Ageing and isokinetic plantar flexion

Abstract

Isokinetic torques (Cybex II) of the plantar flexors in 25 healthy men were compared at 5 angular velocities (30, 60, 90, 120 and 180° · s⁻¹). The purposes were to compare plantar flexion torques in young and old subjects, and to determine whether the expected decrease was significantly associated with age, physical activity, or aerobic fitness. Four groups were studied: young (21.7±2.0 years) and older (63.3±2.8 years), active and sedentary. Measurements of height, weight, % body fat, \(\dot V_{{\text{O}}_{{\text{2 max}}} } \) and daily leisure energy expenditure (questionnaire) were determined for each subject. Statistical measures of analysis of variance were used to determine significant differences among groups; product moment correlation and stepwise regression analysis were used to describe the degree of association between the dependent variable of plantar flexion torque and the independent variables at each velocity. A decline in torque was observed as the isokinetic velocity of angular motion increased. Age alone was a significant determinant of plantar flexion torque, whereas at the slowest speed, when \(\dot V_{{\text{O}}_{{\text{2 max}}} } \) was used as an explanatory variable, age was not a significant determinant of torque. At 30° · s⁻¹ 47% of the variance in torque was explained by \(\dot V_{{\text{O}}_{{\text{2 max}}} } \) while at 180° · s⁻¹ 49% of the variance was explained by age.