Is muscle strength ratio a criterion for diagnosis of site-specific muscle loss?
OBJECTIVE
Recently, 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.


METHODS
A total of 55 men aged 18-79 years 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.


RESULTS
Age 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.


CONCLUSIONS
Strength 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.
Department of Kinesiology, School of Public Health, Indiana University, Bloomington, Indiana, USA; Active Aging Research Center, Toyo Gakuen University, Nagareyama, Japan.
Takashi
T
Abe
Madoka
M
Ogawa
Robert S
RS
Thiebaud
Jeremy P
JP
Loenneke
Naotoshi
N
Mitsukawa
D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D003430:Cross-Sectional Studies; D003937:Diagnosis, Differential; D005500:Follow-Up Studies; D005684:Gait / Q000502:physiology; D018737:Hand Strength / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging* / Q000503:physiopathology; D055948:Sarcopenia / Q000175:diagnosis* / Q000503:physiopathology; D014463:Ultrasonography; D055815:Young Adult
aging; healthy adults; muscle thickness; site-specific sarcopenia; ultrasound