Effects of sprint interval training on VO2max and aerobic exercise performance: A systematic review and meta-analysis

Acute and Chronic Effects of Interval Aerobic Exercise on Hepcidin, Ferritin, and Liver Enzymes in Adolescents With Beta-Thalassemia Major

PURPOSE

This study aimed to determine the acute and chronic effects of interval aerobic exercise on hepcidin, ferritin, and liver enzymes in adolescents with beta-thalassemia major.

METHODS

Twenty-six beta-thalassemia major adolescents referred to the Thalassemia Clinic and Research Center were selected as study participants and randomly divided into control (n = 13) and training (n = 13) groups. Participants performed 3 sessions per week for 45 minutes in each session for 8 weeks of aerobic interval exercise with an intensity of 50% to 65% of the heart rate reserve. Blood samples were taken before, immediately after the exercise session, and 48 hours after the last training session, and liver enzymes aspartate aminotransferase, alanine aminotransferase (ALT), alkaline phosphatase (ALP), ferritin, and hepcidin were evaluated.

RESULTS

The results showed a decrease in aspartate aminotransferase, ALT, ALP, ferritin, and hepcidin levels due to 8 weeks of aerobic interval training (P = .14, P = .97, P = .03, P < .001, P < .001; respectively). Intergroup changes in all variables except ALT and hepcidin were significant (P < .05). Besides, acute aerobic exercise increased levels of aspartate aminotransferase, ALT, ferritin, and hepcidin (P = .04, P = .52, P < .001, P < .001; respectively), whereas ALP levels decreased (P < .001). In addition, changes in ALP and hepcidin levels were significant between the 2 groups (P = .05, P < .001; respectively).

CONCLUSION

Based on the study's results, it can be concluded that 8 weeks of aerobic interval training can decrease ferritin and hepcidin levels, but acute aerobic exercise increases them.

Effects of combining a high-intensity interval training programme with a standard programme on mobility and function in lower limb amputees

High-energy expenditure during walking is one of the most important limiting factors for lower limb amputees. Although several physical training methods have been proposed to reduce energy expenditure, little is known about the effects of high-intensity interval training in lower limb amputees. This study aimed to test the effects of a 6-week high-intensity interval training protocol in subjects with lower limb amputation on walking distance, physiological cost of walking, and functional mobility. A quasi-experimental pre and post-study included 13 subjects with lower limb amputation. They performed 12 sessions of a high-intensity interval training protocol with a frequency of 2 days/week for 6 weeks. Walking distance, physiological cost of walking, and functional mobility before and after the training protocol were assessed. Walking distance increased from 204.48 to 229.09 m ( P  = 0.003), physiological cost of walking decreased from 0.66 to 0.31 beats/m ( P  = 0.001), and functional mobility improved from 30.38 to 33.61 points ( P  = 0.001). High-intensity interval training improved walking distance, physiological cost of walking, and functional mobility in subjects with lower limb amputation.

The effects of high-intensity interval training versus moderate-intensity continuous training on athletes' aerobic endurance performance parameters

OBJECTIVE

To systematically evaluate and meta-analyze the effects of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on athletes of aerobic endurance performance parameters.

METHODS

PubMed, Web of Science, EBSCO, Embase, and Cochrane databases were searched. The assessment of quality was conducted employing The Cochrane Risk of Bias Assessment Tool, while heterogeneity examination and subgroup analysis were performed. Moreover, regression and sensitivity analyses were executed.

RESULTS

There was no significant difference between the effects of HIIT and MICT on the enhancement of athletes' running economy (RE) (P > 0.05); 1-3 weeks and 4-9 weeks of HIIT were more effective in improving athletes' maximum oxygen uptake (VO2max) (P < 0.05), and 10 weeks and above were not significant (P > 0.05); 1-3 weeks of HIIT was more effective in improving athletes' anaerobic threshold (AT) (P < 0.05), and 4-10 weeks was not significant (P > 0.05); 3 weeks of high-intensity interval training (HIIT) did not significantly enhance athletes' minute ventilation (VE) (P > 0.05), whereas a duration of 6-10 weeks yielded superior results (P < 0.05); 8 weeks of moderate-intensity continuous training (MICT) did not significantly enhance athletes' hemoglobin (Hb) level (P > 0.05), whereas a duration of 2-3 weeks yielded superior results (P < 0.05).

CONCLUSIONS

(1) HIIT and MICT have similar effects on enhancing athletes' RE. (2) 6-9 weeks' HIIT was more effective in improving athletes' VO2max and VE, and 3 weeks' HIIT was more effective in improving athletes' AT. (3) Within 3 weeks, MICT was more effective in improving the Hb level of athletes.

REGISTRATION NUMBER ON PROSPERO

CRD42024499039.

A training goal-oriented categorization model of high-intensity interval training

There are various categorization models of high-intensity interval training (HIIT) in the literature that need to be more consistent in definition, terminology, and concept completeness. In this review, we present a training goal-oriented categorization model of HIIT, aiming to find the best possible consensus among the various defined types of HIIT. This categorization concludes with six different types of HIIT derived from the literature, based on the interaction of interval duration, interval intensity and interval:recovery ratio. We discuss the science behind the defined types of HIIT and shed light on the possible effects of the various types of HIIT on aerobic, anaerobic, and neuromuscular systems and possible transfer effects into competition performance. We highlight various research gaps, discrepancies in findings and not yet proved know-how based on a lack of randomized controlled training studies, especially in well-trained to elite athlete cohorts. Our HIIT "toolbox" approach is designed to guide goal-oriented training. It is intended to lay the groundwork for future systematic reviews and serves as foundation for meta-analyses.

The Standard Error/Standard Deviation Mix-Up: Potential Impacts on Meta-Analyses in Sports Medicine

BACKGROUND

A recent review found that 45% of meta-analyses included statistical errors, of which, the most common was the calculation of effect sizes based on standard error (SE) rather than standard deviation (SD) [the SE/SD mix-up].

OBJECTIVES

The first aim of this study was to assess the impact of the SE/SD mix-up on the results of one highly cited meta-analysis. Our second aim was to identify one potential source of the SE/SD mix-up, by assessing how often SE is reported as a measure of sample variability in randomised controlled trials in sports medicine.

METHODS

We checked for potential SE/SD mix-ups in a 2015 meta-analysis of randomised controlled trials reporting the effects of recreational football interventions on aerobic fitness in adults. We corrected effect sizes affected by SE/SD mix-ups and re-analysed the data according to the original methodology. We compared pooled estimates of effect sizes from our re-analysis of corrected values with those of the original study. To assess how often SE was reported instead of SD as a measure of sample variance, we text mined results of randomised controlled trials from seven sports medicine journals and reported the proportion reporting of SE versus SD.

RESULTS

We identified potential SE/SD mix-ups in 9/16 effect sizes included in the meta-analysis describing the effects of football-based interventions versus non-exercise control. The published effect size was standardised mean difference (SMD) = 1.46 (95% confidence interval [CI] 0.91, 2.01). After correcting for SE/SD mix-ups, our re-analysis produced a smaller pooled estimate (SMD = 0.54 [95% CI 0.37, 0.71]). The original pooled estimate for trials comparing football versus running interventions was SMD = 0.68 (95% CI 0.06, 1.4). After correcting for SE/SD mix-ups and re-analysis, the effect was no longer statistically significant (SMD = 0.20 [95% CI - 0.10, 0.49)]). We found that 19.3% of randomised controlled trials reported SE rather than SD to describe sample variability. The relative frequency of the practice ranged from 0 to 25% across the seven journals sampled.

CONCLUSIONS

We found the SE/SD mix-up had inflated estimates for the effects of football on aerobic fitness. Meta-analysts should be vigilant to avoid miscalculating effect sizes. Authors, reviewers and editors should avoid and discourage (respectively) the practice of reporting SE as a measure of sample variability in sports medicine research.

The contribution of energy systems during 30-second lower body Wingate anaerobic test in combat sports athletes: Intermittent versus single forms and gender comparison

Combat sports, encompassing a range of activities from striking and grappling to mixed and weapon-based disciplines, have witnessed a surge in popularity worldwide. These sports are demanding, requiring athletes to harness energy from different metabolic pathways to perform short, high-intensity activities interspersed with periods of lower intensity. While it is established that the anaerobic alactic (ATP-PC) and anaerobic lactic systems are pivotal for high-intensity training sessions typical in combat sports, the precise contribution of these systems, particularly in varied training modalities such as single (SMT) and intermittent (IST) forms of the 30-second Wingate test, remains inadequately explored. This study aims at comparing performance outputs, physiological responses and gender differences during the SMT and IST forms of the 30-second Wingate test. Thirty-three highly trained combat sports athletes (17 women, 16 men; 10 boxing, 8 wrestling, 8 taekwondo and 7 karate) randomly performed SMT and IST. The IST consisted of three 10-second all-out attempts separated by 30 seconds of passive recovery, whereas the SMT was a single 30-second maximal effort. Resting, exercise and post-exercise oxygen uptake and peak blood lactate value were used to determine the metabolic energy demands via the PCr-LA-O2 method. The findings showed that total metabolic energy expenditure (TEE), ATP-PCr system contribution and the output of mechanical variables were higher in the IST than in the SMT form (all p<0.001). In contrast, the contribution of glycolytic and oxidative systems was higher in the SMT form (all p<0.001). However, exercise form and gender interaction were not significant (p>0.05). In combat sports, performance is not only determined by physiological and technical skills but also by metabolic energy input and efficiency. Therefore, our results can provide a comparison regarding the effects of exercise type and gender on metabolic energy metabolism to design the training of combat sports athletes.

Effect of sprint interval training load on maximal oxygen uptake in trained men

BACKGROUND

Sprint interval training (SIT) improves maximal aerobic and anaerobic performance, including oxygen uptake (VO2max), power output, and sprint performance. This study aimed to investigate the effect of SIT load on V̇O2max in trained subjects.

METHODS

SIT was performed twice a week for three weeks by twenty-four trained men (aged: 20.7±2.7, V̇O2max 43.6±6.5) and consisted of seven bouts of 10-s cycling sprints followed by a 4-min rest. Subjects were divided into two groups depending on the relative resistance of the load compared to their body mass (BM): 7.5% (S7.5) and 10% (S10). We measured the peak power, mean power, and peak cadence in SIT during the first and final sessions. V̇O2max, maximum aerobic power (MAP), heart rate, and lactate (La) concentration were measured before and after SIT using incremental tests.

RESULTS

After 3 weeks of SIT, V̇O2max, MAP, and La improved significantly in both S7.5 and S10 groups. In addition, changes in V̇O2max in S10 were higher than those in S7.5 (2.2±11.2% vs. 9.23±9.57%, P=0.029, adjusted by pre V̇O2max). MAP measurements showed the same results (2.2±11.3% vs. 8.3±10.0%, P=0.015, adjusted by pre-MAP). However, there was no significant interaction between time and group. A significant increase in peak cadence from first session to sixth sessions was observed in S7.5 (P=0.01, ES = 0.93, 95% confidence interval [CI]: 0.02-1.78) but not in S10 (P=0.132, ES = 0.22, 95% [CI]: -0.59-1.01).

CONCLUSIONS

Our results suggest that 3 weeks of SIT improves endurance performance in trained subjects. It seems that SIT at 10% load may tend to be more effective.

The Effects of Repeated-Sprint Training on Physical Fitness and Physiological Adaptation in Athletes: A Systematic Review and Meta-Analysis

BACKGROUND

Repeated-sprint training (RST) is a common training method for enhancing physical fitness in athletes. To advance RST prescription, it is important to understand the effects of programming variables on physical fitness and physiological adaptation.

OBJECTIVES

This study (1) quantifies the pooled effects of running RST on changes in 10 and 20 m sprint time, maximal oxygen consumption (VO2max), Yo-Yo Intermittent Recovery Test Level 1 (YYIR1) distance, repeated-sprint ability (RSA), countermovement jump (CMJ) height and change of direction (COD) ability in athletes, and (2) examines the moderating effects of program duration, training frequency, weekly volume, sprint modality, repetition distance, number of repetitions per set and number of sets per session on changes in these outcome measures.

METHODS

Pubmed, SPORTDiscus and Scopus databases were searched for original research articles up to 04 July 2023, investigating RST in healthy, able-bodied athletes, between 14 and 35 years of age, and a performance calibre of trained or above. RST interventions were limited to repeated, maximal running (land-based) sprints of ≤ 10 s duration, with ≤ 60 s recovery, performed for 2-12 weeks. A Downs and Black checklist was used to assess the methodological quality of the included studies. Eligible data were analysed using multi-level mixed-effects meta-analysis, with standardised mean changes determined for all outcomes. Standardised effects [Hedges G (G)] were evaluated based on coverage of their confidence (compatibility) intervals (CI) using a strength and conditioning specific reference value of G = 0.25 to declare an improvement (i.e. G > 0.25) or impairment (i.e. G < - 0.25) in outcome measures. Applying the same analysis, the effects of programming variables were then evaluated against a reference RST program, consisting of three sets of 6 × 30 m straight-line sprints performed twice per week for 6 weeks (1200 m weekly volume).

RESULTS

40 publications were included in our investigation, with data from 48 RST groups (541 athletes) and 19 active control groups (213 athletes). Across all studies, the effects of RST were compatible with improvements in VO2max (G 0.56, 90% CI 0.32-0.80), YYIR1 distance (G 0.61, 90% CI 0.43-0.79), RSA decrement (G - 0.61, 90% CI - 0.85 to - 0.37), linear sprint times (10 m: G - 0.35, 90% CI - 0.48 to - 0.22; 20 m: G - 0.48, 90% CI - 0.69 to - 0.27), RSA average time (G - 0.34, 90% CI - 0.49 to - 0.18), CMJ height (G 0.26, 90% CI 0.13-0.39) and COD ability (G - 0.32, 90% CI - 0.52 to - 0.12). Compared with the reference RST program, the effects of manipulating training frequency (+ 1 session per week), program duration (+ 1 extra training week), RST volume (+ 200 m per week), number of reps (+ 2 per set), number of sets per session (+ 1 set) or rep distance (+ 10 m per rep) were either non-substantial or comparable with an impairment in at least one outcome measure per programming variable.

CONCLUSIONS

Running-based RST improves speed, intermittent running performance, VO2max, RSA, COD ability and CMJ height in trained athletes. Performing three sets of 6 × 30 m sprints, twice per week for 6 weeks is effective for enhancing physical fitness and physiological adaptation. Additionally, since our findings do not provide conclusive support for the manipulation of RST variables, further work is needed to better understand how programming factors can be manipulated to augment training-induced adaptations.

STUDY REGISTRATION

Open Science Framework registration https://doi.org/10.17605/OSF.IO/RVNDW .

Effects of Passive or Active Recovery Regimes Applied During Long-Term Interval Training on Physical Fitness in Healthy Trained and Untrained Individuals: A Systematic Review

BACKGROUND

Intermittent exercise programs characterized through intensive exercise bouts alternated with passive or active recovery (i.e., interval training), have been proven to enhance measures of cardiorespiratory fitness. However, it is unresolved which recovery type (active or passive) applied during interval training results in larger performance improvements.

OBJECTIVES

This systematic review aimed to summarize recent evidence on the effects of passive or active recovery following long-term interval exercise training on measures of physical fitness and physiological adaptations in healthy trained and untrained individuals. The study protocol was registered in the Open Science Framework (OSF) platform ( https://doi.org/10.17605/OSF.IO/9BUEY ).

METHODS

We searched nine databases including the grey literature (Academic Search Elite, CINAHL, ERIC, Open Access Theses and Dissertations, Open Dissertations, PsycINFO, PubMed/MEDLINE, Scopus, and SPORTDiscus) from inception until February 2023. Key terms as high-intensity interval training, recovery mode, passive or active recover were used. A systematic review rather than a meta-analysis was performed, as a large number of outcome parameters would have produced substantial heterogeneity.

RESULTS

After screening titles, abstracts, and full texts, 24 studies were eligible for inclusion in our final analysis. Thirteen studies examined the effects of interval training interspersed with passive recovery regimes on physical fitness and physiological responses in trained (6 studies) and untrained (7 studies) individuals. Eleven out of 13 studies reported significant improvements in physical fitness (e.g., maximal aerobic velocity (MAV), Yo-Yo running test, jump performance) and physiological parameters (e.g., maximal oxygen uptake [VO2max], lactate threshold, blood pressure) in trained (effect sizes from single studies: 0.13 < Cohen's d < 3.27, small to very large) and untrained individuals (effect sizes: 0.17 < d < 4.19, small to very large) despite the type of interval training or exercise dosage (frequency, intensity, time, type). Two studies were identified that examined the effects of passive recovery applied during interval training in young female basketball (15.1 ± 1.1 years) and male soccer players (14.2 ± 0.5 years). Both studies showed positive effects of passive recovery on VO2max, countermovement jump performance, and the Yo-Yo running test. Eleven studies examined the effects of interval training interspersed with active recovery methods on physical fitness and physiological parameters in trained (6 studies) and untrained individuals (5 studies). Despite the type of interval training or exercise dosage, nine out of eleven studies reported significant increases in measures of physical fitness (e.g., MAV) and physiological parameters (e.g., VO2max, blood pressures) in trained (effect sizes from single studies: 0.13 < d < 1.29, small to very large) and untrained individuals (effect sizes: 0.19 < d < 3.29, small to very large). There was no study available that examined the effects of active recovery on physical fitness and physiological responses in youth.

CONCLUSIONS

The results of this systematic review show that interval training interspersed with active or passive recovery regimes have the potential to improve measures of physical fitness and physiology outcomes in trained and untrained adults and trained youth. That is, the applied recovery type seems not to affect the outcomes. Nonetheless, more research is needed on the effects of recovery type on measures of physical fitness and physiological adaptations in youth.

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSION

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

Extremely Low-Volume Burpee Interval Training Equivalent to 8 Minutes Per Session Improves Vertical Jump Compared with Sprint Interval Training in Real-World Circumstances

ABSTRACT

Pérez-Ifrán, P, Magallanes, CA, de S. Castro, FA, Astorino, TA, and Benítez-Flores, S. Extremely low-volume burpee interval training equivalent to 8 minutes per session improves vertical jump compared with sprint interval training in real-world circumstances. J Strength Cond Res 38(1): 10-20, 2024-The aim of this study was to compare the cardiometabolic and physical effects of 2 time-matched high-intensity programs in a real-world environment. Forty-three active and healthy adults (sex = 31 men and 12 women; age = 27 ± 5 years; peak heart rate [HR peak ] = 190.7 ± 10.6 beat·min -1 ) were randomized to 2 very low-volume protocols (∼8 minutes): sprint interval training (SIT) ( n = 15), burpee interval training (BIT) ( n = 15), and control (CON) ( n = 13). Subjects in SIT and BIT performed 5 days of 10 × 4 second "all-out" efforts with 30 seconds of recovery. Body composition, blood pressure, countermovement jump (CMJ), 10-m sprint, shuttle run test (SRT), autonomic modulation , self-efficacy, and intention were evaluated before and after training. Sprint interval training elicited a higher %HR peak , energy expenditure, rating of perceived exertion category ratio 10 scale, and feeling scale than BIT ( p < 0.05). SRT distance was significantly improved in SIT ( p = 0.03, d = 0.62), whereas CMJ height was significantly enhanced in BIT ( p = 0.0014, d = 0.72). Self-efficacy progressively worsened for SIT than for BIT as sessions increased, and significant differences were found in 5× a week frequency between protocols ( p = 0.040, d = 0.79). No differences in intention to engage were detected between the regimens ( p > 0.05). No changes were observed in body composition, blood pressure, 10-m sprint, SRTV̇O 2max , or autonomic variables with training ( p > 0.05). Results exhibit that extremely low-volume SIT improved running performance, whereas BIT increased the vertical jump.

Effects of 10-Week Online Moderate- to High-Intensity Interval Training on Body Composition, and Aerobic and Anaerobic Performance during the COVID-19 Lockdown

The present study aimed to investigate the effects of a 10-week online high-intensity interval training (HIIT) program on body composition and aerobic and aerobic performance in physically sedentary women. A parallel, two-group, longitudinal (pre, post) design was used with physical tests performed before (preintervention) and after (postintervention) the 10-week intervention period. A total of forty-eight healthy and physically sedentary women (defined as an individual who lacks regular exercise or a structured fitness routine) were recruited to participate in this study. The participants were distributed in two groups: the experimental group (EG) with 24 women (mean ± SD: age 21.21 ± 2.15 years; weight: 61.16 ± 8.94 kg; height: 163.96 ± 4.87 cm; body mass index (BMI): 22.69 ± 2.49 kg/m2) and the control group (CG) with another 24 women (mean ± SD: age 20.50 ± 1.29 years; weight: 62.0 ± 6.65 kg; height: 163.92 ± 4.89 cm; body mass index: 23.04 ± 1.74 kg/m2). The EG performed an online HIIT program for 10 weeks, while the CG continued with their daily life routines. The repeated measures ANCOVA indicated a significant effect in the within-group analysis for weight (p = 0.001; d = -0.96) and for BMI (p = 0.001; d = 0.24), with a significant decrease in the experimental group (EG). The control group (CG) did not show any significant decrease in either body weight or BMI. Regarding the maximal oxygen uptake (VO2 max) values, the EG exhibited a significant improvement (p = 0.001; d = -1.07), whereas the CG did not demonstrate a significant improvement (p = 0.08; d = -0.37). The EG's power output (W) (p = 0.001; d = -0.50) and power output standardized by body weight (W/kg) (p = 0.001; d = -0.96) were significantly improved. The CG did not show a significant improvement in either power output (W/kg) or power output. Lastly, the within-group analysis with load revealed that the EG significantly improved (p = 0.001; d = -0.50), while CG did not show a significant improvement in load (p = 0.10.; d = -0.10). The present study showed that 10 weeks of HIIT in an online environment during the COVID-19 lockdown significantly improved maximum oxygen consumption and caused weight loss and a significant decrease in body mass index in physically sedentary women. These results suggest that HIIT may be used as a time-efficient strategy to improve body composition and cardio-respiratory fitness in sedentary women.

Periodized Aerobic Training between Thresholds Improves Submaximal Cardiorespiratory Parameters in Octogenarians

BACKGROUND AND AIMS

The worldwide aging population is expanding, with more individuals living into their 80s. Physiological functions decline gradually with age, compounded by sedentary lifestyles. Incorporating physical activity into daily routine is crucial for maintaining independence. This study aimed to assess a periodized high-intensity aerobic training program (PEZO-BT) in octogenarians, focusing on submaximal ergospirometry effects.

METHODS

A total of 48 non-frail octogenarian subjects (12 females, 36 males) were randomized into control and intervention groups. All subjects underwent submaximal cardiopulmonary exercise testing with gas analysis at baseline, stopping after the respiratory compensation point (RCP). Our intervention group completed a 14-week PEZO-BT aerobic training program. The outcomes were oxygen consumption at first ventilatory threshold (VO2AT), ventilatory efficiency slope (VE/VCO2), oxygen uptake efficiency slope (OUES), cardiorespiratory optimal point (COP), oxygen pulse change (ΔVO2/HR) from anaerobic threshold (AT) to respiratory compensation point (RCP), and power output at anaerobic threshold (POAT).

RESULTS

Mixed ANOVA examined time and treatment effects. If significance emerged, post hoc t-tests were used to compare significances between groups. The homogeneity of variance was assessed using Levene's test. Chi-square tests compared ergospirometry criteria and ventilatory performance within groups. The mean differences at post intervention were significant in VO2AT (p < 0.001), VE/VCO2 (p < 0.001), ΔVO2/HR (p < 0.05), and POAT (p < 0.001), while OUES and COP were not significant (p > 0.05). However, clinical effects were observed in the entire intervention group.

CONCLUSIONS

Training improved exercise capacity and workload. Overall, this periodic aerobic and high-intensity interval training (HIIT) program yielded significant improvements in cardiorespiratory fitness (CRF) in previously untrained octogenarians with and without comorbidities. The findings suggest implications for promoting long-term healthy aging.

Acute and Chronic Performance Enhancement in Rowing: A Network Meta-analytical Approach on the Effects of Nutrition and Training

INTRODUCTION

This systematic review and network meta-analysis assessed via direct and indirect comparison the occurrence and magnitude of effects following different nutritional supplementation strategies and exercise interventions on acute and chronic rowing performance and its surrogates.

METHODS

PubMed, Web of Science, PsycNET and SPORTDiscus searches were conducted until March 2022 to identify studies  that met the following inclusion criteria: (a) controlled trials, (b) rowing performance and its surrogate parameters as outcomes, and (c) peer-reviewed and published in English. Frequentist network meta-analytical approaches were calculated based on standardized mean differences (SMD) using random effects models.

RESULTS

71 studies with 1229 healthy rowers (aged 21.5 ± 3.0 years) were included and two main networks (acute and chronic) with each two subnetworks for nutrition and exercise have been created. Both networks revealed low heterogeneity and non-significant inconsistency (I² ≤ 35.0% and Q statistics: p ≥ 0.12). Based on P-score rankings, while caffeine (P-score 84%; SMD 0.43) revealed relevantly favorable effects in terms of acute rowing performance enhancement, whilst prior weight reduction (P-score 10%; SMD - 0.48) and extensive preload (P-score 18%; SMD - 0.34) impaired acute rowing performance. Chronic blood flow restriction training (P-score 96%; SMD 1.26) and the combination of β-hydroxy-β-methylbutyrate and creatine (P-score 91%; SMD 1.04) induced remarkably large positive effects, while chronic spirulina (P-score 7%; SMD - 1.05) and black currant (P-score 9%; SMD - 0.88) supplementation revealed impairment effects.

CONCLUSION

Homogeneous and consistent findings from numerous studies indicate that the choice of nutritional supplementation strategy and exercise training regimen are vital for acute and chronic performance enhancement in rowing.

Aerobically trained older adults show impaired resting, but preserved exercise-induced circulating progenitor cell count, which was not improved by sprint interval training

Older adults exhibit a reduced number and function of CD34 + circulating progenitor cells (CPC), a known risk factor for cardiovascular disease. Exercise promotes the mobilisation of CPCs from bone marrow, so whether ageing per se or physical inactivity in older age reduces CPCs is unknown. Thus, this study examined the effect of age on resting and exercise-induced changes in CPCs in aerobically trained adults and the effect of 8 weeks of sprint interval training (SIT) on resting and exercise-induced CPCs in older adults. Twelve young (22-34 years) and nine older (63-70 years) adults participated in the study. Blood was sampled pre and immediately post a graded exercise test to exhaustion in both groups. Older participants repeated the process after 8 weeks of SIT (3 × 20 s 'all-out' sprints, 2 × a week). Total CPCs (CD34⁺) and endothelial progenitor cells (EPCs: CD34⁺KDR⁺) were determined by flow cytometry. Older adults exhibited lower basal total CD34⁺ CPCs (828 ± 314 vs. 1186 ± 272 cells·mL^-1, p = 0.0149) and CD34⁺KDR⁺ EPCs (177 ± 128 vs. 335 ± 92 cells·mL^-1, p = 0.007) than younger adults. The maximal exercise test increased CPCs in young (CD34⁺: p = 0.004; CD34⁺KDR⁺: p = 0.017) and older adults (CD34⁺: p < 0.001; CD34⁺KDR⁺: p = 0.008), without difference between groups (p = 0.211). SIT did not alter resting or exercise-induced changes in CPCs in the older cohort (p > 0.232). This study suggests age per se does not impair exercise-induced CPC counts, but does lower resting CPC counts.

Individual and Group Responses of Cardiorespiratory Fitness to Running and Cycling Sprint Interval Training

Digby, L, McCarthy, SF, Bornath, DPB, Copeland, JL, and Hazell, TJ. Individual and group responses of cardiorespiratory fitness to running and cycling sprint interval training. J Strength Cond Res 37(4): e313–e316, 2023—Sprint interval training (SIT) has gained popularity as an effective way to improve peak oxygen consumption (V̇O2peak) and subsequently health in a time-efficient manner. In addition, SIT has demonstrated improvements of ∼5–12% in V̇O2peak for both running and cycling protocols, although comparisons of differing modalities have yet to be examined. Therefore, this study sought to determine group and individual responses to running and cycling SIT while examining any crossover effects of running and cycling SIT when V̇O2peak is tested in different modes of exercise where 18 subjects completed either 3 weeks of cycling SIT (6 male, 3 female) or running SIT (5 male, 4 female) consisting of 4–6 repeated 30-second all-out bouts interspersed with 240 seconds of recovery. Cycling and running V̇O2peak tests were completed pretraining and post-training for the investigation of mode-specific cardiorespiratory fitness improvements. There were main effects of time for cycling V̇O2peak (P = 0.022, = 0.499) and running V̇O2peak (P = 0.080, = 0.334) that seem greater when testing in the same mode as training (∼+5.5%). A similar proportion of responders were identified in both training modes (∼67%) suggesting running and cycling SIT are both effective for improving cardiorespiratory fitness. These results suggest that the specificity of testing and training are important for SIT and that both running and cycling SIT are similarly effective at improving V̇O2peak.

Fasted Sprint Interval Training Results in Some Beneficial Skeletal Muscle Metabolic, but Similar Metabolomic and Performance Adaptations Compared With Carbohydrate-Fed Training in Recreationally Active Male

Endurance training in fasted conditions (FAST) induces favorable skeletal muscle metabolic adaptations compared with carbohydrate feeding (CHO), manifesting in improved exercise performance over time. Sprint interval training (SIT) is a potent metabolic stimulus, however nutritional strategies to optimize adaptations to SIT are poorly characterized. Here we investigated the efficacy of FAST versus CHO SIT (4-6 × 30-s Wingate sprints interspersed with 4-min rest) on muscle metabolic, serum metabolome and exercise performance adaptations in a double-blind parallel group design in recreationally active males. Following acute SIT, we observed exercise-induced increases in pan-acetylation and several genes associated with mitochondrial biogenesis, fatty acid oxidation, and NAD+-biosynthesis, along with favorable regulation of PDK4 (p = .004), NAMPT (p = .0013), and NNMT (p = .001) in FAST. Following 3 weeks of SIT, NRF2 (p = .029) was favorably regulated in FAST, with augmented pan-acetylation in CHO but not FAST (p = .033). SIT induced increases in maximal citrate synthase activity were evident with no effect of nutrition, while 3-hydroxyacyl-CoA dehydrogenase activity did not change. Despite no difference in the overall serum metabolome, training-induced changes in C3:1 (p = .013) and C4:1 (p = .010) which increased in FAST, and C16:1 (p = .046) and glutamine (p = .021) which increased in CHO, were different between groups. Training-induced increases in anaerobic (p = .898) and aerobic power (p = .249) were not influenced by nutrition. These findings suggest some beneficial muscle metabolic adaptations are evident in FAST versus CHO SIT following acute exercise and 3 weeks of SIT. However, this stimulus did not manifest in differential exercise performance adaptations.

Targeted Lipidomics and Inflammation Response to Six Weeks of Sprint Interval Training in Male Adolescents

Lipids play an important role in coordinating and regulating metabolic and inflammatory processes. Sprint interval training (SIT) is widely used to improve sports performance and health outcomes, but the current understanding of SIT-induced lipid metabolism and the corresponding systemic inflammatory status modification remains controversial and limited, especially in male adolescents. To answer these questions, twelve untrained male adolescents were recruited and underwent 6 weeks of SIT. The pre- and post-training testing included analyses of peak oxygen consumption (VO2peak), biometric data (weight and body composition), serum biochemical parameters (fasting blood glucose, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triacylglycerol, testosterone, and cortisol), inflammatory markers, and targeted lipidomics. After the 6-week SIT, the serum C-reactive protein (CRP), interleukin (IL)-1β, IL-2, IL-4, IL-10, tumor necrosis factor (TNF)-α, and transforming growth factor (TGF)-β significantly decreased (p < 0.05), whereas IL-6 and IL-10/TNF-α significantly increased (p < 0.05). In addition, the targeted lipidomics revealed changes in 296 lipids, of which 33 changed significantly (p < 0.05, fold change > 1.2 or <1/1.2). The correlation analysis revealed that the changes in the inflammatory markers were closely correlated with the changes in some of the lipids, such as LPC, HexCer, and FFA. In conclusion, the 6-week SIT induced significant changes in the inflammatory markers and circulating lipid composition, offering health benefits to the population.

The Effects of Sprint Interval Training on Physical Performance: A Systematic Review and Meta-Analysis

ABSTRACT

Hall, AJ, Aspe, RR, Craig, TP, Kavaliauskas, M, Babraj, J, and Swinton, PA. The effects of sprint interval training on physical performance: a systematic review and meta-analysis. J Strength Cond Res 37(2): 457-481, 2023-The present study aimed to synthesize findings from published research and through meta-analysis quantify the effect of sprint interval training (SIT) and potential moderators on physical performance outcomes (categorized as aerobic, anaerobic, mixed aerobic-anaerobic, or muscular force) with healthy adults, in addition to assessing the methodological quality of included studies and the existence of small study effects. Fifty-five studies were included (50% moderate methodological quality, 42% low methodological quality), with 58% comprising an intervention duration of ≤4 weeks and an array of different training protocols. Bayesian's meta-analysis of standardized mean differences (SMD) identified a medium effect of improved physical performance with SIT (ES 0.5 = 0.52; 95% credible intervals [CrI]: 0.42-0.62). Moderator analyses identified overlap between outcome types with the largest effects estimated for anaerobic outcomes (ES 0.5 = 0.61; 95% CrI: 0.48-0.75). Moderator effects were identified for intervention duration, sprint length, and number of sprints performed per session, with larger effects obtained for greater values of each moderator. A substantive number of very large effect sizes (41 SMDs > 2) were identified with additional evidence of extensive small study effects. This meta-analysis demonstrates that short-term SIT interventions are effective for developing moderate improvements in physical performance outcomes. However, extensive small study effects, likely influenced by researchers analyzing many outcomes, suggest potential overestimation of reported effects. Future research should analyze fewer a priori selected outcomes and investigate models to progress SIT interventions for longer-term performance improvements.

Skeletal muscle mechanisms contributing to improved glycemic control following intense interval exercise and training

High-intensity and sprint interval training (HIIT and SIT, respectively) enhance insulin sensitivity and glycemic control in both healthy adults and those with cardiometabolic diseases. The beneficial effects of intense interval training on glycemic control include both improvements seen in the hours to days following a single session of HIIT/SIT and those which accrue with chronic training. Skeletal muscle is the largest site of insulin-stimulated glucose uptake and plays an integral role in the beneficial effects of exercise on glycemic control. Here we summarize the skeletal muscle responses that contribute to improved glycemic control during and following a single session of interval exercise and evaluate the relationship between skeletal muscle remodelling and improved insulin sensitivity following HIIT/SIT training interventions. Recent evidence suggests that targeting skeletal muscle mechanisms via nutritional interventions around exercise, particularly with carbohydrate manipulation, can enhance the acute glycemic benefits of HIIT. There is also some evidence of sex-based differences in the glycemic benefits of intense interval exercise, with blunted responses observed after training in females relative to males. Differences in skeletal muscle metabolism between males and females may contribute to sex differences in insulin sensitivity following HIIT/SIT, but well-controlled studies evaluating purported muscle mechanisms alongside measurement of insulin sensitivity are needed. Given the greater representation of males in muscle physiology literature, there is also a need for more research involving female-only cohorts to enhance our basic understanding of how intense interval training influences muscle insulin sensitivity in females across the lifespan.

Effects of 8-Week Online, Supervised High-Intensity Interval Training on the Parameters Related to the Anaerobic Threshold, Body Weight, and Body Composition during Pregnancy: A Randomized Controlled Trial

We aimed to assess the effects of an 8-week, online high-intensity interval training (HIIT) program on the parameters related to the anaerobic threshold (AT), body weight, and body composition in pregnant women. A total of 69 Caucasian women with an uncomplicated singleton pregnancy (age: 31 ± 4 years; gestational age: 22 ± 5 weeks; mean ± standard deviation) were randomly allocated to either an 8-week HIIT program (HIIT group) or to a comparative 8-week educational program (EDU group). Our most important finding was that even with the 8-week progression of pregnancy and physiological weight gain, the HIIT group maintained the same level of parameters related to AT: volume of oxygen at the AT (VO2/AT), percentage of maximal oxygen uptake at the AT (%VO2max/AT), and heart rate at the AT (HR/AT). In contrast, in the EDU group we observed a substantial deterioration of parameters related to the AT. The HIIT intervention substantially reduced the fat mass percentage (median: 30 to 28%; p < 0.01) and improved the total fat-free mass percentage (median: 70% to 72%; p < 0.01). In the EDU group, the body composition did not change significantly. An online, supervised HIIT program may be used to prevent the pregnancy-related risk of excessive weight gain and reduction in exercise capacity without yielding adverse obstetric or neonatal outcomes.

Change in Central Cardiovascular Function in Response to Intense Interval Training: A Systematic Review and Meta-analysis

INTRODUCTION

High-intensity interval training and sprint interval training significantly increase maximal oxygen uptake (V̇O 2max ), which enhances endurance performance and health status. Whether this response is due to increases in central cardiovascular function (cardiac output (CO) and blood volume) or peripheral factors is unknown.

PURPOSE

This study aimed to conduct a systematic review and meta-analysis to assess the effects of high-intensity interval training and sprint interval training (referred to as intense interval training) on changes in central cardiovascular function.

METHODS

We performed a systematic search of eight databases for studies denoting increases in V̇O 2max in which CO, stroke volume (SV), blood volume, plasma volume, end-diastolic/systolic volume, or hematocrit were measured.

RESULTS

Forty-five studies were included in this analysis, comprising 946 men and women of various health status (age and V̇O 2max , 20-76 yr and 13-61 mL·kg -1 ·min -1 ) who performed 6-96 sessions of interval training. Results showed an increase in V̇O 2max with intense interval training that was classified as a large effect ( d = 0.83). SV ( d = 0.69), and CO ( d = 0.49) had moderate effect sizes in response to intense interval training. Of 27 studies in which CO was measured, 77% exhibited significant increases in resting CO or that obtained during exercise. Similarly, 93% of studies revealed significant increases in SV in response to intense interval training. Effect sizes for these outcomes were larger for clinical versus healthy populations. Plasma volume, blood volume, and hematocrit had small effect sizes after training ( d = 0.06-0.14).

CONCLUSIONS

Increases in V̇O 2max demonstrated with intense interval training are attendant with increases in central O 2 delivery with little contribution from changes in hematocrit, blood volume, or plasma volume.

Effects of a School-Based Physical Activity Intervention for Obesity, Health-Related Physical Fitness, and Blood Pressure in Children with Intellectual Disability: A Randomized Controlled Trial

Children with intellectual disability (ID) are more vulnerable to health conditions than their typically developing peers. Evidence of effective interventions is scarce. A randomized controlled trial was conducted in 30 overweight and obese children with intellectual disability (ID) in China to evaluate a 12-week school-based physical activity intervention for obesity, health-related physical fitness (HRPF), and blood pressure. The intervention consisted of 24 physical activity (PA) sessions (2 sessions/week, 60 min/session), with exercise intensity progressively increasing from a moderate level to a vigorous level. All participants were followed up for 12 weeks after the intervention period to evaluate sustained effects. Outcomes were repeatedly measured at baseline, after the intervention, and after follow-up. The intervention was effective in reducing some obesity-related outcomes (including weight and body mass index) and improving some HRPF-related outcomes (including the 6 min walk test and the 30 s sit-to-stand test), with the significant effects being sustained after the 12-week follow-up. No effect was observed on blood pressure. The findings of this study contribute to the development and implementation of PA interventions to reduce obesity and improve HRPF in children with ID.

Risk of bias and reporting practices in studies comparing VO2max responses to sprint interval vs. continuous training: A systematic review and meta-analysis

BACKGROUND

It remains unclear whether studies comparing maximal oxygen uptake (VO2max) response to sprint interval training (SIT) vs. moderate-intensity continuous training (MICT) are associated with a high risk of bias and poor reporting quality. The purpose of this study was to evaluate the risk of bias and quality of reporting in studies comparing changes in VO2max between SIT and MICT.

METHODS

We conducted a comprehensive literature search of 4 major databases: AMED, CINAHL, EMBASE, and MEDLINE. Studies were excluded if participants were not healthy adult humans or if training protocols were unsupervised, lasted less than 2 weeks, or utilized mixed exercise modalities. We used the Cochrane Collaboration tool and the CONSORT checklist for non-pharmacological trials to evaluate the risk of bias and reporting quality, respectively.

RESULTS

Twenty-eight studies with 30 comparisons (3 studies included 2 SIT groups) were included in our meta-analysis (n = 360 SIT participants: body mass index (BMI) = 25.9 ± 3.7 kg/m2, baseline VO2max = 37.9 ± 8.0 mL/kg/min; n = 359 MICT participants: BMI = 25.5 ± 3.8 kg/m2, baseline VO2max = 38.3 ± 8.0 mL/kg/min; all mean ± SD). All studies had an unclear risk of bias and poor reporting quality.

CONCLUSION

Although we observed a lack of superiority between SIT and MICT for improving VO2max (weighted Hedge's g = -0.004, 95% confidence interval (95%CI): -0.08 to 0.07), the overall unclear risk of bias calls the validity of this conclusion into question. Future studies using robust study designs are needed to interrogate the possibility that SIT and MICT result in similar changes in VO2max.

The Effects of High-Intensity Interval Training on Exercise Capacity and Prognosis in Heart Failure and Coronary Artery Disease: A Systematic Review and Meta-Analysis

Objective

The purpose of this study is to compare the effects of high-intensity interval training (HIIT) versus moderate-intensity continuous training (MICT) on exercise capacity and several prognostic markers in patients with coronary artery disease (CAD) and heart failure (HF).

Methods

This systematic review is registered on the INPLASY website (number: INPLASY202080112). We conducted a comprehensive search in eight databases of literature before September 13, 2019. Trials comparing HIIT and MICT in participants with CAD or HF aged 52–78 years were included. Exercise capacity (peak oxygen consumption (peak VO₂)) and prognostic markers, such as the anaerobic threshold (AT), minute ventilation/carbon dioxide production (VE/VCO₂) slope, left ventricular ejection fraction (LVEF), and prognostic value of the predicted VO₂ max per cent (the predicted VO₂ peak (%)) were examined.

Results

A total of 15 studies were included comprising 664 patients, 50% of which were male, with an average age of 60.3 ± 13.2 years. For patients with CAD, HIIT significantly improved peak VO₂ values (95% CI 0.7 to 2.11) compared with MICT, but peak VO₂ values in patients with HF did not seem to change. For training lasting less than eight weeks, HIIT significantly improved peak VO₂ values (95% CI 0.70 to 2.10), while HIIT lasting 12 weeks or longer resulted in a modestly increased peak VO₂ value (95% CI 0.31 to 5.31). High-intensity interval training significantly increased the AT when compared with MICT (95% CI 0.50 to 1.48). High-intensity interval training also caused a moderate increase in LVEF (95% CI 0.55 to 5.71) but did not have a significant effect on the VE/VCO₂ slope (95% CI −2.32 to 0.98) or the predicted VO₂ peak (95% CI −2.54 to 9.59) compared with MICT.

Conclusions

High-intensity interval training is an effective therapy for improving peak VO₂ values in patients with CAD. High-intensity interval training in the early stage (eight weeks or fewer) is superior to MICT. Finally, HIIT significantly improved prognostic markers, including the AT and LVEF in patients with CAD and HF.

Exercise-Induced Circulating microRNAs: Potential Key Factors in the Control of Breast Cancer

Losses in skeletal muscle mass, strength, and metabolic function are harmful in the pathophysiology of serious diseases, including breast cancer. Physical exercise training is an effective non-pharmacological strategy to improve health and quality of life in patients with breast cancer, mainly through positive effects on skeletal muscle mass, strength, and metabolic function. Emerging evidence has also highlighted the potential of exercise-induced crosstalk between skeletal muscle and cancer cells as one of the mechanisms controlling breast cancer progression. This intercellular communication seems to be mediated by a group of skeletal muscle molecules released in the bloodstream known as myokines. Among the myokines, exercise-induced circulating microRNAs (c-miRNAs) are deemed to mediate the antitumoral effects produced by exercise training through the control of key cellular processes, such as proliferation, metabolism, and signal transduction. However, there are still many open questions regarding the molecular basis of the exercise-induced effects on c-miRNA on human breast cancer cells. Here, we present evidence regarding the effect of exercise training on c-miRNA expression in breast cancer, along with the current gaps in the literature and future perspectives.

Sprint Interval Exercise Improves Cognitive Performance Unrelated to Postprandial Glucose Fluctuations at Different Levels of Normobaric Hypoxia

Objective: The aim of our study was to examine cognition response to sprint interval exercise (SIE) against different levels of hypoxia. Research design and methods: 26 recreational active males performed SIE (20 × 6 s of all-out cycling bouts, 15 s of passive recovery) under normoxia (FIO2: 0.209), moderate hypoxia (FIO2: 0.154), and severe hypoxia (FIO2: 0.112) in a single-blinded crossover design. Cognitive function and blood glucose were assessed before and after 0, 10, 30, and 60 min of the SIE. Heart rate (HR), peripheral oxygen saturation (SpO2), and ratings of perceived exertion (RPE, the Borg 6−20-point scale) during each SIE trial were recorded before and immediately after every five cycling bouts, and after 0, 10, 30, and 60 min of the SIE. Results: All the three SIE trials had a significantly faster overall reaction time in the Stroop test at 10 min after exercise as compared to that of the baseline value (p = 0.003, ƞ2 = 0.606), and returned to normal after 60 min. The congruent RT at 10 min after SIE was significantly shorter than that of the baseline (p < 0.05, ƞ2 = 0.633), while the incongruent RT at both 10 min and 30 min were significantly shorter than that measured at baseline (p < 0.05, ƞ2 = 0.633). No significant differences in terms of accuracy were found across the three trials at any time points (p = 0.446, ƞ2 = 0.415). Blood glucose was significantly reduced at 10 min and was sustained for at least 60 min after SIE when compared to pre-exercise in all trials (p < 0.05). Conclusions: Acute SIE improved cognitive function regardless of oxygen conditions, and the sustained improvement following SIE could last for at least 10−30 min and was unaffected by the altered blood glucose level.

Low-Volume Sprint Interval Swimming Is Sufficient to Increase Blood Metabolic Biomarkers in Master Swimmers

Purpose: Sprint interval exercise is a time-efficient way of inducing beneficial adaptations. However, little is known about its minimal effective volume, especially in swimming. The aim of the present study was to evaluate and compare the effects of two sprint interval swimming sets of different low volumes on blood biomarkers. Method: Twenty-one master swimmers [11 females aged 38.5 (8.5) years, 10 males aged 42.7 (5.7) years] completed two freestyle swimming sets of 4 × 50 m and 4 × 25 m at maximal intensity and a work-to-rest ratio of 1:1, on different days, in random and counterbalanced order. Blood samples were taken before, immediately after and one hour after exercise for determination of a number of biochemical parameters. Results: Swimming speed was higher in the 4 × 25-m set. Lactate, glucose, insulin, glucagon, cortisol, and reduced glutathione increased immediately post-exercise, while uric acid increased 1 h post-exercise (p < .05). All aforementioned biomarkers, excluding glucagon, increased more with the 4 × 50-m set, compared to the 4 × 25-m set (p < .05). Session rating of perceived exertion was higher after the 4 × 50-m set (p = .011). Conclusion: Both sprint interval swimming sets elicited increases in blood biomarkers in master swimmers. The set of higher volume elicited greater increases in most of the biochemical markers studied but also in subjective load. Thus, although the set of higher volume was more efficient in perturbing blood biomarkers, even the very low-volume set induced metabolic stress that may trigger adaptive mechanisms.

Impact of Intermittent Fasting Combined With High-Intensity Interval Training on Body Composition, Metabolic Biomarkers, and Physical Fitness in Women With Obesity

Background

Intermittent fasting (IF) is a dietary approach that is widely popular due to its effects on weight and body fat loss, but it does not appear to ensure muscle mass preservation. Incorporating high-intensity interval training (HIIT) into an individual’s routine could be an attractive and viable therapeutic option for improving body composition, lifestyle and health promotion. Problematizing the emerging situation of fighting obesity, led us to clarify gaps about IF and hypothesize that IF and HIIT in conjunction may protect against muscle mass decline without impairing nitrogen balance (NB), in addition to improving the physical fitness of women with obesity.

Objectives

To evaluate the effects of IF alone and combined with HIIT on body composition, NB and strength and physical fitness in women with obesity.

Methods

Thirty-six women (BMI 34.0 ± 3.2; 32.2 ± 4.4 years) participated and were randomly distributed into three groups: (1) Intermittent fasting combined with exercise group (IF + EX); (2) Exercise group (EX); and (3) Intermittent fasting group (IF). The interventions took place over 8 weeks and all evaluations were performed pre and post-intervention. The HIIT circuit was performed 3x/week, for 25 mins/session, at 70–85% of the maximum heart rate. The intermittent fasting protocol was a 5:2 diet with two meals within 6 h on fasting days, being 25% of total energy intake, plus 18 h of complete fasting. The protocol was performed 2x/week and 5 days of ad libitum ingestion. Resting metabolic rate (RMR) was measured by indirect calorimetry, body composition by BodPod®, NB from urinary nitrogen, food consumption by food records and physical and strength performance were measured by physical tests. ANOVA two-way repeated measures mixed model was performed followed by Sidak post hoc (p &lt; 0.05). This project was registered in ClinicalTrials.gov, NCT05237154.

Results

There were a reduction in body weight (P = 0.012) and BMI (P = 0.031) only in the IF + EX group. There was body fat loss in the IF + EX group (−4%, P &lt; 0.001) and in the EX group (−2.3%, P = 0.043), an increase in fat-free mass in the IF + EX group (+3.3%, P &lt; 0.001) and also in the EX group (+2%, P = 0.043), without differences between groups and the IF group showed no changes. The NB was equilibrium in all groups. All parameters of aerobic capacity and strength improved.

Conclusion

Combining IF with HIIT can promote increments in fat-free mass, NB equilibrium and improve physical fitness and strength.

State of Knowledge on Molecular Adaptations to Exercise in Humans: Historical Perspectives and Future Directions

For centuries, regular exercise has been acknowledged as a potent stimulus to promote, maintain, and restore healthy functioning of nearly every physiological system of the human body. With advancing understanding of the complexity of human physiology, continually evolving methodological possibilities, and an increasingly dire public health situation, the study of exercise as a preventative or therapeutic treatment has never been more interdisciplinary, or more impactful. During the early stages of the NIH Common Fund Molecular Transducers of Physical Activity Consortium (MoTrPAC) Initiative, the field is well-positioned to build substantially upon the existing understanding of the mechanisms underlying benefits associated with exercise. Thus, we present a comprehensive body of the knowledge detailing the current literature basis surrounding the molecular adaptations to exercise in humans to provide a view of the state of the field at this critical juncture, as well as a resource for scientists bringing external expertise to the field of exercise physiology. In reviewing current literature related to molecular and cellular processes underlying exercise-induced benefits and adaptations, we also draw attention to existing knowledge gaps warranting continued research effort. © 2021 American Physiological Society. Compr Physiol 12:3193-3279, 2022.

Using Bodyweight as Resistance Can Be a Promising Avenue to Promote Interval Training: Enjoyment Comparisons to Treadmill-Based Protocols

Purpose: Even though multiple training methods appear to be effective to improve cardiorespiratory fitness, they also need to be perceived as tolerable or enjoyable by exercisers to maximize long-term behavioral maintenance. Therefore, the purpose of the current study was to compare perceived enjoyment between whole-body interval training (SIT-WB), treadmill-based interval training (SIT-T) and moderate-intensity continuous training (MICT). Method: Forty-one healthy adult men (age: 23.7 ± 0.7 years, height: 1.79 ± 0.01 m, body mass: 78.5 ± 1.7 kg; VO_2max: 46.7 ± 7.3 ml.kg^-1.min^-1) were randomly assigned to SIT-WB, SIT-T, or MICT and underwent 16 weeks of training (3x/w). SIT-WB and SIT-T completed eight 20 s bouts interspersed by 10 s passive recovery, differing as to the exercise mode performed (i.e., calisthenics exercises and treadmill running, respectively) whereas MICT participants ran for 30 min at an intensity below the second ventilatory threshold. Perceived enjoyment was assessed 10 min post-exercise at weeks 1, 5, 9, 13, and 16, using the Physical Activity Enjoyment Scale. Results: Compliance was high (~90%) across all three training groups (p = .803). All training modes were rated as enjoyable and no significant within- (F_{(4, 152)} = 1.132, p = .344) or between-group (F_{(2, 38)} = 0.662, p = .521) differences were found during the intervention period. Conclusions: These results suggest that SIT-WB can be employed as an enjoyable low-cost alternative to traditional treadmill-based SIT and MICT for up to 16 weeks.

Davies R. The Effect of Exercise Training Intensity on VO2max in Healthy Adults: An Overview of Systematic Reviews and Meta-Analyses

This study aimed to evaluate systematic reviews and meta-analyses that have examined the effect of exercise training on VO2max in healthy individuals at different intensities. Five databases were searched: EBSCOhost, MEDLINE/PubMed, SPORTDiscus, Web of Science, and Google Scholar. Eligibility criteria for selecting reviews included systematic reviews and meta-analyses of healthy adults that examined the effect of lower intensity training (LIT) and/or high intensity training (HIT) on VO2max. Eleven reviews met the eligibility criteria. All reviews were of moderate-to-very strong methodological quality. The included reviews reported data from 179 primary studies with an average of 23 ± 10 studies per review. All reviews included in this overview showed that exercise training robustly increased VO2max at all intensities. Three meta-analyses that compared LIT versus HIT protocols on VO2max reported small/moderate beneficial effects for HIT over LIT; however, the beneficial effects of HIT on VO2max appear to be moderated by training variables other than intensity (e.g., training impulse, interval length, training volume, and duration) and participants' baseline characteristics (e.g., age and fitness levels). Overall, evidence from this overview suggests that the apparent differences between LIT and HIT protocols on VO2max were either small, trivial, or inconclusive, with several methodological considerations required to standardise research designs and draw definitive conclusions.

Effects of low-volume, high-intensity interval training on maximal oxygen consumption, body fat percentage and health-related quality of life in women with overweight: A randomized controlled trial

Background

Several investigations suggest that high-intensity interval training (HIIT) provokes larger changes in VO_2max compared to moderate-intensity continuous training (MICT); other studies associate HIIT with significant decreases in total, abdominal and visceral fat mass. However, some meta-analyses express that the enhancements with HIIT on VO_2max are slightly higher concerning MICT. These studies had low-to-moderate methodological quality, and the exercise protocols were completed mostly on treadmills or cycle ergometers. Thus, the objective of this study was to compare the effect of a low-volume HIIT versus a MICT program on VO_2max, body fat percentage (BFP), and health-related quality of life (HRQoL) in overweight women. It followed a research protocol with high methodological rigor and good reporting quality.

Methods

After two physical adaptation weeks (run-in period), thirty-five volunteers were randomized to HIIT (n = 16) or MICT (n = 19). Both groups performed 24 sessions on a grass sports field (walking, jogging or running). The HIIT group completed 15 bouts of 30 s [90–95%, maximal heart rate (HR_max)], while the MICT group completed 30 min of continuous exercise (65–75% HR_max).

Results

The difference between HIIT and MICT post-intervention on VO_2max was not statistically significant (0.8 ml/kg/min. CI 95%, −1.0 to 2.7, p = 0.37). Similarly, no statistically significant differences were found between groups for BFP and HRQoL.

Conclusions

Low-volume HIIT program has no quantitative advantage compared with that resulting from MICT, in VO2max, BFP, and HRQoL. ClinicalTrials.gov Identifier: NCT03300895.

Performance and Recovery of Well-Trained Younger and Older Athletes during Different HIIT Protocols

Due to physiological and morphological differences, younger and older athletes may recover differently from training loads. High-intensity interval training (HIIT) protocols are useful for studying the progression of recovery. It was the objective of this study to determine age differences in performance and recovery following different HIIT protocols. Methods: 12 younger (24.5 ± 3.7 years) and 12 older (47.3 ± 8.6 years) well-trained cyclists and triathletes took part in this study. Between the age groups there were no significant differences in relative peak power to fat-free mass, maximal heart rate (HR), training volume, and VO_2max-percentiles (%). Participants performed different HIIT protocols consisting of 4 × 30 s Wingate tests with different active rest intervals (1, 3, or 10 min). Peak and average power, lactate, HR, respiratory exchange ratio (RER), subjective rating of perceived exertion (RPE), and recovery (Total Quality Recovery scale, TQR) were assessed. Results: During the different HIIT protocols, metabolic, cardiovascular, and subjective recovery were similar between the two groups. No significant differences were found in average lactate concentration, peak and average power, fatigue (%), %HR_max, RER, RPE, and TQR values between the groups (p > 0.05). Conclusion: The findings of this study indicate that recovery following HIIT does not differ between the two age groups. Furthermore, older and younger participants displayed similar lactate kinetics after the intermittent exercise protocols.

The Influence of Acute Sprint Interval Training on Cognitive Performance of Healthy Younger Adults

There is considerable evidence showing that an acute bout of physical exercises can improve cognitive performance, but the optimal exercise characteristics (e.g., exercise type and exercise intensity) remain elusive. In this regard, there is a gap in the literature to which extent sprint interval training (SIT) can enhance cognitive performance. Thus, this study aimed to investigate the effect of a time-efficient SIT, termed as "shortened-sprint reduced-exertion high-intensity interval training" (SSREHIT), on cognitive performance. Nineteen healthy adults aged 20-28 years were enrolled and assessed for attentional performance (via the d2 test), working memory performance (via Digit Span Forward/Backward), and peripheral blood lactate concentration immediately before and 10 min after an SSREHIT and a cognitive engagement control condition (i.e., reading). We observed that SSREHIT can enhance specific aspects of attentional performance, as it improved the percent error rate (F%) in the d-2 test (t (18) = -2.249, p = 0.037, d = -0.516), which constitutes a qualitative measure of precision and thoroughness. However, SSREHIT did not change other measures of attentional or working memory performance. In addition, we observed that the exercise-induced increase in the peripheral blood lactate levels correlated with changes in attentional performance, i.e., the total number of responses (GZ) (rm = 0.70, p < 0.001), objective measures of concentration (SKL) (rm = 0.73, p < 0.001), and F% (rm = -0.54, p = 0.015). The present study provides initial evidence that a single bout of SSREHIT can improve specific aspects of attentional performance and conforming evidence for a positive link between cognitive improvements and changes in peripheral blood lactate levels.

Relevance of a Sprint Interval Swim Training Set to the 100-Meter Freestyle Event Based on Blood Lactate and Kinematic Variables

Sprint interval training (SIT) sets are commonly used by coaches in the training routine of swimmers competing in short-distance events; however, data regarding their relevance to competitive events are scarce. The aim of this study was to examine whether performance variables differed or correlated between a 4 × 50-m maximal swimming set (with a work-to-rest ratio of 1:4) and the 100-m freestyle event. Eleven male and 16 female competitive swimmers aged 16.1 ± 1.1 years participated in the study. All swimmers trained at least six times a week and had training experience of more than 4 years. They completed the two freestyle tests on different days, in random and counterbalanced order. In each test, speed, blood lactate, stroke rate (SR), and stroke index (SI) were measured. Speed, blood lactate, and SR were higher at the 4 × 50 m compared to the 100 m and were positively correlated between tests (p < 0.001). The SI did not differ significantly, but was positively correlated between tests. Males were faster and had a higher SI than females, but genders did not differ in lactate. Since performance variables were better in the SIT set and correlated with those in the 100-m bout, we suggest that the 4 × 50-m set can be used to improve performance in the 100-m freestyle event. Moreover, this set can help coaches identify which swimmers will swim fastest in the event.

Physiological Responses to Low-Volume Interval Training in Women

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

Divergent serum metabolomic, skeletal muscle signaling, transcriptomic, and performance adaptations to fasted versus whey protein-fed sprint interval training

Sprint interval training (SIT) is a time-efficient alternative to endurance exercise, conferring beneficial skeletal muscle metabolic adaptations. Current literature has investigated the nutritional regulation of acute and chronic exercise-induced metabolic adaptations in muscle following endurance exercise, principally comparing the impact of training in fasted and carbohydrate-fed (CHO) conditions. Alternative strategies such as exercising in low CHO, protein-fed conditions remain poorly characterized, specifically pertaining to adaptations associated with SIT. Thus, this study aimed to compare the metabolic and performance adaptations to acute and short-term SIT in the fasted state with preexercise hydrolyzed (WPH) or concentrated (WPC) whey protein supplementation. In healthy males, preexercise protein ingestion did not alter exercise-induced increases in PGC-1α, PDK4, SIRT1, and PPAR-δ mRNA expression following acute SIT. However, supplementation of WPH beneficially altered acute exercise-induced CD36 mRNA expression. Preexercise protein ingestion attenuated acute exercise-induced increases in muscle pan-acetylation and PARP1 protein content compared with fasted SIT. Acute serum metabolomic differences confirmed greater preexercise amino acid delivery in protein-fed compared with fasted conditions. Following 3 wk of SIT, training-induced increases in mitochondrial enzymatic activity and exercise performance were similar across nutritional groups. Interestingly, resting muscle acetylation status was downregulated in WPH conditions following training. Such findings suggest preexercise WPC and WPH ingestion positively influences metabolic adaptations to SIT compared with fasted training, resulting in either similar or enhanced performance adaptations. Future studies investigating nutritional modulation of metabolic adaptations to exercise are warranted to build upon these novel findings.NEW & NOTEWORTHY These are the first data to show the influence of preexercise protein on serum and skeletal muscle metabolic adaptations to acute and short-term sprint interval training (SIT). Preexercise whey protein concentrate (WPC) or hydrolysate (WPH) feeding acutely affected the serum metabolome, which differentially influenced acute and chronic changes in mitochondrial gene expression, intracellular signaling (acetylation and PARylation) resulting in either similar or enhanced performance outcomes when compared with fasted training.

Effect of high-intensity interval training protocols on VO2max and HbA1c level in people with type 2 diabetes: A systematic review and meta-analysis

BACKGROUND

The effect of high-intensity interval training (HIIT) protocols according to different work intervals, session volumes and training periods has not been evaluated in patients with type 2 diabetes mellitus (T2DM).

OBJECTIVE

This was a systematic review and meta-analysis of the effect of HIIT and its different protocols compared to moderate-intensity continuous training (MICT) and the control group on VO₂max and glycated hemoglobin (HbA1c) level in patients with T2DM.

METHODS

The search strategy considered studies published up to September 2020 in the databases MEDLINE (PubMed), EMBASE, Cochrane CENTRAL, Web of Science and SPORTDiscus. Two authors independently searched the selected databases for randomized clinical trials that compared HIIT to MICT or the control in adults with T2DM. A random-effects meta-analysis was performed and the data are presented as the mean difference (95% confidence intervals [95% CIs]) between HIIT, MICT and control groups.

RESULTS

A total of 20 studies (738 participants) were included. Overall, HIIT increased VO₂max by 5.09 mL/kg/min (95% CI 2.99; 7.19, I² = 80.89) versus the control and by 1.9 mL/kg/min (95% CI 0.81; 2.98, I² = 25.62) versus MICT. HIIT promoted a significant reduction in HbA1c level of -0.8% (95% CI -1.06; -0.49, I² = 77.31) versus the control but with no difference versus MICT. Moderate-interval, high-volume and long-term training promoted a greater increase in VO₂max. A long interval and moderate volume and period conferred a greater increase in VO₂max versus MICT. A short interval and moderate volume and period conferred a greater reduction in HbA1c level versus the control. No publication bias was detected, as evaluated by a funnel chart and Egger's test (p > 0.05).

CONCLUSIONS

As compared with MICT, HIIT had better effect on VO₂max and a similar effect on HbA1C level. Interval protocols, moderate to long training period and moderate to high volume may maximize the HIIT effect in patients with T2DM.

Effects of high intensity interval training and sprint interval training in patients with asthma: a systematic review

OBJECTIVE

The aim of this study is to review the effects of high-intensity interval training (HIIT)/sprint interval training (SIT) on asthma symptoms, cardiorespiratory functions, and other variables among asthmatic patients.

DATA SOURCES

Randomized controlled trials published between January 2000 and January 2021 were searched in PubMed/MEDLINE, Web of Science, and Cochrane Library databases.

STUDY SELECTIONS

Following pre-specified inclusion criteria, this review included 7 randomized controlled studies that compare HIIT/SIT as an intervention with any other intervention and/or control group.

RESULTS

Of the included studies only four reported the chronic phase effects of the HIIT/SIT protocols. HIIT and SIT protocols applied in studies differ. HIIT improved forced expiratory volume in 1 s (FEV₁) in the acute phase and maximal oxygen consumption (VO_2max) in the chronic phase in the asthmatic patients (p < 0.05).

CONCLUSION

To our knowledge, our systematic review is the first study evaluating the effects of HIIT/SIT protocols on asthma patients. HIIT/SIT protocols have beneficial effects on asthma patients. In order to better understand the results of these training procedures, studies that will be designed with high methodology are needed.

The Effects of Running Compared with Functional High-Intensity Interval Training on Body Composition and Aerobic Fitness in Female University Students

High-intensity interval running (HIIT-R) and high-intensity functional training (HIFT) are two forms of HIIT exercise that are commonly used. The purpose of this study was to determine the effects of HIFT on aerobic capacity and body composition when compared to HIIT-R in females. Twenty healthy, untrained female university students (age 20.5 ± 0.7 year) were randomly assigned to a 12-week HIIT-R or HIFT intervention. The HIIT-R group involved a 30 s maximal shuttle run with a 30 s recovery period, whereas the HIFT involved multiple functional exercises with a 2:1 work-active recovery ratio. Body composition, VO₂max, and muscle performance were measured before and post intervention. As a result, HIIT-R and HIIT-F stimulated similar improvements in VO₂max (17.1% ± 5.6% and 12.7% ± 6.7%, respectively, p > 0.05). Only the HIIT-F group revealed significant improvements in muscle performance (sit-ups, 16.5% ± 3.1%, standing broad jump 5.1% ± 2.2%, p < 0.05). Body fat percentage decreased (17.1% ± 7.4% and 12.6% ± 5.1%, respectively, p < 0.05) in both HIIT-R and HIIT-F with no between-group differences. We concluded that HIFT was equally effective in promoting body composition and aerobic fitness compared to HIIT-R. HIFT resulted in improved muscle performance, whereas the HIIT-R protocol demonstrated no gains.

Concentric not eccentric cycling sprint intervals acutely impair balance and jump performance in healthy active young adults: A randomized controlled cross-over study

INTRODUCTION

Moderate aerobic, high-intensity and sprint running or cycling training can transiently impair postural control. However, the acute effects of modified sprint interval training (mSIT) at different muscle working modes have not yet been examined. Thus, this study aimed at investigating acute effects of time-matched eccentric (ECC) versus concentric mSIT cycling session (CON) on jumping and functional balance performance.

METHODS

Twenty-five healthy and active males (30.0 ± 6.0 years; 80.1 ± 9.1 kg; V̇O_2max: 64.2 ± 7.9 mL kg^-1 min^-1) were enrolled in this acute randomized controlled crossover trial. Counter-Movement-Jump (CMJ) and functional balance testing (Y-Balance-Test composite score [YBT_CS]; Posturomed total distance: Posturomed_TD) were assessed as primary outcomes before, and immediately after cessation of ECC and CON (10 × 10 s maximum sprints and 50 s of active recovery).

RESULTS

A significant mode × time interaction effect for CMJ (F = 9.620, p = 0.005, η_p² = 0.29) was observed. Subsequent post-hoc testing revealed significant moderate reductions in jumping height after CON (0.31 ± 0.06 vs. 0.27 ± 0.06m; p = 0.004, SMD = 0.59), whilst ECC remained unchanged. YBT_CS (mode × time interaction: F = 6.880, p = 0.015, η_p² = 0.22) showed small but significant balance impairments after CON (0.964 ± 0.068 vs. 0.960 ± 0.063 AU; p = 0.009, SMD = 0.28) and did not significantly change after ECC. Although large significant interaction effects (p = 0.029, η_p² = 0.18) were observed for Posturomed_TD, follow up post-hoc testing did not reveal relevant pre-post differences, neither for ECC nor CON.

CONCLUSION

Both functional balance and jumping performance are deteriorated after acute concentric but not eccentric mSIT cycling. Although higher pedal forces at lower perceived efforts and heart rates during eccentric mSIT were observed, it seems that the cardiocirculatory demanding CON session elicited more pronounced balance and jump performance impairments than eccentric cycling.

Vitamin C and E Treatment Blocks Changes in Kynurenine Metabolism Triggered by Three Weeks of Sprint Interval Training in Recreationally Active Elderly Humans

The kynurenine pathway (KP) is gaining attention in several clinical fields. Recent studies show that physical exercise offers a therapeutic way to improve ratios of neurotoxic to neuroprotective KP metabolites. Antioxidant supplementation can blunt beneficial responses to physical exercise. We here studied the effects of endurance training in the form of sprint interval training (SIT; three sessions of 4–6 × 30 s cycling sprints per week for three weeks) in elderly (~65 years) men exposed to either placebo (n = 9) or the antioxidants vitamin C (1 g/day) and E (235 mg/day) (n = 11). Blood samples and muscle biopsies were taken under resting conditions in association with the first (untrained state) and last (trained state) SIT sessions. In the placebo group, the blood plasma level of the neurotoxic quinolinic acid was lower (~30%) and the neuroprotective kynurenic acid to quinolinic acid ratio was higher (~50%) in the trained than in the untrained state. Moreover, muscle biopsies showed a training-induced increase in kynurenine aminotransferase (KAT) III in the placebo group. All these training effects were absent in the vitamin-treated group. In conclusion, KP metabolism was shifted towards neuroprotection after three weeks of SIT in elderly men and this shift was blocked by antioxidant treatment.

Comparison of Aerobic Capacity Changes as a Result of a Polarized or Block Training Program among Trained Mountain Bike Cyclists

This study compared the effectiveness of a block training program and a polarized training program in developing aerobic capacity in twenty trained mountain bike cyclists. The cyclists were divided into two groups: the block training program group (BT) and the polarized training program group (PT). The experiment lasted 8 weeks. During the experiment, the BT group alternated between 17-day blocks consisting of dominant low-intensity training (LIT) and 11-day blocks consisting of sprint interval training (SIT), and high-intensity interval training (HIIT), while the PT group performed SIT, HIIT, and LIT simultaneously. Before and after the experiment, the cyclists performed incremental tests during which maximal oxygen uptake (VO₂max), maximal aerobic power (Pmax), power achieved at the first ventilatory threshold (P_VT1), and at the second ventilatory threshold (P_VT2) were measured. VO₂max increased in BT group (from 3.75 ± 0.67 to 4.00 ± 0.75 L∙min^-1) and PT group (from 3.66 ± 0.73 to 4.20 ± 0.89 L∙min^-1). In addition, Pmax, P_VT1, and P_VT2 increased in both groups to a similar extent. In conclusion, the polarized training program was more effective in developing the VO₂max compared to the block program. In terms of developing other parameters characterizing the cyclists' aerobic capacity, the block and polarized program induced similar results.

Under the Hood: Skeletal Muscle Determinants of Endurance Performance

In the past decades, researchers have extensively studied (elite) athletes' physiological responses to understand how to maximize their endurance performance. In endurance sports, whole-body measurements such as the maximal oxygen consumption, lactate threshold, and efficiency/economy play a key role in performance. Although these determinants are known to interact, it has also been demonstrated that athletes rarely excel in all three. The leading question is how athletes reach exceptional values in one or all of these determinants to optimize their endurance performance, and how such performance can be explained by (combinations of) underlying physiological determinants. In this review, we advance on Joyner and Coyle's conceptual framework of endurance performance, by integrating a meta-analysis of the interrelationships, and corresponding effect sizes between endurance performance and its key physiological determinants at the macroscopic (whole-body) and the microscopic level (muscle tissue, i.e., muscle fiber oxidative capacity, oxygen supply, muscle fiber size, and fiber type). Moreover, we discuss how these physiological determinants can be improved by training and what potential physiological challenges endurance athletes may face when trying to maximize their performance. This review highlights that integrative assessment of skeletal muscle determinants points toward efficient type-I fibers with a high mitochondrial oxidative capacity and strongly encourages well-adjusted capillarization and myoglobin concentrations to accommodate the required oxygen flux during endurance performance, especially in large muscle fibers. Optimisation of endurance performance requires careful design of training interventions that fine tune modulation of exercise intensity, frequency and duration, and particularly periodisation with respect to the skeletal muscle determinants.

The physiological impact of high-intensity interval training in octogenarians with comorbidities

BACKGROUND

Declines in cardiorespiratory fitness (CRF) and fat-free mass (FFM) with age are linked to mortality, morbidity and poor quality of life. High-intensity interval training (HIIT) has been shown to improve CRF and FFM in many groups, but its efficacy in the very old, in whom comorbidities are present is undefined. We aimed to assess the efficacy of and physiological/metabolic responses to HIIT, in a cohort of octogenarians with comorbidities (e.g. hypertension and osteoarthritis).

METHODS

Twenty-eight volunteers (18 men, 10 women, 81.2 ± 0.6 years, 27.1 ± 0.6 kg·m^-2 ) with American Society of Anaesthesiology (ASA) Grade 2-3 status each completed 4 weeks (12 sessions) HIIT after a control period of equal duration. Before and after each 4 week period, subjects underwent body composition assessments and cardiopulmonary exercise testing. Quadriceps muscle biopsies (m. vastus lateralis) were taken to quantify anabolic signalling, mitochondrial oxidative phosphorylation, and cumulative muscle protein synthesis (MPS) over 4-weeks.

RESULTS

In comorbid octogenarians, HIIT elicited improvements in CRF (anaerobic threshold: +1.2 ± 0.4 ml·kg^-1 ·min^-1 , P = 0.001). HIIT also augmented total FFM (47.2 ± 1.4 to 47.6 ± 1.3 kg, P = 0.04), while decreasing total fat mass (24.8 ± 1.3 to 24 ± 1.2 kg, P = 0.0002) and body fat percentage (33.1 ± 1.5 to 32.1 ± 1.4%, P = 0.0008). Mechanistically, mitochondrial oxidative phosphorylation capacity increased after HIIT (i.e. citrate synthase activity: 52.4 ± 4 to 67.9 ± 5.1 nmol·min^-1 ·mg^-1 , P = 0.005; membrane protein complexes (C): C-II, 1.4-fold increase, P = 0.002; C-III, 1.2-fold increase, P = 0.03), as did rates of MPS (1.3 ± 0.1 to 1.5 ± 0.1%·day^-1 , P = 0.03). The increase in MPS was supported by up-regulated phosphorylation of anabolic signalling proteins (e.g. AKT, p70S6K, and 4E-BP1; all P < 0.05). There were no changes in any of these parameters during the control period. No adverse events were reported throughout the study.

CONCLUSIONS

The HIIT enhances skeletal muscle mass and CRF in octogenarians with disease, with up-regulation of MPS and mitochondrial capacity likely underlying these improvements. HIIT can be safely delivered to octogenarians with disease and is an effective, time-efficient intervention to improve muscle mass and physical function in a short time frame.

Jumping into a Healthier Future: Trampolining for Increasing Physical Activity in Children

OBJECTIVES

Physical activity in children and adolescents has positive effects on cardiopulmonary function in this age group as well as later in life. As poor cardiopulmonary function is associated with higher mortality and morbidity, increasing physical activity especially in children needs to become a priority. Trampoline jumping is widely appreciated in children. The objective was to investigate its use as a possible training modality.

METHODS

Fifteen healthy children (10 boys and 5 girls) with a mean age of 8.8 years undertook one outdoor incremental running test using a mobile cardiopulmonary exercise testing unit. After a rest period of at least 2 weeks, a trampoline test using the mobile unit was realized by all participants consisting of a 5-min interval of moderate-intensity jumping and two high-intensity intervals with vigorous jumping for 2 min, interspersed with 1-min rests.

RESULTS

During the interval of moderate intensity, the children achieved [Formula: see text]-values slightly higher than the first ventilatory threshold (VT1) and during the high-intensity interval comparable to the second ventilatory threshold (VT2) of the outdoor incremental running test. They were able to maintain these values for the duration of the respective intervals. The maximum values recorded during the trampoline test were significantly higher than during the outdoor incremental running test.

CONCLUSION

Trampoline jumping is an adequate tool for implementing high-intensity interval training as well as moderate-intensity continuous training in children. As it is a readily available training device and is greatly enjoyed in this age group, it could be implemented in exercise interventions.