Abstract
To evaluate upper arm muscles size and strength in contemporary Japanese adults, the cross-sectional area (CSA) and maximum voluntary isometric strength of elbow flexor and extensor muscles were examined on 102 men and 116 women. Each subject was assigned to one of three age groups (3rd, 4th-5th, and 6th-7th decade). The cross-sectional areas of upper arm flexor and extensor muscles were estimated by our previously developed ultrasonographic measurement system. Voluntary strength of the elbow flexors and extensors was measured isometrically. While there were no difference in elbow flexor and extensor CSA with age in men, the elbow flexor and extensor CSA for the 3rd decade of women were significantly smaller compared to those for middle-age and elderly women. Male isometric elbow flexor strength in the 4th-5th decade was significantly larger than those in the 6th-7th decade, whereas no such age-dependent change was evident in extensor strength. For women, both elbow flexor and extensor strengths for the 3rd decade were the smallest among the three age groups. The aging-associated reduction of muscle strength per unit of muscle CSA in the elbow flexors started from the 6th or 7th decade in men. The muscle strength per unit of muscle CSA in the elbow extensors was not significantly different between each age group for both men and women. In conclusion, the fact that contemporary Japanese young women have a relatively small CSA and strength in their elbow flexors and extensors should be recognized for exercise-health programs.
