MUSCLE CSA, FORCE PRODUCTION, AND ACTIVATION OF LEG EXTENSORS DURING ISOMETRIC AND DYNAMIC ACTIONS IN MIDDLE-AGED AND ELDERLY MEN AND WOMEN

Forty-two healthy men and women in two age groups (40 and 70 years) we re examined for muscle cross-sectional area (CSA), maximal voluntary b ilateral isometric force, force-time characteristics, maximal concentr ic 1 RM, and power performance of the leg extensors in a sitting posit ion, squat jump, and standing long-jump. The results suggested that th e decline in maximal strength with increasing age is related to the de cline in muscle CSA; however, particularly in older women, the force/C SA ratio may also be lowered. Explosive force seems to decrease with i ncreasing age even more than maximal strength, suggesting that muscle atrophy with aging is greater in fast-twitch fibers. The voluntary act ivation of the agonist and antagonist muscles seems to vary depending on the type of muscle action and/or velocity and time duration of the action in both age groups but to a greater extent, in older people. Th ere appears to be an age-related increase in antagonist coactivation, especially in dynamic explosive movements.