Abstract details
| Abstract-ID: | 1887 |
| Title of the paper: | Exercise-induced hypohydration impairs endurance running performance in the heat in female, but not male, runners: evidence of a sex-hydration interaction |
| Authors: | Cable, T., Funnell, M., Peden, D., Reynolds, K., Taylor, L., Mears, S., James, L. |
| Institution: | Loughborough University |
| Department: | School of Sport, Exercise and Health Sciences |
| Country: | United Kingdom |
| Abstract text | INTRODUCTION: Exercise-induced hypohydration impairs endurance performance in the heat, but most data is in cycling, with less known about running. Furthermore, the impact of biological sex on physiological and performance responses to hypohydration is unclear. Females have a smaller relative total body water (TBW) compared to males, and thus symptoms of hypohydration may be exacerbated in females. Therefore, this study assessed the impact of exercise-induced hypohydration on running performance in the heat in male and female runners. METHODS: 11 male (M; age 37 ± 3 y; V?O2peak 61 ± 3 mL/kg/min) and 8 female (F; age 34 ± 4 y; V?O2peak 54 ± 4 mL/kg/min) trained runners completed a familiarisation (ad-libitum water intake) and two experimental trials, involving a preload (PL; 7 x 10 min at 60% V?O2peak, 1 min rest) and a 3 km time-trial (TT) on a treadmill in the heat (32°C, 50% RH). Water to replace sweat loss (EU) or a total of 80 mL water (HH) was provided during the PL to manipulate hydration, aiming for ~3% reduction in TBW in HH. TBW was estimated by bioelectrical impedance and used to compare relative TBW loss between sexes. Venous blood was collected, and nude body mass measured at baseline, post-PL and post-TT, with gastrointestinal (GI)/skin temperature, heart rate, perceptual responses and oxygen uptake measured throughout trials. 3 km TT performance was the primary outcome. RESULTS: Post-PL relative TBW loss in EU (M -0.6 ± 0.2%; F -0.7 ± 0.3%) and HH (M -3.5 ± 0.6%; F -3.1 ± 0.4%) was not different between sexes (P=0.109). Hypohydration increased heart rate, GI temperature and thirst, and decreased body mass and plasma volume (P=0.041), but did not alter skin temperature, oxygen uptake, RPE, GI comfort or thermal sensation (P=0.380). However, there were no trial*time*sex interactions for any physiological or perceptual variable (P=0.108). There was a trial*sex interaction for 3 km TT performance (P=0.034), with females 5% slower in HH (EU 970 ± 286 s; HH 1020 ± 316 s; P=0.037), with no significant difference between trials in males (EU 715 ± 52 s; HH 722 ± 55 s; P=0.405). During familiarisation, ad-libitum water intake in PL replaced more of the sweat loss in females (M 47 ± 26%; F 67 ± 28%; P<0.001), meaning relative TBW loss was less in females (M 3.3 ± 1.3%; F 2.4 ± 1.4%; P<0.001). CONCLUSION: These data demonstrate that hypohydration impairs endurance performance in female, but not male, runners, but sex did not significantly alter any physiological or perceptual variables. Interestingly, during familiarisation, ad-libitum water intake replaced a greater proportion of sweat losses in females, producing a lower relative TBW deficit. This indicates some sex-based differences in hydration behaviour that might explain some of the observed performance effects of hypohydration. These results suggest that where high sweat rates are likely during running, females might need to pay more attention to hydration strategies than males. |
| Topic: | Nutrition |
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