High-intensity interval training in patients with lifestyle-induced cardiometabolic disease: a systematic review and meta-analysis

Time-efficient physical training for enhancing cardiovascular function in midlife and older adults: promise and current research gaps

Cardiovascular diseases (CVD) remain the leading cause of death in developed societies, and "midlife" (50-64 yr) and older (65+) men and women bear the great majority of the burden of CVD. Much of the increased risk of CVD in this population is attributable to CV dysfunction, including adverse changes in the structure and function of the heart, increased systolic blood pressure, and arterial dysfunction. The latter is characterized by increased arterial stiffness and vascular endothelial dysfunction. Conventional aerobic exercise training, as generally recommended in public health guidelines, is an effective strategy to preserve or improve CV function with aging. However, <40% of midlife and older adults meet aerobic exercise guidelines, due in part to time availability-related barriers. As such, there is a need to develop evidence-based time-efficient exercise interventions that promote adherence and optimize CV function in these groups. Two promising interventions that may meet these criteria are interval training and inspiratory muscle strength training (IMST). Limited research suggests these modes of training may improve CV function with time commitments of ≤60 min/wk. This review will summarize the current evidence for interval training and IMST to improve CV function in midlife/older adults and identify key research gaps and future directions.

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.

High-Intensity Interval Training Versus Moderate-Intensity Continuous Training in Middle-Aged and Older Patients with Type 2 Diabetes: A Randomized Controlled Crossover Trial of the Acute Effects of Treadmill Walking on Glycemic Control

Background: This study aimed to compare the acute effects of high-intensity interval training (HIIT) versus moderate-intensity continuous training (MICT) on glycemic control in middle-aged and older patients with type 2 diabetes (T2D), using treadmill walking as aerobic exercise mode. Methods: Fifteen patients with T2D (60.25 ± 3.14 years; glycated hemoglobin 7.03 ± 0.33%; medicated with metformin and/or gliptins), participated in a randomized controlled crossover trial. They underwent three experimental conditions (treadmill walking HIIT session (5 × (3 min at 70% of heart rate reserve (HRR) + 3 min at 30% HRR)); treadmill walking MICT session (30 min at 50% HRR); and a control session of rest (CON)) in random order and in the postprandial state. Measurements of capillary blood glucose (BG) were taken immediately before, during, and until 50 min after the experimental conditions. Results: Both HIIT and MICT treadmill walking sessions reduced BG levels during exercise and laboratory 50 min recovery period compared to CON (time*condition interaction effect; p < 0.001). The effect of HIIT was greater compared with MICT (p = 0.017). Conclusions: Treadmill walking HIIT seems a safe and more effective exercise strategy on immediate acute glycemic control compared with MICT in middle-aged and older patients with T2D under therapy with metformin and/or gliptins. Trial Registration Number: ISRCTN09240628.

A Randomized Clinical Trial Comparing Three Different Exercise Strategies for Optimizing Aerobic Capacity and Skeletal Muscle Performance in Older Adults: Protocol for the DART Study

Background: Age-related declines in physical function lead to decreased independence and higher healthcare costs. Individuals who meet the endurance and resistance exercise recommendations can improve their physical function and overall fitness, even into their ninth decade. However, most older adults do not exercise regularly, and the majority of those who do only perform one type of exercise, and in doing so are not getting the benefits of endurance or resistance exercise. Herein we present the study protocol for a randomized clinical trial that will investigate the potential for high-intensity interval training (HIIT) to improve maximal oxygen consumption, muscular power, and muscle volume (primary outcomes), as well as body composition, 6-min walk distance, and muscular strength and endurance (secondary outcomes). Methods and Analysis: This is a single-site, single-blinded, randomized clinical trial. A minimum of 24 and maximum of 30 subjects aged 60-75 that are generally healthy but insufficiently active will be randomized. After completion of baseline assessments, participants will be randomized in a 1:1:1 ratio to participate in one of three 12-week exercise programs: stationary bicycle HIIT, stationary bicycle moderate-intensity continuous training (MICT), or resistance training. Repeat assessments will be taken immediately post intervention. Discussion: This study will examine the potential for stationary bicycle HIIT to result in both cardiorespiratory and muscular adaptations in older adults. The results will provide important insights into the effectiveness of interval training, and potentially support a shift from volume-driven to intensity-driven exercise strategies for older adults. Clinical Trial Registration: This trial is registered with ClinicalTrials.gov (registration number: NCT03978572, date of registration June 7, 2019).

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.

Exercise and sport science australia position stand update on exercise and hypertension

Hypertension is the most common circulatory system condition, accounting for >40% of the cardiovascular disease total burden. One-third of Australians aged over 18 years have hypertension and in 68% of these it is uncontrolled. Australian data show hypertension accounts for 6% of general practitioner (GP) consults. Recent evidence has confirmed exercise is an effective adjunct therapy for hypertension management and the objective of this document is to provide a contemporary, evidence-based guide for optimal delivery of an exercise programme for blood pressure management. This work is an update to the 2009 Exercise and Sport Science Australia (ESSA) position stand. In most cases, the first line treatment to reduce BP is initiation of lifestyle changes, of which regular aerobic exercise is a principal component. Aerobic and resistance activities remain the cornerstone of exercise-based management of blood pressure, but recent work has uncovered variations on traditional delivery of exercise, such as high intensity interval training (HIIT) and a new exercise modality, isometric resistance training (IRT) may offer alternative management regimens. Exercise Physiologists, as well as other health care professionals, play an important role in helping to achieve BP control in patients with hypertension by reinforcing healthy lifestyle habits and prescribing appropriate exercise.

Study Protocol: Does an Acute Intervention of High-Intensity Physical Exercise Followed by a Brain Training Video Game Have Immediate Effects on Brain Activity of Older People During Stroop Task in fMRI?-A Randomized Controlled Trial With Crossover Design

Background: Elderly people are affected by processes leading to decline in various aspects of daily living that impair their quality of life. Regarding neurological aspects, executive functions have been shown to be valuable for daily life and to slow decline during aging. Most intervention studies intended to improve cognitive functions during aging specifically address long-term destructive processes and countermeasures. However, to an increasing degree, studies also investigate the acute benefits that prove to be useful for daily life, such as physical exercise or video games in the form of exercise video gaming (“exergaming”). Because little is known about the change in cognitive ability following acute intervention of a combination of physical exercise and video gaming, especially for older people, this work is designed as an attempt to address this matter.

Methods: This study is a randomized crossover controlled trial to test the response to an acute bout of high-intensity physical exercise followed by a short session with a brain training (Brain Age) video game in physically active and cognitively healthy older adults (60–70 years). The response is measured using Stroop task performance (cognitive task for executive function) and related brain activity assessed with functional magnetic resonance imaging (fMRI). The control conditions are low-intensity physical exercise and Tetris for video gaming.

Discussion: This study is intended to provide insight into the alteration of executive function and its related brain activity from an acute intervention with a combination of physical exercise and video gaming in older people. The protocol might not be implementable in daily life to improve cognitive abilities. However, the results can support future studies that investigate cognition and the combination of physical exercise and video gaming. Moreover, it can provide real-life implications.

Trial registration: This trial was registered in The University Hospital Medical Information Network Clinical Trials Registry (UMIN000033054). Registered 19 July 2018, https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000037687.

Carbohydrate-restricted Diet and High-intensity Interval Training Exercise Improve Cardio-metabolic and Inflammatory Profiles in Metabolic Syndrome: A Randomized Crossover Trial

Introduction

One approach to slow the pandemic of obesity and chronic disease is to look to our evolutionary past for clues of the changing behaviors contributing to the emergence of 'diseases of civilization'. Modern humans have deviated from the lifestyle behaviors of our ancestors that have introduced pressures (i.e. diet and activity changes) quicker than our genetic ability to respond. This caused a 'mismatch' between our biological systems and environment, leading to 'man-made' chronic diseases.

Purpose

The purpose of the study was to investigate the effects of a short-term evolutionarily informed dietary and lifestyle intervention on inflammatory and cardio-metabolic profiles in individuals characterized as having metabolic syndrome (MetS).

Methods

Twelve subjects with MetS followed a crossover design with two, four-week interventions, including a carbohydrate (CHO)-restricted Paleolithic-based diet (CRPD; <50g CHO) with sedentary activity (CRPD-Sed) and CRPD with high-intensity interval training (CRPD-Ex), separated by a four-week washout period. The HIIT exercise consisted of 10 X 60 seconds (s) cycling intervals interspersed with 60s of active recovery three d/wk for four weeks. The effects of a diet with sedentary activity as compared to a diet with exercise on body composition, as well as the cardiovascular, inflammatory, and metabolic profiles, were assessed. A two-way analysis of variance (ANOVA) with repeated measures was performed with a post-hoc analysis using a simple effects analysis with a Bonferroni adjustment. The level of statistical significance was established a priori as p < 0.05.

Results

Compared to baselines, CRPD-Sed and CRPD-Ex improved cardio-metabolic markers, including reductions in waist adiposity (-15%, -18%), body mass (-3%, -5%), body fat % (BF%; -7%, -12%), fasting plasma glucose (GLU; -20%, -27%), triglycerides (TG; -47%, -52%), fasting insulin (-34%, -39%), insulin resistance (-35%, -46%), and increased HDL-C (+22%, +36%) and VO_2max (+22% and +29%), respectively. CRPD-Sed and CRPD-Ex also reduced inflammatory markers, including hsCRP (-32% and-36%), TNF-alpha (-35% and -41%), IL-6 (-29% and -40%), and ICAM-1 (-19%, -23%), respectively, when compared to baseline.

Conclusion

Adopting behaviors from our evolutionary past, including diet and exercise, shows favorable cardio-metabolic and inflammatory profiles in those individuals characterized with MetS.

Current Concepts in Healthy Aging and Physical Activity: A Viewpoint

Physical activity plays an important role for achieving healthy aging by promoting independence and increasing the quality of life. However, current guidelines for physical activity in older adults may be difficult to achieve in an older population. Indeed, there is evidence to suggest that increasing exercise intensity in older adults may be associated with greater reductions in the risk of cardiovascular disease and mortality. Therefore, the idea prescribing high-intensity exercise protocols such as high-intensity interval training and high-intensity resistance training becomes an intriguing strategy for healthy aging. Collectively, the literature review in this viewpoint will briefly focus on summarizing alternative/novel time-efficient approaches in physical activity toward healthy aging. Our goal is to hopefully open a discussion on possibly revising the current physical activity guidelines in older adults.

Effects of high-intensity interval training compared to moderate-intensity continuous training on maximal oxygen consumption and blood pressure in healthy men: A randomized controlled trial

Introduction:

Aerobic exercise generates increased cardiorespiratory fitness, which results in a protective factor for cardiovascular disease. High-intensity interval training (HIIT) might produce higher increases on cardiorespiratory fitness in comparison with moderate-intensity continuous training (MICT); however, current evidence is not conclusive.

Objective:

To compare the effects of a low-volume HIIT and a MICT on maximal oxygen consumption (VO2max), systolic blood pressure, and diastolic blood pressure during eight weeks in healthy men between 18 and 44 years of age.

Materials and methods:

We conducted a randomized controlled trial. Forty-four volunteers were randomized to HIIT (n=22) or MICT (n=22). Both groups performed 24 sessions on a treadmill. The HIIT group completed 15 bouts of 30 seconds (90-95%, maximal heart rate, HRmax), while the MICT group completed 40 minutes of continuous exercise (65-75% HRmax). The study is registered as a clinical trial via clinicaltrials.gov with identifier number: NCT02288403.

Results:

Intra-group analysis showed an increase in VO2max of 3.5 ml/kg/min [95% confidence interval (CI) 2.02 to 4.93; p=0.0001] in HIIT and 1.9 ml/kg/min (95% CI -0.98 to 4.82; p=0.18) in MICT. However, the difference between the two groups was not statistically significant (1.01 ml/kg/min. 95% CI -2.16 to 4.18, p=0.52). MICT generated a greater reduction in systolic blood pressure compared to HIIT (median 8 mm Hg; p<0.001). No statistically significant differences were found between the groups for DBP.

Conclusions:

Results indicated no significant change in VO2max with a low-volume HIIT protocol versus MICT after 24 sessions. In contrast, MICT provided a greater reduction in systolic blood pressure compared to HIIT

[Optical coherence tomography angiography as a future diagnostic tool in sports medicine?]

BACKGROUND

High-intensity interval training (HIIT) proved to be efficient for increasing health-related fitness in general and in patients with life style-induced chronic diseases. This study aimed to evaluate if (I) individual physical fitness and (II) a HIIT intervention affects optical coherence tomography angiography (OCTA) measurements at the ocular fundus of healthy young adults.

METHODS

A total of 65 healthy participants performed a standardized incremental running test to determine their physical fitness. This was defined as speed at the individual anaerobic threshold and maximum running speed followed by a 4-week HIIT with two exercise sessions/week. The OCTA measurements of the foveal avascular zone (FAZ) and flow densities in various segments of the macula and optic nerve head were performed at rest before and after HIIT.

RESULTS

An inverse correlation between individual fitness and FAZ area was detected. No further correlations between individual physical fitness and other OCTA parameters were found. In response to HIIT the mean FAZ area in the deep retinal plexus and macular flow density of the superficial layer decreased by 14.00 ± 13.02% and 1.26 ± 3.20%, respectively. The flow density of the nerve head layer in the peripapillary area showed an increase of 1.94 ± 2.39%. All other parameters showed no differences between measurements before and after HIIT.

CONCLUSION

Differences were found in the OCTA measurements of the FAZ depending on the individual physical fitness. Performing HIIT can induce significant changes in certain OCTA parameters. Therefore, OCTA imaging appears to be a promising imaging modality in the field of sports medicine.

Impaired Exercise Tolerance in Heart Failure: Role of Skeletal Muscle Morphology and Function

PURPOSE OF REVIEW

To discuss the impact of deleterious changes in skeletal muscle morphology and function on exercise intolerance in patients with heart failure with reduced ejection fraction (HFrEF) and heart failure with preserved ejection fraction (HFpEF), as well as the utility of exercise training and the potential of novel treatment strategies to preserve or improve skeletal muscle morphology and function.

RECENT FINDINGS

Both HFrEF and HFpEF patients exhibit a reduction in percent of type I (oxidative) muscle fibers and oxidative enzymes coupled with abnormal mitochondrial respiration. These skeletal muscle abnormalities contribute to impaired oxidative metabolism with an earlier shift towards glycolytic metabolism during exercise that is strongly associated with exercise intolerance. In both HFrEF and HFpEF patients, peripheral "non-cardiac" factors are important determinants of the improvement in exercise tolerance following aerobic exercise training. Adjunctive strategies that include nutritional supplementation with amino acids and/or anabolic drugs to stimulate anabolic molecular pathways in skeletal muscle show great promise for improving exercise tolerance and treating heart failure-associated sarcopenia, but these efforts remain early in their evolution, with no immediate clinical applications. There is consistent evidence that heart failure is associated with multiple skeletal muscle abnormalities which impair oxygen uptake and utilization and contribute greatly to exercise intolerance. Exercise training induces favorable adaptations in skeletal muscle morphology and function that contribute to improvements in exercise tolerance in patients with HFrEF. The contribution of skeletal muscle adaptations to improved exercise tolerance following exercise training in HFpEF remains unknown and warrants further investigation.

Exergame-Driven High-Intensity Interval Training in Untrained Community Dwelling Older Adults: A Formative One Group Quasi- Experimental Feasibility Trial

Purpose

To investigate the feasibility of an exergame-driven high-intensity interval training (HIIT) and its effects on cardiovascular fitness in untrained community dwelling older adults.

Methods

Twelve older participants [10 women, age 72.3 (SD: 4.44) years] performed a high-intensity interval exergame intervention three times a week for 4 weeks. Data was acquired during two baseline and one final measurement. Feasibility outcomes included attrition, adherence, acceptability [Technology Acceptance Model Questionnaire (TAM)], usability [System Usability Scale (SUS)], and enjoyment of exergaming. Furthermore, participants' physical activity levels pre and post intervention were compared to physical activity levels for similar types of training. The secondary outcome was exercise capacity [heart rate at rest (HRrest), heart rate variability (HRV), maximum heart rate (HRmax), and maximum workload (W, in watt)] evaluated through maximal exercise testing.

Results

Eleven participants completed the study (8% attrition), without any adverse events. Adherence to the HIIT intervention was 91% and participants showed high acceptance of the intervention with TAM scores between 5.8 and 6.7 points. User satisfaction was rated as excellent (SUS total score: 93.5 of 100) and the overall enjoyment of exergaming scored 4.5 of 5 possible points. Total exercise time ranged from 19 to 35 min with a mean of 30.8 (SD: 3.6) min. Actual high-intensity exercise time showed consistency with the target exercise time in 98% percent of trainings. Eighty-six percent of high-intensity intervals met the targeted intensity range (>70-90% of HRmax). Thirty-six percent of the recovery periods were completed with a heart rate above the target range of 50-70% of HRmax. Maximum workload (W) during the incremental exercise test post-training increased significantly compared to the baseline measurements one and two (p = 0.032, effect size r = 0.77 and p = 0.012, r = 0.87).

Conclusion

High-intensity interval training through exergaming is feasible, safe, and shows high usability and acceptance in community dwelling older people. Exergame-driven HIIT had a significant effect on maximum power output on an incremental exercise test. A more extensive exergame intervention period, higher work to recovery ratios as well as a higher-intensity activity should be considered in future projects.

SIX HIT TREADMILL SESSIONS IMPROVE LIPID OXIDATION AND VENTILATORY THRESHOLD INTENSITIES

ABSTRACT Introduction: High-intensity interval training (HIT) has been used as an alternative to cardiorespiratory training performed continuously at submaximal intensity and over long periods. Objectives: Propose a treadmill HIT protocol and verify the influence of six HIT sessions with this protocol on ventilatory anaerobic thresholds (VATs) and substrate oxidation pattern during submaximal continuous exercise (SCE). Methods: Fifteen sporadically active subjects underwent maximal progressive testing before and after six HIT treadmill running sessions to determine peak oxygen uptake (VO2peak), peak velocity (Vpeak), and VATs followed by SCE to determine lipid (LIPox) and carbohydrate (CHOox) oxidation rates. The HIT sessions consisted of eight sets of 60s at 100%Vpeak, interspersed with 75s of passive recovery between sets and a 48h interval between sessions. Results: Our results showed increases in VAT intensities of 4.4% for VAT1 and 8.8% for VAT2, a decrease of 12.8% in CHOox and an increase of 23.7% for LIPox; accordingly, the relative energy derived from LIPox was 20.3% higher after the training period. Vpeak was ~15 km/h, producing intensities corresponding to ~84%VO2peak and ~91%FCpeak over the training period. Conclusion: The proposed protocol produced adaptations and intensities which are similar to those described in the literature, but unlike others, it can be applied in sporadically active individuals. Level of Evidence II; Comparative prospective study.

Effects of high intensity interval training among overweight individuals with psychotic disorders: A randomized controlled trial

Physical activity has been suggested to reduce the high prevalence of metabolic complications in individuals with psychosis. Although high intensity interval training (HIIT) is efficacious in other populations, it remains poorly studied in psychosis.

METHODS

Randomized controlled study comparing the effects of 6 months HIIT supervised program (30-minute treadmill sessions twice a week) to usual-care waiting-list control group. Anthropometric (primary outcome: waist circumference), body composition, blood profile, blood pressure, psychiatric symptoms and global functioning were measured at baseline and 6 months.

RESULTS

Sixty-six individuals with psychosis (62% men; 30.7 ± 7.2 years old; mean BMI: 32.7 ± 5.7 kg/m²) were randomly assigned to either HIIT (n = 38) or control group (n = 28). Mean attendance rate to HIIT sessions was 64%, although 50% dropped-out the intervention before the end. Few minor adverse events were reported. The intent to treat analysis showed no impact of HIIT on waist circumference (p = 0.25). However, in a post-hoc analysis among the compliant participants (>64% of prescribed sessions), significant improvements in waist circumference (-2.94, SE = 1.41, p = 0.04), negative symptoms (PANSS negative -3.7, SE = 1.39; p = 0.01), social (SOFAS +6.16, SE = 1.76, p = 0.001) and global functioning (GAF +5.38, SE = 2.28, p = 0.02) were observed.

DISCUSSION

HIIT seems to be safe and well accepted in overweight individuals with psychosis. Exercise compliance to HIIT is associated with improvements in waist circumference as well as negative symptoms and functioning. Interventions improving attendance are needed.

The Acute Effect of High-Intensity Exercise on Executive Function: A Meta-Analysis

High-intensity exercise has recently emerged as a potent alternative to aerobic regimens, with ramifications for health and brain function. As part of this trend, single sessions of intense exercise have been proposed as powerful, noninvasive means for transiently enhancing cognition. However, findings in this field remain mixed, and a thorough synthesis of the evidence is lacking. Here, we synthesized the literature in a meta-analysis of the acute effect of high-intensity exercise on executive function. We included a total of 1,177 participants and 147 effect sizes across 28 studies and found a small facilitating effect ( d = 0.24) of high-intensity exercise on executive function. However, this effect was significant only compared with rest ( d = 0.34); it was not significant when high-intensity exercise was compared with low-to-moderate intensity exercise ( d = 0.07). This suggests that intense and moderate exercise affect executive function in a comparable manner. We tested a number of moderators that together explained a significant proportion of the between-studies variance. Overall, our findings indicate that high-intensity cardiovascular exercise might be a viable alternative for eliciting acute cognitive gains. We discuss the potential of this line of research, identify a number of challenges and limitations it faces, and propose applications to individuals, society, and policies.

Sustained Muscle Deoxygenation vs. Sustained High VO2 During High-Intensity Interval Training in Sprint Canoe-Kayak

Recent data suggests that peripheral adaptations, i.e., the muscle ability to extract and use oxygen, may be a stronger predictor of canoe-kayak sprint performance compared to VO₂max or central adaptations. If maximizing the time near VO₂max during high-intensity interval training (HIIT) sessions is believed to optimize central adaptations, maximizing the time near maximal levels of muscle desaturation could represent a critical stimulus to optimize peripheral adaptations.

Purpose: Therefore, the purpose of this study was to assess the VO₂, muscle oxygenation and cardiac output responses to various HIIT sessions, and to determine which type of HIIT elicits the lowest muscle oxygenation and the longest cumulated time at low muscle O₂ saturation.

Methods: Thirteen well-trained canoe-kayak athletes performed an incremental test to determine VO₂max and peak power output (PPO), and 4 HIIT sessions (HIIT-15: 40x[15 s at 115%PPO, 15 s at 30%PPO]; HIIT-30: 20x[30 s at 115%PPO, 30 s at 30%PPO]; HIIT-60: 6x[1 min at 130%PPO, 3 min rest]; sprint interval training (SIT): 6x[30 s all-out, 3 min 30 rest]) on a canoe or kayak ergometer. Portable near-infrared spectroscopy monitors were placed on the Latissimus dorsi (LD), Biceps brachii (BB), and Vastus lateralis (VL) during every session to assess changes in muscle O₂ saturation (SmO₂, % of physiological range).

Results: HIIT-15 and HIIT-30 elicited a longer time >90%VO₂max (HIIT-15: 8.1 ± 6.2 min, HIIT-30: 6.8 ± 4.6 min), compared to SIT (1.7 ± 1.3 min, p = 0.006 and p = 0.035) but not HIIT-60 (4.1 ± 1.7 min). SIT and HIIT-60 elicited the lowest SmO₂ in the VL (SIT: 0 ± 1%, HIIT-60: 8 ± 9%) compared to HIIT-15 (26 ± 12%, p < 0.001 and p = 0.007) and HIIT-30 (25 ± 12%, p < 0.001 and p = 0.030). SIT produced the longest time at >90% of maximal deoxygenation in all 3 muscles, with effect sizes ranging from small to very large.

Conclusions: Short HIIT performed on a canoe/kayak ergometer elicits the longest time near VO₂max, potentially conducive to VO₂max improvements, but SIT is needed in order to maximize muscle deoxygenation during training, which would potentially conduct to greater peripheral adaptations.

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.

Acute Demands and Recovery From Common Interval Training Protocols

Elmer, DJ, Barron, EN, and Chavez, JL. Acute demands and recovery from common interval training protocols. J Strength Cond Res XX(X): 000-000, 2019-The definition of interval training is quite broad, with no accepted procedure for classifying protocols with different workloads and work and recovery interval times. In addition, little is known about the differences in training load and recovery from common interval protocols. The purpose of this study was to evaluate the differences in acute physiological demands and perceived difficulty between 3 common interval training protocols and a moderate, continuous exercise session. Eight subjects completed the training sessions on a cycle ergometer in a randomized order, with at least 1 week between sessions: 30-second/4-minute, 1-minute/1-minute, 4-minute/3-minute, and a 45-minute continuous session. Metabolic variables were measured throughout exercise and 30 minutes of recovery. Training impulse (TRIMP), session-RPE, and RPE-training load were also measured. There were significant differences between protocols, including between interval training protocols, for average V[Combining Dot Above]O2 (p < 0.001) and heart rate (HR) (p = 0.02), total O2 consumption (p < 0.001), peak lactate (p < 0.001), TRIMP (p = 0.02), session-RPE (p = 0.01), and RPE-training load (p < 0.001). There were no significant differences between interval training protocols for peak V[Combining Dot Above]O2 or peak HR attained during exercise. There were also no differences in V[Combining Dot Above]O2 or HR after 5 or 30 minutes of recovery. Blood lactate was only significantly higher after 30 minutes of recovery from the 30-second/4-minute compared with the 4-minute/3-minute protocol (p = 0.001) and the 45-minute session (p < 0.001). These findings show a range of differences in acute physiological demands and perceptions from interval training protocols, which should be accounted for when planning training sessions or research studies or when interpreting past research.

Comparison of perceptual responses between different upper-body sprint interval exercise protocols

This study examined the perceptual responses to various upper-body sprint interval exercise (SIE) protocols matched for total work and work/rest ratio. Fourteen active men (24 ± 4 years, BMI = 26.2 ± 2.7 kg/m², body fat = 11.5 ± 4.4%) participated in 3 all-out SIE protocols consisting of battling rope exercise: P10:30 (12 × 10-s bouts with 30-s recovery); P15:45 (8 × 15-s bouts with 45 s recovery); and P30:90 (4 × 30-s bouts with 90-s recovery). During exercise, affective valence (FS +5 to -5), arousal (FAS 1-6), rating of perceived exertion (RPE 6-20), and heart rate (HR) were assessed. Post-exercise, enjoyment, self-efficacy, and intentions were measured. Results revealed a significant decline in FS (p = .02; partial eta squared [η²_p] = 0.27) and a progressive increase in FAS (p = .001; η²_p = 0.86), RPE (p = .001; η²_p = 0.88), and HR (p = .001; η²_p = 0.94), but no protocol X time interaction. Affective valence reached a nadir at values equal to -0.36 ± 3.41 (Cohen's d = -0.49), -0.43 ± 3.75 (Cohen's d = -0.44), and - 0.93 ± 3.49 (Cohen's d = -0.56) in response to P10:30, P15:45, and P30:90, respectively. There were no differences between protocols for enjoyment, intention, or self-efficacy. A negative relationship exhibited between FS and RPE was moderated by participants' tolerance of exercise intensity (β = 1.84, p < .05). Further, the association between FS and future intention was mediated by self-efficacy. Overall, upper-body SIE protocols exhibit similar perceptual responses when volume and work to rest ratio (1:3) are matched. Tolerance of exercise intensity may be used to predict changes in FS during SIE.

Exercise duRing Active Surveillance for prostatE cancer-the ERASE trial: a study protocol of a phase II randomised controlled trial

INTRODUCTION

Active surveillance (AS) is the preferred primary treatment strategy for men with low-risk clinically localised prostate cancer (PCa); however, the majority of these men still receive radical treatment within 10 years due to disease progression and/or fear of cancer progression. Interventions designed to suppress tumour growth, mitigate fear of cancer progression and precondition men for impending radical treatments are an unmet clinical need. Exercise has been shown to delay the progression of prostate tumours in animal models, improve physical and functional health and manage psychological outcomes in cancer patients; however, these outcomes have not been demonstrated in PCa patients undergoing AS.

METHODS AND ANALYSIS

This phase II randomised controlled trial will randomise 66 men undergoing AS to either an exercise group or a usual care group. The exercise group will perform a 12-week, supervised, high-intensity interval training programme, consisting of 3 sessions/week for 28-40 min/session. The primary outcome will be cardiorespiratory fitness. Secondary outcomes will include immunosurveillance and cancer-related biomarkers, psychosocial outcomes including fear of cancer progression and quality of life and physical function. Exploratory outcomes will include clinical indicators of disease progression. The trial has 80% power to detect a significant between-group difference in VO2peak of 3.5 mL/kg/min with a two-tailed alpha level <0.05 and a 10% dropout rate.

ETHICS AND DISSEMINATION

The study has received full ethical approval from the Health Research Ethics Board of Alberta - Cancer Committee (Protocol Number: HREBA.CC-17-0248). The findings of the study will be disseminated through public and scientific channels.

TRIAL REGISTRATION NUMBER

NCT03203460; Pre-results.

Tabata training: one of the most energetically effective high-intensity intermittent training methods

For decades, high-intensity interval/intermittent exercise training methods have been used by elite athletes to improve their performance in sports. One of the most effective training methods, i.e., 'Tabata training,' is reviewed herein from the viewpoint of the energetics of exercise. The prior research describing the metabolic profile and effects of Tabata training is also summarized, with some historical anecdotes.

Effect of interval exercise versus continuous exercise on excess post-exercise oxygen consumption during energy-homogenized exercise on a cycle ergometer

PURPOSE

The purpose of this study was to confirm that the difference in excess post-exercise oxygen consumption (EPOC) during exercise of the spending the same calories between the continuous and interval exercise.

METHODS

Thirty-four healthy college students who did not regularly exercise volunteered to participate in our study. Continuous exercise was performed on an ergometer for 30 min at 60% of maximal oxygen consumption (VO2 max). Interval exercise was performed on a cycle ergometer at 80% VO2 max for 2 min initially, followed by 40% VO2 max for 1 min, and 80% VO2 max for 3 min. This was repeated six times for a total of 26 min.

RESULTS

The major findings were as follows: (1) energy consumption during exercise was not significantly different between continuous exercise and interval exercise groups; (2) EPOC was higher in interval exercise than in continuous exercise for all dependent variables (i.e., total oxygen consumption, total calories, summation of heart rate); and (3) there were no significant differences in the lipid profile between continuous and interval groups.

CONCLUSION

Our study confirmed that after equalizing energy expenditure for continuous and interval exercise on a cycle ergometer in subjects in their twenties, interval exercise results in higher EPOC than continuous exercise. These data suggest that interval exercise may be more effective than continuous exercise in reducing body fat, for a given amount of energy expenditure.

Interval Endurance and Resistance Training as Part of a Community-Based Secondary Prevention Program for Patients With Diabetes Mellitus and Coronary Artery Disease

PURPOSE

High-intensity interval training (HIIT) has been observed to improve health and fitness in patients with cardiovascular disease. High-intensity interval training may not be appropriate in community-based settings. Moderate-intensity interval training (MIIT) and resistance training (RT) are emerging as effective alternatives to HIIT. These have not been well investigated in a community-based cardiac maintenance program.

METHODS

Patients with coronary artery disease and/or diabetes mellitus participated in clinical examinations and a 6-mo exercise program. Center-based MIIT and home-based moderate continuous intensity exercise were performed for 3-5 d/wk for 30-40 min/session. RT, nutritional counseling, coping, and behavioral change strategies were offered to all patients. Within-group changes in clinical metrics and exercise performance were assessed on a per-protocol basis after 6 mo.

RESULTS

Two hundred ninety-two patients (74%) concluded the 6-mo program. There were no serious adverse events. The peak oxygen uptake and peak workload increased significantly, 21.8 ± 6.1 to 22.8 ± 6.3 mL/kg/min and 128 ± 39 to 138 ± 43 W, respectively (both P < .001). Submaximal exercise performance increased from 68 ± 19 to 73 ± 22 W (P < .001). Glycated hemoglobin decreased from 6.57 ± 0.93% to 6.43 ± 0.12%, (P = .023). Daily injected insulin dosage was reduced from 42 IU (interquartile range: 19.0, 60.0) to 26 IU (interquartile range: 0, 40.3, P < .001).

CONCLUSIONS

MIIT and RT were feasible and effective in a community-based cardiac maintenance program for patients with cardiovascular disease, improving exercise performance, and blood glucose control.

Personalized Moderate-Intensity Exercise Training Combined with High-Intensity Interval Training Enhances Training Responsiveness

This study sought to determine if personalized moderate-intensity continuous exercise training (MICT) combined with high-intensity interval training (HIIT) was more effective at improving comprehensive training responsiveness than MICT alone. Apparently healthy, but physically inactive men and women (n = 54) were randomized to a non-exercise control group or one of two 13-week exercise training groups: (1) a personalized MICT + HIIT aerobic and resistance training program based on the American Council on Exercise guidelines, or (2) a standardized MICT aerobic and resistance training program designed according to current American College of Sports Medicine guidelines. Mean changes in maximal oxygen uptake (VO_2max) and Metabolic (MetS) z-score in the personalized MICT + HIIT group were more favorable (p < 0.05) when compared to both the standardized MICT and control groups. Additionally, on the individual level, there were positive improvements in VO_2max (Δ > 4.9%) and MetS z-score (Δ ≤ -0.48) in 100% (16/16) of participants in the personalized MICT + HIIT group. In the present study, a personalized exercise prescription combining MICT + HIIT in conjunction with resistance training elicited greater improvements in VO_2max, MetS z-score reductions, and diminished inter-individual variation in VO_2max and cardiometabolic training responses when compared to standardized MICT.

A 12-Week Pilot Exercise Program for Inactive Adults With Celiac Disease: Study Protocol

Background

Individuals with celiac disease must follow a strict gluten-free diet (GFD) in order to avoid negative short- and long-term health consequences. Unfortunately, many people with celiac disease report poor quality of life (QoL) despite following a strict GFD, and up to 30% still report negative symptoms (eg, gastrointestinal upset).

Purpose

The purpose of the MOVE-C (understanding the relationship between the MicrobiOme, Vitality, and Exercise in Celiac disease) pilot study is to explore the effects of a 12-week supervised progressive high-intensity interval training (HIIT) and lifestyle intervention on physiological, behavioral, and psychosocial outcomes among inactive adults with celiac disease.

Methods/Design: Sixty inactive adults diagnosed with celiac disease will be randomized to HIIT+ or waitlist control (WLC). Participants in the HIIT+ will engage in a 12-week HIIT + lifestyle education program. HIIT sessions will be comprised of 2 workouts per week, working up to 14 × 30-second intervals at 90% maximal heart rate (HRmax) followed by 2 minutes recovery at 50% HRmax. The 6 biweekly lifestyle sessions will involve education on the promotion of a whole foods GFD, sleep hygiene, psychosocial coping skills (eg, self-compassion), and self-regulatory skills to master changes in behaviors. Assessments will occur at pre and post 12-week intervention and 3-month follow-up. WLC participants will be offered a 12-week HIIT program + online lifestyle education sessions after completing the final assessment. The primary outcomes are QoL and gut microbiota composition assessed with 16S rRNA sequencing. The secondary outcomes are markers of metabolic syndrome (waist circumference, fasting glucose, serum lipids, blood pressure, and body composition), gastrointestinal symptoms, sleep quality, adherence to a GFD, exercise behavior, self-regulatory efficacy, and self-compassion. It is hypothesized that participants in the HIIT+ will experience improvements in all outcomes when compared to those in the WLC. These improvements are expected to be maintained at the 3-month follow-up.

Discussion

The findings from this study will advance the knowledge regarding the effects of HIIT and lifestyle education on key outcomes for an at-risk chronic disease population. Furthermore, the findings can be used to inform future programs to improve fitness and physical and mental health outcomes for people with celiac disease.

Sprint interval exercise versus continuous moderate intensity exercise: acute effects on tissue oxygenation, blood pressure and enjoyment in 18-30 year old inactive men

BACKGROUND

Sprint interval training (SIT) can be as effective, or more effective, than continuous moderate intensity exercise (CMIE) for improving a primary risk factor for cardiometabolic disease, low cardiorespiratory fitness (CRF). However, there has been no direct comparison in inactive individuals, of the acute effects of a session of SIT with a work-matched session of CMIE on local oxygen utilisation, which is a primary stimulus for increasing CRF. Furthermore, post-exercise blood pressure (BP) and enjoyment, if symptomatic and low, respectively, have implications for safety and adherence to exercise and have not been compared between these specific conditions. It was hypothesised that in young inactive men, local oxygen utilisation would be higher, while post-exercise BP and enjoyment would be lower for SIT, when compared to CMIE.

METHODS

A total of 11 inactive men (mean ± SD; age 23 ± 4 years) completed a maximal ramp-incremental exercise test followed by two experiment conditions: (1) SIT and (2) work-matched CMIE on a cycle ergometer on separate days. Deoxygenated haemoglobin (∆HHb) in the pre-frontal cortex (FH), gastrocnemius (GN), left vastus lateralis (LVL) and the right vastus lateralis (RVL) muscles, systemic oxygen utilisation (VO2), systolic (SBP) and diastolic (DBP) blood pressure and physical activity enjoyment scale (PACES) were measured during the experiment conditions.

RESULTS

During SIT, compared to CMIE, ∆HHb in FH (p = 0.016) and GN (p = 0.001) was higher, while PACES (p = 0.032) and DBP (p = 0.043) were lower. No differences in SBP and ∆HHb in LVL and RVL were found between conditions.

CONCLUSIONS

In young inactive men, higher levels of physiological stress occurred during SIT, which potentially contributed to lower levels of post-exercise DBP and enjoyment, when compared to CMIE.

Effects of high-intensity interval training on microvascular glycocalyx and associated microRNAs

High-intensity interval training (HIIT) has been proposed to exert vasculoprotective effects. This study aimed to evaluate whether HIIT affects the microvasculature, including the endothelial glycocalyx barrier, and to identify associated microRNAs (miRNAs). Fifty healthy participants (23.1 ± 3.0 yr) performed a 4-wk 4 × 30-s all-out running HIIT. Sidestream dark-field imaging was performed at baseline and follow-up to detect changes of the sublingual microvasculature including the endothelial glycocalyx. Exercise parameters were determined by continuous running field test and documentation of high-intensity runs. miRNAs potentially associated with glycocalyx thickness were selected by structured literature search and blood samples for miRNA, and lactate measurements were drawn at baseline and follow-up HIIT. At baseline, a correlation between maximal exercise performance capacity and glycocalyx thickness (determined by perfused boundary region) was detected ( P = 0.045, r = 0.303). Increased exercise performance at follow-up also correlated with glycocalyx thickness ( P = 0.031, r = 0.416), and increased high-intensity sprinting speed was associated with an increased number of perfused vessels ( P = 0.0129, r = 0.449). Literature search identified miR-143, -96-5p, and -24, which were upregulated by HIIT already at baseline and showed an association with peak blood lactate levels after sprints (all P < 0.05). Moreover, increased baseline miR-143 levels predicted increased glycocalyx thickness at follow-up (AUCmiR-143 = 0.92, 95% confidence interval, 0.81–1.0, P = 0.0008). Elevated resting miR-126 levels after the intervention were associated with cell-free versican mRNA levels. We conclude that HIIT induces changes in the endothelial glycocalyx of the microvasculature. Associated miRNAs such as miR-143 may represent a tool for monitoring early vasculoprotective adaptations to physical activity.

NEW & NOTEWORTHY High-intensity interval training is known to improve health-related fitness in general and in lifestyle-induced chronic diseases. To visualize microvasculature structure and to detect exercise-induced changes, sublingual sidestream dark-field imaging microscopy was used, and circulating miRNAs were measured. This study shows that exercise-induced changes correlate with associated circulating miRNA, which might be useful for monitoring vasculoprotective effects. Furthermore, sidestream dark-field imaging may represent a sensitive tool for the early detection of exercise-induced systemic vascular changes.

Effects of one-legged high-intensity interval training on insulin-mediated skeletal muscle glucose homeostasis in patients with type 2 diabetes

AIM

To examine the effect of high-intensity interval training (HIIT) on glucose clearance rates in skeletal muscle and explore the mechanism within the muscle.

METHODS

Ten males with type 2 diabetes mellitus (T2DM) and ten matched healthy subjects performed 2 weeks of one-legged HIIT (total of eight sessions, each comprised of 10 × 1 minute ergometer bicycle exercise at >80% of maximal heart rate, interspersed with one min of rest). Insulin sensitivity was assessed by an isoglycaemic, hyperinsulinaemic clamp combined with arteriovenous leg balance technique of the trained (T) and the untrained (UT) leg and muscle biopsies of both legs.

RESULTS

Insulin-stimulated glucose clearance in T legs was ~30% higher compared with UT legs in both groups due to increased blood flow in T vs UT legs and maintained glucose extraction. With each training session, muscle glycogen content decreased only in the training leg, and after the training, glycogen synthase and citrate synthase activities were higher in T vs UT legs. No major changes occurred in the expression of proteins in the insulin signalling cascade. Mitochondrial respiratory capacity was similar in T2DM and healthy subjects, and unchanged by HIIT.

CONCLUSION

HIIT improves skeletal muscle insulin sensitivity. With HIIT, the skeletal muscle of patients with T2DM becomes just as insulin sensitive as untrained muscle in healthy subjects. The mechanism includes oscillations in muscle glycogen stores and a maintained ability to extract glucose from the blood in the face of increased blood flow in the trained leg.

Dose-response effects of high-intensity interval neuromuscular exercise training on weight loss, performance, health and quality of life in inactive obese adults: Study rationale, design and methods of the DoIT trial

Obesity is associated with high mortality and morbidity rates and low levels of quality of life among adults globally. It is critical to examine evidence-based practices for developing lifestyle behavioral changes such as physical movement and structured exercise training. The DoIT protocol, a high-intensity interval exercise training (HIIT) program, effectively reduces body mass, alters energy balance, and improves performance of obese adults with a high adherence rate. This study aims to determine the dose-response effects of the DoIT protocol on body composition, health, performance and quality of life in sedentary obese adults. This study will recruit 88 sedentary, obese males and females (BMI 25.0–34.9; 30–50 years) who will be randomly assigned to one of four groups: (i) control (n = 22), (ii) one session/week (n = 22), (iii) two sessions/week (n = 22) or (iv) three sessions/week (n = 22). DoIT will use a supervised, circuit-type (1–3 rounds), functional/neuromotor and progressive exercise program for 12 months. DoIT incorporates 8–12 multi-planar, fundamental and complex, whole body movements and uses bodyweight and alternative exercise modes as a resistance. DoIT utilizes prescribed work-to-rest ratios which will be varied every four weeks. Each session will last less than 30 min. DoIT will be implemented for a year and its effects on body mass and body composition, physical fitness, functional capacity, bone health, leptin, adiponectin, blood lipids, glycemic control, inflammation, oxidative stress and quality of life will be assessed. The outcomes of the proposed study will provide insight on optimal exercise prescription guidelines for such HIIT-type exercise protocols for overweight or obese individuals.

Prevalence and predictors of dropout from high-intensity interval training in sedentary individuals: A meta-analysis

Recent evidence suggests that high-intensity interval training (HIIT) is an effective method to improve fitness and various health markers. However, the tolerability and acceptability of HIIT among sedentary individuals is currently controversially discussed. Therefore, our objective was to investigate the prevalence and predictors of dropout among sedentary individuals in HIIT-based exercise interventions. MEDLINE/PubMed, SPORTDiscus, and Web of Science were searched systematically for relevant articles until 06/2018. Studies included were required to (a) be written in English, (b) include sedentary healthy adults, (c) use some form of HIIT without any complementary intervention, (d) last ≥4 weeks, (e) report detailed description of the applied HIIT protocol, and (f) report data that allow calculation of a dropout rate. Fifty-five studies reporting results from 67 HIIT interventions with 1318 participants met the eligibility criteria. The trim and fill adjusted pooled dropout rate across all interventions was 17.6% (95% confidence interval 14.2-21.5%). Dropout rates were significantly lower in cycling-based interventions compared with studies using running/walking as exercise modality (P < 0.001). Longer session time (β = 0.02, P < 0.05), higher time effort/week (β = 0.005, P < 0.05), and overall time effort/intervention (β = 0.0003, P < 0.05) predicted greater dropout. Exercise intensity was not related to dropout. Our data suggest that HIIT-based interventions are tolerable and acceptable for previously sedentary individuals, exhibiting generally lower dropout rates than commonly reported for traditional exercise programs. Given the association between HIIT volume and dropouts, future studies should further focus on identifying the minimally effective dose of practical HIIT for improving health status. Such efforts would be important to increase implementation and public health impact of HIIT.

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.

School-based physical activity intervention for older adolescents: rationale and study protocol for the Burn 2 Learn cluster randomised controlled trial

INTRODUCTION

This trial aims to investigate the impact of a school-based physical activity programme, involving high-intensity interval training (HIIT), on the physical, mental and cognitive health of senior school students.

METHODS AND ANALYSIS

The Burn 2 Learn (B2L) intervention will be evaluated using a two-arm parallel group cluster randomised controlled trial with allocation occurring at the school level (to treatment or wait-list control). Schools will be recruited in two cohorts from New South Wales, Australia. The trial will aim to recruit ~720 senior school students (aged 16-18 years) from 20 secondary schools (ie, 10 schools per cohort). A range of implementation strategies will be provided to teachers (eg, training, equipment and support) to facilitate the delivery of HIIT sessions during scheduled classes. In phase I and II (3 months each), teachers will facilitate the delivery of at least two HIIT sessions/week during lesson-time. In phase III (6 months), students will be encouraged to complete sessions outside of lesson-time (teachers may continue to facilitate the delivery of B2L sessions during lesson-time). Study outcomes will be assessed at baseline, 6 months (primary end point) and 12 months. Cardiorespiratory fitness (shuttle run test) is the primary outcome. Secondary outcomes include: vigorous physical activity, muscular fitness, cognition and mental health. A subsample of students will (i) provide hair samples to determine their accumulated exposure to stressful events and (ii) undergo multimodal MRI to examine brain structure and function. A process evaluation will be conducted (ie, recruitment, retention, attendance and programme satisfaction).

ETHICS AND DISSEMINATION

This study has received approval from the University of Newcastle (H-2016-0424) and the NSW Department of Education (SERAP: 2017116) human research ethics committees.

TRIAL REGISTRATION NUMBER

ACTRN12618000293268; Pre-results.

Does exercise prescription based on estimated heart rate training zones exceed the ventilatory anaerobic threshold in patients with coronary heart disease undergoing usual-care cardiovascular rehabilitation? A United Kingdom perspective

Background

In the United Kingdom (UK), exercise intensity is prescribed from a fixed percentage range (% heart rate reserve (%HRR)) in cardiac rehabilitation programmes. We aimed to determine the accuracy of this approach by comparing it with an objective, threshold-based approach incorporating the accurate determination of ventilatory anaerobic threshold (VAT). We also aimed to investigate the role of baseline cardiorespiratory fitness status and exercise testing mode dependency (cycle vs. treadmill ergometer) on these relationships.

Design and methods

A maximal cardiopulmonary exercise test was conducted on a cycle ergometer or a treadmill before and following usual-care circuit training from two separate cardiac rehabilitation programmes from a single region in the UK. The heart rate corresponding to VAT was compared with current heart rate-based exercise prescription guidelines.

Results

We included 112 referred patients (61 years (59–63); body mass index 29 kg·m–2 (29–30); 88% male). There was a significant but relatively weak correlation ( r = 0.32; p = 0.001) between measured and predicted %HRR, and values were significantly different from each other ( p = 0.005). Within this cohort, we found that 55% of patients had their VAT identified outside of the 40–70% predicted HRR exercise training zone. In the majority of participants (45%), the VAT occurred at an exercise intensity <40% HRR. Moreover, 57% of patients with low levels of cardiorespiratory fitness achieved VAT at <40% HRR, whereas 30% of patients with higher fitness achieved their VAT at >70% HRR. VAT was significantly higher on the treadmill than the cycle ergometer ( p < 0.001).

Conclusion

In the UK, current guidelines for prescribing exercise intensity are based on a fixed percentage range. Our findings indicate that this approach may be inaccurate in a large proportion of patients undertaking cardiac rehabilitation.

High- or moderate-intensity training promotes change in cardiorespiratory fitness, but not visceral fat, in obese men: A randomised trial of equal energy expenditure exercise

This study compared the effects of two exercise programs performed in different intensities, but equal overall energy expenditure (EE). Adult men with obesity (29.6 ± 4.9 years; BMI = 35.1 ± 3.3 kg/m²) were randomised to one of three groups: High-intensity interval training (HIIT- 10 × 1:1 min 100% VO_2max; n = 13); Moderate-intensity continuous training (MICT - ˜35 min 65% VO_2max; n = 13) or Control (no training; n = 6). The session EE (HIIT = 278.0 ± 37.1; MICT = 299.4 ± 17.8 kcal) was calculated by adding the aerobic contribution (VO₂ of the session minus VO₂ at rest) and anaerobic (difference between the VO₂ estimated and VO₂ measured in session). The anaerobic contribution in HIIT was 30%, showing that a substantial portion of the energy for 10 x 1 min HIIT comes from non-oxidative metabolism. VO_2max improved in both trained groups (p =  0.006), while systolic blood pressure decreased (p <  0.001) and diastolic blood pressure was not altered. Visceral and subcutaneous fat stores did not change after the intervention, indicating a longer intervention may be necessary for changes in adiposity. Six weeks of HIIT or MICT were effective in improving cardiorespiratory fitness and blood pressure in previously inactive obese men.

The greater effect of high-intensity interval training versus moderate-intensity continuous training on cardioprotection against ischemia-reperfusion injury through Klotho levels and attenuate of myocardial TRPC6 expression

BACKGROUND

Myocardial ischemia-reperfusion (IR) injury is a leading cause of death all over the world, so developing practical approaches to promote cardioprotection against IR injury is essential. Exercise training is an effective strategy to improve cardioprotection. Hence, the purpose of this study was to investigate the effect of short-term preconditioning with two types of high-intensity interval training (HIIT) and moderate intensity continuous training (MICT) on klotho and TRPC6 mechanisms in cardioprotection.

METHODS

Eighty Male Wistar rats (250-300 g) were randomly divided into 7 groups, including Control, HIIT, MICT, Sham, IR, HIIT+IR, and MICT+IR. Training was performed in 5 consecutive days. HIIT protocol consisted of running on the treadmill at intervals 85-90% vo2max that separated by slow intensity periods at 50-60% vo2max. MICT program was performed at 70% VO2max at the same running distance with HIIT groups. The cardiac IR injury was induced by LAD occlusion followed by reperfusion. ELISA kit was used in order to measure the plasma levels of klotho, LDH and CK-MB, and TRPC6 expression was determined using the western blot technique. Data were analyzed using one way ANOVA and Tukey's post hoc tests.

RESULTS

The results of this study showed that both types of exercise training programs significantly increase plasma levels of klotho and reduce the infarct size and heart injury. In addition, the exercise training decreased the amount of TRPC6 channels expression during IR. However, the effect of HIIT on increasing the klotho and cardioprotection was greater compared to MICT.

CONCLUSIONS

Based on the results, even a short-term of aerobic exercise training, especially HIIT, promotes cardioprotection against IR injury and decreases infarct size via an increase in klotho and attenuate of protein expression of myocardial TRPC6 during IR.