February 1, 1997
View Full PaperSkeletal muscle adaptations to training under normobaric hypoxic versus normoxic conditions
Structured PICO
Does training under normobaric hypoxic conditions enhance physical performance and muscle adaptations compared to normoxic training in healthy males?
P
Population
10 healthy males (19-25 yr)
I
Intervention
8 weeks of unilateral cycle ergometry training while breathing an inspirate of 13.5% O2 (normobaric hypoxic conditions)
C
Comparator
8 weeks of unilateral cycle ergometry training while breathing normal ambient air (normoxic conditions) in the contralateral leg
O
Outcome
Physical performance (single leg VO2max, time to fatigue at 95% VO2max) and muscle adaptations (oxidative and glycolytic enzyme activity, capillary density, fiber area, % fiber type, mitochondrial and lipid volume density)surrogate
Training under moderate normobaric hypoxic conditions enhances muscle citrate synthase activity to a greater extent than normoxic training, though both improve overall physical performance.
Abstract
This study examined whether training under normobaric hypoxic conditions (simulating medium level altitude) would enhance physical performance and selected muscle adaptations over and above that which occurs with normoxic training. Ten healthy males (19-25 yr) underwent 8 wk of unilateral cycle ergometry training so that one leg was trained while breathing an inspirate of 13.5% O2 and the other while breathing normal ambient air. Pre- and post-training measurements included single leg VO2max and time to fatigue at 95% VO2max. Needle biopsies from quadriceps were assayed for oxidative and glycolytic enzyme activity and analyzed for capillary density, fiber area, % fiber type, and mitochondrial and lipid volume density. VO2max, time to fatigue, citrate synthase (CS), succinate dehydrogenase, and phosphofructokinase activity increased significantly (P > 0.05) in both legs following training. The increase in CS activity in the hypoxically trained leg was also significantly greater than that in the normoxically trained leg. It thus appears that training under moderate normobaric hypoxic conditions enhances muscle citrate synthase activity to a greater extent than training under normoxic conditions.