Quercetin supplementation promotes recovery after exercise-induced muscle damage: a systematic review and meta-analysis of randomized controlled trials.

Quercetin (Q) is one of the most frequently consumed flavonoids in the human diet. The purpose of this systematic review and meta-analysis was to determine the effects of Q supplementation on muscle damage, muscle soreness and biochemical markers of inflammation, antioxidant capacity and oxidative stress after intense exercise. A literature search of SPORTDiscus, PubMed, Web of Science and Scopus was performed from inception to May 31, 2022. Forest plots were generated with fixed or random-effect models and standardized mean differences (SMD). Data extraction and quality assessment were performed independently by two authors. After application of the inclusion and exclusion criteria, 13 studies with a total of 249 sedentary to well-trained participants were included. For all studies there were some concerns about the risk of bias. All but one study used a supplementation dosage of 1000 mg/day. Q supplementation accelerated recovery of muscle function and significantly decreased muscle soreness 0/24 h after exercise (SMD: -1.33; p = 0.03), creatine kinase levels 24/48 h after exercise (SMD: -1.15; p = 0.02), and post-exercise oxidative stress (SMD: -0.92; p = 0.03). However, Q supplementation had no effect on IL-6 concentration. Q supplementation with a dose of 1000 mg/day for periods of more than seven days and a maximum of 12 weeks appears to be a safe and efficacious strategy to reduce muscle damage and muscle soreness, as well as to enhance recovery after intense exercise in sedentary to well-trained young men. Systematic review registration: PROSPERO CRD42021266801.

Body Composition, Somatotype and Raw Bioelectrical Impedance Parameters of Adolescent Elite Tennis Players: Age and Sex Differences.

Studies analyzing tennis players' body composition and morphological and bioelectrical characteristics are scarce, especially among adolescents. This study aimed to explore sex- and age-based differences in body composition, somatotype, and bioelectrical properties among elite young male and female tennis players aged 13-16 years. Twenty-two male (14.45 ± 1.10 years) and 20 female (14.30 ± 1.03 years) elite tennis players participated in this study and were compared according to sex (males vs. females) and, within each sex, according to age (13-14 years vs. 15-16 years). Female adolescent elite tennis players had higher body fat (BF) percentage and higher endomorphy than males. They also had lower skeletal muscle mass and total body water (TBW) percentages. Older boys had lower resistance and a higher TBW and phase angle (PhA) than younger boys, likely due to maturation and performance. No significant differences were found between younger and older girls, except for the PhA, potentially associated with better cell function and performance. This study provides valuable reference data for coaches of elite youth tennis players. Due to the few differences found in body composition and somatotype in the different age groups, the PhA may be used by practitioners as a reference for cell function and performance.

Effects of Beetroot Supplementation on Recovery After Exercise-Induced Muscle Damage: A Systematic Review.

CONTEXT: Beetroots have antioxidant and anti-inflammatory properties, which may help attenuate inflammation and oxidative stress, enhancing recovery from exercise-induced muscle damage (EIMD). OBJECTIVE: To evaluate the effects of beetroot supplementation on oxidative stress, inflammation, and recovery after EIMD. DATA SOURCES: SPORTDiscus, PubMed, Web of Science, and Scopus databases were searched, and hand-searching was performed by looking to relevant studies that were cited in other studies. STUDY SELECTION: For a study to be included in this review, the following inclusion criteria had to be met: (1) research conducted with human participants, (2) original articles in peer-reviewed publications, (3) original studies that had investigated beetroot supplementation intervention on muscle damage and recovery, (4) research conducted with 1 control/placebo group, and (5) articles published from inception to October 2020. STUDY DESIGN: Systematic review using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement. LEVEL OF EVIDENCE: Level 3. DATA EXTRACTION: Two of the 4 authors independently extracted data and assessed the methodological quality of the articles with the PEDro scale. All discrepancies were resolved through a consensus meeting. RESULTS: A total of 9 studies were included in this review. The methodological quality of the included studies ranged from moderate to high. Most of the studies found a better recovery of functional variables and muscle soreness, but improvements in markers of muscle damage, inflammation, and oxidative stress were not reported. CONCLUSION: The existing evidence suggests that a short-term beetroot supplementation has the potential to accelerate recovery of functional measures and muscle soreness, but further research is needed to clarify if a longer supplementation period (with some days before exercise and some days after) could also promote recovery of markers of muscle damage, inflammation, and oxidative stress.

Kinetics and Vertical Stiffness of Female Volleyball Players: Effect of Low-Intensity Plyometric Training.

Purpose: The purpose of this study was threefold: 1) to assess kinematic/kinetic variables and vertical stiffness of recreational young female volleyball players during a vertical jump, 2) to identify the changes in those variables that occurred after low-intensity plyometric training, 3) to determine the relationship between stiffness and performance. Method: Twenty-eight female volleyball players aged 14-18 years were randomly allocated to plyometric group and control group. All participants performed a countermovement jump (CMJ) 3 days prior to and 3 days after the 7-week plyometric training and kinematic and kinetic variables, along with vertical stiffness, were measured. Results: Jump height, average force, average power, peak power and absolute vertical stiffness significantly increased in plyometric group (p < .01). Propulsion impulse and normalized vertical stiffness also increased (p < .05). Maximum displacement of the center of mass significantly decreased in plyometric group (p < .01). Changes in vertical stiffness after the plyometric training showed very strong significant correlations with changes in average force (r = 0.818, p < .01), average power (r = 0.784, p < .01), maximum displacement of the center of mass (r = -0.850, p < .01) and propulsion duration (r = -0.781, p < .01). Conclusion: The 7-week low-intensity plyometric training produced changes in most kinematic and kinetic variables improving CMJ performance. The increase in vertical stiffness after plyometric training may not directly enhance jump performance but it makes the jump quicker increasing the probability of success in volleyball games.