Influence of body adiposity on structural characteristics of skeletal muscle in men and women.

ABSTRACT

The structure of skeletal muscle (SM) can be characterized by quantitative (size) and qualitative (composition) attributes, which are disparately reported to be influenced by body adiposity. This study tests the hypothesis that body adiposity exerts a systematic influence on these muscle characteristics and evaluates the possible functional implications for movements. Lower limb SM volume (VSM) and attenuation (ATTSM), an inverse measure of lipid infiltration in muscle, were determined with computed tomography in 21 men (BMI = 21-36 kg m(-2) ; age = 31-71 years.) and 18 women (BMI = 19-35 kg m(-2) ; age = 32-76 years.). After adjusting for age, a multivariate regression analysis revealed that body adiposity positively correlated (P<0·05-0·001) with absolute VSM and cross-sectional area (CSA) in both genders, while VSM per unit body mass (VSM/BM) decreased with adiposity (P<0·001) in women and was constant in men. ATTSM was higher in men (P<0·05) and decreased (P<0·05) with adiposity in both genders. The product of ATTSM by average muscle CSA (predictor of maximal strength) and by VSM/BM (predictor of maximal dynamic performance) was lower in women (P<0·001) and was reduced by age in both genders (P<0·05-0·01), while obesity had a negative effect (P<0·001) only on the predictor of performance. In conclusion, body adiposity significantly increases SM size and reduces ATTSM. Structural indicators accounting for both quantitative and qualitative characteristics of SM may be useful predictors of the effects of obesity on motor function at different ages. With rising body adiposity and advancing age, women appear mostly affected by the decline of SM features relevant for motor performance.