Title

Effect of hydration state on performance of and hormonal responses to acute resistance exercise

Date of Completion

January 2006

Keywords

Health Sciences, Recreation

Degree

Ph.D.

Abstract

Although significant research documents the effects of hypohydration (i.e. reduced total body water) on endurance exercise performance, only a small conflicting body of literature examines the effect of hypohydration on exercises requiring strength, power, and high-intensity endurance (i.e. resistance exercise). The purpose of this study was to examine the effect of hydration state on the performance, metabolism, and hormonal responses to resistance exercise. Seven healthy resistance trained males (age = 23 ± 4 y, height = 1.79 ± 0.58 m, body mass = 87.8 ± 6.8 kg, body fat = 11.5 ± 5.2%) completed three identical resistance exercise bouts in different hydration states: euhydrated (EU), hypohydrated by ∼2.5% body mass (HY25), and hypohydrated by ∼5.0% body mass (HY50). Investigators manipulated hydration status via controlled water deprivation, exercise-heat stress, and fluid intake. Cortisol, epinephrine, norepinephrine, testosterone, growth hormone, IGF-1, insulin, glucose, lactate, glycerol, and free fatty acids were measured during euhydrated rest, immediately preceding resistance exercise, immediately post-exercise, and during 60 minutes of recovery. Body mass decreased 0.2 ± 0.4%, 2.4 ± 0.4%, and 4.8 ± 0.4% during EU, HY25, and HY50, respectively. No significant differences existed among trials in vertical jump height, peak lower body power, peak lower body force, or central activation, but total work completed during the first three sets of the resistance exercise bout was decreased in HY25 and HY50. Hypohydration had little demonstrable effect on the anabolic endocrine response to exercise, but significantly increased the exercise-induced stress hormonal response (cortisol and the catecholamines), stimulating an influx of metabolic substrates (glucose, free fatty acids, and glycerol) and regulatory hormones (insulin) to the circulation. These novel data indicate that body water status is an important consideration in the goal of acutely maximizing and chronically increasing resistance exercise performance.^