Skeletal muscle determinants of maximum aerobic power in man

The interrelationship between whole body maximum O2 uptake capacity (VO2max), skeletal muscle respiratory capacity, and muscle fiber type were examined in 20 physically active men. The capacity of homogenates of vastus lateralis muscle biopsy specimes to oxidize pyruvate was significantly related to VO2max (r = 0.81). Correlations of 0.75 and 0.74 were found between % slow twitch fibers (%ST) and VO2max, and between %ST fibers and muscle respiratory capacity, respectively (P less than 0.01). Multiple correlation analysis (R = 0.85) indicated that 72% (R2 = 0.72) of the variance in VO2max could be accounted for by the combined effect of muscle respiratory capacity and the %ST fibers. When the %ST fibers was correlated with VO2max, with the effect of respiratory capacity statistically removed, the relationship became insignificant (r = 0.38). These data suggest that muscle respiratory capacity plays an important role in determining VO2max, and that the relationship between %ST fibers and VO2max is due primarily to the high oxidative capacity of this muscle fiber type.