Characterization of the human quadriceps muscle in active elders.

Department of Physical Therapy, University of Delaware, Newark, DE 19716, USA. jensteve@udel.edu

OBJECTIVE: To compare muscle activation deficits and muscle physiology in older versus younger adults. DESIGN: A maximal volitional isometric contraction of the quadriceps muscle with burst-superimposition was used to assess strength and activation. In addition, force-frequency testing during fresh, fatigue, and recovery conditions and electrically elicited fatigue testing were performed. SETTING: Muscle performance laboratory. PATIENTS: Healthy, active young (age range, 20-28 yr) and older (age range, 66-83 yr) subjects. MAIN OUTCOME MEASURES: Torque production, activation of the quadriceps, F50 values from the force-frequency relationships (frequency at which 50% of the maximum normalized force is produced), and the average amount of fatigue. RESULTS: Older subjects were weaker (574.4 +/- 156 N) than younger subjects (900.9 +/- 295 N) and had significantly greater deficits in central activation in the quadriceps muscles (elderly = 95.5% activation; younger = 98.1% activation). The force-frequency curves for the elderly were to the left of the younger subjects for all 3 testing conditions. Aged muscles fatigued to the same extent as younger muscle (young = 49.8% +/- 2.6%, elderly = 51.1% +/- 2.8%). CONCLUSIONS: These results can be used to modify high-intensity strength training protocols designed to optimize sustainable strength gains in the elderly during rehabilitation. Copyright 2001 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation

PMID: 11441388 [PubMed - indexed for MEDLINE]