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This study compared oxygen consumption and substrate oxidation while exercising in hot and temperate conditions in individuals with different physical activity status (i.e., inactive individuals vs. trained runners). 10 inactive individuals (IA: 26 ± 6 y; 79.1 ± 14.1 kg; 40.7 ± 5.1 ml·kg -1 ·min -1 ) and 10 trained runners (TR: 25 ± 6 y; 69.5 ± 9.1 kg; 63.1 ± 5.1 ml·kg -1 ·min -1 ) completed two incremental exercise tests (4 min stages) until exhaustion in temperate (TEMP: 18.7 ± 0.1 °C; 43.2 ± 4.1% relative humidity) and hot (HOT: 34.4 ± 0.2 °C and 42.6 ± 1.6% relative humidity) conditions. Expired gas and blood lactate concentrations were measured at the end of each stage. Peak oxygen consumption similarly decreased in HOT compared to TEMP for IA and TR (-13.2 ± 4.5% vs. -15.2 ± 7%; p =0.571; ES=0.25). In HOT compared to TEMP, lipid oxidation, from 30 to 70% of V̇O 2peak , was reduced for both groups (IA: p =0.023, ES=0.43; TR: p <0.001, ES=0.72) while carbohydrate oxidation was increased for TR ( p =0.011; ES=0.45) but not for IA ( p =0.268; ES=0.21). Core temperature was different between conditions for TR (higher in HOT, p =0.017; ES=0.66) but not for IA ( p =0.901; ES=0.25). Despite reduced physiological capacities in IA, both populations demonstrated reductions in lipid utilisation and peak oxygen consumption in hot compared to temperate conditions. However, the increased carbohydrate oxidation in HOT for TR were not observed in IA, potentially explained by lower thermal strain.

Purpose: 7 days L-citrulline supplementation has been reported to improve blood pressure, V . O 2 kinetics, gastrointestinal (GI) perfusion and endurance cycling performance through increasing arterial blood flow. In situations where blood volume is compromised (e.g., hyperthermia/hypohydration), L-citrulline may improve thermoregulation and exercise performance by redistributing blood flow to aid heat loss and/or muscle function. This study assessed 7 days L-citrulline supplementation on running performance in the heat, whilst mildly hypohydrated., Methods: 13 endurance runners (2 female, 31 ± 8 y, V . O 2 peak 60 ± 6 mL/kg/min) participated in a randomised crossover study with 7 days L-citrulline (CIT; 6 g/d) or placebo (maltodextrin powder; PLA) supplementation. Participants completed a 50 min running 'preload' at 65% V . O 2 peak (32 °C, 50% relative humidity) to induce hyperthermia and hypohydration before a 3 km running time trial (TT). Body mass and blood samples were collected at baseline, pre-preload, post-preload and post-TT, whilst core and skin temperature, heart rate and perceptual responses were collected periodically throughout., Results: TT performance was not different between trials (CIT 865 ± 142 s; PLA 892 ± 154 s; P = 0.437). Core and skin temperature and heart rate (P ≥ 0.270), hydration (sweat rate, plasma volume, osmolality) indices (P ≥ 0.216), GI damage (P ≥ 0.260) and perceptual responses (P ≥ 0.610) were not different between trials during the preload and TT., Conclusions: 7 days of L-citrulline supplementation had no effect on 3 km running performance in the heat or any effects on thermoregulation or GI damage in trained runners in a hypohydrated state., Competing Interests: Declarations. Conflict of interest: This is a summary of independent research funded by Loughborough University and carried out at the National Institute for Health and Care Research (NIHR) Leicester Biomedical Research Centre (BRC). The views expressed are those of the author(s) and not necessarily those of Loughborough University, the NIHR or the Department of Health and Social Care. M.P.F. is funded by the National Institute for Health Research (NIHR) Applied Research Collaboration East Midlands (ARC EM). S.J.B. has current/previous funding from KIRIN Central Research Institute, Fitoplancton Marino SL, Kaneka Medical Europe, Bio-gen Extracts and Herbalife Europe Ltd. In all cases, monies have been paid to S.J.B’s institution and not directly to SJB. S.A.M. has current/previous funding from Entrinsic Beverage Company LLP and Herbalife Europe Ltd and has received honorariums from Unilever PLC to present at conferences. L.J.J. has current/previous funding from Bunge Loders Croklaan B.V., Herbalife Europe Ltd, Bridge Farm Nurseries ltd., Entrinsic Beverage Company LLP, Decathlon SA, PepsiCo Inc. and Volac International, has performed consultancy for The British Horseracing Authority, Lucozade, Ribena Suntory and PepsiCo Inc., and has received conference fees from PepsiCo Inc. and Danone Nutricia. In all cases, monies have been paid to LJJ’s institution. LJJ is part of the National Institute for Health Research’s Leicester Biomedical Research Centre, which is a partnership between University Hospitals of Leicester NHS Trust, Loughborough University, and the University of Leicester., (© 2024. The Author(s).)

Background: Understanding the reliability and validity of field-based mobility and performance tests used within the wheelchair sports of basketball (WCB), rugby (WCR) and tennis (WCT) can assist in understanding an athletes' physiological state, training effects, and/or assist with optimising their wheelchair-user interface., Purpose: To examine, evaluate and synthesize current aerobic and anaerobic field-based mobility and performance tests used in WCB, WCR and WCT., Methods: A systematic search was performed according to PRISMA guidelines. Studies were included if they investigated performance tests in WCB, WCR and WCT and reported reliability., Results: Twenty-one studies covering 45 mobility/performance tests were included (anaerobic, n  = 35; aerobic, n  = 10), with agility and repeated sprints ( n  = 13) being the most common, followed by linear-sprints ( n  = 11). Repeated sprint ability ( n  = 2) and submaximal field-tests ( n  = 2) were the least frequent. Intra-class correlations among all tests ranged from 0.62 to 0.99, with agility and repeated sprints being 0.65-0.98, followed by values of 0.62-0.99 for linear-sprint, 0.96-0.99 for repeated sprints and 0.85-0.97 for submaximal field-tests., Conclusion: The most frequently measured performance tests were anaerobic tests focusing on agility and repeated sprints. Given the low number of aerobic tests in WCB, WCR and WCT, future research should focus on reliable and valid ways to measure and track performance.

Research assessing exercise-induced hypohydration on running performance in a temperate environment is scarce. Given the weight-bearing nature of running, the negative effects of hypohydration might be offset by the weight-loss associated with a negative fluid balance. Therefore, this study investigated the effect of exercise-induced hypohydration on running performance in temperate conditions. Seventeen intermittent games players (age 22 ± 1 y; VO 2peak 52.5 ± 4.1 mL∙kg -1 ∙min -1 ) completed preliminary and familiarisation trials, and two experimental trials consisting of 12 blocks of 6 min of running (65% VO 2peak ; preload) with 1 min passive rest in-between, followed by a 3 km time trial (TT). During the preload, subjects consumed minimal fluid (60 mL) to induce hypohydration (HYP) or water to replace 95% sweat losses (1622 ± 343 mL; EUH). Body mass loss (EUH -0.5 ± 0.3%; HYP -2.2 ± 0.4%; P  < 0.001), and other changes indicative of hypohydration, including increased serum osmolality, heart rate, thirst sensation, and decreased plasma volume ( P ≤ 0.022), were apparent in HYP by the end of the preload. TT performance was ~6% slower in HYP (EUH 900 ± 87 s; HYP 955 ± 110 s; P  < 0.001). Exercise-induced hypohydration of ~2% body mass impaired 3 km running TT performance in a temperate environment.