Interval training versus moderate-intensity continuous training for cardiorespiratory fitness improvements in middle-aged and older adults: a systematic review and meta-analysis

High-intensity interval training and cardiorespiratory fitness in adults: An umbrella review of systematic reviews and meta-analyses

BACKGROUND

High-intensity interval training (HIIT) is characterized by repeated bouts of relatively intense exercise interspersed with recovery periods. Previous studies have evaluated this exercise strategy with various population subgroups, regimens, and comparator groups, limiting the generalizability of findings. We performed a novel umbrella review to generate an up-to-date synthesis of the available evidence regarding the effect of HIIT on cardiorespiratory fitness (CRF) in adults as compared to non-exercise control and traditional continuous forms of exercise such as moderate-intensity continuous training (MICT).

METHODS

An umbrella review was conducted in accordance with the Preferred Reporting Items for Overviews of Reviews guideline. Seven databases (MEDLINE, EMBASE, Cochrane Database, CINAHL, Scopus, SPORTDiscus, and Web of Science) were searched until February 2024. Systematic reviews with meta-analyses comparing HIIT and active/non-active control conditions were included. Literature search, data extraction, and methodological quality assessment (AMSTAR-2) were conducted independently by two reviewers.

RESULTS

Twenty-four systematic reviews with meta-analyses, representing 429 primary studies and 12 967 unique participants, met the inclusion criteria. Most of the systematic reviews received moderate-to-critically low AMSTAR-2 scores. The data showed that HIIT, including the particularly intense variant "sprint interval training" (SIT), significantly increases CRF in adults compared to non-exercise control (standardized mean difference [SMD]: 0.28 to 4.31; weighted mean difference [WMD]: 3.25 to 5.5 mL/kg/min) and MICT (SMD: 0.18 to 0.99; WMD: 0.52 to 3.76 mL/kg/min). This effect was consistently observed across specific groups of individuals (e.g., apparently healthy adults, individuals with overweight/obesity, older adults, and high-level athletes) and HIIT modalities (e.g., low-volume HIIT, whole-body HIIT, home-based HIIT, aquatic HIIT, and short SIT).

CONCLUSION

Existing evidence from systematic reviews consistently supports the effect of HIIT on enhancing CRF in adults when compared to non-exercise control and MICT. Our findings offer a comprehensive basis that may potentially contribute to informing physical activity guidelines aimed at improving CRF in the general population.

Applicability of a supramaximal high-intensity interval training program for older adults previously not engaged in regular exercise; analyses of secondary outcomes from the Umeå HIT Study

This analysis of secondary outcomes investigated the applicability of supramaximal high-intensity interval training (HIT) with individually prescribed external intensity performed on stationary bicycles. Sixty-eight participants with a median (min; max) age of 69 (66; 79), at the time not engaged in regular exercise were randomized to 25 twice-weekly sessions of supramaximal HIT (20-min session with 10 × 6-s intervals) or moderate-intensity training (MIT, 40-min session with 3 × 8-min intervals). The primary aim was outcomes on applicability regarding; adherence to prescribed external interval intensity, participant reported positive and negative events, ratings of perceived exertion (RPE 6-20), and affective state (Feeling Scale, FS -5-5). A secondary aim was to investigate change in exercise-related self-efficacy (Exercise Self-Efficacy Scale) and motivation (Behavioural Regulations in Exercise Questionnaire-2). Total adherence to the prescribed external interval intensity was [median (min; max)] 89 % (56; 100 %) in supramaximal HIT, and 100 % (95; 100 %) in MIT. The supramaximal HIT group reported 60 % of the positive (112 of 186) and 36 % of the negative (52 of 146) events. At the end of the training period, the median (min; max) session RPE was 15 (12; 17) for supramaximal HIT and 14 (9; 15) for MIT. As for FS, the median last within-session rating was 3 (-1; 5) for supramaximal HIT and 3 (1; 5) for MIT. Exercise-related motivation increased (mean difference in Relative Autonomy Index score = 1.54, 95 % CI [0.69; 2.40]), while self-efficacy did not change (mean difference = 0.55, 95 % CI [-0.75; 1.82]), regardless of group. This study provide support for supramaximal HIT in supervised group settings for older adults.

Effectiveness of tele-exercise training on physical fitness, functional capacity, and health-related quality of life in non-hospitalized individuals with COVID-19: The COFIT-HK study

Background

The use of tele-exercise programs as an option for post-COVID-19 rehabilitation has been suggested, but its effectiveness in non-hospitalized individuals is not well understood.

Objective

This study aimed to determine the effectiveness of an 8-week tele-exercise training program (COFIT-HK) on physical fitness, functional capacity, and health-related quality of life (HRQoL) in non-hospitalized post-COVID-19 individuals.

Methods

Forty-one non-hospitalized individuals (age:47.4 ± 7.8 yrs) who had COVID-19 history were divided into two groups: the tele-exercise training group (TELE; n = 21) and the non-intervention control group (CON; n = 20). TELE engaged in online supervised multicomponent low-to-moderate intensity exercise training (including respiratory muscle, aerobic, and resistance training) three times per week, whereas CON received standardized educational leaflets based on World Health Organization (WHO) guidelines for post-COVID-19-related illness rehabilitation only. Various components of physical fitness, functional capacity, and HRQoL were assessed at baseline and after the 8-week intervention.

Results

TELE showed significant improvements in handgrip strength, arm flexibility, functional lower extremity endurance, and HRQoL after the 8-week intervention (all p < 0.05, ES = 0.50-1.10). When comparing the groups, TELE demonstrated significantly greater improvements in both the physical and mental component summary scores of HRQoL compared to CON (both p < 0.05). Other outcomes did not reveal significant group differences.

Conclusion

Our tele-exercise intervention was effective in improving physical fitness, functional capacity and HRQoL among non-hospitalized post-COVID-19 individuals. Further research is needed to explore the utility and limitations of tele-exercise programs for post-COVID-19 rehabilitation and beyond.

The intensity paradox: A systematic review and meta-analysis of its impact on the cardiorespiratory fitness of older adults

AIM

The present systematic review and meta-analysis aimed to compare the effect of moderate- versus high-intensity aerobic exercise on cardiorespiratory fitness (CRF) in older adults, taking into account the volume of exercise completed.

METHODS

The databases MEDLINE (Ovid), EMBASE (Ovid), and CENTRAL (Cochrane Library) were searched to identify randomized controlled trials (RCTs). Two reviewers extracted data and assessed bias. Comprehensive Meta-Analysis software calculated overall effect size, intensity differences, and performed meta-regression analyses using pre-to-post intervention or change scores of peak oxygen uptake (V̇O2 peak). The review included 23 RCTs with 1332 older adults (intervention group: n = 932; control group: n = 400), divided into moderate-intensity (435 older adults) and high-intensity (476 older adults) groups.

RESULTS

Meta-regression analysis showed a moderate, but not significant, relationship between exercise intensity and improvements in V̇O2 peak after accounting for the completed exercise volume (β = 0.31, 95% CI = [-0.04; 0.67]). Additionally, studies comparing moderate- versus high-intensity revealed a small, but not significant, effect in favor of high-intensity (Hedges' g = 0.20, 95% CI = [-0.02; 0.41]). Finally, no significant differences in V̇O2 peak improvements were found across exercise groups employing various methods, modalities, and intensity monitoring strategies.

CONCLUSION

Findings challenge the notion that high-intensity exercise is inherently superior and indicate that regular aerobic exercise, irrespective of the specific approach and intensity, provides the primary benefits to CRF in older adults. Future RCTs should prioritize valid and reliable methodologies for monitoring and reporting exercise volume and adherence among older adults.

Effect of high-intensity interval training in physiotherapy primary care for patients with inflammatory arthritis: the ExeHeart randomised controlled trial

OBJECTIVES

To assess the effect of high-intensity interval training (HIIT) delivered in physiotherapy primary care on the primary outcome of cardiorespiratory fitness (CRF) in patients with inflammatory arthritis (IA). Additionally, to explore the effects of HIIT on secondary outcomes, including cardiovascular disease (CVD) risk factors and disease activity.

METHODS

Single-blinded randomised controlled trial with 60 patients randomly assigned to either a control group receiving usual care or an exercise group receiving usual care and 12 weeks of individualised HIIT at 90%-95% peak heart rate. Outcomes were assessed at baseline, 3 months and 6 months post baseline and included CRF measured as peak oxygen uptake (VO2peak), classic CVD risk factors, disease activity, anthropometry and patient-reported physical activity, pain, fatigue, disease impact and exercise beliefs and self-efficacy.

RESULTS

Intention-to-treat analysis demonstrated a significant between-group difference in VO2peak at 3 months (2.5 mL/kg/min, 95% CI 0.9 to 4.0) and 6 months (2.6 mL/kg/min, 95% CI 0.8 to 4.3) in favour of the exercise group. A beneficial change in self-reported physical activity in favour of the exercise group was observed at 3 and 6 months. The HIIT intervention was well-tolerated with minimal adverse events and no apparent impact on disease activity. Differences in secondary outcomes related to CVD risk factors, disease impact, pain, fatigue and exercise beliefs and self-efficacy were generally small and non-significant.

CONCLUSION

After 12 weeks of supervised HIIT delivered in physiotherapy primary care, patients with IA demonstrated a favourable improvement in CRF, with sustained effects at 6-month follow-up.

TRIAL REGISTRATION NUMBER

NCT04922840.

Effects on cardiorespiratory fitness of moderate-intensity training vs. energy-matched training with increasing intensity

Introduction

The present study investigated the role of training intensity in the dose-response relationship between endurance training and cardiorespiratory fitness (CRF). The hypothesis was that beginners would benefit from an increase in training intensity after an initial training phase, even if the energy expenditure was not altered. For this purpose, 26 weeks of continuous moderate training (control group, CON) was compared to training with gradually increasing intensity (intervention group, INC) but constant energy expenditure.

Methods

Thirty-one healthy, untrained subjects (13 men, 18 women; 46 ± 8 years; body mass index 25.4 ± 3.3 kg m-2; maximum oxygen uptake, VO2max 34 ± 4 ml min-1 kg-1) trained for 10 weeks with moderate intensity [3 days/week for 50 min/session at 55% heart rate reserve (HRreserve)] before allocation to one of two groups. A minimization technique was used to ensure homogeneous groups. While group CON continued with moderate intensity for 16 weeks, the INC group trained at 70% HRreserve for 8 weeks and thereafter participated in a 4 × 4 training program (high-intensity interval training, HIIT) for 8 weeks. Constant energy expenditure was ensured by indirect calorimetry and corresponding adjustment of the training volume. Treadmill tests were performed at baseline and after 10, 18, and 26 weeks.

Results

The INC group showed improved VO2max (3.4 ± 2.7 ml kg-1 min-1) to a significantly greater degree than the CON group (0.4 ± 2.9 ml kg-1 min-1) (P = 0.020). In addition, the INC group exhibited improved Vmax (1.7 ± 0.7 km h-1) to a significantly greater degree than the CON group (1.0 ± 0.5 km h-1) (P = 0.001). The reduction of resting HR was significantly larger in the INC group (7 ± 4 bpm) than in the CON group (2 ± 6 bpm) (P = 0.001). The mean heart rate in the submaximal exercise test was reduced significantly in the CON group (5 ± 6 bpm; P = 0.007) and in the INC group (8 ± 7 bpm; P = 0.001), without a significant interaction between group and time point.

Conclusion

Increasing intensity leads to greater adaptations in CRF than continuing with moderate intensity, even without increased energy expenditure. After 26 weeks of training in the moderate- and higher-intensity domain, energy-matched HIIT elicited further adaptations in cardiorespiratory fitness. Thus, training intensity plays a crucial role in the dose-response relationship between endurance training and fitness in untrained but healthy individuals.

Clinical Trial Registration

https://www.drks.de/DRKS00031445, identifier DRKS00031445.

A Perspective on High-Intensity Interval Training for Performance and Health

Interval training is a simple concept that refers to repeated bouts of relatively hard work interspersed with recovery periods of easier work or rest. The method has been used by high-level athletes for over a century to improve performance in endurance-type sports and events such as middle- and long-distance running. The concept of interval training to improve health, including in a rehabilitative context or when practiced by individuals who are relatively inactive or deconditioned, has also been advanced for decades. An important issue that affects the interpretation and application of interval training is the lack of standardized terminology. This particularly relates to the classification of intensity. There is no common definition of the term "high-intensity interval training" (HIIT) despite its widespread use. We contend that in a performance context, HIIT can be characterized as intermittent exercise bouts performed above the heavy-intensity domain. This categorization of HIIT is primarily encompassed by the severe-intensity domain. It is demarcated by indicators that principally include the critical power or critical speed, or other indices, including the second lactate threshold, maximal lactate steady state, or lactate turnpoint. In a health context, we contend that HIIT can be characterized as intermittent exercise bouts performed above moderate intensity. This categorization of HIIT is primarily encompassed by the classification of vigorous intensity. It is demarcated by various indicators related to perceived exertion, oxygen uptake, or heart rate as defined in authoritative public health and exercise prescription guidelines. A particularly intense variant of HIIT commonly termed "sprint interval training" can be distinguished as repeated bouts performed with near-maximal to "all out" effort. This characterization coincides with the highest intensity classification identified in training zone models or exercise prescription guidelines, including the extreme-intensity domain, anaerobic speed reserve, or near-maximal to maximal intensity classification. HIIT is considered an essential training component for the enhancement of athletic performance, but the optimal intensity distribution and specific HIIT prescription for endurance athletes is unclear. HIIT is also a viable method to improve cardiorespiratory fitness and other health-related indices in people who are insufficiently active, including those with cardiometabolic diseases. Research is needed to clarify responses to different HIIT strategies using robust study designs that employ best practices. We offer a perspective on the topic of HIIT for performance and health, including a conceptual framework that builds on the work of others and outlines how the method can be defined and operationalized within each context.

Aquatic high-intensity interval training (HIIT) may be similarly effective to land-based HIIT in improving exercise capacity in people with chronic conditions: a systematic review and meta-analysis

Objective

To investigate the effect of aquatic high-intensity interval training (AHIIT) on exercise capacity in people with chronic conditions.

Design

Systematic review and meta-analysis.

Participants

Adults (age ≥18 years) with any chronic conditions (long duration, continuing health problems).

Data sources

The databases Medline, EMBASE, CINAHL, SPORTSDiscus, PEDro and The Cochrane Library were searched from inception to 11 August 2023.

Eligibility criteria

Randomised or non-randomised controlled trials of adults reporting one or more chronic conditions were included, comparing the effect of AHIIT with a non-exercising control group, land-based high-intensity interval training (LBHIIT) or aquatic moderate-intensity continuous training (AMICT).

Results

Eighteen trials with 868 participants with chronic musculoskeletal, respiratory, cardiovascular, metabolic or neurological conditions were included. Adherence to AHIIT was high, ranging from 84% to 100%. There was moderate certainty in evidence according to the Grading of Recommendations Assessment, Development and Evaluation system for a moderate beneficial effect on exercise capacity standardised mean differences (SMD) 0.78 (95% CI 0.48 to 1.08), p<0.00001) of AHIIT compared with a non-exercising control group. There was moderate certainty in evidence for no difference of effects on exercise capacity (SMD 0.28 (95% CI -0.04 to 0.60), p=0.08) of AHIIT compared with LBHIIT. There was moderate certainty in evidence for small effect on exercise capacity (SMD 0.45 (95% CI 0.10 to 0.80), p=0.01) of AHIIT compared with AMICT.

Conclusion

There are beneficial effects of AHIIT on exercise capacity in people with a range of chronic conditions. AHIIT has similar effects on exercise capacity as LBHIIT and may represent an alternative for people unable to perform LBHIIT.

PROSPERO registration number

CRD42022289001.

Effects of low-versus high-volume high-intensity interval training on glycemic control and quality of life in obese women with type 2 diabetes. A randomized controlled trial

Background/objective

Comparison between different training volumes of high-intensity interval training (HIIT) is understudied in type 2 diabetes. This study aimed to compare the effects of low- and high-volume HIIT on glycemic control, blood lipids, blood pressure, anthropometric adiposity measures, cardiorespiratory fitness, and health-related quality of life (HRQoL) in women with type 2 diabetes.

Methods

Seventy-two obese women with type 2 diabetes aged 36-55 were randomly assigned to a low-volume HIIT group (i.e., 2 × 4-min high-intensity treadmill exercise at 85%-90% of peak heart rate, with a 3-min active recovery interval in between), a high-volume HIIT group (i.e., 4 × 4-min high-intensity treadmill exercise at 85%-90% of peak heart rate, with three 3-min active recovery intervals in between), and a non-exercising control group. Patients in HIIT groups exercised three days a week for 12 weeks. All patients received oral hypoglycemic medications with no calorie restrictions. The outcome measures were glycosylated hemoglobin (HbA1c), fasting blood glucose (FBG), 2-hour postprandial blood glucose (2-hr PPBG), total cholesterol (TC), triglyceride (TG), low-density lipoprotein (LDL), high-density lipoprotein (HDL), systolic blood pressure (SBP), diastolic blood pressure (DBP), body mass index (BMI), waist circumference (WC), waist-to-hip ratio, time to maximal exhaustion determined from a maximal treadmill exercise test (i.e., a measure of cardiorespiratory fitness), and HRQoL assessed by the 12-item Short Form (SF-12) Health Survey.

Results

The low- and high-volume HIIT groups showed significant improvements in all outcome measures compared to the baseline and the non-exercising group (P < 0.05), except for DBP in the low-volume HIIT group (p > 0.05). Also, both low- and high-volume HIIT groups showed similar improvements in TC, HDL, SBP, DBP, BMI, WC, waist-to-hip ratio, and the SF-12 scores, with no significant between-groups difference (p > 0.05). The high-volume HIIT group, however, showed more significant improvements in HbA1c, FBG, 2-hr PPBG, TG, LDL, and treadmill time to maximal exhaustion than the low-volume HIIT group (p < 0.05). The non-exercising group showed non-significant changes in all outcome measures (p > 0.05).

Conclusion

Low-volume HIIT could be equally effective as high-volume HIIT for improving TC, HDL, blood pressure, anthropometric adiposity measures, and HRQoL in obese women with type 2 diabetes. Nevertheless, high-volume HIIT could have a greater impact on glycemic control, TG, LDL, and cardiorespiratory fitness in these patients.

Trial registration

ClinicalTrials.gov, NCT05110404.

Acute Physiological and Perceptual Responses to Whole-Body High-Intensity Interval Training Compared with Equipment-Based Interval and Continuous Training

Low-volume, time-efficient high-intensity interval training (HIIT), which involves whole-body (WB) callisthenics exercises, has gained worldwide popularity in recent years. However, the physiological and perceptual impact of WB-HIIT in comparison to specialised, equipment-based training is relatively less studied. This study compared the acute physiological and perceptual responses to a single session of WB-HIIT, ergometer-based HIIT (ERG-HIIT) and conventional moderate-intensity continuous training (MICT). Fourteen physically inactive adults (age: 28.4 ± 6.5 years, VO2peak: 31.0 ± 6.2 mL· kg-1· min-1) underwent three main trials (WB-HIIT: 12 x 30-s high-intensity callisthenics workout; ERG: HIIT: 12 x 30-s high-intensity cycling bouts; MICT: 30-min cycling at 50% peak power output) in a randomized cross-over order 3-7 days apart. The mean session heart rate (HR) and perceived exertion were comparable across all three protocols (p > 0.05). WB-HIIT attained a similar peak HR (87.4 ± 9.4 %HRmax) as that of ERG-HIIT (83.0 ± 8.6 %HRmax), and significantly greater than that of MICT (78.7 ± 5.5 %HRmax, p = 0.001). However, WB-HIIT induced significantly higher blood lactate levels (7.2 ± 1.8 mmol/L) compared to both ERG-HIIT (5.1 ± 1.3 mmol/L, p < 0.05) and MICT (3.1 ± 1.5 mmol/L, p < 0.001). The participants reported higher self-efficacy and greater enjoyment with WB-HIIT compared to MICT (p < 0.05). The mean HR and perceived exertion responses to WB-HIIT are comparable to those of equipment-based HIIT and MICT; however, WB-HIIT results in greater metabolic strain than both other modalities. Despite this, the overall perceptual responses to WB-HIIT are positive, suggesting that it could be a viable exercise alternative, especially for individuals with limited exercise time and restricted access to facilities and equipment.

Effects of Controlled Supramaximal High-Intensity Interval Training on Cardiorespiratory Fitness and Global Cognitive Function in Older Adults: The Umeå HIT Study-A Randomized Controlled Trial

BACKGROUND

This study examined the effects of regulated and controlled supramaximal high-intensity interval training (HIT) adapted for older adults, compared to moderate-intensity training (MIT), on cardiorespiratory fitness; cognitive, cardiovascular, and muscular function; and quality of life.

METHODS

Sixty-eight nonexercising older adults (66-79 years, 44% males) were randomized to 3 months of twice-weekly HIT (20-minute session including 10 × 6-second intervals) or MIT (40-minute session including 3 × 8-minute intervals) on stationary bicycles in an ordinary gym setting. Individualized target intensity was watt controlled with a standardized pedaling cadence and individual adjustment of the resistance load. Primary outcomes were cardiorespiratory fitness (V̇o2peak) and global cognitive function (unit-weighted composite).

RESULTS

V̇o2peak increased significantly (mean 1.38 mL/kg/min, 95% CI [0.77, 1.98]), with no between-group difference (mean difference 0.05 [-1.17, 1.25]). Global cognition did not improve (0.02 [-0.05, 0.09]), nor differed between groups (0.11 [-0.03, 0.24]). Significant between-group differences in change were observed for working memory (0.32 [0.01, 0.64]), and maximal isometric knee extensor muscle strength (0.07 N·m/kg [0.003, 0.137]), both in favor of HIT. Irrespective of the group, there was a negative change in episodic memory (-0.15 [-0.28, -0.02]), a positive change in visuospatial ability (0.26 [0.08, 0.44]), and a decrease in systolic (-2.09 mmHg [-3.54, -0.64]) and diastolic (-1.27 mmHg [-2.31, -0.25]) blood pressure.

CONCLUSIONS

In nonexercising older adults, 3 months of watt-controlled supramaximal HIT improved cardiorespiratory fitness and cardiovascular function to a similar extent as MIT, despite half the training time. In favor of HIT, there was an improvement in muscular function and a potential domain-specific effect on working memory.

CLINICAL TRIAL REGISTRATION

NCT03765385.

Does Higher Intensity Increase the Rate of Responders to Endurance Training When Total Energy Expenditure Remains Constant? A Randomized Controlled Trial

BACKGROUND

Standardized training prescriptions often result in large variation in training response with a substantial number of individuals that show little or no response at all. The present study examined whether the response in markers of cardiorespiratory fitness (CRF) to moderate intensity endurance training can be elevated by an increase in training intensity.

METHODS

Thirty-one healthy, untrained participants (46 ± 8 years, BMI 25.4 ± 3.3 kg m^-2 and [Formula: see text]O_2max 34 ± 4 mL min^-1 kg^-1) trained for 10 weeks with moderate intensity (3 day week^-1 for 50 min per session at 55% HR_reserve). Hereafter, the allocation into two groups was performed by stratified randomization for age, gender and VO_2max response. CON (continuous moderate intensity) trained for another 16 weeks at moderate intensity, INC (increased intensity) trained energy-equivalent for 8 weeks at 70% HR_reserve and then performed high-intensity interval training (4 × 4) for another 8 weeks. Responders were identified as participants with VO_2max increase above the technical measurement error.

RESULTS

There was a significant difference in [Formula: see text]O_2max response between INC (3.4 ± 2.7 mL kg^-1 min^-1) and CON (0.4 ± 2.9 mL kg^-1 min^-1) after 26 weeks of training (P = 0.020). After 10 weeks of moderate training, in total 16 of 31 participants were classified as VO_2max responders (52%). After another 16 weeks continuous moderate intensity training, no further increase of responders was observed in CON. In contrast, the energy equivalent training with increasing training intensity in INC significantly (P = 0.031) increased the number of responders to 13 of 15 (87%). The energy equivalent higher training intensities increased the rate of responders more effectively than continued moderate training intensities (P = 0.012).

CONCLUSION

High-intensity interval training increases the rate of response in VO_2max to endurance training even when the total energy expenditure is held constant. Maintaining moderate endurance training intensities might not be the best choice to optimize training gains. Trial Registration German Clinical Trials Register, DRKS00031445, Registered 08 March 2023-Retrospectively registered, https://www.drks.de/DRKS00031445.

Chronic Effects of Different Intensities of Interval Training on Hemodynamic, Autonomic and Cardiorespiratory Variables of Physically Active Elderly People

Interval training (IT) is a very efficient method. We aimed to verify the chronic effects of IT with different intensities on hemodynamic, autonomic and cardiorespiratory variables in the elderly. Twenty-four physically active elderly men participated in the study and were randomized into three groups: Training Group A (TG_A, n = 8), Training Group B (TG_B, n = 8) and control group (CG, n = 8). The TG_A and TG_B groups performed 32 sessions (48 h interval). TG_A presented 4 min (55 to 60% of HRmax) and 1 min (70 to 75% of HRmax). The TGB training groups performed the same protocol, but performed 4 min at 45 to 50% HRmax and 1 min at 60 to 65% HRmax. Both training groups performed each set six times, totaling 30 min per session. Assessments were performed pre (baseline) after the 16th and 32nd intervention session. The CG performed only assessments. Hemodynamic, autonomic and cardiorespiratory (estimated VO_2max) variables were evaluated. There were no significant differences between protocols and times (p > 0.05). However, the effect size and percentage delta indicated positive clinical outcomes, indicating favorable responses of IT. IT may be a strategy to improve hemodynamic, autonomic and cardiorespiratory behavior in healthy elderly people.

The effect of exercise on walking economy in patients with chronic neurological conditions: A systematic review and meta-analysis

Introduction

To investigate the effect of exercise on the walking economy (WE) of patients with chronic neurological conditions (CNCs) and to determine the type of physical activity that best improves the WE of patients with CNCs.

Methods

Four electronic databases were searched until December 2022 (Web of Science, PubMed, Cochrane, and CINAHL). Studies were screened using the following inclusion criteria: 1. randomized controlled or non-randomized controlled trials; 2. exercise interventions >4 weeks in duration; 3. patients aged ≥18 years with a diagnosis of CNCs. 4. walking economy of patients measured before and after the intervention. The PEDro scale was used to assess the methodological quality of the included studies.

Results and discussion

Twenty-two studies met the inclusion criteria. Meta-analysis results showed that exercise significantly improved WE (g = -0.352, 95% CI, -0.625 to -0.078, P = 0.012). Subgroup analysis revealed that patients who received exercise showed better WE compared with those who underwent no control intervention (g = -0.474, 95% CI, -0.636 to -0.311, P < 0.001). However, exercise therapy did not show a significant improvement of WE compared with control groups (g = -0.192, 95% CI, -0.451 to 0.067, P = 0.146). In addition, we found that endurance combined with resistance, high-intensity intermittent, and other training modalities resulted in better WE compared with the pre-intervention. Of these, interval training has the greatest effect on improving WE. In conclusion, exercise can improve WE in patients with CNCs. More randomized controlled trials are necessary for the future.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022361455, identifier: CRD42022361455.

Extraordinary claims in the literature on high-intensity interval training (HIIT): IV. Is HIIT associated with higher long-term exercise adherence?

Nonadherence to and dropout from regular exercise and physical activity are important reasons why the field of exercise science has yet to fulfill its promise of improving public health on a global scale. Researchers have claimed that High-Intensity Interval Training (HIIT) is a feasible and sustainable exercise modality that may result in higher long-term adherence than moderate-intensity continuous exercise. If true, this would be a breakthrough discovery that could unlock the potential of exercise as a health-promoting intervention. We performed a systematic search of the literature and identified eight trials comparing HIIT to moderate-intensity continuous exercise, all of which involved follow-up periods of at least 12 months (i.e., SWIFT, Small Steps for Big Changes, SAINTEX-CAD, SMARTEX-HF, Generation 100, FITR, OptimEx-Clin, HITTS). Findings from these trials demonstrate that, while unsupervised, individuals initially assigned to HIIT tend to exercise at lower-than-prescribed intensities and HIIT groups demonstrate no advantage in long-term adherence.

High Intensity Interval Training reduces hypoglycemic events compared with continuous aerobic training in individuals with type 1 diabetes: HIIT and hypoglycemia in type 1 diabetes

AIMS

to investigate if a High Intensity Interval Training (HIIT) protocol improves glycemic control and fitness capacity, compared to traditional moderate Intensity Continuous Training (MICT) exercise.

METHODS

30 sedentary individuals with type 1 diabetes (T1D) and 26 healthy controls were assigned to a 3-week HIIT or MICT protocol. Blood glucose levels by continuous glucose monitoring system and fitness status were compared before and after the study period.

RESULTS

During workouts, blood glucose levels remained stable in HIIT exercise (+3.2 ± 16.2 mg/dl (p = 0.43)), while decreased in MICT (-27.1 ± 17.5 mg/dl (p < 0.0001)) exercise. In addition, out of the 9 training sessions, HIIT volunteers needed to take carbohydrate supplements to avoid hypoglycemia in 0.56 ± 0.9 sessions, compared to 1.83 ± 0.5 sessions (p < 0.04) in MICT individuals. In the analysis of blood glucose levels between rest and training days (24h-period), training significantly reduced mean glycemic levels in both groups, but the MICT exercise results in an increase in the frequency of hypoglycemic episodes. The response to exercise seems to be attenuated in individuals with T1D, especially in HIIT group.

CONCLUSION

HIIT training results in a greater glycemic stability, with reduction of hypoglycemic episodes.

Effects of Acute Interval Exercise on Arterial Stiffness and Cardiovascular Autonomic Regulatory Responses: A Narrative Review of Potential Impacts of Aging

The physiological changes associated with aging deleteriously impact cardiovascular function and regulation and therefore increase the risk of developing cardiovascular disease. There is substantial evidence that changes in the autonomic nervous system and arterial stiffness play an important role in the development of cardiovascular disease during the aging process. Exercise is known to be effective in improving autonomic regulation and arterial vascular compliance, but differences in the type and intensity of exercise can have varying degrees of impact on vascular regulatory responses and autonomic function. There is still little evidence on whether there are differences in the response of exercise interventions to cardiovascular modulatory effects across the lifespan. In addition, acute interval exercise challenges can improve autonomic modulation, although the results of interval exercise on autonomic physiological parameters vary. Therefore, this narrative review focuses on evaluating the effects of acute interval exercise on blood pressure regulation and autonomic responses and also incorporates studies investigating different age groups to evaluate the effects of acute interval exercise on the autonomic nervous system. Herein we also summarize existing literature examining the acute cardiovascular responses to varied modes of interval exercise, as well as to further compare the benefits of interval exercise with other types of exercise on autonomic regulation and arterial stiffness. After reviewing the existing literature, it has been shown that with advancing age, changes in the autonomic nervous activity of interval exercise result in significant impacts on the cardiovascular system. We document that with advancing age, changes in the autonomic nerves lead to aging of the nervous system, thereby affecting the regulation of blood pressure. According to the limited literature, interval exercise is more effective in attenuating arterial stiffness than continuous exercise, but the difference in exercise benefits may depend on the training mode, intensity, duration of exercise, and the age of participants. Therefore, the benefits of interval exercise on autonomic and arterial stiffness improvement still warrant investigation, particularly the impact of age, in future research.

Home-Based High-Intensity Interval Exercise Improves the Postprandial Glucose Response in Young Adults with Postprandial Hyperglycemia

Postprandial hyperglycemia can be corrected by exercise; however, the effect of home-based high-intensity interval exercise (HIIE), a new time-efficient exercise, on glycemic control is unclear. This study aimed to investigate the effect of home-based HIIE on postprandial hyperglycemia. Twelve young adult males (mean age: 24.3 ± 2.3 y) with postprandial hyperglycemia that had not yet led to diabetes completed home-based HIIE, moderate-intensity continuous exercise (MICE), and control conditions on separate days, randomly. The intervention began 30 min after the start of a standardized meal intake, with 11 min of HIIE completed at maximal effort in the home-based HIIE condition, 30 min of running performed at 50% maximum oxygen uptake in the MICE condition, or 30 min of sitting at rest completed in the control condition. The participants sat at rest after each intervention for up to 120 min. Interstitial fluid glucose concentrations were measured using a continuous glucose monitoring system that scanned every 15 min for up to 2 h after the meal. The glucose concentrations after the meal were significantly lower in the home-based HIIE and MICE conditions than in the control condition (p < 0.001). There were no significant differences in the glucose concentrations between the home-based HIIE and MICE conditions. In conclusion, home-based HIIE was able to correct postprandial hyperglycemia.

Effects of high-intensity interval training on blood lactate levels and cognition in healthy adults: protocol for systematic review and network meta-analyses

BACKGROUND

High-intensity interval training (HIIT) has shown to confer cognitive benefits in healthy adults, via a mechanism purportedly driven by the exercise metabolite lactate. However, our understanding of the exercise parameters (e.g., work interval duration, session volume, work-to-rest ratio) that evoke a peak blood lactate response in healthy adults is limited. Moreover, evidence relating HIIT-induced blood lactate and cognitive performance has yet to be reviewed and analyzed. The primary objective of this systematic review is to use network meta-analyses to compare the relative impact of different HIIT work-interval durations, session volumes, and work-to-rest ratios on post-exercise blood lactate response in healthy adults. The secondary objective is to determine the relationship between HIIT-induced blood lactate and acute post-HIIT cognitive performance.

METHODS

A systematic review is being conducted to identify studies measuring blood lactate response following one session of HIIT in healthy adults. The search was carried out in (1) MEDLINE, (2) EMBASE, (3) Cochrane Central Register of Controlled Trials, (4) Sport Discus, and (5) Cumulative Index to Nursing and Allied Health Literature Plus with Full Text (CINAHL+). After abstract and full-text screening, two reviewers will independently extract data on key outcomes variables and complete risk of bias assessment using the Cochrane Risk of Bias Tool and the Risk of Bias in Non-Randomized Studies of Interventions tool. Network meta-analyses will be used to generate estimates of the comparative effectiveness of blood lactate on cognitive outcomes using corresponding rankings for each work-interval duration, session volume, and work-to-rest ratio category. Where applicable, meta-regressions analyses will be performed to test the relationship between changes in the blood lactate and changes in cognitive performance. Analyses will be conducted using MetaInsight Software.

DISCUSSION

This study will provide evidence on how to structure a HIIT protocol to elicit peak blood lactate response in healthy adults and will increase our understanding of the relationship between HIIT-induced blood lactate response and associated cognitive benefits.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42020204400.

Alternating high-intensity interval training and continuous training is efficacious in improving cardiometabolic health in obese middle-aged men

Background

High-intensity interval training (HIIT) or moderate-intensity continuous training (MICT) alone has been shown to improve metabolic health, but the effects of alternating the two training approaches as often practiced in real life remained unclear.

Purpose

To examine the effects of HIIT or MICT alone or alternating HIIT-MICT on cardiometabolic responses in inactive obese middle-aged men.

Methods

Forty-two participants (age: 42 ± 5 y; BMI: 26.3 ± 2.1 kg m⁻²) were randomly assigned to four groups: HIIT (12 x 1-min running bouts at 80–90% HR_max interspersed with 1-min active recovery at 50% HR_max), MICT (40-min brisk walk at 65–70% HR_max), alternating HIIT-MICT or a non-exercise control group (CON). Exercise sessions were conducted three times per week for 16 weeks. Maximal oxygen uptake (VO_2max), body composition (by bioelectrical impedance analysis), blood pressure, fasting blood glucose, insulin resistance (HOMA-IR) and lipid profile were assessed at baseline and after the 16-week intervention. Enjoyment and self-efficacy were also assessed at the end of intervention.

Results

All exercise groups showed a similar VO_2max increase of ∼15% (HIIT: 34.3 ± 4.4 vs 39.1 ± 5.4; MICT: 34.9 ± 5.0 vs 39.4 ± 7.2; and alternating HIIT-MICT: 34.4 ± 5.0 vs 40.3 ± 4.6 mL kg⁻¹min⁻¹) compared to baseline and CON (all p < 0.05). Weight, BMI, % fat and waist circumference also showed similar reductions in all exercise groups compared to baseline and CON (all p < 0.05). No significant group difference was observed for all blood markers. Compared to baseline, total cholesterol decreased after HIIT-MICT, while HIIT significantly decreased fasting insulin level and improved insulin resistance (p < 0.05). Enjoyment, self-efficacy and adherence were similar among all exercise groups.

Conclusion

HIIT or MICT alone or alternating HIIT-MICT similarly improve cardiovascular fitness and body composition in obese middle-aged men despite differences in total training volume and time commitment.