The present study was designed to investigate the isokinetic peak torque at the highest speed of muscle shortening (210 degrees/second) related to age, sex, and physical performance. The subjects were 569 normal boys and girls, 13 to 17 years of age, and 35 swimmers, 11 to 21 years of age. Peak torque of knee extensor muscles increased linearly with age for boys from 13 to 17 years, while it remained relatively constant for girls 14 to 17 years of age. The relationship (boys r =.688, p `.001; girls r =.373, p `.01) between peak torque of knee extensors and mean speed in meters per second of 50 meters maximal run was significant. Significant correlations (boys r =.728, p `.001; girls r =.515, p `.05) were also obtained between peak torque of arm pull muscles and the best record in time of 100 meters free style swimming. © 1979 Taylor 8 Francis Group, LLC.