This study compared maximal voluntary-contraction (MVC) force and twitch-contractile properties of the plantar-flexor muscles in resting and postactivation potentiation slates of 2 groups of men matched for similar levels of physical activity: young (19- to 22-year-olds. n = 13) and 52–63 years old (n = 12). MVC force, twitch peak force (PT), maximal rates of force development and relaxation, and postactivation potentiation were higher (p < .05) in young than in 52- to 63-year-old men. In young men. potentiated-twitch PT was 23.3% higher (p < .01) than resting twitch. Resting- and potentialed-twitch-contraction times were 16.7% and 18.3% shorter, respectively (p < .001), in young than in 52- to 63-year-old men. These Findings suggest that late middle age is characterized by reduced capacity for evoked twitch-force generation and potentiation and slowed speed of contraction of the plantar-flexor muscles.
The authors are with the Institute of Exercise Biology, University of Tartu, 51014 Tartu, Estonia.