Impact of 4 weeks of interval training on resting metabolic rate, fitness, and health-related outcomes

High-intensity interval training exercise decreases brain CB1 receptor levels in male and female adult rats

The numerous health benefits of exercise are well-documented, including its efficacy in treating substance use disorders (SUDs). Several exercise regimens have been proposed; however, the most effective regimen for patients with addiction has yet to be elucidated. High-intensity interval training (HIIT) exhibits considerable potential compared to aerobic and resistance exercise. Dopamine signaling is recognized as a key neurobiological mechanism contributing to HIIT's therapeutic potential for SUDs; however, the role of the endocannabinoid system in this context is not well understood. The present study investigated the effects of HIIT exercise on endocannabinoid signaling by measuring cannabinoid receptor 1 (CB1R) binding in the brains of male and female rats using [3H]SR141716A autoradiography. Male and female rats were separated into sedentary and HIIT exercise groups. For six weeks, exercise was completed daily on a treadmill for 30 min (10 3-min intervals) progressively increasing speed to 0.8 mph (21.5 m/min). The HIIT program significantly reduced CB1R binding in both sexes across multiple brain regions, including the striatum, thalamus, and distinct areas of the cortex. Sex differences were observed wherein males exhibited greater CB1R binding than females across brain regions, including the cerebellum, striatum, and parts of the cortex. Males experienced an increase in mean cerebellum CB1R binding due to HIIT, whereas females showed no effect in this region. The results suggest HIIT exercise can modulate endocannabinoid signalling by way of decreased CB1R binding. These findings further support the intensity dependence of endocannabinoid modulation and highlight potential pathways for exercise-induced neurobiological and behavioural change.

Effects of 10 weeks of walking-based exercise training on resting substrate oxidation in postmenopausal women with obesity

BACKGROUND AND AIMS

Accumulating evidence supports the effectiveness of moderate-intensity aerobic training on metabolic health, with limited studies investigating change in resting substrate oxidation. The aim of this study was to explore whether 10 weeks of walking-based aerobic training would alter substrate oxidation in postmenopausal women with obesity.

METHODS AND RESULTS

Twenty-four postmenopausal women with obesity who were assigned into the control (n = 12) or exercise groups (n = 12) undertook a 10-week aerobic training program (3 d·week-1) that involved walking exercises at 50-70% of heart rate reserve on a treadmill, with exercise volume increased from 25 to 40 min·day-1. Resting metabolic rate (RMR) and body composition were measured pre- and post-training. Whole-body substrate oxidation was calculated using respiratory data collected during RMR measurement via indirect calorimetry. No significant change was noted (p > 0.05) in resting fat oxidation and carbohydrate oxidation in the exercise group. Resting respiratory exchange ratio and RMR did not alter in response to the training program (p > 0.05).

CONCLUSION

Our results show that a 10-week of moderate-intensity aerobic training does not modify substrate oxidation in postmenopausal women with obesity.

Effect of different forms of high-intensity interval training on V̇O2max, strength, flexibility, and body fat percentage among middle-aged males

BACKGROUND

High-intensity interval training (HIIT) has become a popular exercise approach due to its potential to elicit significant physiological adaptations. However, limited research has compared the effects of different HIIT modalities on fitness parameters in middle-aged males. This study aimed to determine the effect of different HIIT on V̇O2max, strength, flexibility, and body fat percentage among middle-aged males.

METHODS

Thirty sedentary males aged 40-50 years were randomly assigned to HIIT-Weight Training Circuit (WTC), HIIT-Shuttle Run (SR), or HIIT-Bodyweight Exercise (BWE) groups. Training consisted of 20 sessions over 5 weeks of 4×4 minutes at 90-95% HRmax with 3 minutes recovery at 70% HRmax between intervals. Outcome measures including V̇O2max, strength, flexibility, and body fat percentage were assessed pre- and postintervention.

RESULTS

The result for the Two-Way Mixed ANOVA indicated there was no significant interaction effect between the three training groups. There was no significant main effect for the three training groups, whereas there was a significant effect for the repeated measure time existed. A significant improvement in V̇O2max, strength, flexibility has been shown between post-test and pre-test for the HIIT-SR, HIIT-WTC, and HIIT-BWE group. Whereas A significant decrease has been shown between post and pretest for all the groups in body fat percentage.

CONCLUSIONS

This research findings suggested that different forms of HIIT can elicit differential adaptation in middle-aged males. Incorporating different form of HIIT as HITT-SR, HITT-WTC, and HITT-BWE into exercise program may be an effective way to systematically improve V̇O2max, strength, flexibility, and body composition in middle-age male population. These findings provide guidance on HIIT prescription according to fitness goals.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Protein Supplementation Increases Adaptations to Low-Volume, Intra-Session Concurrent Training in Untrained Healthy Adults: A Double-Blind, Placebo-Controlled, Randomized Trial

Combined endurance and resistance training, also known as "concurrent training", is a common practice in exercise routines. While concurrent training offers the benefit of targeting both cardiovascular and muscular fitness, it imposes greater physiological demands on the body compared to performing each modality in isolation. Increased protein consumption has been suggested to support adaptations to concurrent training. However, the impact of protein supplementation on responses to low-volume concurrent training is still unclear. Forty-four untrained, healthy individuals (27 ± 6 years) performed two sessions/week of low-volume high-intensity interval training on cycle ergometers followed by five machine-based resistance training exercises for 8 weeks. Volunteers randomly received (double-blinded) 40 g of whey-based protein (PRO group) or an isocaloric placebo (maltodextrin, PLA group) after each session. Maximal oxygen consumption (VO2max) and overall fitness scores (computed from volunteers' VO2max and one-repetition maximum scores, 1-RM) significantly increased in both groups. The PRO group showed significantly improved 1-RM in all major muscle groups, while the PLA group only improved 1-RM in chest and upper back muscles. Improvements in 1-RM in leg muscles were significantly greater in the PRO group versus the PLA group. In conclusion, our results indicate that adaptations to low-volume concurrent training, particularly leg muscle strength, can be improved with targeted post-exercise protein supplementation in untrained healthy individuals.

Comparison of Polarized Versus Other Types of Endurance Training Intensity Distribution on Athletes' Endurance Performance: A Systematic Review with Meta-analysis

BACKGROUND

Polarized training intensity distribution (POL) was recently suggested to be superior to other training intensity distribution (TID) regimens for endurance performance improvement.

OBJECTIVE

We aimed to systematically review and meta-analyze evidence comparing POL to other TIDs on endurance performance.

METHODS

PRISMA guidelines were followed. The protocol was registered at PROSPERO (CRD42022365117). PubMed, Scopus, and Web of Science were searched up to 20 October 2022 for studies in adults and young adults for ≥ 4 weeks comparing POL with other TID interventions regarding VO2peak, time-trial (TT), time to exhaustion (TTE) or speed or power at the second ventilatory or lactate threshold (V/P at VT2/LT2). Risk of bias was assessed with RoB-2 and ROBINS-I. Certainty of evidence was assessed with GRADE. Results were analyzed by random effects meta-analysis using standardized mean differences.

RESULTS

Seventeen studies met the inclusion criteria (n = 437 subjects). Pooled effect estimates suggest POL superiority for improving VO2peak (SMD = 0.24 [95% CI 0.01, 0.48]; z = 2.02 (p = 0.040); 11 studies, n = 284; I2 = 0%; high certainty of evidence). Superiority, however, only occurred in shorter interventions (< 12 weeks) (SMD = 0.40 [95% CI 0.08, 0.71; z = 2.49 (p = 0.01); n = 163; I2 = 0%) and for highly trained athletes (SMD = 0.46 [95% CI 0.10, 0.82]; z = 2.51 (p = 0.01); n = 125; I2 = 0%). The remaining endurance performance surrogates were similarly affected by POL and other TIDs: TT (SMD = - 0.01 [95% CI -0.28, 0.25]; z =  - 0.10 (p = 0.92); n = 221; I2 = 0%), TTE (SMD = 0.30 [95% CI - 0.20, 0.79]; z = 1.18 (p = 0.24); n = 66; I2 = 0%) and V/P VT2/LT2 (SMD = 0.04 [95% CI -0.21, 0.29]; z = 0.32 (p = 0.75); n = 253; I2 = 0%). Risk of bias for randomized controlled trials was rated as of some concern and for non-randomized controlled trials as low risk of bias (two studies) and some concerns (one study).

CONCLUSIONS

POL is superior to other TIDs for improving VO2peak, particularly in shorter duration interventions and highly trained athletes. However, the effect of POL was similar to that of other TIDs on the remaining surrogates of endurance performance. The results suggest that POL more effectively improves aerobic power but is similar to other TIDs for improving aerobic capacity.

Exercise snacks are a time-efficient alternative to moderate-intensity continuous training for improving cardiorespiratory fitness but not maximal fat oxidation in inactive adults: a randomized controlled trial

The aims of this study were (1) to determine how stair-climbing-based exercise snacks (ES) compared to moderate-intensity continuous training (MICT) for improving cardiorespiratory fitness (CRF), and (2) to explore whether ES could improve maximal fat oxidation rate (MFO) in inactive adults. Healthy, young, inactive adults (n: 42, age: 21.6 ± 2.3 years, BMI: 22.5 ± 3.6 kg·m-2, peak oxygen uptake (VO2peak): 33.6 ± 6.3 mL·kg-1·min-1) were randomly assigned to ES, MICT, or Control. ES (n = 14) and MICT (n = 13) groups performed three sessions per week over 6 weeks, while the control group (n = 15) maintained their habitual lifestyle. ES involved 3 × 30 s "all-out" stair-climbing (6 flight, 126 steps, and 18.9 m total height) bouts separated by >1 h rest, and MICT involved 40 min × 60%-70% HRmax stationary cycling. A significant group × time interaction was found for relative VO2peak (p < 0.05) with ES significantly increasing by 7% compared to baseline (MD = 2.5 mL·kg-1·min-1 (95% CI = 1.2, 3.7), Cohen's d = 0.44), while MICT had no significant effects (MD = 1.0 mL·kg-1·min-1 (-1.1, 3.2), Cohen's d = 0.17), and Control experienced a significant decrease (MD = -1.7 mL·kg-1·min-1 (-2.9, -0.4), Cohen's d = 0.26). MFO was unchanged among the three groups (group × time interaction, p > 0.05 for all). Stair climbing-based ES are a time-efficient alternative to MICT for improving CRF among inactive adults, but the tested ES intervention appears to have limited potential to increase MFO.

The relationship between resting metabolic rate and quality of life is moderated by age and body composition in women: a cross-sectional study

BACKGROUND

Health-related quality of life (HRQOL) is related to body composition, which is also related to resting metabolic rate (RMR). RMR can be increased by exercise and diet interventions that are not dependent on changes in body composition, so a link between RMR and HRQOL may provide interventions that directly improve HRQOL in women.

METHODS

One hundred twenty women (median age 63.5 [IQR: 53.0-71.0] years) completed one-time measurement of body composition (multi-frequency bioelectrical impedance), RMR (handheld calorimetry), and HRQOL (RAND-36). Physical (PCS) and mental (MCS) composite scores were calculated for the RAND-36. Pearson correlations were used to identify relationships between RMR, body composition, and HRQOL. Variables at the p < .01 level were entered into multiple regression models.

RESULTS

Median body mass index was 26.1 [IQR: 23.2-30.9] kg/m2 and median lean mass index was 16.1 [IQR: 14.6-17.3] kg/m2. Body composition consisted of fat mass (median 27.2 [IQR: 20.3-34.7] kg) and lean mass (median 42.7 [IQR: 38.2-46.9] kg). Median RMR was 1165.0 [IQR: 1022.5-1380.0] kcal/day. Median HRQOL scores were PCS (84.0 [IQR: 74.0-93.0]) and MCS (85.0 [IQR: 74.3-90.0]). RMR was not directly related to PCS, but was directly and negatively related to MCS (p = .002). RMR was significantly and positively related to body composition (lean mass: p < .001; fat mass: p < .001), body mass index (p = .005), and lean mass index (p < .001); but only fat mass (PCS: p < .001; MCS: p < .001) and body mass index (PCS: p < .001; MCS: p < .001) were related to HRQOL, although the relationship was negative. In addition, age was found to be significantly negatively related to RMR (p < .001) and PCS (p = .003). Regression models confirmed the moderating influence of age and body composition on the relationship between RMR and HRQOL. RMR, age, fat mass, and body mass index explained 24% (p < .001) of variance in PCS; and RMR, fat mass, and body mass index explained 15% (p < .001) of variance in MCS.

CONCLUSION

In women, the relationship between RMR and HRQOL is moderated by age and body composition. Understanding these pathways will allow clinicians and researchers to direct interventions more effectively.

Is low-volume high-intensity interval training a time-efficient strategy to improve cardiometabolic health and body composition? A meta-analysis

The present meta-analysis aimed to assess the effects of low-volume high-intensity interval training (LV-HIIT; i.e., ≤5 min high-intensity exercise within a ≤15 min session) on cardiometabolic health and body composition. A systematic search was performed in accordance with PRISMA guidelines to assess the effect of LV-HIIT on cardiometabolic health and body composition. Twenty-one studies (moderate to high quality) with a total of 849 participants were included in this meta-analysis. LV-HIIT increased cardiorespiratory fitness (CRF, SMD = 1.19 [0.87, 1.50]) while lowering systolic blood pressure (SMD = -1.44 [-1.68, -1.20]), diastolic blood pressure (SMD = -1.51 [-1.75, -1.27]), mean arterial pressure (SMD = -1.55 [-1.80, -1.30]), MetS z-score (SMD = -0.76 [-1.02, -0.49]), fat mass (kg) (SMD = -0.22 [-0.44, 0.00]), fat mass (%) (SMD = -0.22 [-0.41, -0.02]), and waist circumference (SMD = -0.53 [-0.75, -0.31]) compared to untrained control (CONTROL). Despite a total time-commitment of LV-HIIT of only 14%-47% and 45%-94% compared to moderate-intensity continuous training and HV-HIIT, respectively, there were no statistically significant differences observed for any outcomes in comparisons between LV-HIIT and moderate-intensity continuous training (MICT) or high-volume HIIT. Significant inverse dose-responses were observed between the change in CRF with LV-HIIT and sprint repetitions (β = -0.52 [-0.76, -0.28]), high-intensity duration (β = -0.21 [-0.39, -0.02]), and total duration (β = -0.19 [-0.36, -0.02]), while higher intensity significantly improved CRF gains. LV-HIIT can improve cardiometabolic health and body composition and represent a time-efficient alternative to MICT and HV-HIIT. Performing LV-HIIT at a higher intensity drives higher CRF gains. More repetitions, longer time at high intensity, and total session duration did not augment gains in CRF.

Cardiorespiratory Fitness and Performance Adaptations to High-Intensity Interval Training: Are There Differences Between Men and Women? A Systematic Review with Meta-Analyses

BACKGROUND

It is important to consider biological sex as a variable that might influence exercise adaptation in order to optimize exercise prescription for men and women.

OBJECTIVE

The aim of this study was to quantify the impact of biological sex on maximal oxygen uptake ([Formula: see text]O2max) and performance outcomes after high-intensity interval training (HIIT).

METHODS

A systematic search and review was conducted by two independent reviewers up to 8 September 2022 using MEDLINE, SPORTDiscus, and Sports Medicine & Education Index in ProQuest. Trials including healthy adults were included if they presented data for or compared male and female [Formula: see text]O2max or performance outcomes in response to HIIT. Performance outcomes included measures of exercise performance and concurrently measured physiological adaptations. Where appropriate, a random-effects, pre-post meta-analysis was undertaken. Data were sub-grouped for men and women, baseline training level, mean age, intervention type, and intervention length. Heterogeneity was assessed using Chi2, Cochran's Q, and Higgins I2 and sensitivity analyses, where required. Study quality was assessed using the Newcastle-Ottawa Scale and publication bias was assessed through visual inspection of funnel plots.

RESULTS

Thirty-three references from 28 trials were included in the review (n = 965; 462 women and 503 men). Meta-analyses included 19 studies for [Formula: see text]O2max, eight for peak power output from [Formula: see text]O2max testing (PPO), and five for threshold power (powerAT). Meta-analyses revealed similar increases in [Formula: see text]O2max in women (g = 0.57; 95% CI 0.44-0.69) and men (g = 0.57; 95% CI 0.42-0.72), and powerAT in women (g = 0.38; 95% CI 0.13-0.64) and men (g = 0.38; 95% CI 0.11-0.64). Raw mean differences for change in [Formula: see text]O2max were Δ 0.32 L·min-1 and 3.50 mL·kg-1·min-1 in men, versus Δ 0.20 L·min-1 and 3.34 mL·kg-1·min-1 for women. No significant sex differences were present for the primary analysis of any outcome. After sub-grouping, significant differences were present for PPO where the effect size was higher for well-trained women (g = 0.37) compared with well-trained men (g = 0.17), and for [Formula: see text]O2max where interventions with a duration of 4 weeks or less had significantly smaller effect sizes compared with those longer than 4 weeks (p < 0.001). Unweighted mean percentage change in [Formula: see text]O2max, PPO, and powerAT across studies was 11.16 ± 7.39%, 11.16 ± 5.99%, and 8.07 ± 6.55% for women, and 10.90 ± 5.75%, 8.22 ± 5.09%, and 7.09 ± 7.17% for men, respectively. Significant heterogeneity was present for both [Formula: see text]O2max and PPO (I2, range: 62.06-78.80%). Sub-grouping by baseline training status and intervention length decreased heterogeneity in most groups. A qualitative synthesis of other outcomes indicated similar improvements in fitness and performance for men and women with some evidence suggesting differences in the mechanisms of adaptation.

LIMITATIONS AND RISK OF BIAS

Publication bias is unlikely to have significantly influenced results for [Formula: see text]O2max or powerAT, but the meta-analysis of PPO could have benefitted from additional study data to strengthen results. The overlap in age categories and sensitivity of the analysis limits the accuracy of the results of the sub-grouping by age.

CONCLUSIONS

Findings indicated no sex-specific differences for any fitness or performance outcomes. Baseline training status and intervention length accounted for most variability in outcomes. PROSPERO registration number: CRD42021272615.

Chronic high-intensity interval training and moderate-intensity continuous training are both effective in increasing maximum fat oxidation during exercise in overweight and obese adults: A meta-analysis

Objective

to (1) systematically review the chronic effect of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on maximal fat oxidation (MFO) in overweight and obese adults, and (2) explore MFO influencing factors and its dose-response relationships with HIIT and MICT.

Methods

Studies using a between-group design involving overweight and obese adults and assessing the effect of HIIT and MICT on MFO were included. A meta-analysis on MFO indices was conducted, and the observed heterogeneities were explored through subgroup, regression, and sensitivity analyses.

Results

Thirteen studies of moderate to high quality with a total of 519 overweight and obese subjects were included in this meta-analysis (HIIT, n = 136; MICT, n = 235; Control, n = 148). HIIT displayed a statistically significant favorable effect on MFO compared to no-training (MD = 0.07; 95%CI [0.03 to 0.11]; I2 = 0%). Likewise, MICT displayed a statistically significant favorable effect on MFO compared to no-training (MD = 0.10; 95%CI [0.06 to 0.15]; I2 = 95%). Subgroup and regression analyses revealed that exercise intensity (Fatmax vs. non-Fatmax; %VO2peak), exercise mode, BMI, and VO2peak all significantly moderated MICT on MFO. When analyzing studies that have directly compared HIIT and MCIT in obese people, it seems there is no difference in the MFO change (MD = 0.01; 95%CI [-0.02 to 0.04]; I2 = 64%). No publication bias was found in any of the above meta-analyses (Egger's test p > 0.05 for all).

Conclusion

Both HIIT and MICT are effective in improving MFO in overweight and obese adults, and they have similar effects. MCIT with an intensity of 65-70% VO2peak, performed 3 times per week for 60 min per session, will optimize MFO increases in overweight and obese adults. Given the lack of studies examining the effect of HIIT on MFO in overweight and obese adults and the great diversity in the training protocols in the existing studies, we were unable to make sound recommendations for training.

Accuracy of Resting Metabolic Rate Prediction Equations in Sport Climbers

Resting metabolic rate (RMR) represents the energy required to maintain vital body functions. In dietary practice, RMR is determined by predictive equations on the basis of using body weight or fat-free mass. Our study aimed to assess whether predictive equations used to estimate RMR are reliable tools for estimating the energy requirements of sport climbers. The study included 114 sport climbers whose RMR was measured with a Fitmate WM. Anthropometric measurements were performed with X-CONTACT 356. The resting metabolic rate was measured by indirect calorimetry and was compared with the RMR estimated by 14 predictive equations on the basis of using body weight/fat-free mass. All equations underestimated RMR in male and female climbers, except for De Lorenzo's equation in the group of women. The De Lorenzo equation demonstrated the highest correlation with RMR in both groups. The results of the Bland-Altman tests revealed an increasing measurement error with increasing metabolism for most of the predictive equations in male and female climbers. All equations had low measurement reliability according to the intraclass correlation coefficient. Compared with the indirect calorimetry measurement results, none of the studied predictive equations demonstrated high reliability. There is a need to develop a highly reliable predictive equation to estimate RMR in sport climbers.

Adaptations to 4 weeks of high-intensity interval training in healthy adults with different training backgrounds

PURPOSE

This study investigated the physical fitness and oxygen uptake kinetics ([Formula: see text]) along with the exercise-onset O₂ delivery (heart rate kinetics, τHR; changes in normalized deoxyhemoglobin/[Formula: see text] ratio, Δ[HHb]/[Formula: see text]) adaptations of individuals with different physical activity (PA) backgrounds responding to 4 weeks of high-intensity interval training (HIIT), and the possible effects of skeletal muscle mass (SMM) on training-induced adaptations.

METHODS

Twenty subjects (10 high-PA level, HIIT-H; 10 moderate-PA level, HIIT-M) engaged in 4 weeks of treadmill HIIT. Ramp-incremental (RI) test and step-transitions to moderate-intensity exercise were performed. Cardiorespiratory fitness, body composition, muscle oxygenation status, VO₂ and HR kinetics were assessed at baseline and post-training.

RESULTS

HIIT improved fitness status for HIIT-H ([Formula: see text], + 0.26 ± 0.07 L/min; SMM, + 0.66 ± 0.70 kg; body fat, - 1.52 ± 1.93 kg; [Formula: see text], - 7.11 ± 1.05 s, p < 0.05) and HIIT-M ([Formula: see text], 0.24 ± 0.07 L/min, SMM, + 0.58 ± 0.61 kg; body fat, - 1.64 ± 1.37 kg; [Formula: see text], - 5.48 ± 1.05 s, p < 0.05) except for visceral fat area (p = 0.293) without between-group differences (p > 0.05). Oxygenated and deoxygenated hemoglobin amplitude during the RI test increased for both groups (p < 0.05) except for total hemoglobin (p = 0.179). The Δ[HHb]/[Formula: see text] overshoot was attenuated for both groups (p < 0.05) but only eliminated in HIIT-H (1.05 ± 0.14 to 0.92 ± 0.11), and no change was observed in τHR (p = 0.144). Linear mixed-effect models presented positive effects of SMM on absolute [Formula: see text] (p < 0.001) and ΔHHb (p = 0.034).

CONCLUSION

Four weeks of HIIT promoted positive adaptations in physical fitness and [Formula: see text] kinetics, with the peripheral adaptations attributing to the observed improvements. The training effects are similar between groups suggesting that HIIT is effective for reaching higher physical fitness levels.

Effects of the intensity of interval training on aerobic fitness, body composition and resting metabolic rate of women with overweight or obesity: A randomized trial

BACKGROUND: Moderate-intensity interval training (MIIT) may be a viable exercise format for improving body composition, aerobic fitness, and health-related variables. OBJECTIVES: This randomized trial aimed to analyze the effect of MIIT or high-intensity interval training (HIIT) on aerobic fitness, body composition variables, and resting metabolic rate (RMR) in women with overweight or obesity. METHODS: 31 sedentary adult women with overweight or obesity performed 7 weeks × 3 weekly sessions of either HIIT or MIIT. Physical and physiological tests were applied before and after training. RESULTS: In both analyses (intention-to-treat and by adherence to the training), aerobic fitness showed a time effect (p= 0.041 and p= 0.015), but without differences between groups (p> 0.05). No group (HIIT vs. MIIT), time (pre vs. post), or interaction effects (group vs. time) were found for RMR, body composition markers (fat mass, body fat percentage, lean mass), or body mass index – BMI (p> 0.05). In addition, MIIT induced a relatively high drop-out rate. CONCLUSIONS: This study suggested that the short-term (7-weeks) interval exercise training was effective for increasing aerobic fitness, and moderate-intensity intervals were as effective as high-intensity intervals. However, neither training format was effective for changing RMR, body composition variables, or BMI of women with overweight or obesity. Clinical trial ID: RBR-9jd7b7.

Effects of high-intensity interval training (HIIT) and sprint interval training (SIT) on fat oxidation during exercise: a systematic review and meta-analysis

OBJECTIVE

To investigate the effects of high-intensity interval training (HIIT) and sprint interval training (SIT) on fat oxidation during exercise (FatOx) and how they compare with the effects of moderate-intensity continuous training (MICT).

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Academic Search Ultimate, CINAHL, Networked Digital Library of Theses and Dissertations, Open Access Theses and Dissertations, OpenDissertations, PubMed/MEDLINE, Scopus, SPORTDiscus and Web of Science.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Studies using a between-group design, involving adult participants who were not trained athletes, and evaluating effects of HIIT or SIT on FatOx (vs no exercise or MICT) were included.

RESULTS

Eighteen studies of fair-to-good quality were included; nine comparing HIIT or SIT with no exercise and eleven comparing HIIT or SIT with MICT. A significant pooled effect of these types of interval training on FatOx was found (mean difference in g/min (MD)=0.08; 95% confidence interval (CI) 0.04 to 0.12; p<0.001). Significant effects were found for exercise regimens lasting ≥4 weeks, and they increased with every additional week of training (β=0.01; 95% CI 0.00 to 0.02; p=0.003). HIIT and/or SIT were slightly more effective than MICT (MD=0.03; 95% CI 0.01 to 0.05; p=0.005). The effects on FatOx were larger among individuals with overweight/obesity.

CONCLUSION

Engaging in HIIT or SIT can improve FatOx, with larger effects expected for longer training regimens and individuals with overweight/obesity. While some effects seem small, they may be important in holistic approaches to enhance metabolic health and manage obesity.

Six sessions of low-volume high-intensity interval exercise improves resting fat oxidation

It remains unclear whether a practical model of low-volume high-intensity interval exercise improves resting fat oxidation (FatOx) which is associated with metabolic health. We aimed to determine the effects of a short-term practical model of high-intensity interval training (HIIT) on resting FatOx in young, healthy males. Thirty healthy males were randomly assigned to either single (HIITsingle; n=13) or double HIIT (HIITdouble; n=17) group. The HIITsingle group trained once a day, 3 days/week for 2 weeks, whilst the HIITdouble group performed 6 sessions of high-intensity exercise over 5 days by exercising twice a day every second day. Both groups completed 6 high-intensity exercise sessions consisting of 10×60 s of cycling at peak power output, interspersed by 75 s cycling at 60 W. With 1% false discovery rate (FDR) significance threshold, resting respiratory exchange ratio similarly decreased in HIITsingle (pre=0.83±0.03 vs post=0.80±0.03) and HIITdouble group (pre=0.82±0.04 vs post=0.80±0.02) [(p=0.001; partial eta squared () =0.310, FDR-adjusted p value=0.005)]. Resting FatOx increased similarly in HIITsingle (pre=1.07±0.39 mg·kg-1 fat free mass (FFM)·min-1 vs post=1.44±0.36 mg·kg-1 FFM·min-1) and HIITdouble group (pre=1.35±0.45 mg·kg-1 FFM·min-1 vs post=1.52±0.29 mg·kg-1 FFM·min-1) [(p<0.001; =0.411, FDR-adjusted p value=0.005)]. Our results demonstrate that only six sessions of a practical model of low-volume high-intensity exercise improves resting FatOx in young, healthy males.

Changes in Fat Oxidation and Body Composition after Combined Exercise Intervention in Sedentary Obese Chinese Adults

(1) Background: Evidence suggests that aerobic exercise and high-intensity interval training (HIIT) might increase fat oxidation and reduce fat. However, limited research has examined the effects of combining progressive aerobic exercise and HIIT interventions in sedentary adults with overweight and obesity, and differences in its effects between men and women remain unclear. The purpose of this study was to investigate the effects of combined progressive aerobic exercise and HIIT (CAEH) on fat oxidation and fat reduction in sedentary Chinese adults and compare sex differences in sedentary adults after seven weeks. (2) Methods: Eighty-four sedentary obese adults were enrolled and allocated to two groups in baseline (experimental (EXP) group:42; control (CON) group:42), and fifty-six subjects (EXP:31; CON:25) completed the experiments and were included in the final analysis. Subjects in the EXP group performed CAEH three times per week for seven weeks. Subjects in the CON group were advised to continue with their normal daily activities. Anthropometric, lipid profile, cardiorespiratory fitness, and fat oxidation outcomes were assessed before and after the intervention. (3) Results: After seven weeks of the CAEH intervention, compared with the CON group, the EXP group showed significant increases in fat oxidation at rest (FO_rest) (+0.03 g/min, p < 0.01), maximal fat oxidation (MFO) (+0.05 g/min, p < 0.01), and maximal oxygen intake (VO₂max) (+3.2 mL/kg/min, p < 0.01). The changes in the percentages of the FO_rest (+57%) and the VO₂max (+16%) were significantly greater (+20%, +6%) in males than in females (p < 0.05, p < 0.05). The body mass index (BMI) (−1.2 kg/m², p < 0.01), body fat percentage (−3.2%, p < 0.001), visceral fat area (−12.8 cm², p < 0.001), and total cholesterol (TC) levels (−0.4 mmol/L, p < 0.05) were significantly decreased in the EXP group. (4) Conclusions: Seven weeks of the CAEH intervention effectively improved FO_rest, MFO, and VO₂max in sedentary obese adults, and the improvements in FO_rest and VO₂max were more pronounced in males than in females. CAEH also improved body composition and TC levels in sedentary obese adults.

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.

Six high-intensity interval training sessions over 5 days increases maximal oxygen uptake, endurance capacity, and sub-maximal exercise fat oxidation as much as 6 high-intensity interval training sessions over 2 weeks

BACKGROUND

High-intensity interval training (HIIT) induces similar or even superior adaptations compared to continuous endurance training. Indeed, just 6 HIIT sessions over 2 weeks significantly improves maximal oxygen uptake (VO_2max), submaximal exercise fat oxidation, and endurance performance. Whether even faster adaptations can be achieved with HIIT is not known. Thus, we aimed to determine whether 2 sessions of HIIT per day, separated by 3 h, every other day for 5 days (double HIIT (HIIT-D), n = 15) could increase VO_2max, submaximal exercise fat oxidation, and endurance capacity as effectively as 6 sessions of HIIT over 2 weeks (single HIIT (HIIT-S), n = 13).

METHODS

Each training session consisted of 10 × 60 s of cycling at 100% of VO_2max interspersed with 75 s of low-intensity cycling at 60 watt (W). Pre- and post-training assessments included VO_2max, time to exhaustion at ∼80% of VO_2max, and 60-min cycling trials at ∼67% of VO_2max.

RESULTS

Similar increases (p < 0.05) in VO_2max (HIIT-D: 7.7% vs. HIIT-S: 6.0%, p > 0.05) and endurance capacity (HIIT-D: 80.1% vs. HIIT-S: 79.2%, p > 0.05) were observed. Submaximal exercise carbohydrate oxidation was reduced in the 2 groups after exercise training (HIIT-D: 9.2%, p = 0.014 vs. HIIT-S: 18.8%, p = 0.012) while submaximal exercise fat oxidation was significantly increased in HIIT-D (15.5%, p = 0.048) but not in HIIT-S (9.3%, p = 0.290).

CONCLUSION

Six HIIT sessions over 5 days was as effective in increasing VO_2max and endurance capacity and was more effective in improving submaximal exercise fat oxidation than 6 HIIT sessions over 2 weeks.

The Effect of Short-Term Wingate-Based High Intensity Interval Training on Anaerobic Power and Isokinetic Muscle Function in Adolescent Badminton Players

Badminton requires both aerobic fitness and anaerobic ability for high performance. High intensity interval training (HIIT) is a traditional training method for improving fitness. In this study, we investigated whether short-term Wingate-based HIIT is effective for improving anaerobic activity in youth badminton players. Participants included 32 total badminton players in middle school and high school. They were divided into two groups (HIIT and moderate continuous training (MCT)). Training occurred for 4 weeks in total, three times a week, for 30 min each session. A body composition test, isokinetic knee muscle function test (60°/s, 240°/s), Wingate anaerobic power test (30 s × 5 sets), and analysis of heart rate changes were undertaken before and after training. After 4 weeks, body fat decreased in the HIIT group (p = 0.019); they also showed superior anaerobic ability compared to the MCT group. Differences were statistically significant in 3-4 sets (three sets, p = 0.019; four sets, p = 0.021). Regarding fatigue, the HIIT group showed superior fatigue improvement after training and better fatigue recovery ability in 3~5 sets (three sets, p = 0.032; four sets, p = 0.017; five sets, p = 0.003) than the MCT group. Neither group exhibited changes in heart rate during the anaerobic power test after training. Both groups improved in terms of isokinetic knee muscle function at 60°/s with no differences. However, at 240°/s, the HIIT group showed a statistically significant improvement (p = 0.035). Therefore, HIIT for 4 weeks improved the athletes' performance and physical strength.

Effectiveness of HIIE versus MICT in Improving Cardiometabolic Risk Factors in Health and Disease: A Meta-analysis

PURPOSE

We aimed to investigate differences between high-intensity interval exercise (HIIE, including high-intensity interval training and sprint interval training) and moderate-intensity continuous training (MICT) on physical fitness, body composition, blood pressure, blood lipids, insulin and glucose metabolism, inflammation, and endothelial function.

METHODS

Differences between HIIE and MICT were summarized using a random-effects meta-analysis on the effect size (Cohen's d). A meta-regression was conducted using the following subgroups: population, age, training duration, men ratio, exercise type, baseline values (clinical relevant ranges), and type of HIIE. Studies were included if at least one of the following outcomes were reported: maximal oxygen uptake (V˙O2max), flow-mediated dilation (FMD), body mass index (BMI), body mass, percent body fat, systolic and diastolic blood pressure, high-density lipoprotein (HDL), low-density lipoprotein (LDL), triglycerides, total cholesterol, C-reactive protein (CRP), fasting glucose and insulin, glycated hemoglobin (HbA1c), and insulin resistance (HOMA-IR). A total of 55 studies were included.

RESULTS

Overall, HIIE was superior to MICT in improving V˙O2max (d = 0.40, P < 0.001) and FMD (d = 0.54, P < 0.05). Oppositely, MICT was superior to HIIE in improving HbA1c (d = -0.27, P < 0.05). No differences were observed in BMI (d = -0.02), body mass (d = -0.05), percent body fat (d = 0.04), systolic blood pressure (d = -0.04), diastolic blood pressure (d = 0.03), HDL (d = -0.05), LDL (d = 0.08), triglycerides (d = 0.03), total cholesterol (d = 0.14), CRP (d = -0.11), fasting insulin (d = 0.02), fasting glucose (d = 0.02), and HOMA-IR (d = -0.04). Moderator analyses indicated that the difference between HIIE and MICT was affected by different subgroups.

CONCLUSION

Overall, HIIE showed to be more effective in improving cardiovascular health and cardiorespiratory fitness, whereas MICT was superior in improving long-term glucose metabolism. In the process of personalized training counseling, health-enhancing effects of exercise training may be improved by considering the individual risk profiles.

The sub-acute effects of high-intensity interval training in healthy young adults: respiratory parameters, aerobic capacity and perceived stress

BACKGROUND

Although the effects of sub-maximal continuous aerobic training (SCT) and high-intensity interval training (HIIT) are well studied in performance athletes and in several patient groups, there is not much evidence about the effects of these exercises in sedentary healthy young population. The aim of the study was to compare the effects of these two different types of aerobic exercises on respiratory parameters, aerobic capacity and perceived stress in healthy university students.

METHODS

Thirty-six healthy, young subjects with a mean age of 20.83±0.97 years were included in the study (N.=19 in HIIT and N.=17 in SCT). Pulmonary function tests (PFTs) and respiratory muscle strength (RMS) assessments were done using a desktop spirometer. Aerobic capacity was estimated with the Bruce treadmill exercise test. The Perceived Stress Scale (PSS) was used for the assessment of stress perception. All participants exercised 3 times per week for 4 weeks (a total of 12 sessions).

RESULTS

After 12 sessions, the peak expiratory flow parameter (a PFT value) of both groups showed significant increases, but there was no difference between the groups. The RMS of the subjects increased significantly in both the groups (P<0.05), but there was no significant difference between the groups. Both groups showed significant increases in terms of aerobic capacity (P>0.05), and the improvement was significantly higher in the HIIT group. Perceived stress values showed a significant increase in the SCT group.

CONCLUSIONS

Based on the results of this study, the two exercise types were found to have similar effects on RMS. Also, when compared with SCT, HIIT was found to have more effect on aerobic capacity.

Influence of Acute and Chronic Exercise on Abdominal Fat Lipolysis: An Update

Exercise is a powerful and effective preventive measure against chronic diseases by increasing energy expenditure and substrate mobilization. Long-duration acute exercise favors lipid mobilization from adipose tissue, i.e., lipolysis, as well as lipid oxidation by skeletal muscles, while chronic endurance exercise improves body composition, facilitates diet-induced weight loss and long-term weight maintenance. Several hormones and factors have been shown to stimulate lipolysis in vitro in isolated adipocytes. Our current knowledge supports the view that catecholamines, atrial natriuretic peptide and insulin are the main physiological stimuli of exercise-induced lipolysis in humans. Emerging evidences indicate that contracting skeletal muscle can release substances capable of remote signaling to organs during exercise. This fascinating crosstalk between skeletal muscle and adipose tissue during exercise is currently challenging our classical view of the physiological control of lipolysis, and provides a conceptual framework to better understand the pleotropic benefits of exercise at the whole-body level.

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.

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.

Metabolic rate in sedentary adults, following different exercise training interventions: The FIT-AGEING randomized controlled trial

BACKGROUND & AIMS

This study compares the influence of different exercise training programs on basal metabolic rate (BMR) and fat oxidation, in basal conditions (BFox) and during exercise (MFO), in sedentary, middle-aged adults.

METHODS

The study subjects of this 12 week-long, randomised controlled trial, were 71 middle-aged adults (age 53.5 ± 4.9 years; 52% women). Subjects were randomly assigned to one of the following groups: (1) no exercise, (2) concurrent training based on international physical activity recommendations (PAR group), (3) high intensity interval training (HIIT group), and (4) high intensity interval training plus whole-body electromyostimulation (HIIT + EMS group). Subject BMR, BFox and MFO were determined by indirect calorimetry before and after the intervention.

RESULTS

The HIIT + EMS subjects showed significant increases in BFox following the intervention compared with the control group (all P = 0.043); no such differences were seen in the PAR and HIIT compared with the control group (all P ≥ 0.1). A significant increase in post-intervention MFO was noted for the HIIT and HIIT + EMS group compared to the non-exercise control group (P < 0.05); no such difference was seen in the PAR group compared to the control group (all P ≥ 0.05).

CONCLUSIONS

Twelve weeks of high intensity interval training plus whole-body electromyostimulation may increase the BFox and MFO of middle-aged sedentary adults. These findings have important clinical implications; a well-designed high-intensity interval training program plus whole-body electromyostimulation might be followed to help combat the appearance of chronic metabolic diseases characterized by metabolic inflexibility in middle-aged sedentary adults, though it will be necessary to determine how long the effects last.

Does caffeine ingestion before a short-term sprint interval training promote body fat loss?

We investigated the effect of caffeine ingestion combined with a 2-wk sprint interval training (SIT) on training-induced reductions in body adiposity. Twenty physically-active men ingested either 5 mg/kg of cellulose as a placebo (PLA, n=10) or 5 mg/kg of caffeine (CAF, n=10) 60 min before each SIT session (13×30 s sprint/15 s of rest). Body mass and skinfold thickness were measured pre- and post-training. Energy expenditure was measured at rest, during exercise, and 45 min after exercise in the first SIT session. Body fat was similar between PLA and CAF groups at pre-training (P>0.05). However, there was a significant decrease in body fat after training in the CAF group (−5.9±4.2%, P<0.05) but not in PLA (1.5±8.0%, P>0.05). There was no difference in energy expenditure at rest and during exercise between PLA and CAF groups (P>0.05), but the post-exercise energy expenditure was 18.3±21.4% greater in the CAF than in the PLA group (P<0.05). In conclusion, caffeine ingestion before SIT sessions induced a body fat loss that may be associated with higher post-exercise energy expenditure.

High-Intensity Interval Training in Cardiac Rehabilitation: Impact on Fat Mass in Patients With Myocardial Infarction

OBJECTIVE

To examine the effect of high-intensity interval training (HIIT) on body fat mass and distribution in patients with myocardial infarction (MI) who underwent cardiac rehabilitation (CR).

PATIENTS AND METHODS

We retrospectively screened 391 consecutive patients with MI enrolled in CR between September 1, 2015, and February 28, 2018. We included 120 patients who completed 36 CR sessions and underwent pretest-posttest dual-energy x-ray absorptiometry; 90 engaged in HIIT, and 30 engaged in moderate-intensity continuous training (MICT). High-intensity interval training included 4 to 8 alternating intervals of high- (30-60 seconds at a rating of perceived exertion [RPE] of 15-17 [Borg scale range, 6-20]) and low-intensity (1-5 minutes at RPE <14), and MICT performed for 20 to 45 minutes of exercise at an RPE of 12 to 14. Body weight, fat mass, and lean mass were measured via dual-energy x-ray absorptiometry with lipid profile measured via clinical procedures.

RESULTS

The HIIT and MICT groups were similar in age (67 vs 67 years), sex (26.7% [24 of 90 patients in the HIIT group] vs 26.7% [8 of 30 in the MICT group), and body mass index (30.3 vs 29.5 kg/m²) at baseline. The HIIT group had greater reductions in body fat percentage (P<.001), fat mass (P<.001), abdominal fat percentage (P<.001), waist circumference (P=.01), total cholesterol (P=.002), low-density lipoprotein cholesterol (P<.001), and triglycerides (P=.006). Improvements in total body mass and body mass index were not different across groups. After matching exercise duration, exercise intensity, and energy expenditure, HIIT-induced improvements in total fat mass (P=.02), body fat percentage (P=.01), and abdominal fat percentage (P=.02) persisted.

CONCLUSION

Our data suggest that supervised HIIT results in significant reductions in total fat mass (P<.001) and abdominal fat percentage (P<.001) and improved lipid profile in patients with MI who undergo CR.

High-intensity interval training improves metabolic syndrome and body composition in outpatient cardiac rehabilitation patients with myocardial infarction

BACKGROUND

To examine the effect of high-intensity interval training (HIIT) on metabolic syndrome (MetS) and body composition in cardiac rehabilitation (CR) patients with myocardial infarction (MI).

METHODS

We retrospectively screened 174 consecutive patients with MetS enrolled in CR following MI between 2015 and 2018. We included 56 patients who completed 36 CR sessions and pre-post dual-energy X-ray absorptiometry. Of these patients, 42 engaged in HIIT and 14 in moderate-intensity continuous training (MICT). HIIT included 4-8 intervals of high-intensity (30-60 s at RPE 15-17 [Borg 6-20]) and low-intensity (1-5 min at RPE < 14), and MICT included 20-45 min of exercise at RPE 12-14. MetS and body composition variables were compared between MICT and HIIT groups.

RESULTS

Compared to MICT, HIIT demonstrated greater reductions in MetS (relative risk = 0.5, 95% CI 0.33-0.75, P < .001), MetS z-score (- 3.6 ± 2.9 vs. - 0.8 ± 3.8, P < .001) and improved MetS components: waist circumference (- 3 ± 5 vs. 1 ± 5 cm, P = .01), fasting blood glucose (- 25.8 ± 34.8 vs. - 3.9 ± 25.8 mg/dl, P < .001), triglycerides (- 67.8 ± 86.7 vs. - 10.4 ± 105.3 mg/dl, P < .001), and diastolic blood pressure (- 7 ± 11 vs. 0 ± 13 mmHg, P = .001). HIIT group demonstrated greater reductions in body fat mass (- 2.1 ± 2.1 vs. 0 ± 2.2 kg, P = .002), with increased body lean mass (0.9 ± 1.9 vs. - 0.9 ± 3.2 kg, P = .01) than the MICT. After matching for exercise energy expenditure, HIIT-induced improvements persisted for MetS z-score (P < .001), MetS components (P < .05), body fat mass (P = .002), body fat (P = .01), and lean mass (P = .03).

CONCLUSIONS

Our data suggest that, compared to MICT, supervised HIIT results in greater improvements in MetS and body composition in MI patients with MetS undergoing CR.

Energy Expenditure and Intensity of Group-Based High-Intensity Functional Training: A Brief Report

Background

High-intensity functional training (HIFT) may offer an attractive, time-efficient alternative to traditional aerobic exercise. However, limited information is available in the literature regarding HIFT meeting exercise guidelines for energy expenditure (improve health outcomes: ≥1000 kcal/wk; weight management: ≥2000 kcal/wk) and level of intensity (moderate: 3-6 metabolic equivalents [METs], vigorous: ≥6 METs) elicited by this approach. Thus, the primary aim was to objectively measure energy expenditure and intensity of HIFT sessions.

Methods

\Energy expenditure was assessed in 20 adults (18-50 y, 50% females). The HIFT session format included the following segments: warm-up (∼5 min), exercise (∼35 min), and cooldown (∼5 min). Participant oxygen consumption (COSMED, L/min and mL/kg/min), heart rate (Polar RS400), and physical activity (ActiGraph GT3X+) were collected in 15-second intervals. Average kcal per minute, METs, total kcal per session, and percent maximum heart rate (HR_max) were calculated.

Results

METs ranged from 5.5 to 11.6 for the complete session (including warm-up and cooldown). Participant's HR_max was ∼80% (range: 69%-100%). Average energy expenditure was ∼485 kcal per session (∼1400 kcal/wk). The vigorous-intensity exercise portion (∼35 min) contributed to 80% of total energy expenditure.

Conclusions

HIFT has the potential to meet the recommendations for exercise to improve health outcomes.

Effects of a short-term of whole-body, high-intensity, intermittent training program on morphofunctional parameters

BACKGROUND

Few studies have analyzed the application of high-intensity interval training (HIIT) using exercises with body weight among the morphofunctional parameters.

AIM

To analyze and compare the effects of six weeks of high-intensity intermittent calisthenic training (HIICT) and moderate intensity, continuous exercise (MICT) on body composition, hypertrophy, and strength.

MATERIALS AND METHODS

Twenty-five active, healthy adults were randomized in either the HIIT group (n = 14) or the MICT group (n = 11). The HIIT group performed high-intensity intermittent calisthenic training based on full body exercise. The training session involved 5 min of warm-up followed by 20 sets of 30s all-out exercise and 30 s of passive recovery between sets. Jumping jack, mountain climber, burpee and squat jump were used. The MICT group performed continuous moderate running (5 min of warm-up followed by 20 min of running with intensity fixed at 80% of maximum heart rate). Training for both groups was performed three times weekly on nonconsecutive days. All subjects underwent anthropometric measurements and functional tests. Muscle thickness was also measured.

RESULTS

There were no significant changes observed in any anthropometric measurements in both groups. Regarding the functional tests, the analysis of the percentage changes revealed advantages of HIICT over MICT in push-ups only (p = 0.02). The muscular thickness of lower and upper limbs did not present significant differences in the pre- and post-times or between groups (p > 0.05).

CONCLUSION

When compared to MICT, HIIT improved push-up effects, without generating significant changes in body composition and muscle thickness.

Contextualising Maximal Fat Oxidation During Exercise: Determinants and Normative Values

Using a short-duration step protocol and continuous indirect calorimetry, whole-body rates of fat and carbohydrate oxidation can be estimated across a range of exercise workloads, along with the individual maximal rate of fat oxidation (MFO) and the exercise intensity at which MFO occurs (Fatmax). These variables appear to have implications both in sport and health contexts. After discussion of the key determinants of MFO and Fatmax that must be considered during laboratory measurement, the present review sought to synthesize existing data in order to contextualize individually measured fat oxidation values. Data collected in homogenous cohorts on cycle ergometers after an overnight fast was synthesized to produce normative values in given subject populations. These normative values might be used to contextualize individual measurements and define research cohorts according their capacity for fat oxidation during exercise. Pertinent directions for future research were identified.

Lifestyle Intervention Program for Amelioration of Dysmetabolism in Overweight Women

Overweight and obesity, a cluster of multiple risk factors for atherosclerosis such as elevated blood pressure, elevated glucose level, and dyslipidemia, increase the risk of all-cause mortality and cardiovascular morbidity and mortality. Physical activity and a proper diet are essential preventive measures. The aim of the study was to evaluate the effects of a two-month intervention program consisting of a low-caloric diet (1,500 kcal) and increased physical activity on the anthropometric parameters, body composition, resting metabolic rate, and maximum oxygen uptake. The study was conducted in 22 women aged 20-38 with diagnosed overweight or obesity. We found that after completing the eight-week-long intervention program, there were significant changes in body composition, consisting of a smaller proportion of body fat and increased lean body mass. Further, we observed a decrease in body weight by 4.3 ± 2.5 kg (p < 0.01), a reduction in waist and hip circumference of 2.6 ± 4.5 cm (p < 0.01) and 4.4 ± 2.9 cm (p < 0.01), respectively, and an increase in maximum oxygen uptake by about 5.2 ± 8.4 ml/kg/min (p < 0.01). We conclude that the intervention program consisting of counseling on diet and physical activity may be highly motivational for patients with excess body weight and care givers should give it a try before commencing more aggressive psychopharmacological therapies.

Energy compensation after sprint- and high-intensity interval training

Background

Many individuals lose less weight than expected in response to exercise interventions when considering the increased energy expenditure of exercise (ExEE). This is due to energy compensation in response to ExEE, which may include increases in energy intake (EI) and decreases in non-exercise physical activity (NEPA). We examined the degree of energy compensation in healthy young men and women in response to interval training.

Methods

Data were examined from a prior study in which 24 participants (mean age, BMI, & VO₂max = 28 yrs, 27.7 kg•m^-2, and 32 mL∙kg^-1∙min^-1) completed either 4 weeks of sprint-interval training or high-intensity interval training. Energy compensation was calculated from changes in body composition (air displacement plethysmography) and exercise energy expenditure was calculated from mean heart rate based on the heart rate-VO₂ relationship. Differences between high (≥ 100%) and low (< 100%) levels of energy compensation were assessed. Linear regressions were utilized to determine associations between energy compensation and ΔVO₂max, ΔEI, ΔNEPA, and Δresting metabolic rate.

Results

Very large individual differences in energy compensation were noted. In comparison to individuals with low levels of compensation, individuals with high levels of energy compensation gained fat mass, lost fat-free mass, and had lower change scores for VO₂max and NEPA. Linear regression results indicated that lower levels of energy compensation were associated with increases in ΔVO₂max (p < 0.001) and ΔNEPA (p < 0.001).

Conclusions

Considerable variation exists in response to short-term, low dose interval training. In agreement with prior work, increases in ΔVO₂max and ΔNEPA were associated with lower energy compensation. Future studies should focus on identifying if a dose-response relationship for energy compensation exists in response to interval training, and what underlying mechanisms and participant traits contribute to the large variation between individuals.

Changes in fat oxidation in response to various regimes of high intensity interval training (HIIT)

Increased whole-body fat oxidation (FOx) has been consistently demonstrated in response to moderate intensity continuous exercise training. Completion of high intensity interval training (HIIT) and its more intense form, sprint interval training (SIT), has also been reported to increase FOx in different populations. An explanation for this increase in FOx is primarily peripheral adaptations via improvements in mitochondrial content and function. However, studies examining changes in FOx are less common in response to HIIT or SIT than those determining increases in maximal oxygen uptake which is concerning, considering that FOx has been identified as a predictor of weight gain and glycemic control. In this review, we explored physiological and methodological issues underpinning existing literature concerning changes in FOx in response to HIIT and SIT. Our results show that completion of interval training increases FOx in approximately 50% of studies, with the frequency of increased FOx higher in response to studies using HIIT compared to SIT. Significant increases in β-HAD, citrate synthase, fatty acid binding protein, or FAT/CD36 are likely responsible for the greater FOx seen in these studies. We encourage scientists to adopt strict methodological procedures to attenuate day-to-day variability in FOx, which is dramatic, and develop standardized procedures for assessing FOx, which may improve detection of changes in FOx in response to HIIT.