Voluntary muscle function after creatine supplementation in acute hypobaric hypoxia.
OBJECTIVE
To determine whether creatine (Cr) supplementation improves muscle performance during exposure to acute hypobaric hypoxia.


METHODS
Seven healthy men (28 +/- 6 yr, mean +/- SD) performed submaximal intermittent static knee contractions interspersed with maximal voluntary contractions (MVCs) every minute to exhaustion (approximately 50% of rested MVC force) in normoxia and hypobaric hypoxia (separated by 3 d) after supplementation with Cr (20 g.d(-1) for 7 d then 5 g.d(-1) for 4-7 d) or placebo (Pla) in a double-blind, randomized crossover study. A 5-wk period without supplementation separated treatments. Each test day, subjects performed two bouts (separated by 2 min) at their preset submaximal force, 32 +/- 4% rested MVC).


RESULTS
Rested MVC force (860 +/- 66 N) and MVC force at exhaustion (396 +/- 27 N; 47 +/- 3% rested MVC) did not differ among treatments or environments (P > 0.05). For bout 1, endurance time was shorter in hypobaria (26 +/- 3 min) than normoxia (34 +/- 2 min) (P < 0.01), but did not differ between Cr (27 +/- 3 min) and Pla (33 +/- 3 min) (P > 0.05). MVC force returned to similar levels (P >0.05) in bout 2 after recovery in all four sessions (to approximately 615 N). For bout 2, endurance time also was shorter in hypobaria (7 +/- 1 min) than normoxia (9 +/- 1 min) (P < 0.03) but did not differ between Cr and Pla (P > 0.05).


CONCLUSIONS
This study, which used an exercise model designed to impose the same target contraction force under all experimental conditions, found no effect of Cr on maximal force, muscle endurance, or recovery in normoxia or hypobaric hypoxia.
Baker-Fulco
Carol J
CJ
Military Nutrition Division, U.S. Army Research Institute of Environmental Medicine, Natick, MA 01760-5007, USA. carol.baker-fulco@na.amedd.army.mil
Fulco
Charles S
CS
Kellogg
Mark D
MD
Glickman
Ellen
E
Young
Andrew J
AJ
D000328:Adult; D000704:Analysis of Variance; D003401:Creatine / Q000008:administration & dosage / Q000494:pharmacology*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005080:Exercise Test; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D007866:Leg / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue / Q000502:physiology; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000502:physiology*
D003401:Creatine