Associations of muscle stiffness and thickness with muscle strength and muscle power in elderly women

Abstract

The aims of this study were to investigate the influence of age on muscle stiffness and to examine the relationships among muscle stiffness, muscle thickness, subcutaneous fat thickness, muscle strength and muscle power in elderly women. The subjects were 16 young (mean age 20.3 years) and 34 elderly (mean age 84.2 years) women. Muscle stiffness of the right quadriceps femoris muscle was measured at rest and during a maximal voluntary isometric muscle contraction using a myotonometer, a computerized, electronic tissue compliance meter. Thicknesses of the rectus femoris and the vastus intermedius muscles and the overlying subcutaneous fat were measured using ultrasound. Quadriceps strength and the chair stand test were used to represent muscle strength and muscle power, respectively. There were significant differences in muscle stiffness between rest and contraction conditions among the young but not the elderly women. Muscle stiffness during contraction, the rate of change in muscle stiffness during contraction, and muscle thickness were significantly greater in young than in elderly subjects. Pearson correlation coefficient analyses showed that muscle stiffness was significantly associated with muscle power, but not with muscle strength. This study suggests that the increase in muscle stiffness during voluntary muscle contraction is limited in elderly women compared with young women, and that muscle stiffness may be related to muscle power rather than muscle strength in elderly persons.