ABSTRACT:Mason, BRJ, McKune, AJ, Pumpa, KL, Mara, JK, Kilduff, LP, and Ball, NB. The effect of a high load resistance priming intervention on perceptual, physiological, and performance markers in female rugby union players. J Strength Cond Res 40(8): e839-e847, 2026-This study investigated the effects of a high load resistance priming session on perceptual, physiological, and performance responses in female rugby athletes. Using a randomized counter-balanced crossover design, 10 highly trained female rugby players (mean ± standard deviation: age 23.4 ± 3.7 years; height 172.1 ± 4.7 cm; mass 86.7 ± 13.9 kg) completed a resistance priming session and control condition. Perceptual and physiological variables were collected at baseline (PRE), immediately post (POST), and 120 minutes post (POST120) intervention, with performance compared between conditions at POST120. Data were analyzed using linear mixed models within the Bayesian framework. Compared with PRE, the priming protocol had a larger increase in physical readiness (maximum a posteriori [MAP] = 14.6, 95% high-density intervals [HDI] = -3.4 to 30.4, PD % = 94, % in region of practical equivalence [ROPE] = 9.9) at POST than the control with no differences between conditions at POST120. There were no meaningful differences between the priming and control conditions for salivary testosterone, cortisol, or the testosterone-to-cortisol ratio at any time points. Priming led to a lower countermovement jump (CMJ) relative peak power output MAP = -3.2, 95% HDI = -6.7 to -0.2, % in ROPE = 3.9) than the control condition at POST120. There were no meaningful differences in CMJ height, isometric mid-thigh pull relative or absolute force, or 5, 10, or 20 m sprint times between the priming and control conditions at POST120. These findings suggest that high load resistance training may not be an effective strategy to improve performance and readiness 2 hours later in female rugby players.

Dietary supplements are widely used among individuals exposed to hot environments, but whether their consumption confers any thermoregulatory effect is unclear. Therefore, we systematically evaluated the effect of dietary supplementation on key aspects of thermoregulation [core temperature (Tcore) and sweating responses] in the heat. Three databases were searched in April 2024. After screening, 124 peer-reviewed articles were identified for inclusion within three separate meta-analyses: 1) peak Tcore; 2) whole body sweat rate (WBSR); 3) local sweat rate (LSR). The moderating effect of several variables (e.g., training and heat acclimation status), known to influence thermoregulatory function, were assessed via subanalysis and meta-regression. There was no overall effect of the differing supplement types on WBSR (P = 0.405) and LSR (P = 0.769), despite taurine significantly increasing WBSR (n = 3, Hedges' g = 0.79, P = 0.006). Peak Tcore was significantly affected by supplement type (P = 0.011), primarily due to caffeine's "small" significant positive effect (n = 30; Hedges' g = 0.44, P < 0.001) and taurine's (n = 3, Hedges' g = -0.66, P = 0.043) and oligonol's (n = 3; Hedges' g = -0.50, P = 0.014) "medium" significant negative effects. Dietary supplements, such as amino acids (e.g., taurine), some antioxidants and anti-inflammatories (e.g., oligonol) conferred the greatest thermoregulatory benefits during heat exposure. Taurine ingestion in such conditions may lower heat strain, which is likely through its augmentation of thermal sweating. Conversely, caffeine intake may potentially pose the greatest risk in the heat due to its effect on Tcore.NEW & NOTEWORTHY The effects of dietary supplements on core temperature and sweating responses when ingested in the heat varied greatly. Some supplements demonstrated the potential to improve thermoregulatory capacity (e.g., select amino acids, anti-oxidants and anti-inflammatories), while others had no or even deleterious effects on thermal balance (e.g., caffeine). These findings have implications for those ingesting dietary supplements for their health and/or performance effects during exposure to hot environmental conditions. Certain supplements should possibly be avoided in the heat, while others may elicit a thermoregulatory benefit.

Sport science researchers and practitioners have noted a gap between research and practice for some time. Although several solutions have been proposed, few recommendations have been made for researchers to follow that are based on successful, long-term sport science research programmes aimed at translating research into practice. Therefore, the purpose of this article is to outline a decade of work completed by the Welsh Institute of Performance Science as an institute for sport-based integrated knowledge translation. The aim is to provide a framework for other researchers and institutes to follow when engaging with organisations for long-term research-to-practice partnerships. In addition to outlining the development and functioning of the Welsh Institute of Performance Science to guide others, limitations of the approach used are also presented and considered to facilitate the future development of sport-specific models of knowledge translation, ensuring that the excellent research conducted across the disciplines of sport science effectively impacts the work of practitioners.

OBJECTIVES:To investigate associations between genetic variants within COLGALT1, COL1A1, COL3A1, COL5A1, KDR, MIR608, MMP3, NID1, TIMP2 and VEGFA and injury history in elite male rugby athletes. DESIGN:A case-control genetic association study was conducted on 184 elite male rugby athletes. METHODS:Participants were genotyped for 13 genetic polymorphisms previously associated with soft tissue injury using standard PCR assays. Injury data were collected via a self-reported injury-history questionnaire. Single-locus association and Total Genotype Score (TGS) analyses were conducted using χ2 tests. In addition, multifactor dimensionality reduction and inferred haplotype analysis were used to identify genetic interactions. RESULTS:The TT genotype of MMP3 rs679620 was underrepresented in the non-injured ligament group compared to the ligament sprain and ligament rupture groups (10 %, 32 %, 25 %; P < 0.04, respectively). The T allele of MMP3 rs679620 was overrepresented in the non-injured tendon group compared to the tendinopathy group (50 %, 38 %; P < 0.02). The proportion of C allele carriers of COL5A1 rs12722 was higher in the tendon rupture group than the non-injured tendon group (96 %, 75 %; P < 0.02). Furthermore, the T-C inferred haplotype frequency of COL5A1 rs12722 and COL5A1 rs3196378 was higher in the tendon rupture, ligament sprain and total injured athlete groups compared to their respective non-injured groups (P < 0.02). CONCLUSIONS:This study is the first to identify associations between MMP3 rs679620 and COL5A1 rs12722 and soft-tissue injury history in elite male rugby athletes. These findings support the growing evidence that soft-tissue injury could be influenced by an athlete's genetic predisposition.

Rugby training and competition both impose a stress or training load (TL) affecting athlete well-being. Current understanding of the TL dose-response and time-lagged changes (i.e., delayed effects) in well-being is limited. We addressed these gaps using data from a 3-week international series. Twenty-two elite male rugby players were assessed 4-5 days a week for daily TL and well-being (i.e., mood, stress, soreness, fatigue, sleep quality). A distributed lag non-linear model was used to estimate the TL effect, at the within-person mean (358 A.U), +1SD (576 A.U) and +2SD (794 A.U), on well-being at 0-5 lag days. Average daily TL declined by -38% and -45% in weeks two and three (vs. week 1), respectively, with weekly fluctuations of +27% to -58% (vs. Monday training). The well-being subscales oscillated around a stable baseline. Compared to mean-centered scores, a significant decline in mood and sleep quality (-0.6 to -2.0 units; -9 to -30%) emerged at all TLs, with a delayed shift at higher loads. Elevated stress, soreness, and fatigue responses (up to 3.7 units; 76%) emerged with increasing daily TLs, including a biphasic rise in stress and fatigue at higher loads. In conclusion, we gained detailed insight into physical stress and the temporal sequence of well-being during an international rugby series. Different daily TLs predicted adverse well-being responses (i.e., declining mood and sleep quality, rise in stress, soreness, fatigue) that varied in lag timing, duration, and magnitude. Explicating these associations can assist weekly planning and strategies to optimize recovery, performance, and team success.

To determine the effect of taurine supplementation on sweating and core temperature responses, including the transition from compensable to uncompensable heat stress, during prolonged low-intensity exercise of a fixed-heat production ( 200W/m2) in hot conditions (37.5 °C), at both fixed and incremental vapour-pressure. Fifteen females (n = 3) and males (n = 12; 27 ± 5 years, 78 ± 9 kg, V̇ O2max 50.3 ± 7.8 mL/kg/min), completed a treadmill walking protocol ( 200W/m2 heat production [Ḣprod]) in the heat (37.5 ± 0.1 °C) at fixed-(16-mmHg) and ramped-humidity (∆1.5-mmHg/5-min) following 1 week of oral taurine supplementation (50 mg/kg/bm) or placebo, in a double-blind, randomised, cross-over design. Participants were assessed for whole-body sweat loss (WBSL), local sweat rate (LSR), sweat gland activation (SGA), core temperature (Tcore), breakpoint of compensability (Pcrit) and calorimetric heat transfer components. Plasma volume and plasma taurine concentrations were established through pre- and post-trial blood samples. Taurine supplementation increased WBSL by 26.6

Post-exercise passive heating has been reported to augment adaptations associated with endurance training. The current study evaluated the effect of a 4-week remotely administered, post-exercise passive leg heating protocol, using an electrically heated layering ensemble, on determinants of endurance performance. Thirty recreationally trained participants were randomly allocated to either a post-exercise passive leg heating (PAH, n = 16) or unsupervised training only control group (CON, n = 14). The PAH group wore the passive heating ensemble for 90–120 min/day, completing a total of 20 (16 post-exercise and 4 stand-alone leg heating) sessions across 4 weeks. Whole-body (peak oxygen uptake, gas exchange threshold, gross efficiency and pulmonary oxygen uptake kinetics), single-leg exercise (critical torque and NIRS-derived muscle oxygenation), resting vascular characteristics (flow-mediated dilation) and angiogenic blood measures (nitrate, vascular endothelial growth factor and hypoxia inducible factor 1−α) were recorded to characterize the endurance phenotype. All measures were assessed before (PRE), at 2 weeks (MID) and after (POST) the intervention. There was no effect of the intervention on test of whole-body endurance capacity, vascular function or blood markers (p > 0.05). However, oxygen kinetics were adversely affected by PAH, denoted by a slowing of the phase II time constant; τ (p = 0.02). Furthermore, critical torque–deoxygenation ratio was improved in CON relative to PAH (p = 0.03). We have demonstrated that PAH had no ergogenic benefit but instead elicited some unfavourable effects on sub-maximal exercise characteristics in recreationally trained individuals.

Plantar pressure measurement systems are routinely used in sports and health applications to assess locomotion. The purpose of this review is to describe and critically discuss: (a) applications of the pressure measurement systems in sport and healthcare, (b) testing protocols and considerations for clinical gait analysis, (c) clinical recommendations for interpreting plantar pressure data, (d) calibration procedures and their accuracy, and (e) the future of pressure sensor data analysis. Rigid pressure platforms are typically used to measure plantar pressures for the assessment of foot function during standing and walking, particularly when barefoot, and are the most accurate for measuring plantar pressures. For reliable data, two step protocol prior to contacting the pressure plate is recommended. In-shoe systems are most suitable for measuring plantar pressures in the field during daily living or dynamic sporting movements as they are often wireless and can measure multiple steps. They are the most suitable equipment to assess the effects of footwear and orthotics on plantar pressures. However, they typically have lower spatial resolution and sampling frequency than platform systems. Users of pressure measurement systems need to consider the suitability of the calibration procedures for their chosen application when selecting and using a pressure measurement system. For some applications, a bespoke calibration procedure is required to improve validity and reliability of the pressure measurement system. The testing machines that are commonly used for dynamic calibration of pressure measurement systems frequently have loading rates of less than even those found in walking, so the development of testing protocols that truly measure the loading rates found in many sporting movements are required. There is clear potential for AI techniques to assist in the analysis and interpretation of plantar pressure data to enable the more complete use of pressure system data in clinical diagnoses and monitoring.

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.

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.

Objective: It remains unknown whether myonuclei remain elevated post anabolic-androgenic steroid (AAS) usage in humans. Limited data exist on AAS-induced changes in gene expression. Design: Cross-sectional/longitudinal. Setting: University. Participants: Fifty-six men aged 20 to 42 years. Independent Variables: Non–resistance-trained (C) or resistance-trained (RT), RT currently using AAS (RT-AS), of which if AAS usage ceased for ≥18 weeks resampled as Returning Participants (RP) or RT previously using AAS (PREV). Main Outcome Measures: Myonuclei per fiber and cross-sectional area (CSA) of trapezius muscle fibers. Results: There were no significant differences between C (n = 5), RT (n = 15), RT-AS (n = 17), and PREV (n = 6) for myonuclei per fiber. Three of 5 returning participants (RP1-3) were biopsied twice. Before visit 1, RP1 ceased AAS usage 34 weeks before, RP2 and RP3 ceased AAS usage ≤2 weeks before, and all had 28 weeks between visits. Fiber CSA decreased for RP1 and RP2 between visits (7566 vs 6629 μm2; 7854 vs 5677 μm2) while myonuclei per fiber remained similar (3.5 vs 3.4; 2.5 vs 2.6). Respectively, these values increased for RP3 between visits (7167 vs 7889 μm2; 2.6 vs 3.3). Conclusions: This cohort of past AAS users did not have elevated myonuclei per fiber values, unlike previous research, but reported AAS usage was much lower. Training and AAS usage history also varied widely among participants. Comparable myonuclei per fiber numbers despite decrements in fiber CSA postexposure adheres with the muscle memory mechanism, but there is variation in usage relative to sampling date and low numbers of returning participants.

PURPOSE:Mental rehearsal is commonly employed, with positive visualization proposed to enhance complex skill performance. Additionally, video stimulus has been associated with enhanced kinesthetic sensations and rapid hormone fluctuations that may contribute to enhancing mental rehearsal and the conscious and unconscious emotional state for skill execution. Here, we assessed the impact of a 15-minute mental rehearsal intervention on rugby-specific tasks and the associated hormone profile.METHODS:Professional rugby players (N = 10) volunteered for a randomized crossover study. They completed three 15-minute preparatory phases (positive or negative video-guided mental rehearsal or self-directed mental rehearsal alone) prior to an exercise stressor and rugby-specific passing task. Salivary testosterone and cortisol were monitored to assess stress responses.RESULTS:Performance during the rugby passing task was improved following the positive video condition (91% [7.4%]) compared to the negative video (79% [6.0%]; ES: 1.22 ± 0.75) and self-visualization (86% [5.8%]; ES: 0.58 ± 0.75), with a significant correlation observed between passing performance and salivary testosterone (r = .47 ± .34, P = .0087). Positive video imagery prior to an exercise stressor also significantly enhanced physiological stress resilience (r = .39 ± .36, P = .0352).CONCLUSIONS:This pilot study demonstrates that mental rehearsal was enhanced by appropriate, context-specific video presentation. We propose that the interaction between sex steroids, the adrenal axis, and subsequent conscious and unconscious behaviors may be relevant to competitive rugby. Specifically, we suggest that relatively elevated free testosterone imparts a degree of stress resilience, which may lead to enhanced expression of competitive behaviors and provide an enhanced state for rugby skill execution.

PURPOSE:As the start of the 10th Rugby Union World Cup approaches, performance staff will be working on the final elements of their teams' preparation. Much of this planning and preparation will be underpinned by the latest performance science research. In this invited commentary, we discuss contemporary performance science research in rugby union centered around 4 key performance domains. First, we outline a systematic approach to developing an overall understanding of the game demands and how performance staff can enhance the players' preparedness for competition. We then move on to outline our understanding of the training science domain, followed by a brief overview of effective recovery strategies at major tournaments. Finally, we outline research in the area of competition-day strategies and how they can positively impact players' readiness to compete.CONCLUSIONS:Evaluating a team's preparation for the Rugby Union World Cup can be achieved by mapping their performance plan based on the 4 domains outlined above.

Objectives: The aims of this study were to: i) identify performance indicators associated with match outcomes in the United Rugby Championship; ii) compare the efficacy of isolated and relative datasets to predict match out-come; and iii) investigate whether reduced statistical models can reproduce predictive accuracy.Design: Retrospective analysis of key performance indicators in the United Rugby Championship.Methods: Twenty-seven performance indicators were selected from 96 matches (2020-21 United Rugby Cham-pionship). Random forest classification was completed on isolated and relative datasets, using a binary match outcome (win/lose). Maximum relevance and minimum redundancy performance indicator selection was utilised to reduce models. In addition, models were tested on 53 matches from the 2021-22 season to ascertain prediction accuracy.Results: Within the 2020-21 datasets, the full models correctly classified 83% of match performances for the rel-ative dataset and 64% for isolated data, the equivalent reduced models classified 85% and 66% respectively. The reduced relative model successfully predicted 90% of match performances in the 21-22 season, highlighting that five performance indicators were significant: kicks from hand, metres made, clean breaks, turnovers con-ceded and scrum penalties.Conclusions: Relative performance indicators were more effective in predicting match outcomes than isolated data. Reducing features used in random forest classification did not degrade prediction accuracy, whilst also sim-plifying interpretation for practitioners. Increased kicks from hand, metres made, and clean breaks compared to the opposition, as well as fewer scrum penalties and turnovers conceded were all indicators of winning match outcomes within the United Rugby Championship.(c) 2022 The Authors. Published by Elsevier Ltd on behalf of Sports Medicine Australia. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

PURPOSE:This study aimed to determine the effects of a field-based priming session on perceptual, physiological, and performance responses in female rugby sevens athletes.METHODS:Thirteen highly trained female rugby sevens players (age: 20.7 [2.0] y; height: 169.3 [4.8] cm; weight: 68.8 [7.9] kg) completed either a 20-minute field-based priming session or a control condition. Perceptual, physiological, and performance variables were collected at baseline (PRE) and 5 (POST5), 30 (POST30), and 120 minutes (POST120) postintervention. Data were analyzed using Bayesian mixed effects models.RESULTS:The priming protocol had a larger increase in mental readiness (maximum a posteriori [MAP] = 20, 95% high-density intervals [HDI] = -4 to 42, probability of direction [PD]% = 95, % in region of practical equivalence [ROPE] = 9.7), physical readiness (MAP = 20.1, 95% HDI = -4.6 to 42.1, PD% = 93, % in ROPE = 10.6), and testosterone (MAP = 14.9, 95% HDI = 0.5 to 27.7, PD% = 98, % in ROPE = 5.6) than the control POST30. Cognitive performance decreased POST120 in the priming condition for congruent (MAP = 0.02, 95% HDI = -0.06 to 0.00, PD% = 95, % in ROPE = 6.4) and incongruent tasks (MAP = 0.00, 95% HDI = -0.07 to 0.00, PD% = 98, % in ROPE = 3.2) when compared with the control.CONCLUSIONS:Perceptual and physiological markers improved POST30 in the priming condition. Findings indicate that perceptual and physiological responses to priming were not coupled with performance improvements. Priming was not accompanied by perceptual, physiological, or performance improvements at POST120.

The quadrennial showcase of rugby is the Rugby World Cup (RWC), with the 10th Cup being held in France in September and October 2023. The RWC is the third most popular global sporting event after the soccer World Cup and the summer Olympic games. The 2022 Women ’ s RWC fi nal drew a record crowd of 45,000 in New Zealand. World Rugby has the vision of a global sport for all; it can be played by individuals of all sizes, genders, and abilities. The heart of the game centers on possession of the ball, the expression of free running, and the physicality of tackling and contact.

Objective: Concussions are common match injuries in elite rugby, and reports exist of reduced cognitive function and long-term health consequences that can interrupt or end a playing career and produce continued ill health. The aim of this study was to investigate the association between elite rugby status and 8 concussion-associated risk polymorphisms. We hypothesized that concussion-associated risk genotypes and alleles would be underrepresented in elite rugby athletes compared with nonathletes. Design: A case–control genetic association study. Setting: Institutional (university). Participants: Elite White male rugby athletes [n = 668, mean (SD) height 1.85 (0.07) m, mass 102 (12) kg, and age 29 (7) years] and 1015 nonathlete White men and women (48% men). Interventions: Genotype was the independent variable, obtained by PCR of genomic DNA using TaqMan probes. Main Outcome Measure: Elite athlete status with groups compared using χ 2 and odds ratio (OR). Results: The COMT rs4680 Met/Met (AA) genotype, Met allele possession, and Met allele frequency were lower in rugby athletes (24.8%, 74.6%, and 49.7%, respectively) than nonathletes (30.2%, 77.6%, and 54.0%; P < 0.05). The Val/Val (GG) genotype was more common in elite rugby athletes than nonathletes (OR 1.39, 95% confidence interval 1.04-1.86). No other polymorphism was associated with elite athlete status. Conclusions: Elite rugby athlete status is associated with COMT rs4680 genotype that, acting pleiotropically, could affect stress resilience and behavioral traits during competition, concussion risk, and/or recovery from concussion. Consequently, assessing COMT rs4680 genotype might aid future individualized management of concussion risk among athletes.

Day-to-day coordination of the stress (i.e., hypothalamic-pituitary-adrenal [HPA]) and reproductive (i.e., hypothalamic-pituitary-gonadal [HPG]) axes is central to allostatic regulation, reproductive success, and survival. Reports of positive, within-person testosterone and cortisol relationships (or coupling) suggest cross-talk of a facilitative nature, but longitudinal evidence is scarce and has methodological and analytical limitations. To address this, we used a continuous-time (CT) model to investigate day-to-day, within-person coupling of testosterone and cortisol in two male cohorts. Salivary testosterone and cortisol fluctuations were monitored in 35 athletic men across two international tournaments (M = 19.3 tests) and in 41 healthy men during normal daily living (M = 27.9 tests). Bayesian CT analysis revealed a diminishing effect of each hormone on itself as time-interval length or lag increased. In both groups, cortisol had a negative lagged effect on testosterone that persisted for around three days. The cortisol effect on testosterone peaked after 0.71 and 0.51 days in athletic (standardized estimate = -0.13) and healthy men (standardized estimate = -0.11), respectively. Further estimates of non-lagged, contemporaneous correlations revealed positive testosterone and cortisol relationships (athlete r = 0.04, healthy r = 0.46). In summary, complex within-person HPA and HPG interplay emerged in two independent male cohorts. Specifically, a rising cortisol concentration was linked to a fall in testosterone concentration at later time points, but concurrently these hormones tended to rise and fall together. Our results suggest that inhibitory and facilitatory hormonal actions coexist on varying timescales, thereby expanding knowledge of HPG and HPA cross-talk in everyday life.

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.

Stretchable, nanocarbon heaters were screen-printed onto a stretchable film to create a passive heat maintenance device for elite sport. The heat uniformity and the temperature performance of these lightweight, large area electrothermal heaters were evaluated over a range of applied voltages using thermal imaging. The heaters provided a uniform heat over the 15 × 4 cm area with temperatures of 39°C, 54°C, and 72°C at 10, 15, and 20 V, respectively, within 150 s of being switched on. Tensile testing was used to examine the performance of the heaters under strain. At 20% nominal strain, the heaters gave a uniform heat output and a temperature of 44°C at 15 V, making it a promising candidate for wearable applications. The heaters were capable of maintaining temperatures of 40°C over 10 cyclic strains up to 10% nominal strain. The heaters were integrated into a proof-of-concept stretchable base-layer garment, with the effect of the heaters on skin temperature measured and thermal sensation evaluated during a simulated training session in an environmental chamber at an ambient temperature 0°C. The printed heaters maintained skin temperature and thermal sensation when compared with an unheated control.