EFFECTS OF AGE ON RAPID ANKLE TORQUE DEVELOPMENT

Background. When balance is disturbed, often only fractions of a secon d are available in which to make the initial responses needed for its restoration. Abilities to develop joint torques rapidly may be critica l to such responses, We undertook this study to quantify age effects a mong healthy adults in abilities to develop ankle joint torques rapidl y. Methods. Ankle dorsiflexion (DF) and plantarflexion (PF) torque dev elopment during rapid isometric and during isokinetic (30, 60, 120, 18 0, and 240 deg/sec) exertions was assessed in 24 healthy young (mean a ge 23 years) and 24 healthy old adults (mean age 72 years). The effect s of age, gender, and torque direction on the times needed to reach gi ven torque magnitudes, maximum rates of isometric torque development ( MRTD), and maximum isokinetic torques were examined. Results. The old adults required substantially more time to reach given torque magnitud es than the young adults. For example, the young and old females neede d approximately 236 and 337 msec to develop 15 Nm of BF torque, of whi ch 141 and 164 msec were reaction times. Isometric MRTD were 25 to 36% lower in the old than in the young adults, The age declines in isomet ric torque development time were associated with losses in maximum iso metric strength. Maximum isokinetic torques developed by the old were 20 to 40% lower than those of young adults. The percent losses in isok inetic torques with age were independent of joint angular velocity for PF, but increased with velocity for DF. Conclusions. We found substan tial age declines in abilities of healthy old adults to rapidly develo p ankle joint torques. The capacities of even healthy old adults to re cover balance or to carry out other time-critical actions that require moderate-to-substantial strengths may be considerably degraded by the se declines.