title: Effect of age on muscle activation and twitch properties during static and dynamic actions.
abstract: 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.
authors.affiliation: Exercise and Sports Science Laboratories, School of Human Movement Studies, Charles Sturt University, Building N1, Panorama Avenue, Bathurst, New South Wales 2795, Australia.
authors.forename: Melissa R
authors.initials: MR
authors.lastname: Wilder
authors.forename: Jack
authors.initials: J
authors.lastname: Cannon
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging / Q000502:physiology*; D000704:Analysis of Variance; D004558:Electric Stimulation / Q000379:methods; D004576:Electromyography / Q000379:methods; D005260:Female; D006801:Humans; D007717:Knee / Q000294:innervation; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D053581:Muscle Strength Dynamometer; D018482:Muscle, Skeletal / Q000502:physiology*; D013314:Stress, Mechanical; D013997:Time Factors; D019415:Torque; D055815:Young Adult