STRENGTH AND FATIGUE OF LUMBAR EXTENSOR MUSCLES IN OLDER ADULTS

Introduction: Loss of lumbar extensor muscle strength and fatigue resistance may contribute to functional disability. Methods: Two groups of subjects were recruited: young (n = 26, 20-35 years of age) and old (n = 26, >= 65 years of age) adults. Lumbar extensor muscle strength was measured with a load cell, and electromyographic activities were recorded to study muscle fatigue at 60% of maximum voluntary contraction. Results: We found that the muscle moments generated by the extensor muscles decreased with age (P < 0.05). Aging was associated with a significant increase in the power of the lower frequency band (101-200 Hz) of the electromyographic signals (P < 0.05), but the spectral characteristics did not appear to change with sustained contraction (P > 0.05). Conclusions: The changes in strength and spectral properties of the electromyographic signals of lumbar extensor muscles may be related to age-related alterations in muscle fiber composition and recruitment. These changes should be considered in clinical functional task evaluation. Muscle Nerve 44:74-79, 2011