Department of Physical Education, Federal University of Viçosa , Viçosa MG, Brazil.
J Sports Sci Med. 2010 Sep 1;9(3):464-71. eCollection 2010.
Urine specific gravity is often used to assess hydration status. Athletes who are hypohydrated prior to exercise tend to ingest more fluid during the exercise, possibly to compensate for their pre exercise fluid deficit. The purpose of this study was to evaluate the effect of additional fluid intake on fluid balance and gastrointestinal tract comfort during 1h running in a thermoneutral environment when athletes followed their habitual fluid and dietary regimes. Sixteen men and sixteen women ingested a 6% carbohydrate-electrolyte solution immediately prior to exercise and then every 15 minutes during two runs, with a consumption rate of 2 mL.kg(-1) (LV, lower volume) or 3 mL.kg(-1) (HV, higher volume) body mass. Urine specific gravity and body mass changes were determined before and after the tests to estimate hydration status. During exercise subjects verbally responded to surveys inquiring about gastrointestinal symptoms, sensation of thirst and ratings of perceived exertion. Plasma glucose, heart rate and blood pressure were also evaluated. Men had higher preexercise urine specific gravity than women (1.025 vs. 1.016 g·mL(-1) HV; and 1.024 vs. 1.017 g·mL(-1) LV) and greater sweat loss (1.21 ± 0.27 L vs. 0.83 ± 0.21 L HV; and 1.18 ± 0.23 L vs. 0.77 ± 0.17 LV). Prevalence of gastrointestinal discomfort increased after 45 min. No significant differences on heart rate, rate of perceived exertion, blood pressure or glycemia was observed with the additional fluid intake. From these results it appears that additional fluid intake reduces body mass loss and thirst sensation. When compared to the men, however, preexercise euhydration was more common in women and an increased fluid intake increases the risk of body mass gain and gastrointestinal discomfort. Key pointsThere seems to be a wide variability in pre-exercise hydration status between male and female and efforts aimed at educating athletes about the importance of pregame hydration must be emphasized.The fluid ingestion during running exercise in a moderate environment reduces body mass loss and thirst sensation, but an increased fluid intake at rates to match the fluid loss might raise the risk of body mass gain in women during prolonged activities.Individual gastric tolerance and familiarization with fluid replacement should be taken into account when providing athletes with strategies for hydration during exercise.
尿比重常用于评估水合状态。在运动前处于低水合状态的运动员在运动过程中往往会摄入更多的液体，可能是为了弥补运动前的液体亏缺。本研究的目的是评估在热中性环境中 1 小时跑步时，运动员按照习惯的液体和饮食方案，额外摄入液体对液体平衡和胃肠道舒适度的影响。16 名男性和 16 名女性在运动前立即饮用 6%碳水化合物-电解质溶液，然后在两次跑步过程中每 15 分钟饮用一次，摄入量为 2 毫升/千克（LV，低容量）或 3 毫升/千克（HV，高容量）体重。在测试前后测定尿比重和体重变化，以评估水合状态。运动过程中，受试者通过口头回答调查，询问胃肠道症状、口渴感和感知用力程度。还评估了血浆葡萄糖、心率和血压。男性的运动前尿比重高于女性（HV 为 1.025 比 1.016 g·mL(-1)；LV 为 1.024 比 1.017 g·mL(-1)），出汗量也更大（HV 为 1.21 ± 0.27 L 比 0.83 ± 0.21 L；LV 为 1.18 ± 0.23 L 比 0.77 ± 0.17 L）。45 分钟后，胃肠道不适的发生率增加。额外液体摄入对心率、用力感知、血压或血糖没有显著影响。从这些结果来看，额外的液体摄入可以减少体重的损失和口渴感。然而，与男性相比，女性在运动前更常见处于水合状态，而增加液体摄入会增加体重增加和胃肠道不适的风险。关键点在男性和女性之间，运动前的水合状态似乎存在很大的差异，必须强调教育运动员关于比赛前补水重要性的工作。在适度环境下进行的跑步运动中摄入液体可以减少体重的损失和口渴感，但在长时间活动中，以与液体流失相匹配的速度增加液体摄入可能会增加女性体重增加的风险。在为运动员提供运动期间补水策略时，应考虑个体胃耐受性和对液体补充的熟悉程度。
