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

Effects of Exercise Training on Mitochondrial and Capillary Growth in Human Skeletal Muscle: A Systematic Review and Meta-Regression

BACKGROUND

Skeletal muscle mitochondria and capillaries are crucial for aerobic fitness, and suppressed levels are associated with chronic and age-related diseases. Currently, evidence-based exercise training recommendations to enhance these characteristics are limited. It is essential to explore how factors, such as fitness level, age, sex, and disease affect mitochondrial and capillary adaptations to different exercise stimuli.

OBJECTIVES

The main aim of this study was to compare the effects of low- or moderate intensity continuous endurance training (ET), high-intensity interval or continuous training (HIT), and sprint interval training (SIT) on changes in skeletal muscle mitochondrial content and capillarization. Secondarily, the effects on maximal oxygen consumption (VO2max), muscle fiber cross-sectional area, and fiber type proportion were investigated.

METHODS

A systematic literature search was conducted in PubMed, Web of Science, and SPORTDiscus databases, with no data restrictions, up to 2 February 2022. Exercise training intervention studies of ET, HIT, and SIT were included if they had baseline and follow-up measures of at least one marker of mitochondrial content or capillarization. In total, data from 5973 participants in 353 and 131 research articles were included for the mitochondrial and capillary quantitative synthesis of this review, respectively. Additionally, measures of VO2max, muscle fiber cross-sectional area, and fiber type proportion were extracted from these studies.

RESULTS

After adjusting for relevant covariates, such as training frequency, number of intervention weeks, and initial fitness level, percentage increases in mitochondrial content in response to exercise training increased to a similar extent with ET (23 ± 5%), HIT (27 ± 5%), and SIT (27 ± 7%) (P > 0.138), and were not influenced by age, sex, menopause, disease, or the amount of muscle mass engaged. Higher training frequencies (6 > 4 > 2 sessions/week) were associated with larger increases in mitochondrial content. Per total hour of exercise, SIT was ~ 2.3 times more efficient in increasing mitochondrial content than HIT and ~ 3.9 times more efficient than ET, while HIT was ~ 1.7 times more efficient than ET. Capillaries per fiber increased similarly with ET (15 ± 3%), HIT (13 ± 4%) and SIT (10 ± 11%) (P = 0.556) after adjustments for number of intervention weeks and initial fitness level. Capillaries per mm2 only increased after ET (13 ± 3%) and HIT (7 ± 4%), with increases being larger after ET compared with HIT and SIT (P < 0.05). This difference coincided with increases in fiber cross-sectional area after ET (6.5 ± 3.5%), HIT (8.9 ± 4.9%), and SIT (11.9 ± 15.1%). Gains in capillarization occurred primarily in the early stages of training (< 4 weeks) and were only observed in untrained to moderately trained participants. The proportion of type I muscle fibers remained unaltered by exercise training (P > 0.116), but ET and SIT exhibited opposing effects (P = 0.041). VO2max increased similarly with ET, HIT, and SIT, although HIT showed a tendency for greater improvement compared with both ET and SIT (P = 0.082), while SIT displayed the largest increase per hour of exercise. Higher training frequencies (6 > 4 > 2 sessions/week) were associated with larger increases in VO2max. Women displayed greater percentage gains in VO2max compared with men (P = 0.008). Generally, lower initial fitness levels were associated with greater percentage improvements in mitochondrial content, capillarization, and VO2max. SIT was particularly effective in improving mitochondrial content and VO2max in the early stages of training, while ET and HIT showed slower but steady improvements over a greater number of training weeks.

CONCLUSIONS

The magnitude of change in mitochondrial content, capillarization, and VO2max to exercise training is largely determined by the initial fitness level, with greater changes observed in individuals with lower initial fitness. The ability to adapt to exercise training is maintained throughout life, irrespective of sex and presence of disease. While training load (volume × intensity) is a suitable predictor of changes in mitochondrial content and VO2max, this relationship is less clear for capillary adaptations.

Metabolomics analyses and physical interventions in soccer: a systematic review

BACKGROUND

Soccer is the most recognized sports worldwide. It is a fertile ground for the use of metabolomics analyses, considering the multifactorial nature of soccer's physical demands on the body. Although scientific studies have tried using it to better understand the impacts of soccer into different contexts of the sport, no systematic review is available on metabolomics analyses in soccer athletes subjected to physical exertion interventions.

AIM OF REVIEW

Retrieve scientific articles that conducted metabolomics analyses on soccer athletes subjected to physical exertion interventions.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Initially, 271 studies were screened, and 48 were retrieved for abstract analysis. Of these, 26 met the eligibility criteria, but 5 failed to meet inclusion criteria. The 21 studies included in this systematic review demonstrate that responses from physical training or acute exercise sessions, followed by the effects of soccer matches, have been the primary focus of researchers to date, highlighting alterations on metabolites from the energy metabolism, immunological pathway, purines, tryptophan/phenylalanine metabolism, as well as oxidative species and antioxidant capacity. Other studies suggest, albeit preliminarily, that organic metabolites have the potential to distinguish soccer players' performance and physical fitness, as well as provide valuable insights into diet, physical condition, training load, and recovery throughout the season. Despite metabolomics great potential to understand physiological alterations provoked by soccer as shown by the included studies, future studies should consider female athletes, explore the cause-and-effect relationship between metabolites and soccer performance more deeply, and examine the effects of different training periodizations on these markers.

Greater improvement in aerobic capacity after a polarized training program including cycling interval training at low cadence (50-70 RPM) than freely chosen cadence (above 80 RPM)

This study compared the impact of two polarized training programs (POL) on aerobic capacity in well-trained (based on maximal oxygen uptake and training experience) female cyclists. Each 8-week POL program consisted of sprint interval training (SIT) consisting of 8-12 repetitions, each lasting 30 seconds at maximal intensity, high-intensity interval training (HIIT) consisting of 4-6 repetitions, each lasting 4 minutes at an intensity of 90-100% maximal aerobic power, and low-intensity endurance training (LIT) lasting 150-180 minutes with intensity at the first ventilatory threshold. Training sessions were organized into 4-day microcycles (1st day-SIT, 2nd day-HIIT, 3rd day-LIT, and 4th day-active rest), that were repeated throughout the experiment. In the first POL program, exercise repetitions during SIT and HIIT training were performed with freely chosen cadence above 80 RPM (POLFC group, n = 12), while in the second POL program with low cadence 50-70 RPM (POLLC group, n = 12). Immediately before and after the 8-week POL intervention, participants performed an incremental test to measure maximal aerobic power (Pmax), power achieved at the second ventilatory threshold (VT2), maximal oxygen uptake (VO2max), maximal pulmonary ventilation (VEmax), and gross efficiency (GE). Moreover, participants performed VO2max verification test. Analysis of variance showed a repeated measures effect for Pmax (F = 21.62; η2 = 0.5; p = 0.00), VO2max (F = 39.39; η2 = 0.64; p = 0.00) and VEmax (F = 5.99; η2 = 0.21; p = 0.02). A repeated measures x group mixed effect was demonstrated for Pmax (F = 4.99; η2 = 0.18; p = 0.03) and VO2max (F = 6.67; η2 = 0.23; p = 0.02). Post-hoc Scheffe analysis showed that increase in Pmax were statistically significant only in POLLC group. The Friedman test showed that VT2 differed between repeated measures only in the POLLC group (χ2 = 11; p = 0.001; W = 0.917). In conclusion, it was found that POL program where SIT and HIIT were performed at low cadence was more effective in improving aerobic capacity in well-trained female cyclists, than POL with SIT and HIIT performed at freely chosen cadence. This finding is a practical application for athletes and coaches in cycling, to consider not only the intensity and duration but also the cadence used during various interval training sessions.

High-intensity interval training vs. yoga in improving binge eating and physical fitness in inactive young females

Yoga is effective in binge eating disorder (BED) treatment, but it does not seem effective enough to improve low physical fitness. In contrast, high-intensity interval training (HIIT) is effective in improving physical fitness but has never been studied in the context of BED. In the study, 47 young inactive females with mild to moderate BED were recruited and randomly assigned to a HIIT group (HIIT), a Yoga group (YG), or a control group (CG; age, 19.47 ± 0.74, 19.69 ± 0.874, and 19.44 ± 0.63 years; BMI, 21.07 ± 1.66, 21.95 ± 2.67, and 20.68 ± 2.61 kg/m2, respectively). The intervention groups participated in 8-week specific exercises, while the CG maintained their usual daily activity. Before and after the training, participants were evaluated for BED using the binge eating scale (BES) and for physical fitness. The obtained data were compared within groups and between groups, and a correlation analysis between BES and physical fitness parameters was performed. After the training, the YG presented significant improvements in BES (- 20.25%, p = 0.006, ηp2 = 0.408), fat mass (FM, - 3.13%, p = 0.033, ηp2 = 0.269), and maximal oxygen consumption (VO2max, 11.51%, p = 0.000, ηp2 = 0.601), whereas the HIIT showed significant improvements in body weight (BW, - 1.78%, p = 0.006, ηp2 = 0.433), FM (- 3.94%, p = 0.033, ηp2 = 0.285), and BMI (- 1.80%, p = 0.006, ηp2 = 0.428), but not in BES. Comparisons between groups revealed that both HIIT and YG had significantly higher VO2max levels than CG (HIIT 12.82%, p = 0.006, ηp2 = 0.088; YG: 11.90%, p = 0.009, ηp2 = 0.088) with no difference between HIIT and YG. Additionally, YG presented significantly lower BES than both HIIT (15.45%, p = 0.02, ηp2 = 0.03) and CG (11.91%, p = 0.022, ηp2 = 0.03). In conclusion, Yoga is an effective treatment for BED, but HIIT is not, despite its high efficacy in improving physical fitness.

Factors influencing sports performance: A multi-dimensional analysis of coaching quality, athlete well-being, training intensity, and nutrition with self-efficacy mediation and cultural values moderation

This study examines the dynamic relationships between cultural values, training intensity, nutrition, self-efficacy, and coaching quality on Chinese athletes' performance. Bandura's social cognitive theory and cultural psychology ideas enlightened the multi-faceted sports performance analysis. A detailed questionnaire was employed to obtain data from 880 athletes from various places and sports backgrounds. Structural Equation Modeling (SEM) was used for empirical analysis. The results show a significant positive association between coaching quality (β = 0.62, p < 0.001), athlete well-being (β = 0.48, p < 0.001), training intensity (β = 0.55, p < 0.001), nutrition (β = 0.42, p < 0.001), self-efficacy (β = 0.57, p < 0.001), and sports performance. Coaching quality appeared as a critical component. Athletes performed better when they felt their instructors were performing better. Diet, training intensity, and health affected athletes' performance, highlighting the necessity for athlete development. Athletes' confidence in their performance is mediated by coaching, well-being, training, nutrition, and performance. These correlations were further impacted by cultural values, highlighting the need to consider cultural context while attempting to enhance athlete performance outcomes. The study concludes that cultural values, self-efficacy, training, nutrition, coaching, and health are crucial to Chinese athletes' success.

Lifestyle factors as determinants of atherosclerotic cardiovascular health

A sedentary lifestyle, low levels of physical activity and fitness, poor dietary patterns, and psychosocial stress are strongly associated with increased morbidity and mortality from atherosclerotic cardiovascular disease (ASCVD). Conversely, engaging in regular physical activity, maintaining optimal fitness levels, adhering to a heart-healthy dietary pattern, effectively managing body weight, ensuring adequate sleep, implementing stress-reduction strategies, and addressing psychosocial risk factors are associated with a reduced risk of ASCVD. This comprehensive review synthesizes current evidence from large observational studies and randomized controlled trials on lifestyle factors as determinants of ASCVD health. It also briefly reviews mechanistic insights into how factors such as low shear stress, increased reactive oxygen species production, chronic inflammation, platelets and coagulation activation, endothelial dysfunction, and sympathetic hyperactivity contribute to the initiation and exacerbation of ASCVD risk factors. These include obesity, hyperglycemia, type 2 diabetes, hypertension, and dyslipidemia, subsequently leading to the development and progression of atherosclerosis, ultimately resulting in chronic ASCVD or acute cardiovascular events. To bridge the translational gap between epidemiologic and trial-based evidence and clinical practice, practical recommendations are summarized to facilitate the translation of scientific knowledge into actionable interventions to promote ASCVD health. Acknowledged is the gap between the evidence-based knowledge and adoption within healthcare systems, which remains a crucial objective in advancing cardiovascular health at the population level.

Impact of supra-maximal interval training vs. high-intensity interval training on cardiac auto-regulation response in physically active adults

PURPOSE

This study aimed to examine the impact of supra-maximal interval training (SMIT) and high-intensity interval training (HIIT) on cardiac auto-regulation response.

METHODS

Physically active young adults volunteered to participate in the study with a randomized cross-over counterbalanced design (N = 12). HIIT sessions consisted of 20 bouts of 10 s of exercise followed by 50 s of recovery, totaling 20 min at two different intensities; "all-out (SMIT)" vs. "115-130% Wmax (HIIT)". The cardiac auto-regulation included heart rate variability (HRV) and vascular function. HRV and vascular function were measured at baseline and five different time points after acute exercise.

RESULTS

The SMIT was higher in workload (31%), peak heart rate (28%), and rate of perceived exertion (40%) compared with HIIT (all p < 0.001). The R-R interval, NN50, and pNN50 measured until 60 min after acute exercise was higher in the HIIT compared with SMIT (all p < 0.05). The SMIT elicited a greater shift in ln LF/HF ratio immediately after acute exercise (3802%, p < 0.01) and induced a decrease in bilateral ba-PWV at the time point 5 min after acute exercise, persisting until 65 min after (p < 0.05). Yet, HIIT showed no change over time in the frequency domain of HRV and blood vascular tone after cessation of acute exercise.

CONCLUSION

Our findings confirmed that SMIT is a more potent modulator of the autonomic nervous system compared with HIIT. Further study is needed to monitor through complete recovery to baseline, to understand acute cardiac auto-regulation response after cessation of various exercise intensities identical interval training protocol.

Sex Influences the Extent of Physical Performance Adaptations in Response to Small-Sided Games and Running-Based High-Intensity Interval Training: A Parallel Study Design Involving Men and Women Soccer Players

The aim of this study was two-fold: (i) to compare physical fitness adaptations following small-sided games (SSG) and running-based high-intensity interval training (HIIT), considering sex interactions; and (ii) to describe intra-individual variations of adaptations in both men and women developmental/trained soccer players over an 8-week randomized parallel study design involving 25 women and 27 men. Pre and post-intervention assessments included countermovement jump (CMJ), 10-meter linear sprint test, change-of-direction (COD) deficit, and final velocity at 30-15 Intermittent Fitness Test (VIFT). Significant interactions between time, groups and sex were found in 10-m sprint (F1,48 = 6.042; p = 0.018; ηp2 = 0.112). No significant interactions between time, groups and sex were found in CMJ (F F1,48 = 0.609; p = 0.439; ηp2 = 0.013), COD deficit (F F1,48 = 2.718; p = 0.106; ηp2 = 0.054) and VIFT (F F1,48 = 1.141; p = 0.291; ηp2 = 0.023). Significant interactions were found between time and sex in CMJ (F F1,48 = 29.342; p < 0.001; ηp2= 0.379), 10-m sprint (F F1,48 = 4.359; p = 0.042; ηp2 = 0.083), COD deficit (F F1,48 = 5.066; p = 0.029; ηp2= 0.095) and VIFT (F F1,48 = 11.248; p = 0.002; ηp2 = 0.190). In conclusion, this study suggests similar effects of HIIT in both sexes. However, for women, SSG may entail less efficacy and more inter-individual variability compared to men. Therefore, HIIT could potentially be a better solution for women, whereas both training approaches were equally effective in men.