Association of walking speed with sagittal spinal alignment, muscle thickness, and echo intensity of lumbar back muscles in middle-aged and elderly women.

ABSTRACT

BACKGROUND: Age-related change of spinal alignment in the standing position is known to be associated with decreases in walking speed, and alteration in muscle quantity (i.e., muscle mass) and muscle quality (i.e., increases in the amount of intramuscular non-contractile tissue) of lumbar back muscles. Additionally, the lumbar lordosis angle in the standing position is associated with walking speed, independent of lower-extremity muscle strength, in elderly individuals. However, it is unclear whether spinal alignment in the standing position is associated with walking speed in the elderly, independent of trunk muscle quantity and quality. The present study investigated the association of usual and maximum walking speed with age, sagittal spinal alignment in the standing position, muscle quantity measured as thickness, and quality measured as echo intensity of lumbar muscles in 35 middle-aged and elderly women. METHODS: Sagittal spinal alignment in the standing position (thoracic kyphosis, lumbar lordosis, and sacral anterior inclination angle) using a spinal mouse, and muscle thickness and echo intensity of the lumbar muscles (erector spinae, psoas major, and lumbar multifidus) using an ultrasound imaging device were also measured. RESULTS: Stepwise regression analysis showed that only age was a significant determinant of usual walking speed. The thickness of the lumbar erector spinae muscle was a significant, independent determinant of maximal walking speed. CONCLUSIONS: The results of this study suggest that a decrease in maximal walking speed is associated with the decrease in lumbar erector spinae muscles thickness rather than spinal alignment in the standing position in middle-aged and elderly women.