This study compared oxygen consumption and substrate oxidation while exercising in hot and temperate conditions in individuals with different physical activity statuses (i.e., inactive individuals vs. trained runners). Ten inactive individuals (IA: 26 ± 6 yr; 79.1 ± 14.1 kg; 40.7 ± 5.1 mL·kg-1·min-1) and 10 trained runners (TR: 25 ± 6 yr; 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 with TEMP for IA and TR [-13.2 ± 4.5% vs. -15.2 ± 7%; P = 0.571; effect size (ES) = 0.25]. In HOT compared with TEMP, lipid oxidation, from 30% to 70% of peak oxygen consumption (V̇o2peak), was reduced for both groups (IA: P = 0.023, ES = 0.43; TR: P < 0.001, ES = 0.72), whereas 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 utilization and peak oxygen consumption in hot compared with temperate conditions. However, the increased carbohydrate oxidation in HOT for TR was not observed in IA, potentially explained by lower thermal strain. NEW & NOTEWORTHY This study shows that lipid oxidation and oxygen consumption are similarly affected by heat exposure in trained runners and inactive individuals. Carbohydrate oxidation and core temperature are greater in hot conditions in trained runners but not in inactive individuals. A lower metabolic heat production in inactive individuals for a similar relative intensity compared with trained runners could explain these differences in core temperature.

7 days L-citrulline supplementation has been reported to improve blood pressure, V^. O2 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. 13 endurance runners (2 female, 31 ± 8 y, V^. O2peak 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^. O2peak (32 °C, 50

ABSTRACT 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; VO2peak 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% VO2peak; 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.

PURPOSE: Exercise in hot ambient temperatures increases thermal/cardiovascular strain and carbohydrate use, as well as decreasing gastrointestinal (GI) integrity and endurance performance. However, laboratory-based studies have provided little/no facing airflow, potentially exacerbating these effects. Therefore, we examined the effect of cycling exercise in a hot vs moderate environment on exogenous carbohydrate use, GI responses and performance, with appropriate facing airflow. METHODS: Ten trained male cyclists/triathletes (36 ± 6 y; 55 ± 6 ml/kg/min; 9 ± 2 h/week training) completed VO2peak and familiarisation time trial (TT), followed by two experimental trials in 19 °C (MOD) and 32 °C (HOT), involving 2 h at ~50% Wpeak (preload) and an ~15 min TT. Airflow (~18 mph in preload, ~21 mph in TT) covering the cyclist was provided by 4 fans ~0.50 m from the handlebars. A glucose drink containing [U-13C]-glucose was given every 20 min in preload (72 g/h), alongside ad-libitum water, with breath samples collected to determine exogenous oxidation. Venous blood samples and GI scales were collected at 0, 60, 120 min and post-TT, with GI/skin temperature recorded throughout. RESULTS: TT performance was slower in HOT (MOD 819 ± 47 s; HOT 961 ± 130 s; P = 0.004). GI temperature (P = 0.007), heart rate (P < 0.001) and RPE (P = 0.046) were greater during HOT. Average 60-120 min (MOD 0.64 ± 0.15 g; HOT 0.54 ± 0.14 g; P = 0.007) and peak (MOD 0.78 ± 0.20 g; HOT 0.65 ± 0.14 g; P = 0.007) exogenous carbohydrate oxidation were reduced in HOT. Voluntary fluid intake was higher in HOT (MOD 377 ± 376 mL; HOT 745 ± 500 mL; P = 0.004), but as sweat loss was greater in HOT (MOD 1.51 ± 0.23 L; HOT 3.05 ± 0.24 L; P < 0.001), hypohydration was also greater in HOT pre-TT and post-TT (P < 0.001). Plasma osmolality and plasma volume change did not differ (P ≥ 0.112) between trials and neither did GI comfort (P = 0.659) or IFABP-1 (a blood marker of GI permeability; P = 0.211). CONCLUSION: Hot ambient conditions impair laboratory-based cycling performance even with appropriate facing airflow, likely via impairments of thermoregulatory, cardiovascular and metabolic function. Furthermore, these data demonstrate that ability to use glucose provided in drinks is impaired during prolonged cycling in the heat.

ABSTRACT 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.

Background: Blackcurrant is rich in anthocyanins that may protect against exercise-induced muscle damage (EIMD) and facilitate a faster recovery of muscle function. We examined the effects of New Zealand blackcurrant (NZBC) extract on indices of muscle damage and recovery following a bout of strenuous isokinetic resistance exercise. Methods: Using a double-blind, randomised, placebo controlled, parallel design, twenty-seven healthy participants received either a 3 g·day−1 NZBC extract (n = 14) or the placebo (PLA) (n = 13) for 8 days prior to and 4 days following 60 strenuous concentric and eccentric contractions of the biceps brachii muscle on an isokinetic dynamometer. Muscle soreness (using a visual analogue scale), maximal voluntary contraction (MVC), range of motion (ROM) and blood creatine kinase (CK) were assessed before (0 h) and after (24, 48, 72 and 96 h) exercise. Results: Consumption of NZBC extract resulted in faster recovery of baseline MVC (p = 0.04), attenuated muscle soreness at 24 h (NZBC: 21 ± 10 mm vs. PLA: 40 ± 23 mm, p = 0.02) and 48 h (NZBC: 22 ± 17 vs. PLA: 44 ± 26 mm, p = 0.03) and serum CK concentration at 96 h (NZBC: 635 ± 921 UL vs. PLA: 4021 ± 4319 UL, p = 0.04) following EIMD. Conclusions: Consumption of NZBC extract prior to and following a bout of eccentric exercise attenuates muscle damage and improves functional recovery. These findings are of practical importance in recreationally active and potentially athletic populations, who may benefit from accelerated recovery following EIMD.

This study investigated the effect of post-exercise sodium bicarbonate (NaHCO3) ingestion on acid-base balance recovery and time-to-exhaustion (TTE) running performance. Eleven male runners (stature, 1.80 +/- 0.05 m; body mass, 74.4 +/- 6.5 kg; maximal oxygen consumption, 51.7 +/- 5.4 mL.kg(-1).min(-1)) participated in this randomised, single-blind, counterbalanced and crossover design study. Maximal running velocity (v-(V)over dot O-2max) was identified from a graded exercise test. During experimental trials, participants repeated 100% v-(V)over dot O-2max TTE protocols (TTE1, TTE2) separated by 40 min following the ingestion of either 0.3 g.kg(-1) body mass NaHCO3- ( SB) or 0.03 g.kg(-1) body mass sodium chloride (PLA) at the start of TTE1 recovery. Acid-base balance (blood pH and bicarbonate, HCO3-) data were studied at baseline, post-TTE1, after 35 min recovery and post-TTE2. Blood pH and HCO3- concentration were unchanged at 35 min recovery ( p > 0.05), but HCO3- concentration was elevated post-TTE2 for SB vs. PLA (+2.6 mmol.L-1; p = 0.005; g = 0.99). No significant differences were observed for TTE2 performance (p > 0.05), although a moderate effect size was present for SB vs. PLA (+14.3 s; g = 0.56). Post-exercise NaHCO3- ingestion is not an effective strategy for accelerating the restoration of acid-base balance or improving subsequent TTE performance when limited recovery is available. Novelty: Post-exercise sodium bicarbonate ingestion did not accelerate the restoration of blood pH or bicarbonate after 35 min. Performance enhancing effects of sodium bicarbonate ingestion may display a high degree of inter-individual variation. Small-to-moderate changes in performance were likely due to greater up-regulation of glycolytic activation during exercise.