Fatigue curves of isokinetic contractions.

Sixteen men and 16 women volunteer college students were tested for elbow flexion fatigue curve production on the Orthotron, an isokinetic testing device. Maximal voluntary contractions were obtained repeatedly, each contraction taking approximately 2 seconds to complete, with minimal (500 msec) intertrial rest, to exhaustion. To provide a basis for plotting the isokinetic fatigue curve, the degradation of torque values from initial to final contractions, was expressed as percentage of contraction time. Results obtained following statistical analysis of the data indicated that the isokinetic fatigue curve is: (1) curvilinear; (2) independent of sex differences; and (3) a function of initial strength. Moreover, it was found that the use of 50% of initial strength to denote fatigue in repetitive rhythmic isokinetic work has merit as a conservative estimate.