Appendicular lean mass and site-specific muscle loss in the extremities correlate with dynamic strength

Previous studies have reported the non-homogenous loss of muscle mass (site-specific muscle loss) with ageing, but this relationship to the loss of strength is not totally understood.

To investigate the relationship between maximal dynamic strength and site-specific muscle mass of the thigh and upper arm.

Thirty-five recreationally active men were separated into young-aged (YG, 20-39 years, n = 12), middle-aged (MG, 40-59 years, n = 13) and old-aged groups (OG, 60-75 years, n = 10). One-repetition maximum strength (1-RM; leg press, chest press, knee flexion, lat pull-down, and knee extension), muscle thickness (MTH, anterior and posterior thigh and upper arm) and appendicular lean mass (aLM) index were obtained from participants. Site-specific thigh MTH ratio was determined by dividing anterior thigh MTH (50% of thigh length) by posterior thigh MTH (50% of thigh length).

aLM index was not significantly different between age groups, but a significantly smaller site-specific MTH thigh ratio was found in the OG. Collapsed across age groups both site-specific thigh MTH ratio and aLM index were significantly correlated with leg press, knee extension and knee flexion1-RM strength (r = 0·390-0·699), but not with knee extension: knee flexion (KE:KF) 1-RM strength ratios (r = 0·037-0·081). Separated by age groups only aLM index was correlated with KE:KF 1-RM ratio for the OG (r = 0·780).

Site-specific thigh MTH ratio may be an important assessment tool in older individuals as it is different among age groups and is significantly related to dynamic maximal strength. However, maximal dynamic strength ratios appear to be less sensitive to differences in site-specific MTH ratios.