites were differentially phosphorylated by HIIT, respectively, versus MICT. Plasma lactate concentrations throughout HIIT were higher than MICT (P < 0.05), and correlation analyses identified > 3000 phosphosites significantly correlated with lactate (q < 0.05) including top functional phosphosites underlying metabolic regulation.

CONCLUSIONS

Collectively, this first global map of the work-matched HIIT versus MICT signaling networks has revealed rapid exercise intensity-specific regulation of kinases, substrates, and pathways in human skeletal muscle that may contribute to HIIT's skeletal muscle adaptations and health-promoting effects.  Preprint: The preprint version of this work is available on medRxiv, https://doi.org/10:1101/2024.07.11.24310302 .

Narrative Review of High-Intensity Interval Training: Positive Impacts on Cardiovascular Health and Disease Prevention

BACKGROUND

High-intensity interval training (HIIT) has gained recognition for its positive impacts on cardiovascular (CV) health, metabolic outcomes, mental health, and quality of life (QoL). This narrative review aims to comprehensively evaluate the efficacy of HIIT in enhancing CV health and preventing CV disease (CVD).

METHODS

A comprehensive search of PubMed identified 257 articles, of which 39 studies met predefined inclusion and exclusion criteria for quality assessment. Key metrics evaluated included blood pressure, vascular function, lipid profiles, body composition, and CRF.

RESULTS

HIIT significantly improved vascular function, evidenced by reductions in systolic and diastolic blood pressure and enhanced flow-mediated dilation. Improvements in cardiac function were observed through increased cardiac output and heart rate variability. Additionally, HIIT positively influenced lipid profiles, decreasing low-density lipoprotein and triglycerides while increasing high-density lipoprotein. Significant reductions in body fat and improvements in VO2peak were noted, contributing to enhanced CRF. HIIT also positively impacted mental health and QoL, reducing anxiety and depressive symptoms. Importantly, HIIT was safely and effectively applied to high-risk populations-individuals with obesity, metabolic syndrome, CVD, and cancer survivors-with a low incidence of adverse effects.

CONCLUSIONS

This review highlights HIIT as an effective and safe exercise modality for improving CV health, metabolic indicators, mental health, and QoL. Future research should focus on developing tailored HIIT protocols to optimize adherence and efficacy across diverse populations, considering variations in age, sex, health status, and underlying medical conditions.

Acute Effect of High-Intensity Interval Training on Postprandial Glycemia in Overweight and Obese Individuals: A Scoping Review

BACKGROUND/OBJECTIVES

High-intensity interval training (HIIT) has emerged as an effective strategy for mitigating postprandial glycemia in overweight or obese individuals. This scoping review aims to examine randomized controlled trials (RCTs) conducted between 2008 and 2024 that evaluated the impact of HIIT on acute postprandial glycemic response.

METHODS

A comprehensive search strategy was employed using terms such as "high-intensity interval training (HIIT)" and "postprandial glycemia", combined with Boolean operators, with no restrictions on study type. Electronic databases searched included PubMed, SPORTDiscus, Scopus, and Web of Science from their inception through 2024. Of the 67 studies that met the inclusion criteria, five RCTs were selected for final analysis. All selected studies involved individuals with a body mass index (BMI) ≥ 25.

RESULTS

Each of the five included RCTs featured at least one HIIT intervention group, with variations in frequency, duration, intensity, and testing protocols. Despite differences in glucose tolerance test timelines, the glucose-loading protocol (75 g) and exercise interventions demonstrated minimal heterogeneity across studies. The findings suggest that short-term HIIT interventions may positively influence acute postprandial glycemic responses in overweight and obese populations.

CONCLUSIONS

Short-term HIIT appears to be a promising intervention for improving postprandial glycemic control in individuals with elevated BMI. Future research is warranted to further elucidate both the acute and long-term effects of HIIT, particularly the role of skeletal muscle in regulating systemic glucose levels in this population.

HIIT versus MICT in MASLD: mechanisms mediated by gut-liver axis crosstalk, mitochondrial dynamics remodeling, and adipokine signaling attenuation

OBJECTIVE

Compare the effects of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on metabolic dysfunction-associated steatotic liver disease (MASLD), focusing on the mechanisms by which these two exercise modalities influence gut microbiota structure, bile acid metabolism, and intestinal barrier function, as well as their regulatory roles in hepatic lipid synthesis and oxidative dynamics. Explore the synergistic effects of exercise-mediated mitochondrial fusion remodeling and leptin signaling, elucidate the causal relationship between gut-derived factors and hepatic metabolic reprogramming, and reveal the potential multi-scale and cross-organ dominant mechanisms of exercise, providing a theoretical basis for systematically comparing the effects of different exercise modalities.

METHODS

Thirty-two male rats were randomly divided into NFD (n = 8) and HFD (n = 24) groups and fed normal chow and high-fat chow, respectively. After eight weeks, the HFD group was randomly divided into three groups: (1) MICT-8; (2) HIIT-8; and (3) HFD-8. At the end of the experiment, blood, liver, ileum, and skeletal muscle samples were collected for analysis of the rats' baseline conditions, mitochondrial function, hepatic lipid metabolism, bile acid pathway and gut microbiota, and synthesis of analyses.

RESULTS

Both modes of exercise ameliorated metabolic dysregulation and attenuated pathological progression, insulin resistance, and liver fat accumulation in rats with MASLD. Furthermore, both interventions counteracted HFD-induced intestinal barrier dysfunction and restored gut-liver axis homeostasis. HIIT and MICT also upregulated bile acid-related gene expression modulated butyrate-producing bacterial taxa, and adjusted the abundance of butyrate-generating bacteria.

CONCLUSION

Both HIIT and MICT improved lipid metabolism in MASLD rats and the difference between the HIIT and MICT groups was not statistically significant. It is noteworthy that HIIT was more effective in improving mitochondrial function in MASLD than MICT (P < 0.001).

Curcumin supplementation combined with high intensity interval training modulates serum irisin and lipid profile in obese women: "A randomized double-blind clinical trial"

Background

Curcumin is the most widely known active substance of turmeric extract, which attributed numerous functional properties, including anti-inflammatory and cardioprotective properties. Inactivity and changes in lifestyle and subsequent overweight/obesity are becoming major health risk factors.

Objective

the aim of this study was to determine the effect of curcumin supplementation combined with high intensity interval trainings (HIIT) exercise on serum irisin and lipid profile in obese women.

Methods

40 inactive women (aged 30-35 years, and body mass index 30 and above) allocated in four groups (10 in each) as followed; curcumin (C), exercise plus curcumin (EC), placebo (P), and exercise plus placebo (EP). All subjects completed an eight-week HIIT program. The C and EC groups received one capsule containing 80 mg curcumin nanomicelle daily throughout study. Blood samples were taken in the beginning and after eight weeks to measure changes in the study variables (irisin and lipid profile). The ANCOVA and Bonferroni's post hoc test was used to compare variables between 4 groups and pairwise at a significance level of ≤0.05 using SPSS-22.

Results

The results revealed that mean serum irisin (p = 0.023), cholesterol (p = 0.019), triglyceride (p = 0.022), high-density lipoprotein (p = 0.009) and low-density lipoprotein (p = 0.011) were significantly changed in all intervention groups compared to the placebo group.

Conclusion

Based on these results, it can be concluded that HIIT training with curcumin consumption has a greater significancy on obesity reduction in women; Therefore, curcumin and HIIT exercise can be considered as a therapeutic approach to reduce the negative outcomes of obesity.

Clinical trial registry number

IRCT20141004019397N2, link.

Statement of significance

This study investigated the effects of curcumin supplementation combined with high-intensity interval training (HIIT) on human serum Irisin levels for the first time, in a clinical randomized trial. This suggests that HIIT training alongside curcumin consumption may be a promising therapeutic approach to reduce the negative health consequences of obesity in women.

Comparison of body composition, cardiorespiratory, and neuromuscular adaptations induced by three different high intensity training protocols

This study investigated body composition, cardiorespiratory, and neuromuscular adaptations induced by three high intensity trainings easy to fit into daily routine. Thirty-seven adults participated in one of the following 8-week interventions: vigorous intensity continuous training (VICT; 28 min at 70% of peak oxygen uptake [VO2peak]), long interval high intensity interval training (LI-HIIT; 6 × 2 min at 85% VO2peak), or short interval HIIT (SI-HIIT; 12 × 30 s at 125% maximal power output). Heart rate (HR) and rating of perceived exertion (RPE) were measured during sessions. Pre- and post-intervention assessments included fat and lean mass, cardiopulmonary exercise testing, knee extensors maximal isometric torque, voluntary activation, and endurance during a submaximal contraction. Compared to SI-HIIT and VICT, LI-HIIT sessions were characterized by a shorter duration, a similar time spent above 90% HRmax, but a higher RPE (p < 0.05). VO2peak and muscle endurance increased respectively by 14% and 12%, while knee extensors torque, voluntary activation, and lean mass increased to a lesser extent (1%-3%) after the interventions (ANOVA time-effect, all p < 0.05). There was no significant difference between the modalities (intervention × time interaction, all p > 0.05). In conclusion, comparable body composition, cardiorespiratory, and neuromuscular adaptations were induced by the three high intensity training protocols, while RPE was higher during LI-HIIT sessions.

The Impact of Exercise Training in a Hypobaric/Normobaric Hypoxic Environment on Cardiometabolic Health in Adults with Overweight or Obesity: A Systematic Review and Meta-Analysis

This systematic review and meta-analysis aims to comprehensively evaluate the effects of hypoxic training (HT) versus normoxic training (NT) on cardiometabolic health parameters in overweight or obese adults. Searches were performed in PubMed, Web of Science, Embase, Scopus, and the Cochrane Library. A meta-analysis was performed using Stata 18 and RevMan 5.4 software. Seventeen randomized controlled studies involving 517 participants were included. HT significantly improved cardiorespiratory fitness (CRF) and reduced systolic blood pressure (SBP) and diastolic blood pressure (DBP). Compared with NT, HT demonstrated a significant difference in CRF, but no significant differences were observed in SBP and DBP. The subgroup analysis of CRF revealed that HT significantly outperformed NT in six aspects: participants aged < 45 years (Hedges' g = 0.50), an intervention duration of 8 weeks (Hedges' g = 0.43), three sessions per week (Hedges' g = 0.40), each session lasting < 45 min (Hedges' g = 0.23), FiO2 levels > 15% (Hedges' g = 0.69), and high-load-intensity exercise (Hedges' g = 0.57). HT demonstrated favorable effects in improving cardiometabolic health among overweight or obese adults. Compared with NT, this advantage was primarily reflected in CRF while the impacts on SBP and DBP were similar.

High-intensity interval training improves insulin sensitivity in individuals with prediabetes

OBJECTIVE

To examine the separate and combined effects of low-volume high-intensity interval training (HIIT) and walking compared with no training on insulin sensitivity and skeletal metabolic capacity in individuals with prediabetes.

DESIGN

Individuals were randomized to: (1) control (no exercise), (2) HIIT (3 × 20 s's cycle sprint 3 times weekly), (3) HIIT + walking (walking >10 000 steps/day), or (4) walking for 12 weeks.

METHODS

Insulin sensitivity was assessed by an oral glucose tolerance test at baseline and end-of-trial. Additionally, proteins important for mitochondria capacity and insulin sensitivity were measured in the vastus lateralis muscle.

RESULTS

Seventy sedentary individuals with prediabetes (women n = 36; age: 60.8 ± 11.3 years (mean ± SD); body mass index: 31.6 ± 4.4 kg/m2; fasting plasma glucose: 6.6 ± 0.8 mmol/L; glycated hemoglobin A1c 5.7 ± 0.4% (39.0 ± 4.3 mmol/mol) were included. Compared with control, peripheral insulin sensitivity (measured by the Cederholm index) was significantly improved with HIIT (estimated treatment difference [ETD]: 18.5% [95% confidence interval (CI): 7.4; 28.3%] and HIIT + walking [ETD: 15.7% (95% CI: 4.4; 25.6%)]), but not with walking alone (ETD: 9.4% [95% CI: -2.5; 19.9%]). Whole-body insulin sensitivity (measured by the Matsuda index) was significantly increased with HIIT + walking (ETD: 28.0% [95% CI: 10.3; 42.3%]) and walking alone (ETD: 42.3% [95% CI: 28.3; 53.5%]), but not with HIIT alone (ETD: 17.0% [95% CI: -4.0; 33.7%]). Protein expression of proteins involved in mitochondrial capacity in skeletal muscle and glucose uptake were most improved with HIIT + walking, and no significant effects were observed with walking alone.

CONCLUSIONS

Twelve weeks of low-volume HIIT training can improve glucose control and induces adaptations in skeletal muscle important for metabolic health in individuals with prediabetes.

Effects of high-intensity interval training on physical morphology, cardiopulmonary function, and metabolic indicators in older adults: a systematic review and meta-analysis

Background

Despite the growing attention towards the efficacy of high-intensity interval training (HIIT) on older adult health, a consensus regarding the pleiotropic effects of HIIT in this population is yet to be reached. Previous studies have predominantly focused on specific outcomes or particular groups, lacking comprehensive analysis.

Objective

We aimed to conduct a systematic evaluation of the impact of HIIT on body composition, cardiopulmonary function, and metabolic parameters in older adults.

Methods

The databases searched included PubMed, Web of Science, Cochrane Library, Scopus, WanFang, and other relevant sources from the inception of the database until July 2023. Randomized controlled trials (RCTs) on the effects of HIIT on body shape, cardiopulmonary function, and metabolic parameters in the older adult were searched.

Results

A total of 87 RCTs meeting the criteria were included, involving 4,213 older adult people. Meta-analysis results showed that HIIT significantly improved body fat percentage (BF%) [MD: -1.63%, p = 0.005], maximal oxygen uptake (VO2max) [MD: 2.46 mL min-1 kg-1, p < 0.00001], maximal heart rate (HRmax) [MD: 2.83 beats min-1, p = 0.02], and high-density lipoprotein (HDL) levels [MD: 0.04 mmol L-1, p = 0.002]. However, for systolic blood pressure (SBP) [MD: 0.49 mmHg, p = 0.60], resting heart rate (HRrest) [MD: -0.95 BPM -1, p = 0.24], triglycerides (TG) [tendency for MD: -0.02 mmol L-1, p = 0.61], low-density lipoprotein (LDL) [MD: -0.04 mmol L-1, p = 0.27] had no significant effect. Sensitivity analysis found that HIIT significantly improved waist circumference (WC) [MD: -1.89 cm, p = 0.17], diastolic blood pressure (DBP) [MD: -0.63 mmHg, p = 0.23], respiratory exchange rate (RER) [MD: 0.01, p = 0.20], total cholesterol (TC) [MD: 0.10 mmol L-1, p = 0.14], and fasting plasma glucose (FPG) [MD:-0.20 mmol L-1, p = 0.08], but the results lacked robustness. There was no significant improvement in DBP [MD: -0.63 mmHg, p = 0.23] and body mass index (BMI) [MD: -0.36 kg m-2, p = 0.06].

Conclusions

HIIT has shown certain potential and advantages in improving the physical health of the older adult, especially in cardiopulmonary function. However, more high-quality studies are needed to confirm the effects of HIIT on the physical health of the older adult in the future. It also provides a reference for the clinical practice and family health management of HIIT in the older adult and the development of HIIT guidelines.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/myprospero, identifier CRD42023460252.

Effect of high-intensity interval training on clinical parameters in patients with metabolic dysfunction-associated steatotic liver disease: a systematic review and meta-analysis of randomized controlled trials

High-intensity interval training (HIIT) has potential health benefits in the treatment of many chronic diseases. However, the efficacy of HIIT in patients with metabolic dysfunction-associated steatotic liver disease (MASLD) remains unclear. This systematic review and meta-analysis aimed to assess the impact of HIIT on intrahepatic lipids (IHLs) , liver enzymes, and metabolic profiles in individuals with MASLD. All randomized-controlled trials (RCT) that evaluated and compared the effects of HIIT on clinical parameters in patients with MASLD were searched using the PubMed, EMBASE, WOS, and Cochrane databases. Data analysis and integration were performed using RevMan 5.3 (Cochrane Collaboration, Copenhagen, Denmark) and Stata version 18 software (StataCorp LLC, College Station, Texas, USA), and outcomes were assessed using the standardized mean difference (SMD). Our results showed that compared with other types of exercise or no exercise, HIIT could reduce the levels of IHL [SMD: -0.56%, 95% confidence interval (CI): -0.99 to -0.13, P = 0.01], BMI (SMD: -0.31, 95% CI: -0.62 to -0.01, P = 0.04), alanine aminotransferase (ALT) (SMD: -0.61, 95% CI: -0.95 to -0.26, P = 0.0006), and aspartate aminotransaminase (AST) (SMD: -0.43, 95% CI: -0.81 to -0.05, P = 0.03) in patients with MASLD. In addition, subgroup analyses showed that HIIT had a positive impact on clinical indicators in patients with MASLD with an intervention duration of less than equal to 8 weeks. This study supports the idea that HIIT can significantly reduce IHL, BMI, ALT, and AST levels, and further studies are needed to assess the long-term adherence and treatment effects of HIIT.

Effects of exercise training and physical activity advice on HbA1c in people with type 2 diabetes: A network meta-analysis of randomized controlled trials

AIMS

To compare the magnitude of the benefit of different exercise modalities on glycemic control, including aerobic training (AT), resistance training (RT), combined training (CT), high-intensity interval training (HIIT) and physical activity advice.

METHODS

A network meta-analysis was conducted. Seven databases were searched from inception to May 2024. We included randomized clinical trials of at least 12 weeks' duration evaluating different types of physical exercise and physical activity advice to reduce HbA1c in people with type 2 diabetes.

RESULTS

158 studies (17,059 participants) were included. Compared with the control group, all types of exercise were associated with lower HbA1c: HIIT [-0.61 % (95 % CrI -0.84; -0.37)], CT [-0.58 % (95 % CrI -0.73; -0.42], AT [-0.58 % (95 % CrI -0.70; -0.45)], RT [-0.40 % (95 % CrI -0.59; -0.21)] and physical activity advice [-0.35 % (95 % CrI -0.53; -0.16)]. HIIT was the most effective treatment for HbA1c reduction (SUCRA = 82 %), followed by CT (SUCRA = 77 %), AT (SUCRA = 76 %), RT (SUCRA = 37 %) and physical activity advice (SUCRA = 29 %).

CONCLUSIONS

HIIT was associated with the greatest reduction in HbA1c. Physical activity advice, which is easy to implement, accessible and unsupervised, should also be offered to people with type 2 diabetes to improve glycemic control.

Qualitative Description of Exercise Perceptions and Experiences Among People With Human Immunodeficiency Virus in the High-Intensity Exercise to Attenuate Limitations and Train Habits Study

BACKGROUND

The benefits of physical activity (PA), specifically exercise, among older adults in general are well known. Yet globally, there is concern regarding limited engagement in PA, increased obesity, and frailty among older people with human immunodeficiency virus related to low levels of PA.

METHODS

We conducted in-depth interviews among 30 older, sedentary people with human immunodeficiency virus participating in the ongoing High-Intensity Exercise to Attenuate Limitations and Train Habits (HEALTH study, NCT04550676) between February 2021 and August 2022. A semistructured interview guide, informed by two minds theory, which frames behavior change as an intention-behavior gap between 2 neurocognitive systems, was used to elicit data from participants. Interviews explored general exercise perceptions, self-efficacy for exercise, mobile health intervention tailoring, outcome expectations, and PA goals. Thirty interviews from 33 participants were recorded and transcribed verbatim, and deductive and inductive thematic analysis were used using Dedoose.

RESULTS

Physical activity was defined as maintaining daily living activities and addressing health goals. Previous experiences with PA varied among participants and were influenced by chronic illnesses, including human immunodeficiency virus; motivation; work commitments; interest; and social support. Reported barriers to PA included antiretroviral adverse effects, comorbidities, aging, and the COVID-19 pandemic. Changes in health status, body changes, and relationships were identified as benefits of PA. Conversations with healthcare providers supporting exercise goals were perceived to be important but rarely received by the participants.

CONCLUSION

Understanding how older people with human immunodeficiency virus perceive PA is crucial to developing tailored strategies and structuring service delivery within the healthcare setting to promote a physically active life.

Examining the acute cardiovagal consequences of supine recovery during high-intensity interval exercise

PURPOSE

Exercise training requires the careful application of training dose to maximize adaptation while minimizing the risk of illness and injury. High-intensity interval training (HIIT) is a potent method for improving health and fitness but generates substantial autonomic imbalance. Assuming a supine posture between intervals is a novel strategy that could enhance physiological readiness and training adaptations. This study aimed to establish the safety and feasibility of supine recovery within a HIIT session and explore its acute effects.

METHODS

Fifteen healthy, active males (18-34 years) underwent assessment of cardiopulmonary fitness. Participants completed two identical HIIT treadmill sessions (4 x [3 min at 95% VO2max, 3 min recovery]) employing passive recovery in standing (STANDard) or supine (SUPER) posture between intervals. Heart rate variability (HRV), HRV recovery (HRVrec; lnRMSSD) and heart rate recovery at 1 min (HRrec) were assessed using submaximal constant speed running tests (CST) completed prior to, immediately after and 24 h following HIIT.

RESULTS

No severe adverse events occurred with SUPER, and compliance was similar between conditions (100 ± 0%). The change in HRVrec from the CST pre-to-post-HIIT was not different between conditions (p = 0.38); however, HRrec was faster following SUPER (39 ± 7 bpm) vs. STANDard (36 ± 5 bpm). HRV 24 h post-SUPER was also greater (3.56 ± 0.57 ms) compared to STANDard (3.37 ± 0.42 ms). Despite no differences in perceived exertion (p = 0.23) and blood lactate levels (p = 0.35) between SUPER and STANDard, average running HRs were lower (p = 0.04) with SUPER (174 ± 7 bpm) vs. STANDard (176 ± 7 bpm).

CONCLUSIONS

Supine recovery within HIIT attenuates acute cardioautonomic perturbation and accelerates post-exercise vagal reactivation. SUPER enhances recovery of vagal modulation, potentially improving physiological preparedness 24 h post-HIIT. Further research exploring the chronic effects of SUPER are now warranted.

Overview of mechanisms related to citrulline malate supplementation and different methods of high-intensity interval training on sports performance: A narrative review

Regular exercise is a practical non-pharmacological approach to maintaining physical and mental health through rehabilitation and prevention of chronic diseases due to its cardiovascular, cardiorespiratory, neurological, and neuromuscular benefits. Despite awareness of the benefits of exercise, a "lack of time" has proven to be the most common impediment to regular activity. Thus, a time-efficient and potentially enjoyable training modality with growing popularity is high-intensity interval training (HIIT). HIIT incorporates intermittent bouts of work and recovery intervals performed at an intensity close to maximal oxygen consumption (VO2max). HIIT is considered to have equivalent or superior benefits compared to moderate-intensity continuous training (MICT). This narrative review focuses on the mechanisms of Citrulline Malate (CM) supplementation and various modes of HIIT on exercise performance. CM serves as a nitric-oxide enhancer leading to improved aerobic and anaerobic exercise performance by increasing muscle adenosine triphosphate (ATP) production, vasodilation, and blood flow to the active musculature and boosting work capacity. This article reviews the mechanisms related to CM supplementation and different modes of HIIT on exercise performance. Even though a single, acute 8 g dose of CM has been recommended, its mechanism of action remains to be seen due to the synergistic impact of both components (citrulline and malate). Moreover, the limited evidence for the standard level of supplement use and source of purchase results in athletes' self-prescription of supplements. Therefore, to reduce the risk of accidental doping or toxicity, further studies should continue to investigate the optimal dose, timing, mechanism of action, as well as reliable sources of purchase for CM consumption.

Intensive physical training in children with heritable connective tissue disorders is feasible and safe: a pilot study

PURPOSE

This pilot study assessed the feasibility, safety, and acceptability of a physical training program combined with parental meetings for children with heritable connective tissue disorders (HCTD), including Marfan syndrome (MFS), Loeys-Dietz syndrome (LDS), and Ehlers-Danlos syndromes (EDS). Secondary, it aimed to explore preliminary observations regarding the program's impact on individual training goals and physical fitness, including aerobic and anaerobic capacity, strength, agility, pain, fatigue, and disability.

MATERIALS AND METHODS

The intervention comprised functional power training (FPT) and high-intensity interval training (HIIT) conducted three times a week over 12 weeks. Data on feasibility, safety, and acceptability were collected, along with preliminary observations on physical fitness performance.

RESULTS

The intervention was feasible and safe, with no serious adverse events reported. However, acceptability was limited, with a participation rate of 27.8%. Preliminary findings revealed that 80% of participants achieved their training goals, 75% improved their aerobic capacity, and 70% showed gains in strength and agility, alongside reported reductions in pain and fatigue.

CONCLUSION

This study highlights the potential benefits of tailored physical training for children with HCTD. Despite acceptability challenges, the intervention demonstrated feasibility and safety, providing a foundation for larger-scale effectiveness studies that include systematic feedback mechanisms to enhance participant engagement.

High Intensity Interval Training POst-STroke (HIIT-POST): Perspectives of People Living With Stroke and Health Professionals

BACKGROUND

High intensity interval training (HIIT) is a mode of aerobic exercise that can increase neurotrophin concentration, improve cardiovascular health, and enhance recovery post-stroke. However, HIIT is not commonly prescribed in stroke rehabilitation. Exploring the clinical utility of, and barriers and facilitators to, HIIT is necessary to optimize clinical use.

OBJECTIVE

To identify perceptions of HIIT from people with stroke and health professionals working in stroke rehabilitation.

METHODS

People with stroke and health professionals in Australia were invited to participate in an online questionnaire. Participants were further invited to complete a one-on-one semi-structured interview. A Framework Analysis approach was applied to identify key themes.

RESULTS

Twenty-six people with stroke (mean ± standard deviation = 49.2 ± 60.6 months post-stroke, 57.7% female) and 37 health professionals (2 medical and 35 allied health) completed questionnaires. Ten people with stroke (5 female) and 8 allied health professionals completed an interview. Aerobic exercise was not considered a priority after stroke, though participants were interested in HIIT. People with stroke reported a lack of understanding of the benefits of HIIT and use of the term "high intensity" as barriers to participation. Facilitators included education about safety of HIIT and referral to health professionals. Health professionals reported a lack of knowledge of HIIT prescription parameters and participant motivation as barriers to prescription. Facilitators included education of HIIT prescription and benefits and appropriate screening prior to commencement.

CONCLUSIONS

People with stroke and health professionals are interested in HIIT after stroke. Increasing knowledge and confidence to participate in, and prescribe HIIT, may increase clinical use.

Effects of 6-week sprint interval training compared to traditional training on the running performance of distance runners: a randomized controlled trail

Introduction

This study aimed to compare the effects of sprint interval training versus traditional training on running performance in well-trained male distance runners.

Methods

Twenty male distance runners (VO2: 67.4 ± 4.5 mL/kg/min, personal best time for the 5000 m: 14'38″47 ± 00'23″46) were recruited and randomly assigned to either the intervention training (IT) group, which performed sprint interval training, or the control training (CT) group, which engaged in traditional long-distance training. Both groups completed their respective training regimens twice a week for 6 weeks. Measurements for VO2max, O2 cost, time to exhaustion (TTE), and running times for 100, 400, and 3000 m were taken before and after the intervention.

Results

The results indicated that the IT group showed significant improvements in TTE and running performance across 100, 400, and 3000 m (all P < 0.01), while the CT group only demonstrated improvements in 400 m time (P < 0.01). The IT group exhibited superior 3000 m performance compared to the CT group (P < 0.01). Analysis of effect sizes revealed small to moderate improvements in physiological and performance measures for the IT group, with VO2max showing a small effect size of 0.43, O2 cost a moderate effect size of 0.65, and TTE a moderate effect size of 0.77.

Conclusion

These findings suggest that sprint interval training may offer superior benefits for enhancing running performance of well-trained male distance runners, particularly in time to exhaustion and middle-to long-distance events, compared to traditional longdistance training.

Vascular adaptations following an eight-week sprint interval training intervention in healthy men

BACKGROUND

Sprint interval training (SIT) has been shown to improve many indices of cardiovascular risk. The effect of SIT on emerging indicators of cardiovascular health, including arterial stiffness and carotid intima media thickness, remains unclear. Thus, the purpose of this study was to assess changes in augmentation index at 75 beats per minute (AIx@75), pulse wave velocity (cfPWV), and carotid intima media thickness (CIMT) at three time points of an 8-week SIT intervention.

METHODS

Eighteen sedentary men (age: 24.7±5.1 years, BMI: 26.7±5.8 kg/m2) participated in the study. Subjects trained 3 times a week for 8 weeks. Training consisted of 3-6 consecutive 30-second bouts of maximal intensity cycling, with 4.5 minutes of active recovery between bouts. Baseline, 4-week, and 8-week vascular assessments were performed. Training effects were analyzed using repeated measures ANOVA. Pearson correlations were used to determine the relationship between baseline values and the change scores (baseline to 8 weeks) of each vascular measure.

RESULTS

AIx@75 (BL: -3.6±10.9%, 4W: -5.6±8.3%, 8W: -3.2±9.5%), cfPWV (BL: 5.6±1.0 m/s, 4W: 5.8±0.9 m/s, 8W: 5.6±0.7 m/s), and CIMT (BL: 0.51±0.08 mm, 4W: 0.52±0.08 mm, 8W: 0.51±0.08 mm) did not significantly change (all P>0.05). Baseline cfPWV and AIx@75 were negatively correlated to their change from baseline to 8 weeks (P<0.05).

CONCLUSIONS

These findings demonstrate that 8 weeks of SIT is an insufficient stimulus to reduce cfPWV, AIx@75, or CIMT in a group of young, healthy men. Baseline arterial stiffness may modulate vascular adaptations to SIT.

High-intensity interval training improves hepatic redox status via Nrf2 downstream pathways and reduced CYP2E1 expression in female rats with cisplatin-induced hepatotoxicity

Cisplatin (CP) is an antineoplastic drug associated with various cytotoxic adverse effects, including hepatotoxicity. Exercise training may offer hepatoprotection by improving redox status. This study compared the effects of light-intensity continuous training (LICT), moderate-intensity continuous training (MICT), and high-intensity interval training (HIIT) on CP-induced hepatotoxicity in female Wistar rats. The rats were divided into five groups (n = 7): sedentary control (C + S), CP and sedentary (CP + S), CP with LICT (CP + LICT), CP with MICT (CP + MICT), and CP with HIIT (CP + HIIT). The training protocols involved eight weeks of treadmill exercise before CP administration (5 mg/kg). Seven days after CP injection, the rats were euthanized to collect blood and liver tissue samples. Our findings demonstrate that HIIT was the most effective protocol in preventing histopathological alterations and reducing oxidative and nitrosative damage markers in macromolecules, including 4-HNE (lipids), nitrotyrosine (proteins), and 8-OHdG (DNA). The reduction in these markers appears to be linked to decreased CYP2E1 levels. Moreover, HIIT activated the Nrf2 pathway and upregulated its downstream antioxidant enzymes, including SOD1, catalase, GPx, and HO-1. In conclusion, HIIT emerged as the most effective protocol for mitigating hepatic damage, likely through CYP2E1 suppression and enhancement of antioxidant defenses via Nrf2 signaling pathway activation.

Psychosocial Responses to a Cardiovascular Exercise Randomized Controlled Trial: Does Intensity Matter for Individuals Post-stroke?

OBJECTIVE

This study compared the effect of cardiovascular high-intensity interval training (HIIT) vs moderate-intensity continuous training (MICT) on psychosocial responses to exercise, motivation, and enjoyment, in individuals with chronic stroke.

DESIGN

A secondary analysis of motivation and enjoyment outcomes collected from a randomized controlled trial (NCT03614585) comparing 12 weeks of HIIT vs MICT in participants with chronic stroke (6-60mo post-stroke) was conducted.

SETTING

General community.

PARTICIPANTS

Seventy-one individuals (N=71) with chronic stroke (mean ± SD, age: 65.5 ± 8.4y, 19.4 ± 13.4mo post-stroke, 38% women) and mild disability (median ± interquartile range, National Institutes of Health Stroke Scale score 1 ± 2).

INTERVENTIONS

Twelve-week, 3 per week progressive cardiovascular HIIT or MICT program conducted on NuStep recumbent steppers.

MAIN OUTCOME MEASURES

Motivation (Behavioral Regulation in Exercise Questionnaire-3) was measured at weeks 1, 6, and 12. Enjoyment outcomes comprised of affective response (Feeling Scale) assessed at each training session, and post-exercise enjoyment (Physical Activity Enjoyment Scale) assessed at weeks 6 and 12. Linear mixed models, examining group, time and group × time point interactions in motivation constructs and composite scores, mean affective response per session, and post-exercise enjoyment were used to compare the effect of HIIT vs MICT.

RESULTS

HIIT elicited a lower affective response (mean difference [95% CI]: -1.18 [-1.90 to -0.47]; P=.002), that also progressively declined during sessions, in contrast to MICT (group × time point interaction: F [2,63.5]=3.99, P=.02). HIIT and MICT did not elicit any significant difference between groups or change over time for post-exercise enjoyment or any motivation constructs (P>.05).

CONCLUSIONS

Despite lower affective response during exercise, HIIT elicits equivalent motivation and post-exercise enjoyment compared to MICT. This study provides further support for the implementation of HIIT in stroke rehabilitation by demonstrating sustained responses of motivation and post-enjoyment. Future studies should consider potential strategies that positively reinforce these important psychosocial responses to implement HIIT in post-stroke rehabilitation.

High-intensity training on CREB activation for improving brain health: a narrative review of possible molecular talks

Although physical exercise has obvious benefits in brain physiology, the molecular biomarkers induced by exercise protocols are inconclusive. Evidence indicates that exercise interventions are effective in shaping brain physiology. However, the potential mediator for improving brain functions is uncertain. CREB is one of the potential targets of exercise that triggers various molecular cross-talk to improve neurogenesis, long-term potentiation, and synaptogenesis. Therefore, CREB may be situated on the causal path between maintaining brain health and exercising. To support this, studies have shown that exercise-mediated CREB phosphorylation improves cognitive functions and memory. In addition, among the protocols of exercise (types, duration, and frequency), the intensity has been reported to be the most effective in triggering CREB-mediated molecular signaling. For example, HIT increases the synthesis of CREB, which may not only induce brain physiology but also induce brain pathology by higher activation of its downstream targets, such as BDNF. Therefore, this review aims to understand the effects of HIT on CREB function and how HIT can mediate the CREB-induced molecular cross-talk for maintaining brain health.

Effects of exercise intensity and diet on cardiac tissue structure and FGF21/β-Klotho signaling in type 2 diabetic mice: a comparative study of HFD and HFD + STZ induced type 2 diabetes models in mice

BACKGROUND

Structural heart disease is one of the leading causes of death in people with type 2 diabetes (T2D), which is not known to have an effect on exercise training. The aim of this study was to compare the effects of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on heart tissue structure, the serum level of FGF21 and the heart tissue level of β-Klotho, an FGF21 coreceptor, in HFD and HFD + STZ-induced diabetic mice.

METHODS

Thirty-six male C57BL/6J mice were divided into high-fat diet (HFD) and normal chow diet (ND) groups. After 20 weeks of diet, the HFD mice were divided into HFD and HFD + STZ groups, and the latter group was injected with STZ. Then, the mice in the ND, HFD and HFD + STZ groups were divided into three subgroups of control (C), HIIT and MICT, and mice were placed in one of nine groups ND-C, ND-HIIT, ND-MICT, HFD-C, HFD-HIIT, HFD-MICT, HFD + STZ-C, HFD + STZ-HIIT, and HFD + STZ-MICT. The mice in the exercise training (ET) groups were run on a treadmill for eight weeks. Finally, the tissue and serum samples were collected and analyzed by two-way ANOVA.

RESULTS

Statistical analyses showed that the main effect of diabetes inducing model (DIM) was significant for all variables (p < 0.05), except vascular density (p = 0.055); the main effect of ET type on fasting blood glucose and FGF21 was significant (p < 0.001); and the interaction was significant for fasting blood glucose, heart weight and FGF21 (p < 0.001). Post hoc and subgroup analysis showed a superior effect of MICT over HIIT in decreasing fasting blood glucose and serum level of FGF21 (p < 0.001). Additionally, the results of the myocardial tissue qualitative analyses differed between the diabetic mouse models and the ET groups.

CONCLUSIONS

In a mouse model, type 2 diabetes can negatively affect heart tissue structure and FGF21 signaling in cardiac tissue, and both HIIT and MICT can prevent this effect. However, MICT likely more effective that HIIT in reducing circulating FGF21.

Human skeletal muscle possesses an epigenetic memory of high-intensity interval training

Human skeletal muscle displays an epigenetic memory of resistance exercise induced-hypertrophy. It is unknown, however, whether high-intensity interval training (HIIT) also evokes an epigenetic muscle memory. This study used repeated training intervention interspersed with a detraining period to assess epigenetic memory of HIIT. Twenty healthy subjects (25 ± 5 yr) completed two HIIT interventions (training and retraining) lasting 2 mo, separated by 3 mo of detraining. Measurements at baseline, after training, detraining, and retraining included maximal oxygen consumption (V̇o2max). Vastus lateralis biopsies were taken for genome-wide DNA methylation and targeted gene expression analyses. V̇o2max improved during training and retraining (P < 0.001) without differences between interventions (P > 0.58). Thousands of differentially methylated positions (DMPs) predominantly demonstrated a hypomethylated state after training, retained even after 3-mo of exercise cessation and into retraining. Five genes, ADAM19, INPP5a, MTHFD1L, CAPN2, and SLC16A3, possessed differentially methylated regions (DMRs) with retained hypomethylated memory profiles and increased gene expression. The retained hypomethylation during detraining was associated with an enhancement in expression of the same genes even after 3 mo of detraining. SLC16A3, INPP5a, and CAPN2 are involved in lactate transport and calcium signaling. Despite similar physiological adaptations between training and retraining, memory profiles were found at epigenetic and gene expression level, characterized by retained hypomethylation and increased gene expression after training into long-term detraining and retraining. These genes were associated with calcium signaling and lactate transport. Although significant memory was not observed in physiological parameters, our novel findings indicate that human skeletal muscle possesses an epigenetic memory of HIIT.NEW & NOTEWORTHY Cells possess a "memory" such that adaptations can be more quickly regained when a previously encountered challenge is reintroduced. Exercise provides an excellent experimental model to explore the concept of cellular memory to physiologically relevant stressors in humans. This study highlights molecular mechanisms that contribute to muscle memory in response to high-intensity interval training in humans, showing retention of DNA methylation and gene expression profiles from earlier training into detraining and retraining.

Impact of sprint interval training on post-fatigue mitochondrial rate in professional boxers

PURPOSE

Professional boxing is a sport that requires a high aerobic capacity to prevent fatigue and allow athletes to perform over 4-12 rounds. Typically, athletes will go into a heavy training period in a pre-bout camp lasting 6 to 9 weeks. This study investigates the impact of 3 weeks of repeated Wingate sprint interval training, performed on standard gym ergometer bikes, on skeletal muscle endurance and mitochondrial function.

METHODS

Ten male professional boxers (age: 26 ± 4 years, height: 175 ± 5 cm, weight: 70 ± 5 kg) participated in the study. Baseline testing involved a NIRS monitor attached to the rectus femoris muscle prior to an incremental time to exhaustion test on a treadmill. After the treadmill test participants underwent a series of arterial occlusions to determine mitochondrial function post-volitional exhaustion. Participants then continued their own training for 3 weeks and then repeated baseline testing. After the second testing session, participants undertook three weekly sprint sessions consisting of 3 × 30 s maximal sprints with 60 s recovery. Testing was repeated 3 weeks later.

RESULTS

The time to exhaustion increased by > 6% after 3 weeks of sprint interval training as compared to baseline and control (p < 0.05). Skeletal muscle oxygen saturation (SmO2) at exhaustion was increased by 5.5% after 3 weeks of sprint interval training as compared to baseline and control (p = 0.008). Skeletal muscle mitochondrial rate post exhaustion was increased by 160% after 3 weeks of sprint interval training as compared to baseline and control (p < 0.001).

CONCLUSION

The study demonstrated that SIT led to increased incremental time to exhaustion, higher SmO2 levels at volitional exhaustion and increased mitochondrial rates in professional boxers. These findings suggest that SIT should be an integral part of a boxe's conditioning regimen to improve performance and safety within the ring.

Comparative analysis of the effects of high-intensity interval training and traditional aerobic training on improving physical fitness and biochemical indicators in patients with non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD), linked to sedentary lifestyles and metabolic dysfunction, is highly prevalent. Exercise is an established intervention, but the relative efficacy of different exercise modalities remains unclear. The aim of this study was to compare the effects of moderate-intensity continuous aerobic training and High-Intensity Interval Training (HIIT) on physical fitness, biochemical parameters, and liver function in NAFLD patients.

METHODS

Sixty NAFLD patients (32 males, 28 females; age: 49.7±8.7 years; BMI: 31.1±3.3 kg/m2) were randomized into HIIT, aerobic training, and control cohorts. The HIIT cohort performed 4-minute high-intensity intervals at 85-95% of peak heart rate, interspersed with 3-minute active recovery at 60-70% of peak heart rate for 30-40 minutes per session. The aerobic training cohort performed continuous exercise at 60-70% of peak heart rate for 45-60 minutes per session. Both intervention cohorts underwent 12 weeks of supervised training, thrice weekly. Before and after the intervention, assessments included cardiorespiratory fitness, muscular strength, flexibility, lipid profile, liver enzymes, inflammatory markers, insulin sensitivity, and oxidative stress markers.

RESULTS

Compared to controls, both exercise cohorts showed significant improvements in cardiorespiratory fitness, muscular strength, and flexibility. However, HIIT elicited superior enhancements in cardiorespiratory fitness and muscular strength. Biochemically, both exercise cohorts exhibited reductions in triglycerides, low-density lipoprotein (LDL) cholesterol, liver enzymes (alanine aminotransferase [ALT], aspartate aminotransferase [AST]), inflammatory markers (C-reactive protein [CRP], interleukin-6 [IL-6]), insulin resistance (homeostatic model assessment of insulin resistance [HOMA-IR]), and oxidative stress markers (malondialdehyde [MDA], protein carbonyl). Notably, HIIT yielded more substantial improvements in these parameters.

CONCLUSIONS

HIIT and traditional aerobic training are effective in improving physical fitness and ameliorating biochemical indicators in NAFLD patients. Notably, HIIT appears to be more advantageous in enhancing cardiorespiratory fitness, muscular strength, and metabolic, inflammatory, and oxidative stress profiles, suggesting its potential as a time-efficient and effective exercise modality for managing NAFLD.

Energetic activity for depression in young people aged 13-17 years: the READY feasibility RCT

Background

Prevalence of depression is increasing in young people. Behaviour change interventions providing benefits equal to or greater than talking therapies or pharmacological alternatives are needed. Exercise could be beneficial for young people with depression, but we lack robust trials of its effectiveness.

Objective

To test whether an exercise intervention targeting young people with depression is feasible, including recruitment and retention of young people, recruitment and training of exercise professionals and intervention delivery.

Design

Three-arm cluster feasibility randomised controlled trial with embedded process evaluation and health economic data collection.

Setting

Local community venues in Hertfordshire, Bedfordshire and Norfolk.

Participants

Young people aged 13-17 years experiencing mild to moderate low mood or depression (indicated by scoring 17-36 on the Child Depression Inventory version 2) identified by mental health services, schools or self-referral.

Interventions

Participants were randomised to one of three groups: high-intensity exercise, low-intensity exercise or a social activity control. Group sessions ran twice-weekly for 12 weeks delivered by registered exercise professionals, supported by mental health support workers.

Main outcome measures

Referral, recruitment and retention rates; attendance at group sessions; adherence to and ability to reach intensity during exercise sessions; proportions of missing data, and adverse events measured at baseline and at 3 and 6 months; resource use; and reach and representativeness.

Results

Of 321 referrals to the study, 173 were assessed for eligibility, and of the target sample size of 81, 15 were recruited and 14 were randomised (one withdrew). The retention rate was 71.4% and attendance at intervention sessions was > 67%; data completeness was > 80% for baseline assessments. Follow-up completion rate at 14 weeks was > 80% for most outcomes, with 50% for accelerometer data in the low-intensity group. Trial processes and the intervention were acceptable to young people. Barriers to and facilitators of intervention delivery were identified.

Limitations

Findings highlighted challenges around recruitment, delivery of exercise interventions and informed ways of addressing barriers to recruitment for future studies. The study was conducted between October 2020 and August 2022 and consequently the COVID-19 pandemic had a disruptive impact on implementation.

Conclusions

A large randomised trial of the effectiveness of the intervention is not feasible using the current study design, but issues relating to recruitment could be addressed with further work.

Future work

Developing appropriate recruitment strategies via triage services, general practitioner practices, schools and social media and early engagement with the local Clinical Research Network to support recruitment to the study would address the significant shortfalls identified. Young people who are deemed unsuitable for mental health services should be followed up to be offered participation in such interventions. Collaborations between the NHS services and sports delivery partners should consider in-person contact with young people rather than remote consultations. Recruiting through general practitioner practices is effective and relatively inexpensive. The role of community engagement (socialmedia, public health agencies, community groups) needs to be further explored. Strong public and patient involvement and engagement via young people advisory groups is important to ensure that research is relevant to young people.

Funding

This article presents independent research funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme as award number 17/78/10.

Effects of High-Intensity Interval Training on Blood Pressure Levels in Hypertensive Patients: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

OBJECTIVE

This systematic review and meta-analysis aimed to (I) evaluate the evidence on the effects of high-intensity interval training (HIIT) on systolic blood pressure (SBP) and diastolic blood pressure (DBP) in hypertensive patients; (II) determine whether HIIT impacts SBP and DBP differently; and (III) assess the clinical relevance of these effects.

METHODS

A comprehensive search was conducted across multiple electronic databases, resulting in the inclusion of seven randomized clinical trials in the meta-analysis. The outcomes were analyzed using random-effects models to compute mean differences (MD) and standardized mean differences (SMD) for SBP and DBP.

RESULTS

A small reduction in SBP was observed with HIIT interventions (MD -3.00; 95% CI -4.61 to -1.39; p < 0.0001; SMD -0.28; 95% CI -0.42 to -0.13; p = 0.0003). However, no statistically significant reductions were detected for DBP (MD -0.70; 95% CI -1.80 to 0.39; p = 0.21; SMD -0.07; 95% CI -0.22 to 0.08; p = 0.35). Despite demonstrating statistical significance for SBP, the effects did not reach clinical relevance.

CONCLUSIONS

HIIT interventions yield small reductions in SBP, with minimal impact on DBP. These findings suggest limited clinical relevance in the management of hypertension. Further randomized controlled trials are necessary to standardize HIIT protocols, with specific emphasis on intensity control and manipulation, to better understand their potential role in hypertensive populations.

Effects of different supervised and structured physical exercise on the physical fitness trainability of children and adolescents: a meta-analysis and meta-regression : Physical fitness trainability in children and adolescents' health

BACKGROUND

Physical fitness has been considered an important health indicator. Several factors can impact the increase in physical fitness in children and adolescents, including chronological age, sex and BMI, in addition to training variables such as weekly frequency, session and intervention duration, and types of exercises performed. To know the importance of variables that can impact physical fitness, it is important for health professionals to identify the most efficient way of prescribing physical exercises for children and adolescents. The aim is review and meta-analyses of the effects of supervised and structured physical exercise on the physical fitness trainability of children and adolescents.

METHODS

Relevant articles were searched in the PubMed, Cochrane Library, Embase and Scopus platform databases and selected based on the following criteria: children and adolescents aged between 7 and 17 years who performed any type of structured physical exercise compared to a control group without exercise and evaluating physical fitness (strength or muscular power, cardiorespiratory fitness (CRF) or speed. The results are reported in accordance with PRISMA 2020.

RESULTS

Eighty studies were included with a total of 5769 participants. Strength exercises (ES: 1.073; 95% CI, 0.612-1.533; P < 0.001; I2: 74%), concurrent (ES: 1.054; 95% CI, 0.255-1.853; P < 0.010; I2: 72%) and sports (ES: 0.573; 95% CI, 0.015 to 1.132; P < 0.044; I2: 34%) seem to be the most effective in increasing muscular strength. Aerobic activities (ES: 0.400; 95% CI, 0.258-0.542; P < 0.001; I2: 74%), sports (ES: 0.271; 95% IC, 0.148-0.394; P < 0.001; I2: 15), or HIIT (ES: 0.668; 95% IC, 0.333-1.003; P < 0.001; I2: 29%) resulted in increased CRF (ES: 0.514; 95% IC, 0.220-1.808; P < 0.001; I2: 66%). The practice of physical exercise increased muscular power (ES: 0.241; 95% CI, 0.053-0.429; P = 0.012; I2: 0%). The practice of HIIT impacts MAS gains (ES: 0.048; 95% CI, 0.050 - 0.026; P = 0.029; I2: 44%).

CONCLUSION

Supervised and structured physical exercise can improve muscular strength (15-35%), CRF (5.4-8.5%), muscular power (5.6-11.8%), and MAS (5.4%) trainability in children and adolescents. Sex, BMI of the subjects and type of exercise performed (aerobic activities, exclusive to strength, HIIT or sports) should be considered when prescribing the exercise.

Changes in body composition, physical fitness and quality of life on robotic gait assisted training in patients with Guillain-Barré Syndrome: a case report

PURPOSE

This case report evaluates changes in body composition, physical fitness, and quality of life in a patient with Guillain-Barre syndrome (GBS) undergoing training with an end-effector gait robotic device.

METHODS

A 35-year-old man with GBS completed interval training using a robotic gait assistant three times weekly for four weeks. The training intensity was set at 70-75% (Phase 1) and 80-85% (Phase 2) of the target heart rate, calculated using the heart rate reserve. Evaluations included body composition, physical fitness, isometric strength, gait performance, and quality of life indices.

RESULTS

Post-intervention, improvements were observed across all parameters. Body weight increased by 1.2%, while body fat percentage and visceral fat decreased by 5.4% and 3.7%, respectively. Muscle mass increased by 3.3%, and isometric strength improved at all tested sites. Gait speed increased from 0.7 to 1.8 km/h (157.1%), and the number of steps per minute increased from 33 to 77 (133.3%). The timed up-and-go (TUG) test improved by 7.1%, and exercise self-efficacy (ESE) scores increased by 29.1%.

CONCLUSION

These findings align with the principles of neuromuscular adaptation, motor learning, and neuroplasticity. Interval training with a robotic gait device may effectively restore physical function and improve quality of life in patients with GBS. However, the limitations of this single case study highlight the need for randomized controlled trials with larger cohorts and long-term effectiveness assessments.

Long-Term High-Intensity Interval Training Intervention Improves Emotional Conflict Control in Association With Right Ventrolateral Prefrontal Activation in Males With Methamphetamine Use Disorder: A Randomized Controlled Trial

Acute high-intensity interval training (HIIT) has cognitive benefits in individuals with methamphetamine use disorder (MUD), yet it remains largely unknown the benefits of long-term HIIT on emotional conflict control and its neural mechanism in individuals with MUD. The current study conducted a 36-week low-volume HIIT intervention to investigate the effects of HIIT on emotional conflict control in males with MUD and their prefrontal cortex (PFC) activation. This study was a sub-study of the Study for Rehabilitation Training Model Construction and Training Effect of High Intensity Compound Exercise Prescription. Forty males with MUD (31.50 ± 4.33 years) were randomly assigned to the HIIT group and control group. The HIIT group received a 36-week low-volume HIIT intervention, while the control group maintained daily physical exercise. The emotional conflict task (emotional face-word Stroop task) with functional near-infrared spectroscopy (fNIRS) recording and subjective craving test were performed before and after the intervention. The results showed that the HIIT intervention reduced the emotional conflict and increased cortical activations of right dorsolateral PFC (dlPFC) and right ventrolateral PFC (vlPFC). More importantly, the HIIT-induced decreased emotional conflict was associated significantly with increased right vlPFC activation. In addition, subjective craving was also reduced after HIIT intervention. While the control group showed significant changes in neither brain activation nor the craving. These findings suggest that long-term low-volume HIIT can improve PFC activation, promote emotional conflict control, and reduce subjective craving in males with MUD. HIIT seems to be an effective method of withdrawal rehabilitation for males with MUD.

Effect of perioperative rehabilitation exercise on postoperative outcomes in patients aged ≥65 years undergoing gastrointestinal surgery: A multicenter randomized controlled trial

STUDY OBJECTIVES

This study aimed to assess the effect of perioperative rehabilitation exercise, initiated shortly after hospital admission, on postoperative outcomes in elderly patients.

DESIGN

A prospective, multicenter, randomized, controlled, open-label, and assessor-blinded clinical trial.

SETTING

Hospital wards.

PATIENTS

Elderly patients (≥65 years, n = 160) scheduled for gastrointestinal surgery between June 2021 and November 2022 were enrolled and randomly assigned to the intervention or control group.

INTERVENTIONS

Patients were divided into two groups base on whether they had received a specific type of exercise program initiated after hospital admission and continued until 30 days after surgery.

MEASUREMENTS

The primary outcome was the Comprehensive Complications Index (CCI) measured at 30 days after surgery. Secondary outcomes were the rate of complications, number of complications, patient satisfaction, hospital readmission, postoperative length of stay, gastrointestinal function recovery, postoperative quality of life and psychological status. Intention-to-treat (ITT) and per-protocol (PP) analyses were conducted.

MAIN RESULTS

ITT analysis showed a significantly lower 30-day CCI in the intervention group (β: -6.31; 95 % Confidence Interval [CI], -11.26 to -1.37, P = 0.013). Compared to controls, the intervention group had a decreased rate of hospital readmission (Odds Ratio: 0.00; 95 % CI, 0.00 to 0.32, P = 0.022), less number of complications (β: -0.57; 95 % CI, -1.03 to -0.11, P = 0.016), as well as lower rate of postoperative anxiety (β: -0.74; 95 % CI, -1.42 to -0.06, P = 0.033) and depression scores (β: -1.13; 95 % CI, -0.97 to -1.30, P = 0.008). Additionally, the intervention group reported higher satisfaction (β: 0.98; 95 % CI, 0.33 to 1.64, P = 0.004) and Euro quality of life-Visual Analogue Scale scores (β: 8.88; 95 % CI, 2.48 to 15.28, P = 0.007). Similar results were found in the PP analysis.

CONCLUSION

Perioperative rehabilitation exercise has a positive impact on postoperative complications, quality of life and psychological well-being in elderly patients undergoing gastrointestinal surgery, even when implemented after hospital admission.

Intermittent Hypoxic Training Increases and Prolongs Exercise Benefits in Adult Untrained Women

Camacho-Cardenosa, Alba, Marta Camacho-Cardenosa, Johannes Burtscher, Pedro R. Olivares, Guillermo Olcina, and Javier Brazo-Sayavera. Intermittent hypoxic training increases and prolongs exercise benefits in adult untrained women. High Alt Med Biol. 25:274-284, 2024. Background: Exercising in hypoxia may confer multiple health benefits, but the evidence for specific benefits is scarce. Methods: We investigated effects of intermittent hypoxic training (IHT) on the quality of life and functional fitness of healthy adult women, in a double-blind, randomized, placebo-controlled study. Subjects performed 36 sessions of IHT (experimental group, n = 41; fraction of inspired oxygen [FIO2]: 0.17) or the same training in normoxia (control group, n = 41; FIO2: 0.21). Health-related quality of life, fitness tests, and hemoglobin levels were assessed before (T1), directly after (T2), and 4 weeks after (T3) cessation. Results: At T2, upper body strength (+14.96%), lower body strength (+26.20%), and agility (-4.94%) increased significantly in the experimental group compared to baseline but not in controls. The experimental group improved lower body strength more (by 9.85%) than controls at T2 and performed significantly better in walking (by 2.92%) and upper body strength testing (by 16.03%), and agility (by 4.54%) at T3. Perceived general health and vitality was significantly greater in the experimental group at T2 and T3 compared with T1. None of these improvements were observed in the control group. Conclusions: IHT is a promising strategy to induce long-lasting fitness benefits in healthy adult women.

The role of exosomes for sustained specific cardiorespiratory and metabolic improvements in males with type 2 diabetes after detraining

BACKGROUND

High-intensity interval training (HIIT) has been shown to improve cardiorespiratory fitness (V˙O2 max) but may ameliorate insulin sensitivity only in insulin-resistant humans. It is yet unclear whether these benefits persist after detraining and to which extent duration and effectiveness of metabolic improvements differ between individuals without and with prediabetes or type 2 diabetes (T2D). Understanding these differences is relevant for developing targeted exercise training modes for individuals with different stages of dysglycemia.

METHODS

Men with (20 T2D) and without T2D (12 insulin-sensitive, IS-NDM; 10 insulin-resistant, IR-NDM) underwent hyperinsulinemic-euglycemic clamps, spiroergometry, ectopic lipid quantification and muscle biopsies at baseline, after 12-week HIIT and after 4-week detraining.

FINDINGS

After detraining, the HIIT-stimulated V˙O2 max declined in T2D and IR-NDM, but remained higher compared to baseline in all groups. The HIIT-induced changes in hepatic insulin sensitivity and ectopic lipid content were sustained after detraining in T2D and IR-NDM, whereas improvements of whole-body insulin sensitivity were abolished in T2D. T2D and IR-NDM showed persistent increases in the number of small extracellular vesicles, which carry among others antioxidant proteins. The ratio of reduced-to-oxidized glutathione further decreased after detraining in all groups, whereas changes in proteins involved in mitochondrial turnover were dependent on insulin sensitivity, with some evidence for upregulation of fusion and mitophagy in T2D and IR-NDM and upregulation of fission in IS-NDM. Levels of different lipolytic proteins were reduced in all participants after detraining.

INTERPRETATION

HIIT offers sustained improvement of energy metabolism and hepatic insulin sensitivity in insulin-resistant humans, but long-term adherence is required to maintain these benefits.

FUNDING

Funding bodies that contributed to this study are listed in the Acknowledgements section.

Impact of spinach thylakoid extract-induced 12-week high-intensity functional training on specific adipokines in obese males

BACKGROUND

Obesity presents multifarious etiopathologies with its management being a global challenge. This article presents the first ever report on the impact of spinach thylakoid extract-induced high-intensity functional training (HIFT) on obesity management via regulating the levels of novel adipokine, C1q/TNF-related Protein-12 (CTRP-12), furin, and Krüppel-like factor 15 (KLF-15).

METHODS

Sixty-eight obese male subjects were randomly divided into four groups: control group (CG), supplement group (SG), training group (TG), and the combined training and supplement group (TSG). After initial assessments of all groups, the training group commenced a twelve-week HIFT using the CrossFit program (comprising of three training sessions per week, each lasting 30 min). Eligible candidates were randomly assigned to either receive thylakoid-rich spinach extract (5 g per day) or a matching placebo (5 g per day of corn starch, 30 min before lunch) for a total duration of 12 weeks. All required data and investigations were collected at 48 h pre- and post-training.

RESULTS

The results indicated a substantial correlation between exercise and the time of KLF-15, furin, and CTRP-12 demonstrating effect sizes of 0.3, 0.7, and 0.6, respectively. Additionally, the training and supplementation group (TSG) exhibited a substantial decrease in low-density lipoprotein (LDL), total cholesterol (TC), and triglyceride (TG) levels (p < 0.0001). Concurrently, there was a significant increase in high-density lipoprotein-cholesterol (HDL-C) levels (p = 0.0001). Furthermore, a notable difference between the groups emerged in HDL, LDL, TC, and TG levels, supported by effect sizes of 0.73, 0.86, 0.96, and 0.89, respectively (p < 0.05).

CONCLUSION

The study offered novel insights into the management of obesity using supplements induced by spinach-derived thylakoid extract during a 12-week HIFT program. The proposed combination intervention may reverse obesity-induced insulin resistance and metabolic dysfunctions by positive regulation of CTRP-12/adipolin and KLF15 and simultaneous suppression of furin levels.

Exercise Training Counteracts Compromised Mitochondrial Capacity Induced by Energy Restriction in Prediabetics in a Sex-Dependent Manner

The objective of this randomized controlled trial was to examine if exercise training can counteract energy restriction-induced impairment of mitochondrial capacity in skeletal muscle of 55-70-years people with prediabetes and metabolic syndrome. The potential impact of sex was explored. Fifty sedentary men and women with prediabetes and metabolic syndrome (age: 61 ± 6 (±SD) years, BMI: 29.6 ± 4.7 kg·m-2, body fat content: 37.5% ± 8.2% and VO2max: 22.3 ± 5.7 mL·min-1·kg-1) were randomized to either exercise training and dietary advice (EX-DI) or dietary advice only (DI). Dietary advice aimed to induce weight loss and improve glycemic control. Exercise consisted of 32 ± 2 mixed 30-60 min training sessions with recreational small-sided soccer distributed across 16 weeks. Maximal activity and protein abundance of key regulatory mitochondrial enzymes were determined in m. vastus lateralis pre- and post-intervention. Muscle glycogen content was also determined. Dietary advice only (DI), impaired (p < 0.001) citrate synthase (CS), and 3-hydroxyacyl-CoA dehydrogenase (HAD) maximal activity by 18% ± 43% and 23% ± 19%, respectively. When combined with exercise training, no dietary impairment of CS or HAD maximal activity was detectable. Superoxide dismutase 2 (SOD2) and CS protein expression also declined (p < 0.05) in DI and remained unchanged in EX-DI. In terms of sex differences, a decrease in maximal CS activity in both EX-DI and DI was observed exclusively in men (all p < 0.05). In conclusion, 16 weeks of exercise training counteracts energy restriction-induced impairment in skeletal mitochondrial function in 55- to 70-year-old women and men with prediabetes and metabolic syndrome.

High-intensity interval training for cardiometabolic health in adults with metabolic syndrome: a systematic review and meta-analysis of randomised controlled trials

OBJECTIVE

To assess the effectiveness of high-intensity interval training (HIIT) compared with traditional moderate-intensity continuous training (MICT) and/or non-exercise control (CON) for modification of metabolic syndrome (MetS) components and other cardiometabolic health outcomes in individuals with MetS.

DESIGN

Systematic review and meta-analysis DATA SOURCES: Five databases were searched from inception to March 2024.

STUDY APPRAISAL AND SYNTHESIS

Meta-analyses of randomised controlled trials (RCTs) comparing HIIT with MICT/CON were performed for components of MetS (waist circumference (WC), systolic blood pressure (SBP), diastolic blood pressure (DBP), high-density lipoprotein cholesterol (HDL-C), triglyceride (TG), and fasting blood glucose (BG)) and clinically relevant cardiometabolic health parameters. Subgroup moderator analyses were conducted based on the intervention duration and HIIT volume.

RESULTS

Out of 4819 studies, 23 RCTs involving 1374 participants were included (mean age: 46.2-67.0 years, 55% male). HIIT significantly improved WC (weighted mean difference (WMD) -4.12 cm, 95% CI -4.71 to -3.53), SBP (WMD -6.05 mm Hg, 95% CI -8.11 to -4.00), DBP (WMD -3.68 mm Hg, 95% CI -5.70 to -1.65), HDL-C (WMD 0.12 mmol/L, 95% CI 0.04 to 0.20), TG (WMD -0.34 mmol/L, 95% CI -0.41 to -0.27) and BG (WMD -0.35 mmol/L, 95% CI -0.54 to -0.16) compared with CON (all p<0.01). HIIT approaches demonstrated comparable effects to MICT across all parameters. Subgroup analyses suggested that HIIT protocols with low volume (ie, <15 min of high-intensity exercise per session) were not inferior to higher volume protocols for improving MetS components.

CONCLUSION

This review supports HIIT as an efficacious exercise strategy for improving cardiometabolic health in individuals with MetS. Low-volume HIIT appears to be a viable alternative to traditional forms of aerobic exercise.

Salivary spectral signature using ATR-FTIR spectroscopy in different exercise protocols

The Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) has been applied to determine salivary biomarkers with high sensitivity and cost-effectiveness. Our study aimed to test the hypothesis that the spectral profile of saliva demonstrates distinct vibrational modes corresponding to different exercise protocols, thereby facilitating exercise monitoring. Saliva samples were collected from trained male subjects at three intervals: pre-exercise, post-exercise, and 3 h post-exercise. The protocols included acute sessions of continuous exercise (CE), high-intensity interval exercise (HIIE), and resistance exercise (RE). ATR-FTIR analysis revealed that salivary biochemical components changed uniquely with each exercise protocol. Specific spectral vibrational modes were identified as potential biomarkers for each exercise type. Notably, the salivary spectrum pattern of CE closely resembled that of HIIE, whereas RE showed minor alterations. Furthermore, we attempted to apply an algorithm capable of distinguishing the spectral range that differentiates the exercise modalities. This pioneering study is the first to compare changes in saliva spectra following different exercise protocols and to suggest spectrum peaks of vibrational modes as markers for specific types of exercises. We emphasize that the spectral wavenumbers identified by FTIR could serve as practical markers in distinguishing between different exercise modalities, with sensitivity, specificity, and accuracy correlating with the metabolic changes induced by exercise. Therefore, this study contributes a panel of ATR-FTIR spectral wavenumbers that can be referenced as a spectral signature capable of distinguishing between resistance and endurance exercises.

Association of Hibiscus sabdariffa and high-intensity interval training induces reduction in adiposity and beneficial metabolic adaptations in obesity without changes in lipid metabolism

High-intensity interval training (HIIT) has stood out as a treatment for obesity, leading to adaptations of the cardiovascular system and reducing body adiposity. In addition, the search for alternative therapies for weight loss has intensified. The administration of Hibiscus sabdariffa (Hs) has been described as an efficient supplement in weight loss and in the treatment of metabolic changes associated with obesity. In this context, the objective was to investigate the effects of the association of Hs and HIIT on metabolic adaptations and lipid metabolism in obese rats. Wistars rats were subjected to obesity and subsequently randomized into 4 groups: obese (Ob), obese + HS (ObHs), obese + HIIT (ObHIIT), and obese + HS + HIIT (ObHsHIIT). For 8 weeks, ObHs and ObHsHIIT rats received Hs extract daily (150 mg/kg of body weight) and trained groups (ObHIIT and ObHsHIIT) were subjected to a HIIT program on a treadmill. Nutritional profile, glycemic curve, biochemical profile, and liver glycogen were determined. HIIT decreased caloric intake, feed efficiency, body adiposity, total body fat, and body weight gain, associated with improvements in physical performance parameters and a smaller glycemic curve and area. Hs had a hepatoprotective effect, reducing alkaline phosphatase values, but its effects were more pronounced when associated with HIIT. Therefore, the combination of treatments promoted a reduction in food consumption and body adiposity, as well as an improvement in physical performance and glycemic profile, but without changes in lipid metabolism.

Aquatic High-Intensity Interval Deep Water Running Influence on Cardiometabolic Health and Cognitive Psychological Responses in Women

PURPOSE

To investigate the effects of an 8-wk AHIIT-DWR intervention compared with land-based HIT training (LHIIT) on cardiometabolic health, cognitive, and psychological outcomes in inactive elderly women.

METHODS

Seventy inactive elderly women aged 60 yr or above were randomly assigned into two groups: AHIIT-DWR and LHIIT. The AHIIT-DWR group engaged in DWR sessions comprising 30 min of interval training, consisting of ten 2-min exercise bouts at 80%-90% of their maximal heart rate (HR max ), with 1-min active recovery at 70% HR max between bouts, for two sessions per week, for 8 wk. The LHIIT group performed treadmill running at the same intensity.

RESULTS

Both groups showed similar cardiovascular fitness, maximal aerobic capacity (V̇O 2max ), HR max , and RER improvement ( P > 0.05), whereas AHIIT-DWR showed a significant improvement in aerobic capacity minute ventilation (V̇E), metabolic equivalents (METs), and O 2 pulse ( P < 0.05) over the 8-wk intervention. Both AHIIT-DWR and LHIIT significantly decreased triglycerides, total cholesterol, HDL, and LDL postintervention ( P < 0.05). No significant group differences were observed for cognitive function assessed by MMSE and MOCA ( P > 0.05). Both groups showed similar enjoyment levels, self-efficacy scores, and high adherence rates (>90%).

CONCLUSIONS

Our study suggests that AHIIT-DWR can elicit a similar improvement in cardiorespiratory health, metabolic blood markers, cognitive function assessed by MMSE and MOCA, and psychological responses as LHIIT in inactive elderly women.

Efficacy of Interval Training in Improving Body Composition and Adiposity in Apparently Healthy Adults: An Umbrella Review with Meta-Analysis

BACKGROUND

Although the efficacy of interval training for improving body composition has been summarized in an increasing number of systematic reviews in recent years, discrepancies in review findings and conclusions have been observed.

OBJECTIVE

This study aims to synthesize the available evidence on the efficacy of interval training compared with moderate-intensity continuous training (MICT) and nonexercise control (CON) in reducing body adiposity in apparently healthy adults.

METHODS

An umbrella review with meta-analysis was performed. A systematic search was conducted in seven databases (MEDLINE, EMBASE, Cochrane Database, CINAHL, Scopus, SPORTDiscus, and Web of Science) up to October 2023. Systematic reviews with meta-analyses of randomized controlled trials (RCTs) comparing interval training and MICT/CON were included. Literature selection, data extraction, and methodological quality assessment (AMSTAR-2) were conducted independently by two reviewers. Meta-analyses were performed using a random-effects model. Subgroup analyses were conducted based on the type of interval training [high-intensity interval training (HIIT) and sprint interval training (SIT)], intervention duration, body mass index, exercise modality, and volume of HIIT protocols.

RESULTS

Sixteen systematic reviews, including 79 RCTs and 2474 unique participants, met the inclusion criteria. Most systematic reviews had a critically low (n = 6) or low (n = 6) AMSTAR-2 score. Interval training demonstrated significantly greater reductions in total body fat percent (BF%) compared with MICT [weighted mean difference (WMD) of - 0.77%; 95% confidence interval (CI) - 1.12 to - 0.32%] and CON (WMD of - 1.50%; 95% CI - 2.40 to - 0.58%). Significant reductions in fat mass, visceral adipose tissue, subcutaneous abdominal fat, and android abdominal fat were also observed following interval training compared to CON. Subgroup analyses indicated that both HIIT and SIT resulted in superior BF% loss than MICT. These benefits appeared to be more prominent in individuals with overweight/obesity and longer duration interventions (≥ 12 weeks), as well as in protocols using cycling as a modality and low-volume HIIT (i.e., < 15 min of high-intensity exercise per session).

CONCLUSIONS

This novel umbrella review with large-scale meta-analysis provides an updated synthesis of evidence with implications for physical activity guideline recommendations. The findings support interval training as a viable exercise strategy for reducing adiposity in the general population.

Synergistic Effects of Concurrent Aerobic and Strength Training on Fitness in Children and Adolescents: A Multivariate and Network Meta-Analysis

The decline in fitness levels among children and adolescents underscores the urgent need for effective exercise interventions. Aerobic endurance training (ET) and resistance training (RT) are vital for physical development in this demographic. This study employs multivariate and network meta-analysis (NMA) to assess the impact of concurrent training (CT), which integrates both ET and RT, on youth physical fitness. The objective is to identify the distinct advantages of CT over either ET or RT alone, emphasizing demographic and training-specific variables. A systematic literature review of publications from 1980 onward was conducted through ISI Web of Science, PubMed/MEDLINE, and SPORTDiscus databases, adhering to the PICOS criteria for study selection. Data were analyzed using univariate, multivariate, and network meta-analyses in Stata 17.0, focusing on cardiorespiratory fitness and muscular strength. The methodological quality and risk of bias were evaluated using the PEDro scale and Egger's test, along with sensitivity analyses and meta-regression to explore heterogeneity and publication bias. This analysis included 36 studies with 2658 participants (mean age: 14.32 ± 2.29 years) from an initial 11 074 publications, indicating low bias risk (PEDro scores ≥ 6). Univariate meta-analysis showed no significant differences in maximal oxygen uptake (VO2max) between CT and ET (standardized mean difference [SMD] = 0.01; 95% confidence interval [CI]: -0.23 to 0.25; p = 0.93). In contrast, CT significantly improved countermovement jump (CMJ) compared to RT alone (SMD = 0.19; 95% CI: 0.01-0.36; p = 0.04). Multivariate analysis confirmed notable enhancements in endurance and explosiveness for CT compared to ET or RT. NMA indicated significant improvements in lower limb strength, CMJ, and VO2max across interventions compared to controls, with the consecutive resistance training followed by ET (CRE) group yielding the most significant CMJ improvement (SMD = 0.27; 95% CI: 0.07-0.47). Isolated RT showed the highest lower limb strength improvement (SUCRA score 80.1%), while CRE excelled in CMJ advancements (SUCRA score 93.4%), and the CRED group (alternating ET and RT) led in VO2max improvements (SUCRA score 81.6%). Furthermore, high-intensity interval training (HIIT) significantly enhanced VO2max compared to team sports. This meta-analysis emphasizes the effectiveness of CT in improving muscle power and VO2max in children and adolescents, surpassing isolated ET or RT, and advocates for integrating ET and RT to optimize physical performance. Future research should explore the mechanisms underlying these enhancements. Trial Registration: PROSPERO registration number CRD42022368452.

It's about the long game, not epic workouts: unpacking HIIT for endurance athletes

High-intensity interval training (HIIT) prescriptions manipulate intensity, duration, and recovery variables in multiple combinations. Researchers often compare different HIIT variable combinations and treat HIIT prescription as a "maximization problem", seeking to identify the prescription(s) that induce the largest acute VO2/HR/RPE response. However, studies connecting the magnitude of specific acute HIIT response variables like work time >90% of VO2max and resulting cellular signalling and/or translation to protein upregulation and performance enhancement are lacking. This is also not how successful endurance athletes train. First, HIIT training cannot be seen in isolation. Successful endurance athletes perform most of their training volume below the first lactate turn point ( Collapse

Key Words

• endurance athletes
• exercise intensity
• interval training
• molecular signalling
• stress responses
• training monitoring

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MESH Headings

• Humans
• Physical Endurance/physiology
• High-Intensity Interval Training/methods
• Athletes
• Adaptation, Physiological
• Oxygen Consumption
• Athletic Performance/physiology
• Lactic Acid/blood

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Grants Collapse

Affiliation(s)

Stephen Seiler Department of Sport Science and Physical Education, University of Agder, Kristiansand, Norway

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Relationship between histological findings of vastus lateralis muscle and function after total hip arthroplasty in patients with hip fracture: a prospective cohort study

BACKGROUND AND PURPOSE

 We aimed to examine the histological characteristics of vastus lateralis muscles in patients undergoing total hip arthroplasty (THA) following femoral neck fractures and to explore the correlation between muscle fiber types and postoperative functional recovery.

METHODS

 34 patients undergoing THA for femoral neck fractures were included. A biopsy of the vastus lateralis muscle was performed during surgery, followed by immunohistochemical staining. Subsequently, image analysis was conducted to measure the average area of muscle fiber types and the number of type I and II muscle fibers, and the ratio of the area and the number of type II muscle fibers. Functional recovery was assessed 2 weeks post-surgery using the Short Physical Performance Battery (SPPB).

RESULTS

A significant positive correlation was observed between type II muscle fibers and SPPB scores. The ratio of type II muscle fiber area and number strongly correlated with the SPPB scores, indicating a robust static association. The average area of type II fibers showed a strong correlation (r = 0.63, P < 0.001), as did the number of type II fibers (r = 0.53, P = 0.001). Moreover, the ratio of type II muscle fiber area and number significantly correlated with SPPB scores (area: r = 0.77, P < 0.001; number: r = 0.51, P = 0.002), indicating that larger and more numerous type II fibers are associated with better physical performance.

CONCLUSION

The reduction of type II muscle fibers was strongly correlated with a low SPPB postoperative functional recovery in patients who underwent THA following femoral neck fractures.

Effects of variable resistance training within complex training on strength and punch performance in elite amateur boxers

Objectives

This study explored the effects of 6 weeks of variable resistance training (VRT) and constant resistance training (CRT) within complex training, on muscle strength and punch performance.

Methods

Twenty-four elite female boxers from the China National team were divided randomly between an experimental group (VRT) and a control group (CRT). Maximum strength of the upper and lower limbs, countermovement jump (CMJ) performance, and punch performance (single, 10s and 30s continuous) were assessed pre- and post- intervention.

Results

VRT and CRT showed significant increases (p < 0.001) in the bench press (ES = 1.79 and 1.07, respectively), squat (ES = 1.77 and 1.10, respectively), and CMJ (ES = 1.13 and 0.75, respectively). The bench press (p < 0.05) and squat (p < 0.05) improved significantly more following VRT compared to CRT. Additionally, single punch performance (speed, force, and power) increased significantly in the experimental group (ES = 1.17-1.79) and in the control group (ES = 0.58-1.32), except for the lead punch force in the control group (p > 0.05, ES = 0.20). 10s continuous punch performance (number, speed, force, and power) increased significantly (both p < 0.05) in the experimental group (ES = 0.52-1.65) and in the control group (ES = 0.32-0.81). 30s continuous punch performance (number, force, and power) increased significantly increased significantly (both p < 0.05). However, no statistically significant differences were found between groups for punch performance.

Conclusion

These findings provide evidence that VRT may improve maximum muscle strength in both upper and lower limbs, vertical jump and punch performance in elite amateur boxers.

Acute effect of resistive aquatic high-intensity interval training on metabolic costs in adults

Background

The effects of Aquatic High-Intensity Interval Training (AHIIT) and resistive AHIIT (Resistive AHIIT) to improve metabolic responses were not yet known.

Objective

This study was to compare the metabolic responses and perceived effort in young healthy adults in a single session of AHIIT and resistive AHIIT.

Methods

20 healthy subjects (9 females, 11 males) performed a stationary running at a matched exercise intensity prior AHIIT and resistive AHIIT [10 × 1-min bouts of stationary running at 90% maximum heart rate (HR max) separated by 1-min active recovery] to examine the metabolic and cardiometabolic outcomes. Mixed effects models were applied to analyze the effects of group, time, and the interaction between group and time on both outcomes. The level of correlations between metabolic variables was checked by Pearson's linear correlation.

Results

There are significant differences on pre and post resting energy expenditure (REE) within both AHIIT and resistive AHIIT groups (p < 0.01) respectively as well as the subjective rate of perceived exertion (RPE) (p < 0.01) within RAHIIT group. A moderate correlation found on respiratory exertional ratio (RER) and RPE in resistive AHIIT (r = 0.534). No significant differences between groups in terms of HR max, mean heart rate (HR mean), peak oxygen consumption (VO2 peak) and total energy expenditure (TEE) (p = 0.50, p = 0.48, p = 0.81, p = 0.59).

Conclusion

Resistive AHIIT provides comparable benefits of metabolic outcomes with AHIIT. Comparable results allowed AHIIT and resistive AHIIT prescriptions precisely.

Training, environmental and nutritional practices in indoor cycling: an explorative cross-sectional questionnaire analysis

Introduction

Indoor cycling at home has grown rapidly in recent years facilitated by advances in technology and gamification. However, there is limited data on individual's training practices when cycling indoors.

Methods

Using a single-time point, cross-sectional questionnaire, we gathered information on equipment, environmental considerations, training practices and nutrition during indoor cycling.

Results

Following 492 responses, external variables (weather; 88.4%, lack of daylight; 56.3%), time efficiency (81.9%) and general fitness (70.9%) were most frequently cited as reasons to engage in indoor cycling. "Smart" turbo trainers linked to a mixed-reality cycling software were most frequently reported in equipment set-up. 78% of participants attempted to control temperature with 96% of these participants using at least 1 fan to control airflow. The volume of indoor training differed between seasons (winter: 6h10 ± 3 h 30, summer 2h52 ± 2h57, p < 0.001), and structured (61.9%) and unstructured work-outs (64.7%) were completed more than once a week with fewer participants engaging in competitive/racing events (20.9%). 98% percent of participants consumed fluids with an average fluid intake of 0.74 ± 0.28 L/h. Dependent on type of work-out, participants reported less planning of carbohydrate and protein intake during short-duration work-outs (∼40%-60%) relative to longer-duration work-outs (∼56%-80%). Caffeine use was the most frequently reported ergogenic aid.

Conclusion

Together we report indoor cycling practices with respect to training equipment, considerations of environmental and nutritional strategies and training habits. Our findings could be used to support the development of future research and indoor training guidelines.

Effects and mechanisms of supramaximal high-intensity interval training on extrapulmonary manifestations in people with and without chronic obstructive pulmonary disease (COPD-HIIT): study protocol for a multi-centre, randomized controlled trial

BACKGROUND

Beyond being a pulmonary disease, chronic obstructive pulmonary disease (COPD) presents with extrapulmonary manifestations including reduced cognitive, cardiovascular, and muscle function. While exercise training is the cornerstone in the non-pharmacological treatment of COPD, there is a need for new exercise training methods due to suboptimal adaptations when following traditional exercise guidelines, often applying moderate-intensity continuous training (MICT). In people with COPD, short-duration high-intensity interval training (HIIT) holds the potential to induce a more optimal stimulus for training adaptations while circumventing the ventilatory burden often associated with MICT in people with COPD. We aim to determine the effects of supramaximal HIIT and MICT on extrapulmonary manifestations in people with COPD compared to matched healthy controls.

METHODS

COPD-HIIT is a prospective, multi-centre, randomized, controlled trial with blinded assessors and data analysts, employing a parallel-group designed trial. In phase 1, we will investigate the effects and mechanisms of a 12-week intervention of supramaximal HIIT compared to MICT in people with COPD (n = 92) and matched healthy controls (n = 70). Participants will perform watt-based cycling two to three times weekly. In phase 2, we will determine how exercise training and inflammation impact the trajectories of neurodegeneration, in people with COPD, over 24 months. In addition to the 92 participants with COPD performing HIIT or MICT, a usual care group (n = 46) is included in phase 2. In both phases, the primary outcomes are a change from baseline in cognitive function, cardiorespiratory fitness, and muscle power. Key secondary outcomes include change from baseline exercise tolerance, brain structure, and function measured by MRI, neuroinflammation measured by PET/CT, systemic inflammation, and intramuscular adaptations. Feasibility of the interventions will be comprehensively investigated.

DISCUSSION

The COPD-HIIT trial will determine the effects of supramaximal HIIT compared to MICT in people with COPD and healthy controls. We will provide evidence for a novel exercise modality that might overcome the barriers associated with MICT in people with COPD. We will also shed light on the impact of exercise at different intensities to reduce neurodegeneration. The goal of the COPD-HIIT trial is to improve the treatment of extrapulmonary manifestations of the disease.

TRIAL REGISTRATION

Clinicaltrials.gov: NCT06068322. Prospectively registered on 2023-09-28.

The effect of aerobic and high-intensity interval training on plasma pentraxin 3 and lipid parameters in overweight and obese women

Background

It is unclear whether different exercise programs lead to an increase in the concentration of plasma Pentraxin3 (PTX3), an anti-inflammatory protein. This study aimed to investigate the effects of aerobic exercise (AE) and high-intensity interval training (HIIT) on plasma PTX3 levels in overweight and obese women.

Method

A total of 45 sedentary women aged between 32.26 ± 6.30 voluntarily participated in the study. The control group (CG, n = 15) was selected among normal-weight women. Women in the group of participants who partook in exercise consisted of overweight and obese women according to a random method, including the AE group (n = 15) and the HIIT group (n = 15). The AE session conducted was 50 min in duration and consisted of warm-up exercises (5 min), and primary exercises (40 min, basic aerobic-step exercises). HIIT consists of warm-up exercises (5 min), primary exercises (work intervals: 6-10 × 1 min (80-90% HRmax), rest intervals: 1 min (walk, 50% HRmax), 21-29 min running. The exercises were applied for three sessions/week for 12 weeks. Fasting blood samples were taken from all participants before and after exercise and their body composition was measured.

Results

As a result of two different 12-week exercises, serum PTX3 levels increased significantly by 47.53% in the AE group and 50.21% in the HIIT group (p < 0.01). It was determined that the mean PTX3 before and after exercise increased from 1.71 ± 0.43 to 2.47 ± 0.40 ng/dL and HIIT from 1.62 ± 0.39 to 2.31 ± 0.33 ng/dL. A significant decrease in body mass index (BMI) values were detected, approximately 5.81% in the AE group and 5.06% in the HIIT group (p < .01). A significant decrease was detected in glucose, insulin, HOMA-IR, LDL-C, and hsCRP whereas HDL-C and VO2max value increased significantly in both exercise groups (p < .05; p < .01). There were no significant differences in TG and TC levels between groups (p > .05). Also, no significant differences were found between the two types of exercises in terms of parameters. A significant negative correlation in the total sample was found between PTX3 with BMI, fat mass, LDL-C, and hsCRP.

Conclusion

The percentage change in PTX3 values was not different between exercise types, whereas PTX3 was increased with exercise, regardless of the type of exercise. It can be said that both aerobic and HIIT increase PTX3, VO2max levels and improve lipid metabolism in overweight and obese women.

The Impact of Starting Positions and Breathing Rhythms on Cardiopulmonary Stress and Post-Exercise Oxygen Consumption after High-Intensity Metabolic Training: A Randomized Crossover Prospective Study

Background: The exploration of optimizing cardiopulmonary function and athletic performance through high-intensity metabolic exercises (HIMEs) is paramount in sports science. Despite the acknowledged efficacy of HIMEs in enhancing cardiopulmonary endurance, the high metabolic stress imposed on the cardiopulmonary system, especially for amateurs, necessitates a scaled approach to training. Objective: The aim of this study is to ascertain whether adjustments in the initiation posture and the adoption of an appropriate breathing strategy can effectively mitigate the cardiopulmonary stress induced by HIMEs without compromising training efficacy. Methods: Twenty-two subjects were recruited into this study. The post-exercise heart rate (PHR) and post-exercise oxygen consumption rate (POCR) were collected within 30 min after exercise. A two-way ANOVA, multi-variable Cox regression, and random survival forest machine learning algorithm were used to conduct the statistical analysis. Results: Under free breathing, only the maximum POCR differed significantly between standing and prone positions, with prone positions showing higher stress (mean difference = 3.15, p < 0.001). In contrast, the regulated breathing rhythm enhanced performance outcomes compared to free breathing regardless of the starting position. Specifically, exercises initiated from prone positions under regulated breathing recorded a significantly higher maximum and average PHR than those from standing positions (maximum PHR: mean difference = 13.40, p < 0.001; average PHR: mean difference = 6.45, p < 0.001). The multi-variable Cox regression highlighted the starting position as a critical factor influencing the PHR and breathing rhythm as a significant factor for the POCR, with respective variable importances confirmed by the random survival forest analysis. These results underscore the importance of controlled breathing and starting positions in optimizing HIME outcomes. Conclusions: Regulated breathing in high-intensity exercises enhances performance and physiological functions, emphasizing the importance of breathing rhythm over starting position. Effective training should balance exercise volume and technique to optimize performance and minimize stress, reducing overtraining and injury risks.

Effects of High-Intensity Interval Training on the Parameters Related to Physical Fitness and Health of Older Adults: A Systematic Review and Meta-Analysis

BACKGROUND

As a novel and time-efficient exercise form, high-intensity interval training (HIIT) has shown great potential in improving health-related physical fitness among diverse populations. However, empirical evidence on its efficacy among the elderly has not been well summarized. This systematic review and meta-analysis aimed to determine the effect of HIIT interventions on the parameters related to physical fitness and health of older adults, including resting heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), cardiorespiratory fitness (CRF), body mass index (BMI), body fat percent (BF%), waist circumference (WC), muscular endurance (ME), muscular strength (MS), muscular power (MP), balance and flexibility, compared to non-exercise and other-exercise (e.g., moderate-intensity continuous training, resistance training) conditions.

METHODS

Literature published from January 2000 to May 2023 was collected through extensive searches across eight databases and relevant review papers. Randomized controlled trials (RCTs) featuring a minimum 2-week exercise intervention for older adults (≥ 60 years) were included. The pooled effect size of Hedges'g was estimated using random-effects models in R. Meta-regression was performed for both categorical (health status, duration of training programme, and frequency) and continuous moderators (mean age, male rate, and attrition rate).

RESULTS

Forty-four eligible RCTs with 1863 participants (52.1% female; 60.5-81.2 years) were included in the quantitative analysis. Compared to non-exercise condition, HIIT significantly improved resting HR (g = -0.36, 95%CI = [-0.67, -0.05], P = 0.032), SBP (g = -0.29, 95%CI = [-0.54, -0.03], P = 0.008), CRF (g = 0.77, 95%CI = [0.51, 1.04], P < 0.001), BF% (g = -0.26, 95%CI = [-0.41, -0.11], P = 0.006), MS (g = 0.47, 95%CI = [0.23, 0.71], P = 0.004), ME (g = 0.65, 95%CI = [0.10, 1.19], P = 0.036), and balance (e.g., timed-up-and-go) (g = -0.79, 95%CI = [-1.19, -0.40], P = 0.035). Compared to other-exercise condition, HIIT significantly improved resting HR (g = -0.11, 95%CI = [-0.21, -0.01], P = 0.029), SBP (g = -0.14, 95%CI = [-0.28, -0.01], P = 0.038), and CRF (g = 0.23, 95%CI = [0.07, 0.38], P = 0.008). No significant difference was found between HIIT and non-exercise condition for DBP, BMI and WC, as well as between HIIT and other-exercise condition for DBP, BMI, BF%, WC, ME, and balance (all P > 0.05). Meta-regression indicated that mean age moderated the HIIT effect on resting HR (b = -0.02, P = 0.014; HIIT vs. other-exercise condition) and SBP (b = 0.03, P = 0.048; HIIT vs. non-exercise), and attrition rate moderated the effect on CRF (b = 0.03, P = 0.007; HIIT vs. non-exercise).

CONCLUSION

This study supports the efficacy of HIIT in improving resting HR, SBP, CRF, BF%, MS, ME and balance among older adults. More empirical evidence is needed to determine the efficacy of HIIT for MP and flexibility in this population.

TRIAL REGISTRATION

PROSPERO CRD42022316246.