title: Effect of hydration state on strength, power, and resistance exercise performance.
abstract: OBJECTIVE
  Although many studies have attempted to examine the effect of hypohydration on strength, power, and high-intensity endurance, few have successfully isolated changes in total body water from other variables that alter performance (e.g., increased core temperature), and none have documented the influence of hypohydration on an isotonic, multiset, multirepetition exercise bout typical of resistance exercise training. Further, no investigations document the effect of hypohydration on the ability of the central nervous system to stimulate the musculature, despite numerous scientists suggesting this possibility. The purposes of this study were to examine the isolated effect of hydration state on 1) strength, power, and the performance of acute resistance exercise, and 2) central activation ratio (CAR).
  
  
  METHODS
  Seven healthy resistance-trained males (age = 23 +/- 4 yr, body mass = 87.8 +/- 6.8 kg, body fat = 11.5 +/- 5.2%) completed three resistance exercise bouts in different hydration states: euhydrated (EU), hypohydrated by approximately 2.5% body mass (HY25), and hypohydrated by approximately 5.0% body mass (HY50). Investigators manipulated hydration status via exercise-heat stress and controlled fluid intake 1 d preceding testing.
  
  
  RESULTS
  Body mass decreased 2.4 +/- 0.4 and 4.8 +/- 0.4% during HY25 and HY50, respectively. No significant differences existed among trials in vertical jump height, peak lower-body power (assessed via jump squat), or peak lower-body force (assessed via isometric back squat). CAR tended to decrease as hypohydration increased (EU = 95.6 +/- 4.9%, HY25 = 94.0 +/- 3.1%, HY50 = 92.5 +/- 5.1%; P = 0.075, eta(p)(2) = 0.41). When evaluated as a function of the percentage of total work completed during a six-set back squat protocol, hypohydration significantly decreased resistance exercise performance during sets 2-3 and 2-5 for HY25 and HY50, respectively.
  
  
  CONCLUSIONS
  These data indicate that hypohydration attenuates resistance exercise performance; the role of central drive as the causative mechanism driving these responses merits further research.
authors.affiliation: Human Performance Laboratory, Department of Kinesiology, University of Connecticut, Storrs, CT, USA. djudelson@fullerton.edu
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Judelson
authors.forename: Carl M
authors.initials: CM
authors.lastname: Maresh
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Farrell
authors.forename: Linda M
authors.initials: LM
authors.lastname: Yamamoto
authors.forename: Lawrence E
authors.initials: LE
authors.lastname: Armstrong
authors.forename: William J
authors.initials: WJ
authors.lastname: Kraemer
authors.forename: Jeff S
authors.initials: JS
authors.lastname: Volek
authors.forename: Barry A
authors.initials: BA
authors.lastname: Spiering
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Casa
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Anderson
mesh_terms: D000328:Adult; D001834:Body Water; D003681:Dehydration / Q000175:diagnosis; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D013647:Task Performance and Analysis; D014481:United States; D014891:Weight Lifting / Q000502:physiology*