Relationships between skeletal muscle characteristics and aerobic performance in sedentary and active subjects

Summary

Forty-eight sedentary and 39 quite active or well-trained men participated in this study. Muscle biopsy samples were taken from the vastus lateralis for the determination of fiber type composition (I, IIa, IIb), fiber type area, and assay of the following enzymes: malate dehydrogenase (MDH), 3-hydroxyacyl CoA dehydrogenase (HADH) and oxoglutarate dehydrogenase (OGDH). Maximal oxygen uptake ($\dot V_{{\text{O}}_{{\text{2max}}} }$) was determined with a progressive cycle ergometer test, while endurance performance or maximal aerobic capacity (MAC) was defined as the total work output during a 90-min cycle ergometer test. Correlation analysis revealed no evidence of association between fiber type composition and $\dot V_{{\text{O}}_{{\text{2max}}} }$ kg⁻¹ or MAC kg⁻¹ in sedentary subjects, while active men exhibited significant correlation between % type I (r=0.52), % type IIb (r=−0.31) and $\dot V_{{\text{O}}_{{\text{2max}}} }$ kg⁻¹. Enzyme activities were not significantly correlated with MAC kg⁻¹ and $\dot V_{{\text{O}}_{{\text{2max}}} }$ kg⁻¹ in sedentary men while active men exhibited significant correlation for the three enzymes (0.37≤r≤0.51) with $\dot V_{{\text{O}}_{{\text{2max}}} }$ kg⁻¹. These results show that the contribution of muscle fiber type and enzyme activities to aerobic performance may be inflated from a statistiscal point of view by the training status heterogeneity of subjects. They also suggest that variation in these muscle characteristics does not account for the individual differences in aerobic performance of subjects who have never trained before. Therefore, the assessment of muscle characteristics is not as useful as originally thought for the detection of individuals with a high potential for endurance performance among untrained subjects.