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