Objectives: To examine the effects of different protocols of high-intensity interval training (HIIT) on VO2max improvements in healthy, overweight/obese and athletic adults, based on the classifications of work intervals, session volumes and training periods. Design: Systematic review and meta-analysis. Methods: PubMed, Scopus, Medline, and Web of Science databases were searched up to April 2018. Inclusion criteria were randomised controlled trials; healthy, overweight/obese or athletic adults; examined pre-and post-training VO2max/peak; HIIT in comparison to control or moderate intensity continuous training (MICT) groups.Results: Fifty-three studies met the eligibility criteria. Overall, the degree of change in VO2max induced by HIIT varied by populations (SMD = 0.41-1.81, p<0.05). When compared to control groups, even short-intervals (≤ 30s), low-volume (≤ 5 min) and short-term HIIT (≤ 4 weeks) elicited clear beneficial effects (SMD = 0.79-1.65, p<0.05) on VO2max/peak. However, long-interval (≥ 2 min), high-volume (≥ 15 min) and moderate to long-term (≥ 4-12 weeks) HIIT displayed significantly larger effects on VO2max (SMD = 0.50-2.48, p<0.05). When compared to MICT, only long-interval (≥ 2 min), high-volume (≥ 15 min) and moderate to long-term (≥ 4-12 weeks) HIIT showed beneficial effects (SMD = 0.65-1.07, p<0.05) Conclusions: Short-intervals (≤ 30 s), low-volume (≤ 5 min) and short-term (≤ 4 weeks) HIIT represent effective and time-efficient strategies for developing VO2max, especially for the general population. To maximize the training effects on VO2max, long-interval (≥ 2 min), high-volume (≥ 15 min) and moderate to long-term (≥ 4-12 weeks) HIIT are recommended.
The purpose of this paper was to systematically review the literature and examine the research methodological quality, measurement properties and feasibility of the Loughborough Soccer Passing Test (LSPT). Databases were searched up to June 2017. Twenty five studies fulfilled the eligibility criteria. The main methodological limitations of the studies were the small sample size and the lack of information on participants and eligibility criteria. Results showed that test-retest reliability of the LSPT was moderate to excellent. Good discriminative validity was found between playing levels and ages. The LSPT was positively correlated with sprint, dribbling, and agility test; however, a weak correlation was established with in-game performance. Test responsiveness (an ability to detect change over time) to some external interventions was observed in studies. Adjusted Cronbach's alpha (α = 0.67), smallest worthwhile change (SWC = 0.8-3.8) and minimal detectable change (MDC = 1.9-11.3) were calculated based on available data. The findings indicate that the LSPT has acceptable test-retest reliability and discriminative validity. However, it may not be a feasible and effective way to interpret the intra-individual change of skill performance in practice. Future work should be undertaken to establish additional measurement properties of the LSPT, and to improve its practical feasibility.
Background Older and more mature football players have been reported to gain advantages in the selection process during adolescence. The aim of this study was to investigate the influence of skeletal age (SA) on the physical characteristics of elite male football players aged 13–15 years through a cross-sectional study. Methods and Materials We enrolled 167 elite players aged 13–15 from three academic football schools in China, and measured height, body mass, thigh circumference, skinfold (triceps and calf), 10 m/30-m sprint, T-tests (left and right), 5 × 25-m repeated-sprint ability (5 × 25 RSA), standing long jump, and YoYo intermittent recovery test level 1 (YYIR1). Subjects were divided into early-, average-, and late-maturity levels according to their SA and chronological age (CA) based on the following criteria: SA-CA > +1 year, SA-CA = ±1 year, and SA-CA < −1 year, respectively. The differences in parameters among the groups were analyzed using one-way analysis of variance and Bonferroni’s post-hoc test, with statistical significance set at p < 0.05. Results Relative to the late-maturing players, the early- and average-maturing players aged 13–15 years were taller, heavier, had a larger thigh circumference, and scored higher on the standing long jump, 30 m sprint, and 5 × 25-RSA (p < 0.05). The physical (except for body-fat percentage) and athletic characteristics of players aged 13–15 were not only significantly influenced by biological maturity, but also increased significantly with CA. The influence of biological maturity on height, 30-m sprints, and 5 × 25-m RSA diminished with age and exerted no significant effect on body-fat percentage and on YYIR1. Late-maturing players exhibited the greatest increase in physical (except for body-fat percentage) and athletic performance (except for the 10-m sprint) compared to players of early and/or average maturity. Conclusions Although early-maturing players aged 13–15 possessed better anthropometric and physical performance than late- and average-maturing players, the growth and development of physical function of late- and average-maturing players was significantly greater, particularly with respect to height, sprint speed, and muscular power.
Background/Objective. Impaired glucose tolerance (IGT) is an intermediate metabolic state between normal and diabetes and shows insulin resistant (IR) which to be linked with mitochondria dysfunction. This study is aimed at investigating whether aerobic exercise increases Mfn2 to promote mitochondrial function and improve glucose tolerance and insulin sensitivity in mice with high-fat diet. Methods. Male C57BL/6J mice were randomly divided into six different experimental groups (8 animals/group): (1) normal group (NOR), (2) normal control group (NC), (3) normal + exercise group (NE), (4) IGT group (IGT), (5) IGT control group (IC), and (6) IGT+ exercise group (IE).The exercise group received aerobic exercise for 8 weeks. After the intervention, a blood glucose meter was used to detect the level of glucose tolerance in the mouse’s abdominal cavity; a biochemical kit was used to detect serum lipid metabolism indicators, malondialdehyde, and superoxide dismutase levels; the ELISA method was used to detect serum insulin and mouse gastrocnemius homogenate LDH, PDH, SDH, and CCO levels. Western blot method was used to detect the protein expression levels of NOX4, PGC-1α, and Mfn2 in the gastrocnemius muscle of mice. Results. (1) Mice with high-fat diet for 30 weeks showed impaired glucose tolerance, insulin resistance, and lipid metabolism disorders. The level of LDH, PDH, SDH, and CCO in the gastrocnemius homogenate of mice was reduced. The expressions of NOX4 protein were significantly upregulated, while the expressions of PGC-1α and Mfn2 proteins were significantly downregulated. (2) 8-week aerobic exercise improved the disorders of glucose and lipid metabolism in IGT mice and increased homogenized LDH, PDH, SDH, and CCO levels, and the expressions of NOX4, PGC-1α, and Mfn2 proteins in the gastrocnemius muscle of mice were reversed. It is speculated that aerobic exercise can accelerate energy metabolism. Conclusion. (1) C57BL/6 mice were fed high fat for 30 weeks and successfully constructed a mouse model of reduced diabetes; the mice with reduced diabetes have impaired glucose tolerance, insulin resistance, and lipid metabolism disorders; (2) 8 weeks of aerobic exercise improve glucose tolerance, reduce glucose tolerance in mice, reduce insulin resistance, improve lipid metabolism disorders, and reduce oxidative stress; (3) 8-week aerobic exercise reduces skeletal muscle NOX4 expression and increases glucose tolerance; reduces the expression of LDH, PDH, SDH, and CCO in mouse skeletal muscle; increases the expression level of mitochondrial fusion protein 2 and PGC-1α; improves glucose tolerance; reduces energy metabolism of mouse skeletal muscle; reduces oxidative stress; and reduces insulin resistance. It is speculated that aerobic exercise can accelerate energy metabolism. This process may involve two aspects: firstly, increase the expression level of oxidative metabolism enzymes and promote the tricarboxylic acid cycle; secondly, increase the expression of Mfn2 and accelerate mitochondria fission or fusion to regulate energy metabolism, thereby reducing oxidative stress and insulin resistance.
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