INFLUENCE OF AGE ON CONCENTRIC ISOKINETIC TORQUE AND PASSIVE EXTENSIBILITY VARIABLES OF THE CALF MUSCLES OF WOMEN

The purpose of this study was to investigate the influence of age on c oncentric isokinetic torque (CIT) and passive extensibility (PE) varia bles of the calf muscles of healthy women. Ten younger women [31.9 (SD 6.1) years] and ten older women [71.1 (SD 6.6) years] were tested usi ng a KIN-COM 500H dynamometer. The PE was tested by stretching the mus cles from relaxed plantarflexion to the maximal dorsiflexion (DF) angl e at 5 degrees . s(-1) without raw electromyogram (EMG) activity excee ding 0.05 mV. The maximal CIT was tested from the maximal DF angle 60 degrees into plantarflexion at four randomly ordered velocities of 30, 60, 120, and 180 degrees . s(-1). Separate analysis of variance (ANOV A) tests showed that the standardized (% body mass) concentric peak an d mean torques were lower for the older women for all isokinetic veloc ities (p < 0.001). The ''angular delay'' from the onset of concentric activation to peak torque was smaller for the older women at 120 and 1 80 degrees . s(-1) (p < 0.05). Age showed negative relationships (Pear son r) with all standardized peak torques (p less than or equal to 0.0 01) and mean torques (p < 0.001), and the ''angular delay'' at 120 and 180 degrees . s(-1) (p less than or equal to 0.05). Independent t-tes ts showed that the maximal DF angle and the change in the PE angle fro m an initial angle (defined at 10% of the maximal passive torque) to t he maximal DF angle were less for the older women (p < 0.05). Age was negatively related to the maximal DF angle and the change in the PE an gle (p < 0.01). The results suggest an age-related decrease in calf mu scle CIT, muscle length and PE. The smaller ''angular delay'' for the older women at 120 and 180 degrees . s(-1) indicates that CIT testing at rapid velocities can be used to examine age-related changes in calf muscle contractile properties in relation to rapid velocities of move ment.