Contractile muscle volume and agonist-antagonist coactivation account for differences in torque between young and older women.
It is controversial whether specific tension (the ratio between muscle strength and size) declines with aging. Therefore, contractile muscle volume was estimated separately from the intramuscular noncontractile tissue by magnetic resonance imaging, and maximum isometric torque was measured in the knee extensors and flexors of 10 young (22.8 +/- 5.7 years) and 10 older (69.5 +/- 2.4 years) healthy active women. Specific tension was lower in the older women both in the extensors (93.1 +/- 20.1 kN x m(-2) vs. 112.1 +/- 12.3 kN x m(-2); P < 0.05) and in the flexors (100 +/- 31 kN x m(-2) vs. 142.7 +/- 23.9 kN x m(-2); P < 0.01). This was accompanied by an increase in the percentage coactivation of the knee flexors during knee extension. These data suggest that the lower level of muscle torque in the older women can be explained not only by smaller contractile muscle mass but also by increased coactivation of the antagonist muscles during knee extension.
Applied Physiology Group, Strathclyde Institute for Biomedical Science, University of Strathclyde, 76 Southbrae Drive, Glasgow G13 1PP, United Kingdom.
Andrea
A
Macaluso
Myra A
MA
Nimmo
John E
JE
Foster
Muriel
M
Cockburn
Nigel C
NC
McMillan
Giuseppe
G
De Vito
D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D004576:Electromyography; D005080:Exercise Test; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007717:Knee / Q000502:physiology; D008279:Magnetic Resonance Imaging; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000502:physiology*; D012016:Reference Values; D013314:Stress, Mechanical; D019415:Torque