TORQUE-VELOCITY RELATIONSHIPS AND MUSCLE-FIBER COMPOSITION IN ELITE FEMALE ATHLETES

The relationship between the predominance of fast and slow muscle fibers of the vastus lateralis and 'in vivo' torque velocity properties in 22 female athletes was studied. Fiber types were classified according to the histochemical myofibrillar adenosine triphosphatase technique at a basic pH. Maximal extensor torques were recorded at 30° from full extension at four selected velocities. While results confirm earlier reports on muscle fiber type and performance, an additional finding was that as knee extension velocities increased from 0 to 96°/s angle specific extensor torque production did not decline as seen in in vitro muscle preparations. The difference in extensor torque between 0 and 96°/s appeared far more critical than the differences observed between 96 and 288°/s. Significant differences in torque were seen at 96, 192, and 288°/s in those with >50% and <50% slow-twitch fibers. When expressed per kilogram of body weight the subjects with >50% fast-twitch fiber produced the greatest torque at 192°/s. These results suggest that the velocity at which torque begins to decline in vivo is related to the proportion of slow-twitch fibers in the vastus lateralis muscle.