title: Two percent hypohydration does not impair self-selected high-intensity intermittent exercise performance.
abstract: The level of hypohydration at which power output during intermittent exercise performance starts to decrease is not fully understood. The purpose of this study was to investigate the effects of 2% hypohydration without hyperthermia on intermittent exercise performance. Eight collegiate amateur boxers completed 2 exercise tests. On day 1, subjects hypohydrated by 2% of body mass by exercising in a hot environment, and on day 2, subjects performed intermittent exercise (4 × 2 minute per round [R] separated by 1-minute recovery) under a randomly assigned condition of with (HYP) or without (EUH) hypohydration. Each bout consisted of 8 × 5 seconds of maximal cycling exercise (0.05 kp × body mass) separated by 10 seconds of passive recovery. Mean power output per kilogram (MPO), total power output per kilogram (TPO), energy system relative contribution, and core rectal temperature (Tre) were measured. Changes in body mass before the exercise tests were -2.25 ± 0.18% (HYP) and -0.17 ± 0.19% (EUH) (p < 0.001). Mean power output, TPO, and each energy contribution ratio were not significantly different between the trials, and pre- and postexercise test Tre did not differ significantly between trials. Results demonstrated that approximately 2% hypohydration lies below the point at which power output during intermittent exercise starts to decline.
authors.affiliation: 1Laboratory for Exercise Physiology and Biomechanics, Graduate School of Health and Sport Sciences, Chukyo University, Toyota, Japan; 2University Educational Center, Nihon Fukushi University, Mihama-Cho, Japan; and 3Department of Human Health, Faculty of Human Studies, Aichi Toho University, Nagoya, Japan.
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Yamashita
authors.forename: Ryo
authors.initials: R
authors.lastname: Ito
authors.forename: Masataka
authors.initials: M
authors.lastname: Nakano
authors.forename: Takaaki
authors.initials: T
authors.lastname: Matsumoto
mesh_terms: D015308:Anaerobic Threshold; D001831:Body Temperature; D001914:Boxing / Q000502:physiology*; D003681:Dehydration / Q000503:physiopathology*; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005334:Fever; D006358:Hot Temperature / Q000009:adverse effects*; D006801:Humans; D008297:Male; D011897:Random Allocation; D055815:Young Adult