Voluntary muscle function after creatine supplementation in acute hypobaric hypoxia

Purpose: 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 (similar to 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 nonnoxia (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 I min) than normoxia (9 I min) (P < 0.03) but did not differ between Cr and Pla (P > 0.05). Conclusion: 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.