Acute effects of concurrent muscle power and sport-specific endurance exercises on markers of immunological stress response and measures of muscular fitness in highly trained youth male athletes.

PURPOSE: To examine the acute effects of concurrent muscle power and sport-specific endurance exercises order on immunological stress responses, muscular-fitness, and rating-of-perceived-exertion (RPE) in highly trained youth male judo athletes. METHODS: Twenty male participants randomly performed two concurrent training (CT) sessions; power-endurance and endurance-power. Measures of immune response (e.g., white blood cells), muscular-fitness (i.e., counter-movement-jump [CMJ]), RPE, blood-lactate, and -glucose were taken at different time-point (i.e., pre, mid, post, and post6h). RESULTS: There were significant time*order interactions for white blood cells, lymphocytes, granulocytes, granulocyte-lymphocyte-ratio, and systemic-inflammation-index. Power-endurance resulted in significantly larger pre-to-post increases in white blood cells and lymphocytes while endurance-power resulted in significantly larger pre-to-post increases in the granulocyte-lymphocyte-ratio and systemic-inflammation-index. Likewise, significantly larger pre-to-post6h white blood cells and granulocytes increases were observed following power-endurance compared to endurance-power. Moreover, there was a significant time*order interaction for blood-glucose and -lactate. Following endurance-power, blood-lactate and -glucose increased from pre-to-mid but not from pre-to-post. Meanwhile, in power-endurance blood-lactate and -glucose increased from pre-to-post but not from pre-to-mid. A significant time*order interaction was observed for CMJ-force with larger pre-to-post decreases in endurance-power compared to power-endurance. Further, CMJ-power showed larger pre-to-mid performance decreases following power-endurance, compared to endurance-power. Regarding RPE, significant time*order interactions were noted with larger pre-to-mid values following endurance-power and larger pre-to-post values following power-endurance. CONCLUSION: CT induced acute and delayed order-dependent immune cell count alterations in highly trained youth male judo athletes. In general, power-endurance induced higher acute and delayed immunological stress responses compared to endurance-power. CMJ-force and RPE fluctuated during both CT sessions but went back to baseline 6 h post-exercise.

Chronic Effects of Static Stretching Exercises on Muscle Strength and Power in Healthy Individuals Across the Lifespan: A Systematic Review with Multi-level Meta-analysis.

BACKGROUND: The current literature on the chronic effects of static stretching (SS) exercises on muscle strength and power is unclear and controversial. OBJECTIVE: We aimed to examine the chronic effects of SS exercises on muscle strength and power as well as flexibility in healthy individuals across the lifespan. DESIGN: Systematic review with meta-analysis of (randomized) controlled trials. DATA SOURCES: A systematic literature search was conducted in the databases PubMed, Web of Science, Cochrane Library, and SPORTDiscus up to May 2022. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: We included studies that investigated the chronic effects of SS exercises on at least one muscle strength and power outcome compared to an active/passive control group or the contralateral leg (i.e., using between- or within-study designs, respectively) in healthy individuals, irrespective of age, sex, and training status. RESULTS: The main findings of 41 studies indicated trivial-to-small positive effects of chronic SS exercises on muscle strength (standardized mean difference [SMD] = 0.21, [95% confidence interval 0.10-0.32], p = 0.001) and power (SMD = 0.19, 95% confidence interval 0.12-0.26], p < 0.001). For flexibility, moderate-to-large increases were observed (SMD = 0.96, [95% confidence interval 0.70-1.22], p < 0.001). Subgroup analyses, taking the participants' training status into account, revealed a larger muscle strength improvement for sedentary (SMD = 0.58, p < 0.001) compared with recreationally active participants (SMD = 0.16, p = 0.029). Additionally, larger flexibility gains were observed following passive (SMD = 0.97, p < 0.001) compared with active SS exercises (SMD = 0.59, p = 0.001). The chronic effects of SS on muscle strength were moderated by the proportion of female individuals in the sample (ß = 0.004, p = 0.042), with higher proportions experiencing larger gains. Other moderating variables included mean age (ß = 0.011, p < 0.001), with older individuals showing larger muscle strength gains, and the number of repetitions per stretching exercise and session (ß = 0.023, p = 0.004 and ß = 0.013, p = 0.008, respectively), with more repetitions associated with larger muscle strength improvements. Muscle power was also moderated by mean age (ß = 0.006, p = 0.007) with larger gains in older individuals. The meta-regression analysis indicated larger flexibility gains with more repetitions per session (ß = 0.094, p = 0.016), more time under stretching per session (ß = 0.090, p = 0.026), and more total time under stretching (ß = 0.078, p = 0.034). CONCLUSIONS: The main findings indicated that chronic SS exercises have the potential to improve muscle strength and power. Such improvements appear to benefit sedentary more than recreationally active participants. Likewise, chronic SS exercises result in a marked enhancement in flexibility with larger effects of passive, as compared with active, SS. The results of the meta-regression analysis for muscle strength indicated larger benefits of chronic SS exercises in samples with higher proportions of female, older participants, and a higher number of repetitions per stretching exercise and session. For muscle power, results suggested larger gains for older participants. Regarding flexibility, findings indicated larger benefits following a higher number of repetitions per exercise and a longer time under stretching per session as well as a longer total time under stretching.

An Update on Secular Trends in Physical Fitness of Children and Adolescents from 1972 to 2015: A Systematic Review.

BACKGROUND: There is evidence that physical fitness of children and adolescents (particularly cardiorespiratory endurance) has declined globally over the past decades. Ever since the first reports on negative trends in physical fitness, efforts have been undertaken by for instance the World Health Organization (WHO) to promote physical activity and fitness in children and adolescents. Therefore, it is timely to re-analyze the literature to examine whether previous reports on secular declines in physical fitness are still detectable or whether they need to be updated. OBJECTIVES: The objective of this systematic review is to provide an 'update' on secular trends in selected components of physical fitness (i.e., cardiorespiratory endurance, relative muscle strength, proxies of muscle power, speed) in children and adolescents aged 6-18 years. DATA SOURCES: A systematic computerized literature search was conducted in the electronic databases PubMed and Web of Science to locate studies that explicitly reported secular trends in physical fitness of children and adolescents. STUDY ELIGIBILITY CRITERIA: Studies were included in this systematic review if they examined secular trends between at least two time points across a minimum of 5 years. In addition, they had to document secular trends in any measure of cardiorespiratory endurance, relative muscle strength, proxies of muscle power or speed in apparently healthy children and adolescents aged 6-18 years. STUDY APPRAISAL AND SYNTHESIS METHODS: The included studies were coded for the following criteria: nation, physical fitness component (cardiorespiratory endurance, relative muscle strength, proxies of muscle power, speed), chronological age, sex (boys vs. girls), and year of assessment. Scores were standardized (i.e., converted to z scores) with sample-weighted means and standard deviations, pooled across sex and year of assessment within cells defined by study, test, and children's age. RESULTS: The original search identified 524 hits. In the end, 22 studies met the inclusion criteria for review. The observation period was between 1972 and 2015. Fifteen of the 22 studies used tests for cardiorespiratory endurance, eight for relative muscle strength, eleven for proxies of muscle power, and eight for speed. Measures of cardiorespiratory endurance exhibited a large initial increase and an equally large subsequent decrease, but the decrease appears to have reached a floor for all children between 2010 and 2015. Measures of relative muscle strength showed a general trend towards a small increase. Measures of proxies of muscle power indicated an overall small negative quadratic trend. For measures of speed, a small-to-medium increase was observed in recent years. LIMITATIONS: Biological maturity was not considered in the analysis because biological maturity was not reported in most included studies. CONCLUSIONS: Negative secular trends were particularly found for cardiorespiratory endurance between 1986 and 2010-12, irrespective of sex. Relative muscle strength and speed showed small increases while proxies of muscle power declined. Although the negative trend in cardiorespiratory endurance appears to have reached a floor in recent years, because of its association with markers of health, we recommend further initiatives in PA and fitness promotion for children and adolescents. More specifically, public health efforts should focus on exercise that increases cardiorespiratory endurance to prevent adverse health effects (i.e., overweight and obesity) and muscle strength to lay a foundation for motor skill learning.