Article Title



Catalina Capitan, J.D.Adams, LynnDee Summers, Evan C Johnson & Stavros A. Kavouras, FACSM

Human Performance Laboratory, Department of Health, Human Performance and Recreation, University of Arkansas, Fayetteville, Arkansas

PURPOSE: to assess the hydration status and fluid intake during mountain bike race. METHODS: Thirteen healthy, recreational cyclists (82.1±10.4 kg) competed a mountain bike race of 14, 29 or 43 km (1.9±0.5 h) in temperate conditions (23.8ºC and 71% relative humidity). Body weight and urine samples, thirst, and mouth dryness data were collected before and after the race. Thirst and mouth dryness were assessed via visual analog scales. Subjects were instructed to drink only from their bottles during the race. Fluid ingested was calculated based on the weight difference of their bottle before and after the race. The data were analyzed by paired t-test with JMP pro 11. RESULTS: Body weight loss after the race was -1.7±1.1%. Sweat rate ranged from 0.9 to 2.4 L/h, with a mean sweat rate of 1.4±0.4 L/h. Fluid intake ranged from 0.2 to 1.3 L/h, with a mean fluid intake of 0.6±0.3 L/h. Thirst and dry mouth ratings increased after the race (thirst: 23±13 mm, p= 0.0001; mouth dryness 37±30 mm, p=0.002). Before the race 23, 23, and 31% of subjects were hypohydrated, based on urine specific gravity (USG), urine osmolality (UOsm), and color, respectively. After the race 31, 15, and 85% of subjects were hypohydrated based on USG, UOsm and urine color, respectively. Urine osmolality after the race was not correlated with body weight loss during race (R2=0.10, p>0.05). CONCLUSION: Significant percent of dehydration was observed even in a recreational, short, mountain biking race in a temperate environment with access to fluids during exercise. Also urine hydration markers after exercise while drinking ad-libitum do not reflect changes in hydration state.

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