James Lewis J, Moss Jodie, Henry Joshua, Papadopoulou Charikleia, Mears Stephen A
School of Sport, Exercise and Health Sciences, Loughborough University, Leicestershire, LE11 3TU, United Kingdom
School of Sport, Exercise and Health Sciences, Loughborough University, Leicestershire, LE11 3TU, United Kingdom.
Physiol Rep. 2017 Jun;5(12). doi: 10.14814/phy2.13315.
The general scientific consensus is that starting exercise with hypohydration >2% body mass impairs endurance performance/capacity, but most previous studies might be confounded by a lack of subject blinding. This study examined the effect of hypohydration in a single blind manner using combined oral and intragastric rehydration to manipulate hydration status. After familiarization, seven active males (mean ± SD: age 25 ± 2 years, height 1.79 ± 0.07, body mass 78.6 ± 6.2, O 48 ± 7 mL·kg·min) completed two randomized trials at 34°C. Trials involved an intermittent exercise preload (8 × 15 min exercise/5 min rest), followed by a 15-min all-out performance test on a cycle ergometer. During the preload, water was ingested orally every 10 min (0.2 mL·kg body mass). Additional water was infused into the stomach via a gastric feeding tube to replace sweat loss (EU) or induce hypohydration of ~2.5% body mass (HYP). Blood samples were drawn and thirst sensation rated before, during, and after exercise. Body mass loss during the preload was greater (2.4 ± 0.2% vs. 0.1 ± 0.1%; 0.001), while work completed during the performance test was lower (152 ± 24 kJ vs. 165 ± 22 kJ; 0.05) during HYP At the end of the preload, heart rate, RPE, serum osmolality, and thirst were greater and plasma volume lower during HYP (0.05). These results provide novel data demonstrating that exercise performance in the heat is impaired by hypohydration, even when subjects are blinded to the intervention.
科学界的普遍共识是，以超过体重2%的低水合状态开始运动，会损害耐力表现/能力，但此前的大多数研究可能因缺乏对受试者的盲法处理而受到干扰。本研究采用单盲方式，通过口服和胃内补液相结合来控制水合状态，从而研究低水合的影响。在熟悉实验流程后，7名活跃男性（平均±标准差：年龄25±2岁，身高1.79±0.07米，体重78.6±6.2千克，摄氧量48±7毫升·千克·分钟）在34°C环境下完成了两项随机试验。试验包括间歇性运动预负荷（8次15分钟运动/5分钟休息），随后在功率自行车上进行15分钟的全力性能测试。在预负荷期间，每10分钟口服摄入一次水（0.2毫升·千克体重）。通过胃饲管向胃内注入额外的水，以补充汗液流失（EU）或诱导约2.5%体重的低水合状态（HYP）。在运动前、运动中和运动后采集血样并评估口渴感。在HYP组中，预负荷期间的体重减轻更大（2.4±0.2%对0.1±0.1%；P<0.001），而在性能测试期间完成的工作量更低（152±24千焦对165±22千焦；P=0.05）。在预负荷结束时，HYP组的心率、主观用力程度、血清渗透压和口渴感更高，而血浆量更低（P<0.05）。这些结果提供了新的数据，表明即使受试者对干预不知情，低水合状态也会损害高温环境下的运动表现。
