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Skeletal muscle echo intensity (EI) is affected by ageing and physical activity; however, the effects of nutrition are less understood. The aim of this study was to explore whether habitual nutrient intake may be associated with ultrasound-derived EI. Partial least squares regression (PLSR) models were trained on an initial sample (n = 100, M = 45; F = 55; 38 ± 15 years) to predict EI of two quadriceps muscles from 19 variables, using the "jack-knife" function within the "pls" package (RStudio), which was then tested in an additional dataset (n = 30, M = 13; F = 17; 38 ± 16 years). EI was determined using B-mode ultrasonography of the rectus femoris (RF) and vastus lateralis (VL) and nutritional intake determined via 3-day weighed food diaries. Mean daily intake of specific nutrients were included as predictor variables with age, sex, and self-reported physical activity. PLSR training model 1 explained ∼52% and model 2 ∼46% of the variance in RF and VL EI, respectively. Model 1 also explained ∼35% and model 2 ∼30% of the variance in RF and VL EI in the additional testing dataset. Age and biological sex were associated with EI in both models (P < 0.025). Dietary protein (RF: β = −7.617, VL: β = −7.480), and selenium (RF: β = −7.144, VL: β = −4.775) were associated with EI in both muscles (P < 0.05), whereas fibre intake (RF: β = −5.215) was associated with RF EI only and omega-3 fatty acids (n-3/ω-3 FAs, RF: β = 3.145) with VL EI only (P < 0.05). Therefore, absolute protein, selenium, fibre, and n-3 FAs may be associated with skeletal muscle EI, although further mechanistic work is required before claiming causal inference. [ABSTRACT FROM AUTHOR]

Purpose: The efficacy of isolated and relative performance indicators (PIs) has been compared in rugby union; the latter more effective at discerning match outcomes. However, this methodology has not been applied in women's rugby. The aim of this study was to identify PIs that maximize prediction accuracy of match outcome, from isolated and relative data sets, in women's rugby union. Methods: Twenty-six PIs were selected from 110 women's international rugby matches between 2017 and 2022 to form an isolated data set, with relative data sets determined by subtracting corresponding opposition PIs. Random forest classification was completed on both data sets, and feature selection and importance were used to simplify models and interpret key PIs. Models were used in prediction on the 2021 World Cup to evaluate performance on unseen data. Results: The isolated full model correctly classified 75% of outcomes (CI, 65%–82%), whereas the relative full model correctly classified 78% (CI, 69%–86%). Reduced respective models correctly classified 74% (CI, 65%–82%) and 76% (CI, 67%–84%). Reduced models correctly predicted 100% and 96% of outcomes for isolated and relative test data sets, respectively. No significant difference in accuracy was found between data sets. In the relative reduced model, meters made, clean breaks, missed tackles, lineouts lost, carries, and kicks from hand were significant. Conclusions: Increased relative meters made, clean breaks, carries, and kicks from hand and decreased relative missed tackles and lineouts lost were associated with success. This information can be utilized to inform physical and tactical preparation and direct physiological studies in women's rugby. [ABSTRACT FROM AUTHOR]

Biomarkers relating to player "stress balance," immunological (ie, immunoglobulin-A), and hormonal (ie, testosterone and cortisol [T:C]) status are now commonly used in football. This article is our critical review of the scientific literature relating to the response of these measures to player load and their relationships with player health. The commonly reported relationship between immunoglobulin-A and training or match load highlights its sensitivity to changes in psychophysiological stress and the increased risk of compromised mucosal immunity. This is supported by its close relationship with symptoms of upper respiratory tract infection and its association with perceived fatigue in football players. Testosterone and cortisol concentrations and the testosterone–cortisol ratio are sensitive to changes in player load, but the direction of their response is often inconsistent and is likely influenced by player training status and non-sport-related stressors. Some evidence indicates that sustained periods of high training volume can increase resting testosterone and that sustained periods of low and high training intensity can increase resting cortisol, compromising the testosterone–cortisol ratio. These findings are noteworthy, as recent findings indicate interrelationships between testosterone, cortisol, and testosterone:cortisol and perceived measures of fatigue, sleep quality, and muscle soreness in football players. Variability in individual responses suggests the need for a multivariate and individualized approach to player monitoring. Overall, we consider that there is sufficient evidence to support the use of salivary immunoglobulin-A, testosterone, cortisol, and testosterone:cortisol measures as part of a multivariate, individualized player monitoring system in professional football. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effect of discrete passages of play on locomotor demands of international men's and women's rugby sevens matches and their relationship with winning or losing. Thirteen men's and thirteen women's international rugby sevens players wore 10 Hz Global Positioning Systems during twelve Tokyo Olympic games matches (966 observations; 507 for men, 459 for women). Discrete ball-in-play periods were categorised as: 'Single-phase defence', 'single-phase attack', 'multi-phase defence', 'multi-phase attack', 'multi-phase defence to attack', or 'multi-phase attack to defence'. Relative total distance, alongside high-speed (>5.0 m∙s-1), acceleration (>3 m∙s-2), and deceleration (>3 m∙s-2) distances were recorded for each passage. Separately for men and women, linear mixed models examined the effect of passage type and match outcome (win or loss) on locomotor demands, whilst controlling for opposition ranking. In men, relative total distance ranged from 137 m∙min-1 to 174 m∙min-1 for 'multi-phase defence to attack' and 'multi-phase attack', respectively. In women, 'multi-phase attack' elicited the lowest relative total distance (118 m∙min-1), whereas the greatest values (186 m∙min-1) were recorded for 'single-phase defence'. For men, there were significant interactions between match outcome and passage type for relative total (p<0.001) and high-speed (p = 0.006) distance. During 'multi-phase attack', relative total distance was greater for wins versus losses (174 vs 138 m.min-1, p = 0.024). However, for 'single-phase defence', relative total distance was lower for wins (128 vs 164 m.min-1, p<0.001). For women, there were significant interactions between match outcome and passage type for relative total (p = 0.036), high-speed (p = 0.003), and deceleration (p = 0.015) distances. Locomotor responses were influenced by passage type and match result for men and women. Knowing the demands of each passage type may inform training drills targeted at developing match-play-specific physical, technical, and tactical adaptations. Understanding how passages differ between matches won and lost could also inform team technical/tactical preparation including selection. [ABSTRACT FROM AUTHOR]

Purpose: To examine the effect of fast- versus slow-speed eccentric-muscle-action resistance training on lower-body strength, vertical jump height, sprint speed, and change-of-direction performance in elite soccer players during a competitive season. Methods: Twenty-two elite soccer players, from a single team, were randomly assigned to groups that undertook either 1- (fast speed) or 4-second (slow speed) eccentric resistance training during the in-season period. A 5-week program was conducted during an elite top-division European League soccer season. Performance measures including predicted 1-repetition-maximum back squat, countermovement jump, 20-m sprint, and change of direction were tested before and after the intervention period. Total match and training running distance and muscle soreness were also recorded during each week of the intervention. Results: An analysis of covariance showed significant group effects (P =.01) for countermovement jump with a greater jump height in the 1-second fast-speed group postintervention (95% CI, 1.1–6.9 cm). Despite an overall increase in 1-repetition maximum pretraining to posttraining (95% CI, 10.0–15.3 kg, effect size 0.69), there were no significant differences (P >.05) between groups after the intervention. Similarly, there were no differences between groups for change of direction, 20-m sprint, or muscle soreness. Conclusion: Faster eccentric muscle actions may be superior for increasing movements in elite soccer players in-season. [ABSTRACT FROM AUTHOR]