The impact of alterations in hydration status on human physiology and performance responses during exercise is one of the oldest research topics in sport and exercise nutrition. This body of work has mainly focussed on the impact of reduced body water stores (i.e. hypohydration) on these outcomes, on the whole demonstrating that hypohydration impairs endurance performance, likely via detrimental effects on a number of physiological functions. However, an important consideration, that has received little attention, is the methods that have traditionally been used to investigate how hypohydration affects exercise outcomes, as those used may confound the results of many studies. There are two main methodological limitations in much of the published literature that perhaps make the results of studies investigating performance outcomes difficult to interpret. First, subjects involved in studies are generally not blinded to the intervention taking place (i.e. they know what their hydration status is), which may introduce expectancy effects. Second, most of the methods used to induce hypohydration are both uncomfortable and unfamiliar to the subjects, meaning that alterations in performance may be caused by this discomfort, rather than hypohydration per se. This review discusses these methodological considerations and provides an overview of the small body of recent work that has attempted to correct some of these methodological issues. On balance, these recent blinded hydration studies suggest hypohydration equivalent to 2-3% body mass decreases endurance cycling performance in the heat, at least when no/little fluid is ingested.

中文翻译：

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水分不足真的会影响耐力表现吗？解释水化研究的方法学考虑。

运动期间水合状态变化对人体生理和机能反应的影响是运动和运动营养中最古老的研究主题之一。这项工作主要集中在减少体内水分存储（即水分不足）对这些结果的影响上，总体上表明，水分过多会损害耐力性能，这可能是通过对许多生理功能的有害影响。然而，一个很少被重视的重要考虑因素是传统上用来研究体液过少如何影响运动结果的方法，因为所使用的方法可能会混淆许多研究的结果。在许多已发表的文献中，有两个主要的方法学局限性，可能使研究绩效结果的研究结果难以解释。首先，参与研究的受试者通常不会对所进行的干预不知情（即，他们知道自己的水合状态是什么），这可能会引入预期效果。其次，大多数诱发体液过少的方法既不舒服，也不熟悉受试者，这意味着性能的改变可能是由这种不适引起的，而不是体液过低本身。这篇综述讨论了这些方法论上的考虑，并概述了试图纠正其中一些方法论问题的近期工作。总的来说，