Towards the minimal amount of exercise for improving metabolic health: beneficial effects of reduced-exertion high-intensity interval training. Eur J Appl Physiol. 2012;112:2767-2775. [PMID: 22124524 DOI: 10.1007/s00421-011-2254-z]

Physiological Responses to Low-Volume Interval Training in Women

Interval training is a form of exercise that involves intermittent bouts of relatively intense effort interspersed with periods of rest or lower-intensity exercise for recovery. Low-volume high-intensity interval training (HIIT) and sprint interval training (SIT) induce physiological and health-related adaptations comparable to traditional moderate-intensity continuous training (MICT) in healthy adults and those with chronic disease despite a lower time commitment. However, most studies within the field have been conducted in men, with a relatively limited number of studies conducted in women cohorts across the lifespan. This review summarizes our understanding of physiological responses to low-volume interval training in women, including those with overweight/obesity or type 2 diabetes, with a focus on cardiorespiratory fitness, glycemic control, and skeletal muscle mitochondrial content. We also describe emerging evidence demonstrating similarities and differences in the adaptive response between women and men. Collectively, HIIT and SIT have consistently been demonstrated to improve cardiorespiratory fitness in women, and most sex-based comparisons demonstrate similar improvements in men and women. However, research examining insulin sensitivity and skeletal muscle mitochondrial responses to HIIT and SIT in women is limited and conflicting, with some evidence of blunted improvements in women relative to men. There is a need for additional research that examines physiological adaptations to low-volume interval training in women across the lifespan, including studies that directly compare responses to MICT, evaluate potential mechanisms, and/or assess the influence of sex on the adaptive response. Future work in this area will strengthen the evidence-base for physical activity recommendations in women.

High-intensity interval training effects in cardiorespiratory fitness of lung cancer survivors: a systematic review and meta-analysis

PURPOSE

To assess the exercise intervention focused on high-intensity interval training (HIIT) in lung cancer survivors.

DESIGN

We performed a literature search using PubMed, Web of Science, and Science Direct (last search March 2021). Quality assessment and risk of bias were assessed using the Downs and Black scale and the Cochrane tool.

PARTICIPANTS

A total of 305 patients of 8 studies were assessed, with their mean age ranging from 61 ± 6.3 to 66 ± 10 years in the exercise group and from 58.5 ± 8.2 to 68 ± 9 years in the control group.

METHODS

A systematic review and meta-analysis of randomized controlled trials and pilot randomized controlled trials was performed. We included controlled trials testing the effect of HIIT in lung cancer survivors versus the usual care provided to these patients. The data were pooled and a meta-analysis was completed for cardiorespiratory fitness (VO_2peak).

RESULTS

We selected 8 studies, which included 305 patients with lung cancer: 6 studies were performed around surgical moment, one study during radiotherapy's treatment, and other during target therapy. After pooling the data, exercise capacity was included in the analysis. Results showed significant differences in favour to HIIT when compared to usual care in cardiorespiratory fitness (standard mean difference = 2.62; 95% confidence interval = 1.55, 3.68; p < 0.00001).

CONCLUSIONS AND IMPLICATIONS

The findings indicated a beneficial effect of HIIT for improving cardiorespiratory fitness in lung cancer patients in early stages around oncological treatment moment. Nevertheless, this review has several limitations, the total number of studies was low, and the stage and subtype of lung cancer patients were heterogeneous that means that the conclusions of this review should be taken with caution. Review registration: PROSPERO Identifier: CRD42021231229.

Indicators of response to exercise training: a systematic review and meta-analysis

BACKGROUND

Means-based analysis of maximal rate of oxygen consumption (VO2max) has traditionally been used as the exercise response indicator to assess the efficacy of endurance (END), high intensity interval (HIIT) and resistance exercise training (RET) for improving cardiorespiratory fitness and whole-body health. However, considerable heterogeneity exists in the interindividual variability response to the same or different training modalities.

OBJECTIVES

We performed a systematic review and meta-analysis to investigate exercise response rates in the context of VO2max: (1) in each training modality (END, HIIT and RET) versus controls, (2) in END versus either HIIT or RET and (3) exercise response rates as measured by VO2max versus other indicators of positive exercise response in each exercise modality.

METHODS

Three databases (EMBASE, MEDLINE, CENTRAL) and additional sources were searched. Both individual response rate and population average data were incorporated through continuous data, respectively. Of 3268 identified manuscripts, a total of 29 studies were suitable for qualitative synthesis and a further 22 for quantitative. Stratification based on intervention duration (less than 12 weeks; more than or equal to 12 weeks) was undertaken.

RESULTS

A total of 62 data points were procured. Both END and HIIT training exhibited differential improvements in VO2max based on intervention duration. VO2max did not adequately differentiate between END and HIIT, irrespective of intervention length. Although none of the other exercise response indicators achieved statistical significance, LT and HRrest demonstrated common trajectories in pooled and separate analyses between modalities. RET data were highly limited. Heterogeneity was ubiquitous across all analyses.

CONCLUSIONS

The potential for LT and HRrest as indicators of exercise response requires further elucidation, in addition to the exploration of interventional and intrinsic sources of heterogeneity.

Four-Second Power Cycling Training Increases Maximal Anaerobic Power, Peak Oxygen Consumption, and Total Blood Volume

INTRODUCTION

High-intensity interval training (HIIT) is an effective tool to improve cardiovascular fitness and maximal anaerobic power. Different methods of HIIT have been studied but the effects of repeated maximal effort cycling with very short exercise time (i.e., 4-s) and short recovery time (15-30 s) might suit individuals with limited time to exercise.

PURPOSE

We examined the effects of training at near maximal anaerobic power during cycling (PC) on maximal anaerobic power, peak oxygen consumption (VO2peak), and total blood volume in 11 young healthy individuals (age: 21.3 ± 0.5 y) (6 men, 5 women).

METHODS

Participants trained three times a week for eight weeks performing a PC program consisting of 30 bouts of 4-s at an all-out intensity (i.e., 2 minutes of exercise per session). The cardiovascular stress progressively increased over the weeks by decreasing the recovery time between sprints (30 to 24 to 15-s) and thus total session time decreased from 17 to <10 min.

RESULTS

PC elicited a 13.2% increase in VO2peak (Pre: 2.86 ± 0.18 L/min, Post: 3.24 ± 0.21 L/min, (p = 0.003) and a 7.6% increase in total blood volume (Pre: 5,139 ± 199 ml, Post: 5,529 ± 342 ml, p < 0.05). Concurrently, maximal anaerobic power increased by 17.2% (Pre: 860 ± 53 watts, Post: 1,009 ± 71 watts; p < 0.001).

CONCLUSION

A Power Cycling training program employing 30 bouts of 4-s duration for a total of 2 min of exercise, resulting in a total session time of less than 10 min in the last weeks, is effective for improving total blood volume, VO2peak and maximal anaerobic power in young healthy individuals over 8 weeks. These observations require reconsideration of the minimal amount of exercise needed to significantly increase both maximal aerobic and anaerobic power.

Evidence-Based Effects of High-Intensity Interval Training on Exercise Capacity and Health: A Review with Historical Perspective

Engaging in regular exercise results in a range of physiological adaptations offering benefits for exercise capacity and health, independent of age, gender or the presence of chronic diseases. Accumulating evidence shows that lack of time is a major impediment to exercise, causing physical inactivity worldwide. This issue has resulted in momentum for interval training models known to elicit higher enjoyment and induce adaptations similar to or greater than moderate-intensity continuous training, despite a lower total exercise volume. Although there is no universal definition, high-intensity interval exercise is characterized by repeated short bursts of intense activity, performed with a "near maximal" or "all-out" effort corresponding to ≥90% of maximal oxygen uptake or >75% of maximal power, with periods of rest or low-intensity exercise. Research has indicated that high-intensity interval training induces numerous physiological adaptations that improve exercise capacity (maximal oxygen uptake, aerobic endurance, anaerobic capacity etc.) and metabolic health in both clinical and healthy (athletes, active and inactive individuals without any apparent disease or disorder) populations. In this paper, a brief history of high-intensity interval training is presented, based on the novel findings of some selected studies on exercise capacity and health, starting from the early 1920s to date. Further, an overview of the mechanisms underlying the physiological adaptations in response to high-intensity interval training is provided.

Inflammatory Status and Cardio-metabolic Risk Stratification of Rotational Shift Work

OBJECTIVES

To investigate the physiological effects of rotational shift work on measures of cardio-metabolic function.

METHODS

Sedentary, healthy men (n = 87; age 37 ± 9 years; body mass index: 30.7 ± 5.1 kg m2) were recruited and categorized via occupation. SHIFT group: currently employed in rotational shift work defined by 8-12 h morning, afternoon, and night rotations; or NSHIFT: working fixed daytime hours. Testing procedures included baseline objective sleep assessment and laboratory testing, conducted between 0600 and 0900 h to assess body composition, cardiorespiratory fitness (VO2peak), inflammatory status [C-reactive protein, interleukin (IL)-6, and tumour necrosis factor-alpha (TNF-α)], glucose metabolism, heart rate variability (HRV), and self-reported leisure time physical activity (PA).

RESULTS

SHIFT reported significantly less leisure time PA (P = 0.019), reduced VO2peak (P = 0.007), higher body fat percentage (BF%) (P = 0.021), increase response time to oral glucose tolerance test (P = 0.016), and higher IL-6 values (P = 0.008) compared with NSHIFT. A significant difference was observed in actigraphy measured total sleep time, with SHIFT recording reduced sleep following a night shift (P = 0.001). No group difference was observed in HRV or average sleep parameters (P > 0.05). Linear regression identified a significant association between occupation and inflammatory status (P = 0.006).

CONCLUSIONS

Rotational shift work is associated with increased risk factors for cardio-metabolic disorders, despite no differences in sleep quality and quantity. The results suggest rotational shift work has a detrimental effect on the health and wellbeing of employees; with homeostatic desynchronization identified as potential pathogenic mechanisms.

Inertial Load Power Cycling Training Increases Muscle Mass and Aerobic Power in Older Adults

PURPOSE

Reductions in skeletal muscle mass, beginning after the third decade of life, reduce maximal neuromuscular power (Pmax). Maximal aerobic power generation is also reduced. The primary purpose of this study was to investigate the effectiveness of maximal power cycling (PC) training using an inertial load ergometer on skeletal muscle mass and cardiovascular function in untrained 50- to 68-yr-old participants.

METHODS

The study used a pre- or postoutcome exercise intervention testing untrained 50- to 68-yr-old adults (n = 39, M = 15, mean ± SE = 58.5 ± 0.8, range = 50-68 yr). Over the course of 8 wk, participants performed 15 min of training 3 times per week. Each session involved repeated (15-30 times) 4-s sprints of PC. Measurements were thigh muscle volume, total body lean mass, Pmax, peak oxygen consumption, cardio-ankle vascular index, performance on functional tests of living (FTLChair and FTLRamp), and intermuscular fat volume.

RESULTS

Training for 8 wk increased thigh muscle volume (3.7% ± 0.9%, P < 0.001) and total body lean mass (1.5% ± 0.4%, P < 0.01) while increasing total body mass (TBM) (1.4% ± 0.3%, P < 0.01). Physical performance measures increased significantly (all P < 0.05) with improvements in Pmax (12.0% ± 1.5%); peak oxygen consumption (9.8% ± 1.8%), and FTL (8.5% ± 1.3% to 17.2% ± 2%). Cardio-ankle vascular index was significantly decreased -2.3% ± 1.1% (P < 0.05), indicating reduced arterial stiffness.

CONCLUSIONS

These results demonstrate that 8 wk of PC training at true maximal power was effective at increasing muscle mass and maximal power, as well as maximal cardiovascular capacity and functional tasks in untrained 50- to 68-yr-olds.

Chlorella vulgaris in combination with high intensity interval training in overweight and obese women: a randomized double-blind clinical trial

Background

Chlorella vulgaris (CV) as a multifunctional dietary supplement is known with lots of health benefits. It is possible that CV consumption along with high-intensity interval training (HIIT), a short period exercise is more beneficial. This investigation aimed to evaluate the effects of CV and/or HIIT on anthropometric parameters and cardiometabolic risk factors among overweight or obese women.

Methods

Present randomized double-blind clinical trial, included 46 women with overweight or obesity and randomly assigned them to four groups including CV, HIIT, CV+HIIT, and placebo. CV supplementation was 900 mg a day and HIIT program 3 sessions a week. Dietary intake, anthropometric assays and blood samples were taken at the commencement and completion of 8-week intervention.

Results

After 8 weeks, waist circumference (WC) significantly reduced in CV+HIIT group in comparison with placebo group. Significant decreases in triglycerides (TG) and low-density lipoprotein (LDL) cholesterol levels were found after CV supplementation and/or HIIT exercise in comparison with placebo group. A significant rise in high-density lipoprotein (HDL) cholesterol level was observed in HIIT and HIIT + CV groups in comparison with placebo group, however CV consumption failed to affect HDL cholesterol levels. CV and/or HIIT significantly lowered, visceral adiposity index (VAI), lipid accumulating product (LAP) and atherogenic index of plasma (AIP) in comparison with placebo. However, concurrent administration of CV and HII resulted in greater reduction in this indexes. Among glycemic indices a significant reduction in insulin resistance in CV+HIIT group compared with placebo group were seen.

Conclusions

In conclusion, CV and HIIT could improve lipid profile and glycemic status in overweight and obese women.

Can High-Intensity Interval Training Promote Skeletal Muscle Anabolism?

Exercise training in combination with optimal nutritional support is an effective strategy to maintain or increase skeletal muscle mass. A single bout of resistance exercise undertaken with adequate protein availability increases rates of muscle protein synthesis and, when repeated over weeks and months, leads to increased muscle fiber size. While resistance-based training is considered the 'gold standard' for promoting muscle hypertrophy, other modes of exercise may be able to promote gains in muscle mass. High-intensity interval training (HIIT) comprises short bouts of exercise at or above the power output/speed that elicits individual maximal aerobic capacity, placing high tensile stress on skeletal muscle, and somewhat resembling the demands of resistance exercise. While HIIT induces rapid increases in skeletal muscle oxidative capacity, the anabolic potential of HIIT for promoting concurrent gains in muscle mass and cardiorespiratory fitness has received less scientific inquiry. In this review, we discuss studies that have determined muscle growth responses after HIIT, with a focus on molecular responses, that provide a rationale for HIIT to be implemented among populations who are susceptible to muscle loss (e.g. middle-aged or older adults) and/or in clinical settings (e.g. pre- or post-surgery).

Twelve weeks of sprint interval training increases peak cardiac output in previously untrained individuals

INTRODUCTION

Sprint interval training (SIT), characterized by brief bouts of 'supramaximal' exercise interspersed with recovery periods, increases peak oxygen uptake ([Formula: see text]) despite a low total exercise volume. Per the Fick principle, increased [Formula: see text] is attributable to increased peak cardiac output ([Formula: see text]) and/or peak arterio-venous oxygen difference (a-vO_2diff). There are limited and equivocal data regarding the physiological basis for SIT-induced increases in [Formula: see text], with most studies lasting ≤ 6 weeks.

PURPOSE

To determine the effect of 12 weeks of SIT on [Formula: see text], measured using inert gas rebreathing, and the relationship between changes in [Formula: see text] and [Formula: see text].

METHODS

15 healthy untrained adults [6 males, 9 females; 21 ± 2 y (mean ± SD)] performed 28 ± 3 training sessions. Each session involved a 2-min warm-up at 50 W, 3 × 20-s 'all-out' cycling bouts (581 ± 221 W) interspersed with 2-min of recovery, and a 3-min cool-down at 50 W.

RESULTS

Measurements performed before and after training showed that 12 weeks of SIT increased [Formula: see text] (17.0 ± 3.7 vs 18.1 ± 4.6 L/min, p = 0.01, partial η² = 0.28) and [Formula: see text] (2.63 ± 0.78 vs 3.18 ± 1.1 L/min, p < 0.01, partial η² = 0.58). The changes in these two variables were correlated (r² = 0.46, p < 0.01). Calculated peak a-vO_2diff also increased after training (154 ± 22 vs 174 ± 23 ml O₂/L; p < 0.01) and was correlated with the change in [Formula: see text] (r² = 0.33, p = 0.03). Exploratory analyses revealed an interaction (p < 0.01) such that [Formula: see text] increased in male (+ 10%, p < 0.01) but not female participants (+ 0.6%, p = 0.96), suggesting potential sex-specific differences.

CONCLUSION

Twelve weeks of SIT increased [Formula: see text] by 6% in previously untrained participants and the change was correlated with the larger 21% increase in [Formula: see text].

Interval-induced metabolic perturbation determines tissue fluid shifts into skeletal muscle

Intense interval exercise has proven to be as effective as traditional endurance exercise in improving maximal oxygen uptake. Shared by these two exercise regimes is an acute reduction in plasma volume, which is a suggested stimulus behind exercise-induced increases in blood volume and maximal oxygen uptake. This study aimed to link exercise-induced metabolic perturbation with volume shifts into skeletal muscle tissue. Ten healthy subjects (mean age 33 ± 8 years, 5 males and 5 females) performed three 30 s all-out sprints on a cycle ergometer. Upon cessation of exercise magnetic resonance imaging, ³¹ Phosphorus magnetic resonance spectroscopy and blood samples were used to measure changes in muscle volume, intramuscular energy metabolites and plasma volume. Compared to pre-exercise, muscle volume increased from 1147.1 ± 35.6 ml to 1283.3 ± 11.0 ml 8 min post-exercise. At 30 min post-exercise, muscle volume was still higher than pre-exercise (1147.1 ± 35.6 vs. 1222.2 ± 6.8 ml). Plasma volume decreased by 16 ± 3% immediately post-exercise and recovered back to - 5 ± 6% after 30 min. Principal component analysis of exercise performance, muscle and plasma volume changes as well as changes in intramuscular energy metabolites showed generally strong correlations between metabolic and physiological variables. The strongest predictor for the volume shifts of muscle and plasma was the magnitude of glucose-6-phosphate accumulation post-exercise. Interval training leads to large metabolic and hemodynamic perturbations with accumulation of glucose-6-phosphate as a possible key event in the fluid flux between the vascular compartment and muscle tissue.

Sex Comparison of Knee Extensor Size, Strength, and Fatigue Adaptation to Sprint Interval Training

ABSTRACT

Bagley, L, Al-Shanti, N, Bradburn, S, Baig, O, Slevin, M, and McPhee, JS. Sex comparison of knee extensor size, strength, and fatigue adaptation to sprint interval training. J Strength Cond Res 35(1): 64-71, 2021-Regular sprint interval training (SIT) improves whole-body aerobic capacity and muscle oxidative potential, but very little is known about knee extensor anabolic or fatigue resistance adaptations, or whether effects are similar for men and women. The purpose of this study was to compare sex-related differences in knee extensor size, torque-velocity relationship, and fatigability adaptations to 12-week SIT. Sixteen men and 15 women (mean [SEM] age: 41 [±2.5] years) completed measurements of total body composition assessed by dual energy X-ray absorptiometry, quadriceps muscle cross-sectional area (CSAQ) assessed by magnetic resonance imaging, the knee extensor torque-velocity relationship (covering 0-240°·s-1) and fatigue resistance, which was measured as the decline in torque from the first to the last of 60 repeated concentric knee extensions performed at 180°·s-1. Sprint interval training consisted of 4 × 20-second sprints on a cycle ergometer set at an initial power output of 175% of power at V̇o2max, 3 times per week for 12 weeks. Quadriceps muscle cross-sectional area increased by 5% (p = 0.023) and fatigue resistance improved 4.8% (p = 0.048), with no sex differences in these adaptations (sex comparisons: p = 0.140 and p = 0.282, respectively). Knee extensor isometric and concentric torque was unaffected by SIT in both men and women (p > 0.05 for all velocities). Twelve-week SIT, totaling 4 minutes of very intense cycling per week, significantly increased fatigue resistance and CSAQ similarly in men and women, but did not significantly increase torque in men or women. These results suggest that SIT is a time-effective training modality for men and women to increase leg muscle size and fatigue resistance.

Interval training causes the same exercise enjoyment as moderate-intensity training to improve cardiorespiratory fitness and body composition in young Chinese women with elevated BMI

This study examined the effects of 12 weeks of sprint interval training (SIT), high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on cardiorespiratory fitness (peak oxygen uptake, VO_2peak), body composition and physical activity enjoyment in overweight young women. Sixty-six participants (age 21.2 ± 1.4 years, body mass index (BMI) 26.0 ± 3.0 kg·m^-2, body fat percentage 39.0 ± 2.8%) were randomly assigned to non-exercise control (CON), thrice-weekly SIT (80 × 6 s "all-out" cycling interspersed with 9 s rest), and HIIT (4 min cycling at 90% VO_2peak followed with 3 min recovery for ~ 60 min) or MICT (~ 65 min continuous cycling at 60% VO_2peak) with equivalent mechanical work (200/300 KJ). Compared to the CON group, all three training groups had significant and similar improvements in VO_2peak (~ +20%, d = 2.5-3.4), fat mass (~ -10%, d = 1.3-2.1) and body fat percentage (~ -5%, d = 1.0-1.1) after a 12-week intervention. Similar high levels of enjoyment were observed among groups for most (~70%) of the training sessions. The findings suggest that the three training regimes are equally enjoyable and could result in similar improvements in cardiorespiratory fitness and body composition in overweight/obese young women, but SIT is a more time-efficient strategy.

High-intensity interval training and essential amino acid supplementation: Effects on muscle characteristics and whole-body protein turnover

The purpose of this study was to compare the independent and combined effects of high-intensity interval training (HIIT) and essential amino acids (EAA) on lean mass, muscle characteristics of the quadriceps, and 24-hr whole-body protein turnover (WBPT) in overweight and obese adults. An exploratory aim was to evaluate potential modulatory effects of sex. Sixty-six adults (50% female; Age: 36.7 ± 6.0 yrs; %BF: 36.0 ± 7.8%) were assigned to 8 wks of: (a) HIIT, 2 days/wk; (b) EAA supplementation, 3.6 g twice daily; (c) HIIT + EAA; or (d) control. At baseline, 4 wks, and 8 wks, total body, thigh LM and muscle characteristics were measured via dual-energy x-ray absorptiometry and B-mode ultrasound, respectively. In a subsample, changes in WBPT was measured using [N15 ]alanine. Differences between groups were assessed using linear mixed models adjusted for baseline values, followed by 95% confidence intervals on adjusted mean change scores (Δ). HIIT and HIIT + EAA improved thigh LM (Δ: +0.17 ± 0.05 kg [0.08, 0.27]; +0.22 ± 0.05 kg [0.12,0.31]) and vastus lateralis cross-sectional area (Δ: +2.73 ± 0.52 cm2 [1.69,3.77]; +2.64 ± 0.53 cm2 [1.58,3.70]), volume (Δ: +54.50 ± 11.69 cm3 [31.07, 77.92]; +62.39 ± 12.05 cm3 [38.26, 86.52]), and quality (Δ: -5.46 ± 2.68a.u. [-10.84, -0.09]; -7.97 ± 2.76a.u.[-13.49, -2.45]). Protein synthesis, breakdown, and flux were greater with HIIT + EAA and EAA compared to HIIT (p < .05). Sex differences were minimal. Compared to women, men tended to respond more to HIIT, with or without EAA. For women, responses were greater with HIIT + EAA than HIIT. In overweight and obese adults, 8 weeks of HIIT, with or without EAA, improved thigh LM size and quality; EAA may enhance muscular adaptation via increases in protein turnover, supporting greater improvements in muscular size and quality.

Understanding the Neurophysiological and Molecular Mechanisms of Exercise-Induced Neuroplasticity in Cortical and Descending Motor Pathways: Where Do We Stand?

Exercise is a promising, cost-effective intervention to augment successful aging and neurorehabilitation. Decline of gray and white matter accompanies physiological aging and contributes to motor deficits in older adults. Exercise is believed to reduce atrophy within the motor system and induce neuroplasticity which, in turn, helps preserve motor function during aging and promote re-learning of motor skills, for example after stroke. To fully exploit the benefits of exercise, it is crucial to gain a greater understanding of the neurophysiological and molecular mechanisms underlying exercise-induced brain changes that prime neuroplasticity and thus contribute to postponing, slowing, and ameliorating age- and disease-related impairments in motor function. This knowledge will allow us to develop more effective, personalized exercise protocols that meet individual needs, thereby increasing the utility of exercise strategies in clinical and non-clinical settings. Here, we review findings from studies that investigated neurophysiological and molecular changes associated with acute or long-term exercise in healthy, young adults and in healthy, postmenopausal women.

High-intensity interval training in the prehabilitation of cancer patients-a systematic review and meta-analysis

PURPOSE

To evaluate the impact of high-intensity interval training (HIIT) on health-related outcome parameters in the prehabilitation of patients diagnosed with cancer.

METHODS

A systematic review and meta-analysis of comparative studies on HIIT in cancer prehabilitation conducted by screening standard databases from their inception to March 30, 2020. Outcomes of interest included cardiorespiratory fitness, feasibility, safety, clinical, and patient-reported outcomes.

RESULTS

Of the 855 identified studies, 8 articles met the inclusion criteria (7 randomized, 1 non-randomized controlled trial) with a total of 896 patients. The study protocols were heterogeneous, but the methodological quality ranged from good to high according to PEDro scale. Meta-analysis revealed a significant improvement of peak oxygen consumption (VO₂peak) achieved with HIIT compared to usual care. Furthermore, HIIT was feasible and safe, showing low risk of adverse events and positive effects on health-related outcomes in prehabilitative settings.

CONCLUSION

In the phase of prehabilitation, HIIT has potential health benefits in patients diagnosed with cancer and is feasible and safe to perform. Nonetheless, larger randomized controlled trials focusing on long-term effects (such as cancer recurrence or survival rates) are missing, to underline the potential relevance of HIIT for cancer patients.

Training-induced changes in muscle contraction patterns enhance exercise performance after short-term neuromuscular electrical stimulation

BACKGROUND: Neuromuscular electrical stimulation (NMES) is a complementary tool for therapeutic exercise for muscle strengthening and may potentially enhance exercise performance. OBJECTIVE: To determine whether high-intensity interval training (HIIT) and continuous aerobic training (CA) coupled with NMES enhance the changes in the eccentric/concentric muscle contraction patterns of hamstring and quadriceps. METHODS: Forty-five healthy sedentary male participants performed cycling training 3 times per week for 8 weeks combined with/without NMES performed at a load equivalent to 65% and 120% of IVO2max (intensity associated with the achievement of maximal oxygen uptake). Anthropometrics, blood lactate measurements, IVO2max, TLimVO2max (time-to-exhaustion) and isokinetic strength parameters were measured at baseline and post-training using a randomized controlled trial. RESULTS: The conventional hamstring-to-quadriceps-ratio (HQR: Hcon/Qcon) at 60∘/s and the Dynamic Control Ratio (DCR: Hecc/Qcon) at 180∘/s significantly increased both in the dominant (D) and non-dominant (ND) limb in the HIIT + NMES group (p< 0.05). There was a positive significant correlation between the individual changes in D HQR at 60∘/s and IVO2max (r= 0.94, p= 0.005) and the DCR at 180∘/s and TLimVO2max (r= 0.90, p= 0.015), respectively. CONCLUSIONS: The increases in the eccentric muscle contraction and DCR following HIIT + NMES seem to improve fatigue tolerance, cause less fatigue and oxidative stress on the lower limb during pedaling at high intensities.

Influence of Sprint Duration during Minimal Volume Exercise on Aerobic Capacity and Affect

The aims of this study were to investigate the influence of reduced-exertion, high-intensity interval training (REHIT), comparing a novel shortened-sprint protocol (SSREHIT) against a traditional protocol (TREHIT), on perceptual responses and to determine if changes in peak oxygen uptake (V˙O_2peak) are attenuated with shorter sprints. Twenty-four healthy men undertook 15 sessions of SSREHIT or TREHIT. V˙O_2peak was determined at baseline and after completion of each exercise condition. Affective (pleasure-displeasure) responses and perceived exertion were assessed during exercise to capture peak responses. Enjoyment was recorded 5-min after cessation of exercise. Compared to baseline, V˙O_2peak increased in both groups (6% for SSREHIT [d=- 0.36] and 9% for TREHIT [d=- 0.53], p=0.01). Affective responses were more favourable for SSREHIT (p=0.001, d=1.62), but both protocols avoided large negative peaks of displeasure. Peak ratings of perceived exertion were lower for SSREHIT (p=0.001, d=- 1.71), although there were no differences in enjoyment (d=0.25). The results demonstrate both exercise conditions can increase V˙O_2peak without overly compromising perceptual responses. Decreased sprint duration might further circumvent negative perceptual responses but might also attenuate physiological adaptations.

Reduced exertion high-intensity interval training (REHIT) in an adult with Cystic Fibrosis: A mixed-methods case study

Although aerobic capacity has been identified as an important predictor of mortality in Cystic Fibrosis (CF) individuals, many remain insufficiently active. As a 'lack of time' is a commonly cited barrier to exercise, reduced-exertion high-intensity interval training (REHIT) may provide a truly time-effective method to increase aerobic capacity. Six-weeks of REHIT in a CF individual was assessed by a cardiopulmonary exercise test (CPET) and individual perceptions described using a self-report narrative. Peak oxygen uptake (V ˙ O2peak) increased by 6% whilst pulmonary function remained unchanged. Qualitative data indicated social support and low-time commitment positively influenced adherence with fatigue and lack of enjoyment noted as a significant barriers. REHIT was demonstrated as a viable, manageable option for a CF individual with moderate-severe pulmonary limitation. Further research is needed to determine the efficacy of REHIT in a large representative sample to ascertain whether it represents an alternative treatment strategy.

Attributes of Physical Activity and Gut Microbiome in Adults: A Systematic Review

Growing evidence shows the contribution of physical activity interventions to the gut microbiome. However, specific physical activity characteristics that can modify the gut microbiome are unknown. This review's aim was to explore the contribution of physical activity intervention characteristics on human gut microbiome composition, in terms of diversity, specific bacterial groups, and associated gut microbiome metabolites. A literature search in PubMed; Cochrane Library; CINAHL-EBSCO; SCOPUS; Web of Science; ClinicalTrials.gov; PROSPERO; and ProQuest. Five studies met the inclusion criteria of a physical activity intervention duration of at least five weeks, with any description of the type or dose used. All included studies reported an endurance training; two studies used endurance and an additional muscle-strengthening training regimen. All studies reported using a dietary intervention control. Reported gut microbiome α-diversity changes were non-significant, β-diversity changes were mixed (three studies reported an increase, two reported non-significant changes). All studies reported significant changes in the abundances of specific bacterial/archaea groups and bacteria-related metabolites following interventions. In conclusion, physical activity (regardless of specific characteristics) has significant contribution to gut microbiome composition and associated metabolites. There are no current recommendations for physical activity to promote gut microbiome composition. Future studies should focus on the contribution of current recommended physical activity dose to gut microbiome composition.

The Effect of Low-Volume High-Intensity Interval Training on Body Composition and Cardiorespiratory Fitness: A Systematic Review and Meta-Analysis

BACKGROUND

Evidence for the efficacy of low-volume high-intensity interval training (HIIT) for the modulation of body composition is unclear.

OBJECTIVES

We examined the effect of low-volume HIIT versus a non-exercising control and moderate-intensity continuous training (MICT) on body composition and cardiorespiratory fitness in normal weight, overweight and obese adults. We evaluated the impact of low-volume HIIT (HIIT interventions where the total amount of exercise performed during training was ≤ 500 metabolic equivalent minutes per week [MET-min/week]) compared to a non-exercising control and MICT.

METHODS

A database search was conducted in PubMed (MEDLINE), EMBASE, CINAHL, Web of Science, SPORTDiscus and Scopus from the earliest record to June 2019 for studies (randomised controlled trials and non-randomised controlled trials) with exercise training interventions with a minimum 4-week duration. Meta-analyses were conducted for between-group (low-volume HIIT vs. non-exercising control and low-volume HIIT vs. MICT) comparisons for change in total body fat mass (kg), body fat percentage (%), lean body mass (kg) and cardiorespiratory fitness.

RESULTS

From 11,485 relevant records, 47 studies were included. No difference was found between low-volume HIIT and a non-exercising control on total body fat mass (kg) (effect size [ES]: - 0.129, 95% confidence interval [CI] - 0.468 to 0.210; p = 0.455), body fat (%) (ES: - 0.063, 95% CI - 0.383 to 0.257; p = 0.700) and lean body mass (kg) (ES: 0.050, 95% CI - 0.250 to 0.351; p = 0.744), or between low-volume HIIT and MICT on total body fat mass (kg) (ES: - 0.021, 95% CI - 0.272 to 0.231; p = 0.872), body fat (%) (ES: 0.005, 95% CI - 0.294 to 0.304; p = 0.974) and lean body mass (kg) (ES: 0.030, 95% CI - 0.167 to 0.266; p = 0.768). However, low-volume HIIT significantly improved cardiorespiratory fitness compared with a non-exercising control (p < 0.001) and MICT (p = 0.017).

CONCLUSION

These data suggest that low-volume HIIT is inefficient for the modulation of total body fat mass or total body fat percentage in comparison with a non-exercise control and MICT. A novel finding of our meta-analysis was that there appears to be no significant effect of low-volume HIIT on lean body mass when compared with a non-exercising control, and while most studies tended to favour improvement in lean body mass with low-volume HIIT versus MICT, this was not significant. However, despite its lower training volume, low-volume HIIT induces greater improvements in cardiorespiratory fitness than a non-exercising control and MICT in normal weight, overweight and obese adults. Low-volume HIIT, therefore, appears to be a time-efficient treatment for increasing fitness, but not for the improvement of body composition.

Implementing a system-wide cancer prehabilitation programme: The journey of Greater Manchester's 'Prehab4cancer'

Patients undergoing major cancer interventions such as major surgical resection, chemotherapy, radiotherapy, and immunotherapy are prone to the adverse effects of their cancer, as well as to the side effects of the treatments designed to cure them. The Prehabilitation process supports cancer patients in preparing for the physiological challenges of their cancer treatments, whilst aiming to shorten recovery time, reduce peri-operative complications and improve compliance with non-surgical treatments. Prehabilitation will be most useful in older patients. Greater Manchester Integrated Care system is the first regional system in the UK to introduce delivery of system-wide, large scale physical activity supported multi-modal prehabilitation and recovery programme, Prehab4Cancer as a standard of care for cancer patients. It builds upon the successful implementation of Enhanced Recovery After Surgery + programme to improve surgical care in Greater Manchester. During this review we describe the journey to develop a system wide prehabilitation model for patients with cancer. Prehab4Cancer to date has focused on robust co-design, development, and implementation of an effective service model with attention paid to stakeholder engagement. This has led to receipt of high numbers of referrals from across Greater Manchester for the all the cancer groups involved. The successful implementation of the P4C pathway in GM presents a best practice model that might be adopted by other local and combined authority areas nationally.

Impact of high-intensity interval training and sprint interval training on peripheral markers of glycemic control in metabolic syndrome and type 2 diabetes

Glycemic control is essential to reduce the risk of complications associated with metabolic syndrome (MetS) and type 2 diabetes (T2D). Aerobic and resistance exercise performed alone or in combination improve glycemic control in both conditions. However, perceived lack of time and commitment are considered principal barriers to performing exercise regularly. High intensity interval training (HIIT) and sprint interval training (SIT) can be performed in a fraction of the time required for continuous aerobic exercise. A substantial scientific evidence indicates that HIIT/SIT improve glycemic control to a similar or greater extent than aerobic exercise in populations without MetS or T2D. Likewise, growing evidence suggest that HIIT/SIT improve the glycemic control during MetS and T2D. The aim of this review is to discuss the effects of interval training protocols on peripheral markers of glucose metabolism in patients with MetS and T2D.

Time-efficient and computer-guided sprint interval exercise training for improving health in the workplace: a randomised mixed-methods feasibility study in office-based employees

Background

The efficacy of high-intensity interval training (HIT) as a time-efficient exercise strategy for beneficially modifying risk factors for cardiovascular disease has repeatedly been demonstrated in controlled laboratory settings. However, the effectiveness of HIT in an unsupervised workplace setting has not been investigated. The objective of this study was to use mixed methods to investigate the feasibility, acceptability and effectiveness of a short-duration, high-intensity exercise intervention (REHIT) when applied unsupervised in a workplace setting.

Methods

Twenty-five office-workers (mean ± SD age: 47 ± 9 y, BMI: 27.5 ± 4.4 kg·m^− 2, V̇O₂max: 28 ± 7 mL·kg^− 1·min^− 1) completed a 6-week REHIT intervention unsupervised in their workplace (n = 13, 6 men), or acted as a no-intervention control (n = 12, 6 men). The intervention consisted of 2 sessions/week of low-intensity (~ 25 W) cycling interspersed with 2 ‘all-out’ sprints, increasing in duration from 10 to 20 s per sprint over the 6 weeks (total time-commitment: 8:40 min per session). V̇O₂max was assessed pre- and post-training, whilst questionnaire-based measures of exercise enjoyment, self-efficacy, and acceptability were completed post-training. Eight participants also completed post-intervention semi-structured interviews.

Results

V̇O₂max significantly improved in the exercise group (2.25 ± 0.75 L·min^− 1 vs. 2.42 ± 0.82 L·min^− 1; + 7.4%) compared to the control group (2.22 ± 0.72 L·min^− 1 vs. 2.17 ± 0.74 L·min^− 1; − 2.3%; time*intervention interaction effect: p < 0.01). Participants considered the REHIT intervention acceptable and enjoyable (PACES: 89 ± 17 out of 119) and were confident in their ability to continue to perform REHIT (7.8 ± 1.2 out of 9). Qualitative data revealed that REHIT offered a time-efficient opportunity to exercise, that was perceived as achievable, and which encouraged highly valued post-exercise outcomes (e.g. progress towards health/fitness benefits).

Conclusions

REHIT could be implemented as a feasible, effective and acceptable exercise intervention in a workplace setting, with a total time-commitment of < 20 min/week. Consideration of certain psycho-social factors and behaviour-change techniques may ensure adherence to the REHIT programme in the long term.

Trial registration

The study was registered on ClinicalTrials.gov on 07/05/2019 (registration: NCT03941145).

Feasibility of procedures for a randomised pilot study of reduced exertion, high-intensity interval training (REHIT) with non-diabetic hyperglycaemia patients

Background

Physical activity and exercise interventions to improve health frequently bring about intended effects under ideal circumstances but often fail to demonstrate benefits in real-world contexts. The aim of this study was to describe the feasibility of an exercise intervention (reduced-exertion, high-intensity interval training) in non-diabetic hyperglycaemia patients delivered in a National Health Service setting to assess whether it would be appropriate to progress to a future large-scale study.

Methods

The intention was to recruit 40 participants from a single centre (specialist diabesity centre). Patients were eligible to take part if they were diagnostically defined as non-diabetic hyperglycaemic based on a glycated haemoglobin (HbA_1c) value of 42–46 mmol mol. Study procedures including recruitment, occurrence of adverse events, intervention acceptability, and intervention adherence were used to assess feasibility.

Results

Key criteria for progression to a larger study were not met. The study revealed several issues including patient eligibility, challenges to recruitment, patient consent, and poor clinician engagement. Furthermore, despite the simplicity and convenience of using HbA_1c to screen for diabetes risk, the process of accurately screening and case finding eligible patients was problematic. The small sample recruited for this trial (n = 6) also limits the interpretation of data, thus it is not possible to estimate the variability of intended outcomes to use in a formal sample size calculation for a full-scale trial. Some aspects of the intervention worked well. The acceptability of the exercise intervention and outcome measures met progression criteria thresholds and adherence was very high, with 97% of exercise sessions completed for participants that finished the study.

Conclusions

Given the issues, the trial is not feasible in its current form. Yet, this preparatory stage of trial design pre-empted problems with the intervention that could be changed to optimise the design and conduct of future studies. Solutions to the issues identified in this study revolve around using a dedicated local recruiter with a strong relationship among the healthcare team and patients, using participant incentives to take part, and allowing for a longer recruitment period.

Trial registration

ClinicalTrials.gov, NCT04011397. Registered 07 July 2019—retrospectively registered.

Reducing training frequency from 3 or 4 sessions/week to 2 sessions/week does not attenuate improvements in maximal aerobic capacity with reduced-exertion high-intensity interval training (REHIT)

In the present randomised-controlled trial we investigated the effect of reduced-exertion high-intensity interval training (REHIT) training frequency (2, 3, or 4 sessions/week for 6 weeks) on maximal aerobic capacity in 42 inactive individuals (13 women; mean ± SD age: 25 ± 5 years, maximal aerobic capacity: 35 ± 5 mL·kg^-1·min^-1). Changes in maximal aerobic capacity were not significantly different between the 3 groups (2 sessions/week: +10.2%; 3 sessions/week: +8.1%; 4 sessions per week: +7.3%). In conclusion, a training frequency of 2 sessions/week is sufficient for REHIT to improve maximal aerobic capacity. Novelty We demonstrate that reducing REHIT training frequency from 3 or 4 to 2 sessions/week does not attenuate improvements in the key health marker of maximal aerobic capacity.

Supplements and Nutritional Interventions to Augment High-Intensity Interval Training Physiological and Performance Adaptations-A Narrative Review

High-intensity interval training (HIIT) involves short bursts of intense activity interspersed by periods of low-intensity exercise or rest. HIIT is a viable alternative to traditional continuous moderate-intensity endurance training to enhance maximal oxygen uptake and endurance performance. Combining nutritional strategies with HIIT may result in more favorable outcomes. The purpose of this narrative review is to highlight key dietary interventions that may augment adaptations to HIIT, including creatine monohydrate, caffeine, nitrate, sodium bicarbonate, beta-alanine, protein, and essential amino acids, as well as manipulating carbohydrate availability. Nutrient timing and potential sex differences are also discussed. Overall, sodium bicarbonate and nitrates show promise for enhancing HIIT adaptations and performance. Beta-alanine has the potential to increase training volume and intensity and improve HIIT adaptations. Caffeine and creatine have potential benefits, however, longer-term studies are lacking. Presently, there is a lack of evidence supporting high protein diets to augment HIIT. Low carbohydrate training enhances the upregulation of mitochondrial enzymes, however, there does not seem to be a performance advantage, and a periodized approach may be warranted. Lastly, potential sex differences suggest the need for future research to examine sex-specific nutritional strategies in response to HIIT.

A Gamification-Based Intervention Program that Encourages Physical Activity Improves Cardiorespiratory Fitness of College Students: 'The Matrix rEFvolution Program'

The aim of the present study was to examine the effects of a gamification-based program on cardiorespiratory fitness (CRF) levels of college students. We divided 112 college students into an intervention group (IG) and a control group (CG). IG college students followed a 15-week gamification-based program, whereas CG followed traditional lectures. CRF was assessed using the 20-meter shuttle-run test. CRF significantly improved after the program in the IG compared to CG (d ≤ 0.94, p < 0.001). Only participants of IG had significant CRF improvements (d ≤ 0.87, p < 0.001) between pre- and post-assessments. In the IG, from the students who attended 100% of lectures, 87.8% met physical activity recommendations for 100% of weeks, whereas from those who attended <100%, only 26.7% met them them for 100% of weeks (p < 0.001). Participants who met recommendations 100% of weeks had a significant CRF improvement (p < 0.001). Motivating college students throughout innovative teaching methods (e.g., gamification) can lead to health improvements.

Physiological basis of brief vigorous exercise to improve health

This review considers the physiological basis of brief vigorous exercise to improve health, with a focus on cardiorespiratory fitness (CRF) and glycaemic control, and the potential underlying mechanisms involved. We defined 'brief' as a protocol lasting ≤15 min including warm-up, cool-down and recovery, and involving a total of ≤5 min of 'vigorous' exercise, which was classified as meeting or exceeding the lower end of the range for this relative intensity as per the criteria from the American College of Sports Medicine. The physiological mechanisms responsible for the increase in CRF, as measured by maximal oxygen update ( V ̇ O 2 max ), after brief vigorous exercise are unclear and likely depend on various factors including the specific nature of the intervention as well as the time course of the response. Limited available evidence suggests the potential for an increased oxygen extraction by active muscle (i.e. greater arterio-venous oxygen difference), since an increase in V ̇ O 2 max has been reported after several weeks of brief vigorous exercise despite no measurable change in cardiac output. Emerging evidence indicates that brief vigorous exercise can improve glycaemic control, suggesting that this type of exercise could potentially play a role in the prevention and management of type 2 diabetes. The acute response is not well characterized but several studies have shown that several weeks of vigorous exercise improves estimates of insulin sensitivity as determined by various methods including by hyperinsulinaemic-euglycaemic clamp. The physiological mechanisms underlying improved CRF and glycaemic control after brief vigorous exercise, and the broader impact on health, remain fruitful areas of investigation.

Effects of three low-volume, high-intensity exercise conditions on affective valence

A common barrier to exercise is "lack of time". Accordingly, interest in low-volume, high-intensity training has grown exponentially since this activity is considered time-efficient. However, the high-intensity nature of this exercise may frequently result in feelings of displeasure creating another barrier for many people. The purpose of this study was to compare affective (pleasure-displeasure) responses to three low-volume, high-intensity exercise conditions, including a novel shortened-sprint protocol. Using a within-subjects, randomised crossover experiment, healthy participants (N = 36) undertook a single bout of: 1) traditional reduced-exertion, high-intensity interval training (TREHIT), 2) a novel, shortened-sprint REHIT (SSREHIT) protocol, and 3) sprint continuous training (SCT). Affect and perceived efforts were recorded throughout exercise using the Feeling Scale (FS) and the 15-point Borg Rating of Perceived Exertion (RPE) scale, respectively. Enjoyment was recorded 5 min post-exercise using the Exercise Enjoyment Scale (EES). Differences were found for FS (condition by time interaction: P = 0.01_GG, η² = 0.26), RPE (P = 0.01_GG, η² = 0.23), and enjoyment (P < 0.01) with all outcomes favouring SSREHIT. Shortened-sprint protocols may diminish feelings of displeasure and might be a time-efficient yet tolerable exercise choice to help motivate some people to increase their physical activity and fitness.

Similar perceptual responses to reduced exertion high intensity interval training (REHIT) in adults differing in cardiorespiratory fitness

Reduced exertion high intensity interval training (REHIT) is an extremely low-volume approach of sprint interval exercise (SIE) that increases maximal oxygen uptake (VO₂max) and reduces body fat. However, there are concerns regarding implementation of SIE including REHIT in untrained populations due to generation of supramaximal power outputs and potential feelings of displeasure. This study examined perceptual responses to a single REHIT session in adults with above (n = 43, VO₂max = 41 ± 6 mL/kg/min) and below average VO₂max (n = 42, VO₂max = 33 ± 5 mL/kg/min). Initially, incremental exercise was completed to determine VO₂max. Subsequently, participants completed REHIT consisting of two 20 s "all-out" sprints at resistance equal to 5 % body mass. Rating of perceived exertion (RPE), affective valence, and physical activity enjoyment (PACES) were determined. Tolerance and preference to exercise intensity were also measured to examine if they moderated the responses. Compared to participants with below average VO₂max, those with above average VO₂max revealed similar change in affective valence (p = 0.86), RPE (p = 0.41), and enjoyment (p = 0.64) despite attaining significantly higher peak and mean power output in response to REHIT. The lowest value of affective valence ranged from 1.0-1.5, representing "fairly good." Overall, one session of REHIT elicits positive affective valence and similar pleasure:displeasure and enjoyment responses in individuals having diverse cardiorespiratory fitness, although we recommend that REHIT should be individualized for each client as greater frequency of aversive responses was shown in our participants with low fitness.

Gender-dependent evaluation of football as medicine for prediabetes

PURPOSE

Training intensity and health effects of football were investigated gender specifically in individuals with prediabetes.

METHODS

Participants with prediabetes (age 60 ± 6 years) were randomised into a football and dietary advice group (FD-men n = 13 and FD-women n = 14) or a dietary advice only group (D-men n = 12 and D-women n = 11). FD performed football training (twice/week for 16 weeks), while both groups received dietary advice. Body composition, bone variables, blood pressure, blood lipid profile and peak oxygen uptake (VO2peak) were determined pre- and post-intervention.

RESULTS

Mean heart rate during football training was 79 ± 2 and 80 ± 3% HRmax for FD-men and FD-women, respectively, with peak heart rate values of 96 ± 1 and 97 ± 2% HRmax, with no gender differences. VO2peak increased more (P < 0.05) in FD-men and FD-women than in D-men and D-women. However, relative delta change in VO2peak was 21 ± 14% in FD-women, which was greater (P < 0.05) than in FD-men (11 ± 12%). Reduction in SBP and DBP, respectively, was similar in FD-men (- 10.8 ± 13.0 and - 7.3 ± 11.8 mmHg) and FD-women (- 11.3 ± 11.0 and - 7.1 ± 6.2 mmHg), with within-gender differences for men. Total plasma cholesterol and LDL cholesterol decreased (P < 0.05) by - 0.7 ± 1.1 and - 0.5 ± 0.9 mmol L-1, respectively, in FD-women and - 0.2 ± 0.4 and - 0.2 ± 0.3 mmol L-1 in FD-men, with no significant gender differences (P = 0.08). Body fat content was lowered (P < 0.05) by 3 and 4%-points in FD-men and FD-women, respectively.

CONCLUSION

Gender-mixed football training combined with dietary advice causes broad-spectrum health effects for men and women with prediabetes, with minor gender-specific differences. Thus, the intensity and training-induced effects of football training are also high for elderly women with prediabetes.

Exercise Intensities as Factors of Metabolic Outcomes in Type 2 Diabetes: A Systematic Review

Exercise is effective to prevent and treat type 2 diabetes, although currently underutilized. This review analyzes the metabolic response to exercise performance at various intensities in individuals with type 2 diabetes. These findings provide insight into the development of safe and efficacious exercise prescriptions and education. We conducted a systemic review of the literature to examine the association of various exercise protocols with metabolic outcomes in type 2 diabetes. Between 1984 and 2018, 29 studies were categorized per exercise mode and intensity levels according to the American College of Sports Medicine standards. The most consistent improvement was found in HbA1c following moderate- to high-intensity exercise—post-exercise fasting glucose improved to a lesser extent. Low-intensity exercise improved HOMA-IR (homeostasis model assessment for insulin resistance) levels. Glucose and HbA1c improved most following interval compared with continuous exercise, irrespective of intensity. A comparison of high-intensity exercise with moderate-intensity exercise demonstrated few differences in HbA1c, fasting glucose, fasting insulin, and HOMA-IR. Irrespective of exercise intensity, HbA1c improvements were observed, suggesting a delayed progression to diabetes-related complications. Initial low-intensity exercise, with increased quantities when feasible, will contribute to metabolic improvements. The variability in methodology and measurement contributed to inconsistent outcomes; additional research with larger samples sizes is warranted.

High-intensity interval training for health benefits and care of cardiac diseases - The key to an efficient exercise protocol

Aerobic capacity, which is expressed as peak oxygen consumption (VO2peak), is well-known to be an independent predictor of all-cause mortality and cardiovascular prognosis. This is true even for people with various coronary risk factors and cardiovascular diseases. Although exercise training is the best method to improve VO2peak, the guidelines of most academic societies recommend 150 or 75 min of moderate- or vigorous- intensity physical activities, respectively, every week to gain health benefits. For general health and primary and secondary cardiovascular prevention, high-intensity interval training (HIIT) has been recognized as an efficient exercise protocol with short exercise sessions. Given the availability of the numerous HIIT protocols, which can be classified into aerobic HIIT and anaerobic HIIT [usually called sprint interval training (SIT)], professionals in health-related fields, including primary physicians and cardiologists, may find it confusing when trying to select an appropriate protocol for their patients. This review describes the classifications of aerobic HIIT and SIT, and their differences in terms of effects, target subjects, adaptability, working mechanisms, and safety. Understanding the HIIT protocols and adopting the correct type for each subject would lead to better improvements in VO2peak with higher adherence and less risk.

Intensity and temporal patterns of physical activity and cardiovascular disease risk in midlife

Physical activity (PA) and sedentary time (SED) are associated with the risk of cardiovascular disease (CVD), but the temporal patterns of these behaviors most beneficial for cardiovascular health remain unknown. We aimed to identify the intensity and temporal patterns of PA and SED measured continuously by an accelerometer and their relationship with CVD risk. At the age of 46 years, 4582 members (1916 men; 2666 women) of the Northern Finland Birth Cohort 1966 study underwent continuous measurement of PA with Polar Active (Polar Electro, Finland) accelerometers for one week. X-means clustering was applied based on 10 min average MET (metabolic equivalent) values during the measurement period. Ten-year risk of CVD was estimated using the Framingham risk model. Most of the participants had low risk for CVD. Four distinct PA clusters were identified that were well differentiable by the intensity and temporal patterns of activity (inactive, evening active, moderately active, very active). A significant difference in 10-year CVD risk across the clusters was found in men (p = 0.028) and women (p < 0.001). Higher levels of HDL cholesterol were found in more active clusters compared to less active clusters (p < 0.001) in both genders. In women total cholesterol was lower in the moderately active cluster compared to the inactive and evening active clusters (p = 0.001). Four distinct PA clusters were recognized based on accelerometer data and X-means clustering. A significant difference in CVD risk across the clusters was found in both genders. These results can be used in developing and promoting CVD prevention strategies.

The combined effect of high-intensity intermittent training and vitamin D supplementation on glycemic control in overweight and obese adults

High-intensity intermittent training (HIIT) has been shown to reduce the risk of chronic conditions including the development of type 2 diabetes mellitus (T2DM). Independently, a low vitamin D status has also been linked to the prevalence of T2DM. The aim of this study was to investigate if there was a synergistic metabolic effect of HIIT and vitamin D supplementation on glycemic control. A total of 20 male and female participants (age, 34 ± 9 year; BMI, 31.4 ± 2.8 kg·m^-2 ) completed 6 weeks HIIT, and were randomized to ingest 100 μg·day^-1 of vitamin D₃ or placebo. Response to an oral glucose tolerance test (OGTT) was determined at baseline and at 72 h postintervention. Glucose tolerance was improved as a result of the HIIT intervention, shown through a reduction in glucose and insulin concentrations during the OGTT, accompanied by a decrease in glucose (829 ± 110 to 786 ± 139 mmol·h^-1 ·L^-1 ; P = 0.043) and insulin (8101 ± 4755-7024 ± 4489 mU·h^-1 ·L^-1 ; P = 0.049) area under the curve (AUC). Supplementation increased 25-hydroxyvitamin D₃ concentration by 120% to a sufficiency status (P < 0.001). However, the consumption of vitamin D₃ seemed to attenuate the glucose response during an OGTT. Triglyceride content was lowered following the intervention (P = 0.025). There was no effect of the intervention on insulin sensitivity (IS) indices: ISI_Matsuda and HOMA-IR. Our findings demonstrate that HIIT improves glucose tolerance in nondiabetic overweight and obese adults; however vitamin D₃ supplementation did not proffer any additional positive effects on the measured indices of metabolic health.

High-Intensity Interval Training: A Potential Exercise Countermeasure During Human Spaceflight

High-intensity interval training (HIT) is an effective approach for improving a range of physiological markers associated with physical fitness. A considerable body of work has demonstrated substantial improvements in cardiorespiratory fitness following short-term training programmes, while emerging evidence suggests that HIT can positively impact aspects of neuromuscular fitness. Given the detrimental consequences of prolonged exposure to microgravity on both of these physiological systems, and the potential for HIT to impact multiple components of fitness simultaneously, HIT is an appealing exercise countermeasure during human spaceflight. As such, the primary aim of this mini review is to synthesize current terrestrial knowledge relating to the effectiveness of HIT for inducing improvements in cardiorespiratory and neuromuscular fitness. As exercise-induced fitness changes are typically influenced by the specific exercise protocol employed, we will consider the effect of manipulating programming variables, including exercise volume and intensity, when prescribing HIT. In addition, as the maintenance of HIT-induced fitness gains and the choice of exercise mode are important considerations for effective training prescription, these issues are also discussed. We conclude by evaluating the potential integration of HIT into future human spaceflight operations as a strategy to counteract the effects of microgravity.

Development and Feasibility of a Regulated, Supramaximal High-Intensity Training Program Adapted for Older Individuals

Background: High-intensity training (HIT) with extremely short intervals (designated here as supramaximal HIT) is a time-efficient training method for health and performance. However, a protocol for regulation and control of intensity is missing, impeding implementation in various groups, such as older individuals. Methods: This study presents the development and characteristics of a novel training protocol with regulated and controlled supramaximal intervals adapted for older people. Using both quantitative and qualitative analyses, we explored the feasibility of the program, performed in a group training setting, with physically active older individuals (aged 65-75, n = 7; five women). The developed supramaximal HIT program consisted of 10 × 6 s cycle sprint intervals with ∼1 min of active recovery with the following key characteristics: (1) an individual target power output was reached and maintained during all intervals and regulated and expressed as the percentage of the estimated maximum mean power output for the duration of the interval (i.e., 6 s); (2) pedaling cadence was standardized for all participants, while resistance was individualized; and (3) the protocol enabled controlled and systematic adjustments of training intensity following standardized escalation criteria. Aim: Our aim was to test the feasibility of a novel training regimen with regulated and controlled supramaximal HIT, adapted for older people. The feasibility criteria for the program were to support participants in reaching a supramaximal intensity (i.e., power output > 100% of estimated VO2 max), avoid inducing a negative affective response, and have participants perceive it as feasible and acceptable. Results: All feasibility criteria were met. The standardized escalation procedure provided safe escalation of training load up to a supramaximal intensity (around three times the power output at estimated VO2 max). The participants never reported negative affective responses, and they perceived the program as fun and feasible. Conclusion: This novel program offers a usable methodology for further studies on supramaximal HIT among older individuals with different levels of physical capacity. Future research should explore the effects of the program in various populations of older people and their experiences and long-term adherence compared with other forms of training.

High-Intensity Interval Training in the Real World: Outcomes from a 12-Month Intervention in Overweight Adults

PURPOSE

Although high-intensity interval training (HIIT) and moderate-intensity continuous exercise have comparable health outcomes in the laboratory setting, effectiveness studies in real-world environments are lacking. The aim of this study was to determine the effectiveness of an unsupervised HIIT program in overweight/obese adults over 12 months.

METHODS

Two hundred and fifty overweight/obese adults could choose HIIT or current exercise guidelines of 30 min·d moderate-intensity exercise. HIIT participants received a single training session and were advised to independently perform HIIT three times per week using a variety of protocols. Mixed models, with a random effect for participant, compared differences in weight, body composition, blood pressure, aerobic fitness, physical activity, and blood indices at 12 months, adjusting for relevant baseline variables.

RESULTS

Forty-two percent (n = 104) of eligible participants chose HIIT in preference to current guidelines. At 12 months, there were no differences between exercise groups in weight (adjusted difference HIIT vs conventional = -0.44 kg; 95% confidence interval [CI] = -2.5 to 1.6) or visceral fat (-103 cm; -256 to 49), although HIIT participants reported greater enjoyment of physical activity (P = 0.01). Evidence of adherence to ≥2 sessions per week of unsupervised HIIT (from HR monitoring) declined from 60.8% at baseline to 19.6% by 12 months. Participants remaining adherent to HIIT over 12 months (23%) were more likely to be male (67% vs 36%, P = 0.03), with greater reductions in weight (-2.7 kg; -5.2 to 0.2) and visceral fat (-292 cm; -483 to -101) than nonadherent participants.

CONCLUSIONS

HIIT was well accepted by overweight adults, and opting for HIIT as an alternative to standard exercise recommendations led to no difference in health outcomes after 12 months. Although regular participation in unsupervised HIIT declined rapidly, those apparently adherent to regular HIIT demonstrated beneficial weight loss and visceral fat reduction.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry (ACTRN12615000010594), retrospectively registered.

Effect of sodium bicarbonate ingestion during 6 weeks of HIIT on anaerobic performance of college students

Background

Past studies have found that sodium bicarbonate ingestion prior to exercise has a performance-enhancing effect on high-intensity exercise. The aim of this study was to investigate the effects of continuous sodium bicarbonate (NaHCO₃) supplementation on anaerobic performance during six weeks of high-intensity interval training (HIIT).

Methods

Twenty healthy college-age male participants were randomly assigned to either the HCO₃⁻ group (SB) or the placebo group (PL), with 10 subjects in each group. Both groups completed 6 weeks (3 days/week) of HIIT with the SB ingesting an orange-flavored solution containing 15 g xylitol and 0.2 g HCO₃⁻/kg body mass during each training day, and PL ingesting a similar beverage that was HCO₃⁻-free. This study separated 6 weeks of training into two stages with different training intensities, with the first 3 weeks at a lower intensity than the second 3 weeks. Blood samples to measure serum HCO₃⁻ were obtained 5 min before and 30 min after the following HIIT training sessions: Week 1, training session 1; week 3, training session 3; week 6, training session 3. Three 30s Wingate tests (WAnT) were conducted before, in the middle, and after the training and the supplementation interventions, with peak power, mean power, and fatigue index obtained during WAnT, and blood lactate and heart rate obtained after WAnT.

Results

Our findings indicate the following: 1) Serum HCO₃⁻ level of SB was significantly higher than PL (p < 0.05) both before and after each HIIT; 2) Relative peak power in WAnT was significantly higher in the SB group after 6 weeks (p < 0.01); 3) Lactate clearance rate and the lactate clearance velocity after 10 min of WAnT were both significantly higher in SB in the post-test (p < 0.01); 4) Heart rate recovery rate at 10 min after WAnT in both SB and PL after 6 weeks were significantly improved (p < 0.01 and p < 0.05, respectively), resulting in no difference between groups on these measures.

Conclusions

These data suggest that supplementation of HCO₃⁻ at the level of 0.2 g/kg body mass before HIIT training enhances the effect of HIIT on anaerobic performance, and improves the blood lactate clearance rate and the blood lactate clearance velocity following anaerobic exercise.

Combining supervised run interval training or moderate-intensity continuous training with the diabetes prevention program on clinical outcomes

PURPOSE

The present study was designed to evaluate the 16 weeks diabetes prevention program (DPP) combined with instructed run sprint interval training (INT) or moderate-intensity continuous training (MICT) on glycemic control, body composition, fitness, exercise adherence, and perceived exercise enjoyment in sedentary, adults with prediabetes.

METHODS

Participants completed three weekly supervised sessions of INT (4-10 bouts of 30 s maximal sprints followed by a 4 min active recovery) or MICT (30-60 min at 45-55% HRR) exercise coupled with the DPP for 16 weeks. At baseline, 8 and 16 weeks, participants completed fitness and clinical assessments as well as questionnaires to assess group and time differences.

RESULTS

Twenty-nine study participants (INT n = 17, MICT n = 12) were randomized, however, significantly (p = 0.024) more participants withdrew from the INT (n = 11) than MICT (n = 4) treatment. There was no significant difference between groups in perceived exercise enjoyment, but, the MICT group significantly improved their perceived exercise enjoyment (10.8 ± 14.2; p = 0.021) from baseline to 16 weeks. Both INT and MICT groups decreased their body weight (2.0 ± 0.8 vs. - 5.5 ± 1.4 kg; p < 0.001), BMI (- 0.6 ± 0.3 vs. - 2.1 ± 0.5 kg/m²; p < 0.001), body fat mass (1.4 ± 0.6 vs. - 4.2 ± 1.0 kg; p < 0.001), fasting glucose (- 0.09 ± 0.01 vs. - 0.18 ± 0.02 mmol/L; p = 0.020), and HbA1c (- 0.21 ± 0.09 vs. - 0.12 ± 0.12%; p = 0.001), respectively, however, the MICT had greater reductions (GxT: p ≤ 0.05) in body weight, BMI, and body fat than the INT group.

CONCLUSION

Sixteen weeks of MICT is adhered to better and elicits greater improvements in body composition than INT. Nevertheless, both interventions similarly reduced fasting glucose and HbA1c in adults with prediabetes, suggesting either treatment could be effective for T2D prevention.

The Dose Response for Sprint Interval Training Interventions May Affect the Time Course of Aerobic Training Adaptations

Low vs. high volume sprint-interval training (SIT) sessions have shown similar physiological benefits after 8 weeks. However, the dose response and residual effects of shorter SIT bouts (<10 s) are unknown. Following a 6-wk control period, 13 healthy inactive males were assigned to a low dose (LDG: n = 7) or high dose (HDG: n = 6) supervised 6-wk intervention: ×2/wk of SIT (LDG = 2 sets of 5 × 6 s ON: 18 s OFF bouts; HDG = 4–6 sets); ×1/wk resistance training (3 exercises at 3 × 10 reps). Outcome measures were tested pre and post control (baseline (BL) 1 and 2), 72 h post (0POST), and 3-wk post (3POST) intervention. At 0POST, peak oxygen uptake (VO_2peak) increased in the LDG (+16%) and HDG (+11%) vs. BL 2, with no differences between groups (p = 0.381). At 3POST, VO_2peak was different between LDG (−11%) and HDG (+3%) vs. 0POST. Positive responses for the intervention’s perceived enjoyment (PE) and rate of perceived exertion (RPE) were found for both groups. Blood pressure, blood lipids, or body composition were not different between groups at any time point. Conclusion: LDG and HDG significantly improved VO_2peak at 0POST. However, findings at 3POST suggest compromised VO_2peak at 0POST in the HDG due to the delayed time course of adaptations. These findings should be considered when implementing high-dose SIT protocols for non-athletic populations.

Combined effects of very short "all out" efforts during sprint and resistance training on physical and physiological adaptations after 2 weeks of training

PURPOSE

The aim of this study was to compare the combined effects of resistance and sprint training, with very short efforts (5 s), on aerobic and anaerobic performances, and cardiometabolic health-related parameters in young healthy adults.

METHODS

Thirty young physically active individuals were randomly allocated into four groups: resistance training (RTG), sprint interval training (SITG), concurrent training (CTG), and control (CONG). Participants trained 3 days/week for 2 weeks in the high-intensity interventions that consisted of 6-12 "all out" efforts of 5 s separated by 24 s of recovery, totalizing ~ 13 min per session, with 48-72 h of recovery between sessions. Body composition, vertical jump, lower body strength, aerobic and anaerobic performances, heart rate variability (HRV), and redox status were evaluated before and after training. Total work (TW), rating of perceived exertion (CR-10 RPE) and mean HR (HR_mean) were monitored during sessions. Incidental physical activity (PA), dietary intake and perceived stress were also controlled.

RESULTS

Maximum oxygen consumption (VO_2max) significantly increased in SITG and CTG (P < 0.05). Lower body strength improved in RTG and CTG (P < 0.05), while countermovement jump (CMJ) was improved in RTG (P = 0.04) only. Redox status improved after all interventions (P < 0.05). No differences were found in TW, PA, dietary intake, and psychological stress between groups (P > 0.05).

CONCLUSIONS

RT and SIT protocols with very short "all out" efforts, either performed in isolation, or combined, demonstrated improvement in several physical fitness- and health-related parameters. However, CT was the most efficient exercise intervention with improvement observed in the majority of the parameters.

Introduction to the Frontiers Research Topic: Optimization of Exercise Countermeasures for Human Space Flight - Lessons From Terrestrial Physiology and Operational Considerations

Exercise in space has evolved from rudimental testing into the multi-modal countermeasure (CM) program used on the International Space Station (ISS). However, with the constraints of future exploration missions, replicating this program will be a significant challenge. Recent ISS data suggest that crew now experience only relatively moderate levels of microgravity (μG)-induced adaptation, although significant variation remains, with some crew displaying marked changes despite significant time/effort investment. This suggests that the efficacy of exercise CMs is yet to be optimized for all individuals. With the current suite of exercise devices operational for almost a decade, and with exploration approaching, it is timely to re-visit the terrestrial literature to identify new knowledge relevant to the management of μG adaptation. As such, the aim of the Frontiers Research Topic Optimization of Exercise Countermeasures for Human Space Flight - Lessons from Terrestrial Physiology and Operational Considerations, is to synthesize current terrestrial exercise physiology knowledge and consider how this might be employed to optimize the use of exercise CM. The purpose of this Perspective, which serves as a preface to the Research Topic is threefold: to briefly review the use and apparent efficacy of exercise in space, to consider the impact of the transition from ISS to exploration mission vehicles and habitats, and to identify areas of terrestrial exercise physiology where current knowledge might contribute to the optimization of CM exercise for exploration. These areas include individual variation, high intensity interval training, strength development/maintenance, concurrent training, plyometric/impact exercise, and strategies to enhance exercise efficacy.