Abstract
The object of the present experiments was to study the impact of muscle fiber type
composition on “aerobic” and “anaerobic” performance capacities. Muscle fiber type
composition was determined on biopsies from the m. vastus lateralis of 29 healthy
males, consisting of sedentary subjects, physical education students, and short- and
long-distance runners. The subjects performed: (a) a 30-s all-out ride on a cycle
ergometer; b) a short-term (60 s), isokinetic, one-leg exercise test, tc) a 40-m sprint
run; d) a 300 m run; and (e) a 2000-m run. Correlations between msucle fiber composition,
expressed as% fast twitch (FT) fibers on one hand, and peak power, maximal peak torque,
power decrease, and peak torque decrease in the laboratory tests were significant
(P < 0.001) for the trained subjects but not for the sedentaries. Average speed during
the 40-m sprint and the 2000-m run was positively (P < 0.001) and negatively (P < 0.001) related, respectively, to % FT in the trained subjects whereas no such correlations
were present for sedentaries. It is suggested that fiber type composition in trained
males is one factor contributing to ability to perform short-term as well as endurance
exercise. This statement may not be true for the general population.
Key words
muscle fiber type composition - runners - sedentaries - exercise performance capacity
