Is muscle strength ratio a criterion for diagnosis of site-specific muscle loss?

AimRecently, data have questioned the homogenous model of sarcopenia, and suggest that the loss of muscle mass could occur in a site-specific manner. It is unclear, however, whether a muscle strength ratio can be used to assess age-related, site-specific muscle loss. The purpose of the present study was to investigate the relationship between the age-related loss of thigh muscle, muscle function and gait performance. MethodsA total of 55 men aged 18-79years had muscle thickness (MTH) measured by ultrasound at three sites on the anterior (30% and 50% of thigh length) and posterior (70% of thigh length) aspects of the thigh. MTH ratios were calculated to assess the site-specific muscle loss (anterior 30%:posterior 70% MTH [A30:P70] and anterior 50%:posterior 70% MTH [A50:P70]). Walking performance, maximum isometric knee extension/flexion, toe-grasping and handgrip strength were measured. ResultsAge was inversely correlated with the ratios of A30:P70 (r=-0.332) and A50:P70 (r=-0.466). There were no significant correlations between the A30:P70 and A50:P70 ratios, and height and bodyweight. The A30:P70 and A50:P70 ratios were also not correlated with maximal walking speed. However, the A50:P70 ratio was significantly correlated with zig-zag walking (r=-0.350) and handgrip strength (r=0.334). In addition, these MTH ratios were also correlated with knee extension (r=0.309 and r=0.405), flexion (r=0.306 and r=0.412) and toe-grasping strength (r=0.265 and r=0.336). After adjusting for physical activity, the MTH ratios were still not correlated with ratio of muscle strength. ConclusionStrength ratios did not correlate with MTH ratios. Our cross-sectional analysis suggests that age-related site-specific muscle loss could assess the decrease in absolute muscular strength, but not the ratio of muscle strength. Geriatr Gerontol Int 2014; 14: 837-844.