• aging;
  • eccentric;
  • knee extensors;
  • voluntary activation;
  • twitch contractile properties


In this investigation we examined age-associated changes in peak torque, voluntary activation levels, and potentiated twitch properties of the knee extensors during isometric (ISO), shortening (SHO), and lengthening (LEN) actions in 18 young subjects (19–27 years) and 12 elderly subjects (64–77 years). Peak torque was lower for the elderly subjects under the ISO (−31%) and SHO (−28%) conditions (P < 0.05); however, the loss in LEN peak torque in the elderly was less marked (−17%) (P > 0.05). Voluntary activation levels within and between groups were not significantly different and ranged between 96.8% and 98.9% (P > 0.05). Peak twitch torque and some temporal twitch characteristics were altered with age (P < 0.05), but such changes were similar across all muscle actions (P > 0.05). These data suggest that the attenuated reduction in LEN muscle strength associated with age is probably not related to contraction-specific changes in voluntary activation levels or potentiated twitch properties. Muscle Nerve, 2009