A comparison of the mechanogram of the ankle jerk in men and women: observations using an adjustable dorsiflexing torque, high inertia mechanical filter and automatic readout system

Abstract

An instrument of new design has been constructed to measure the contractions of the calf musculature resulting from a tap on the Achilles tendon. The instrument provides a predetermined and adjustable dorsiflexing torque from a printed motor, but the contractions are virtually isometric as the system is one of high inertia. Peak force, half‐contraction time and half‐relaxation time are monitored by electronic circuits equipped with digital output meters. Observations have been made on fifty‐two male and forty‐five female medical students. There were no significant differences in the peak torques generated by the contractions between the men and women students and no difference in the half‐contraction times. The half‐relaxation times of the women were, however, significantly longer than those of the men (P = 0.0001). In another group of students the EMG discharges following a tendon tap were recorded, there was no significant difference in the duration of the activity in men and women. Observations have also been made on twenty‐three male and seventy female subjects whose mean ages were in the mid‐sixties. The peak torques generated by the contractions were significantly higher in the women (P = 0.03). There was no difference in the half‐contraction times, but the half‐relaxation times of the women were significantly longer (P = 0.001). Possible reasons for the differences are discussed.