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Fluid Intake Pattern, Dehydration, And Performance In Young Athletes During A Triathlon In Tropical Climate

2018; Lippincott Williams & Wilkins; Volume: 50; Issue: 5S Linguagem: Inglês

10.1249/01.mss.0000536207.69205.6b

1530-0315

Anita M. Rivera‐Brown, José R. Quiñones-González, Patricia Pagán-Lasalle,

High Altitude and Hypoxia

Mild dehydration is associated with increased core temperature and reduced performance during endurance events in adult athletes. Little is known about hydration practices, hyperthermia, and the effects of insufficient fluid replacement on performance in young athletes during real-life competitions. PURPOSE: Examine voluntary fluid intake, the relation between dehydration and performance, and core temperature in adolescents during a triathlon competition in tropical climate. METHODS: 15 junior (14-15 yr) and 21 senior (16-18 yr) athletes competed in a triathlon (750 m swim, 18 km cycle and 4 km run) in a hot and humid environment (WBGT=27.9°C; water temp=29.0°C), in July, between 7:30 to 9:30 am. Urine specific gravity (USG) was measured upon waking the day of competition. Water and sports drinks were carried in bottles on the bike, and available for each athlete in a fluid station during the run. Sweat loss was calculated from change in body weight [BW] (corrected for urine output) and fluid intake. Dehydration was calculated as % change in BW. Core temperature was measured in two athletes pre-competition, and at the end of the swim, cycle, and run portions, using ingestible sensors. RESULTS: Mean USG (1.025 ± 0.001 g/mL) indicated that athletes were not in an adequate state of hydration upon waking. Fluid intake (juniors=471.8 ± 161.4 and seniors=551.3 ± 263.2 ml) replaced 46% of the sweat loss and was higher during run (juniors=10.2 ± 3.5 and seniors=12.3 ± 8.2 ml/min) compared to cycle (juniors=6.1 ± 2.5 and seniors=8.0 ± 3.4 ml/min), P < 0.05. At the end of the competition, 26% of juniors and 52% of seniors had dehydrated > 1.5%. Dehydration was associated with finishing time in senior boys (r= -0.70; P= 0.01) who also showed the highest sweat rate (1.3 ± 0.8 L/h) and faster times. Core temperature rose to 40.1°C in the girl who placed 2nd, and to 39.6°C in the boy who placed 3rd. No athletes showed symptoms of heat illness. CONCLUSIONS: Young athletes participating in a triathlon in tropical climate show mild to moderate levels of dehydration. Higher dehydration in senior athletes may be due to higher sweat rates and faster racing. Competition organizers should be aware that young, dehydrated athletes may become hyperthermic during triathlons in tropical climate, and should be prepared for medical interventions if needed.