HISTOCHEMICAL AND ENZYMATIC CHARACTERISTICS OF SKELETAL-MUSCLE IN MASTER ATHLETES

Many older athletes are capable of endurance performances equal to those of young runners who have higher maximal O2 uptakes (V̇O2(max)). To determine whether this is a result of differences in skeletal muscle characteristics, gastrocnemius muscle biopsy samples were obtained from eight master athletes [aged 63 ± 6 (SD) yr] and eight young (aged 26 ± 3 yr) runners. The young runners were matched with the master athletes for 10-km running performance and for their volume, pace, and type of training. Despite similar 10-km run times, V̇O2(max) was 11% lower (P < 0.05) in the master athletes. Fiber type distribution did not differ between groups, with both groups having 60% type I and very few type IIb fibers. Succinate dehydrogenase and β-hydroxyacyl-CoA dehydrogenase activities, however, were 31 and 24% higher in the master athletes compared with the matched young runners, whereas lactate dehydrogenase activity was 46% lower (all P < 0.05). The capillary-to-fiber ratio was also greater in the master athletes however, capillary density was similar in the two groups, because of the master athletes' 34% larger (P < 0.05) type I fibers. These differences in skeletal muscle characteristics may explain the master athletes' ability to perform as well as some young runners despite having a lower V̇O2(max).