Muscle volume compared to cross-sectional area is more appropriate for evaluating muscle strength in young and elderly individuals

Objective: the present study examined which of muscle volume (MV) and cross-sectional area (CSA) is appropriate for evaluating the relation with elbow flexor muscle strength in young and elderly individuals. Methods: the subjects were 52 young (20-34 year; 30 men and 22 women) and 51 elderly individuals (60-77 year, 19 men and 32 women). The MV and maximal anatomical CSA (ACSA) of elbow flexors were determined by magnetic resonance imaging. The torque developed during maximal voluntary contraction of isometric elbow joint flexion was converted to force by dividing it by the forearm length of each subject. Results: torque was significantly correlated with MV in young and elderly individuals (r = 0.564-0.926). Similarly, force was also significantly correlated with ACSA in each of them (r = 0.637-0.906). However, the y -intercepts of the regression lines for the ACSA-force relationship in young men and women were significantly higher than zero. There was no age effect on torque per MV, whereas force per ACSA was significantly higher in young adults than in elderly individuals. Conclusion: for elbow flexors, MV compared to ACSA is appropriate for evaluating the size-strength relationship and the existence of age-related difference in muscle strength per size.