EFFECT OF ENDURANCE EXERCISE TRAINING ON SKELETAL MUSCLE FAT CONTENT ASSESSED BY CT IN OBESE WOMEN 343

Recent studies have suggested that the skeletal muscle fat content, which can be estimated by computed tomography (CT) (Kelley, D.E. et al, Am J Clin Nutr, 54, 509-515, 1991), is positively correlated with a reduced oxidative potential of the skeletal muscle and with insulin resistance (Simoneau, J.-A. et al, FASEB J, 9, 273-278, 1995). We have investigated the effect of a 14 month endurance exercise training program (90 min/session, 4-5sessions/wk at 55% VO2 max) in a sample of 13 obese premenopausal women, aged 38.8± 5.3 (SD) years. The exercise program induced significant (p< 0.05) decreases in body weight, fat mass, as well as in plasma insulin levels but not in plasma glucose levels measured during an oral glucose tolerance test. The area of mid-thigh muscle with a low CT attenuation level (LAM) (reflecting an increased fat content of the skeletal muscle) was significantly decreased with training (LAM before: 28.3±7.7 cm2 vs LAM after: 23.6± 8.5 cm2, p< 0.001). In addition, the magnitude of change in LAM area was significantly correlated with changes in plasma glucose levels in the fasting state (r=0.66, p< 0.05) and following the oral glucose load(r=0.76, p< 0.01) but not with changes in insulin levels. These results suggest that changes in the skeletal muscle fat content induced by endurance exercise training may be associated with favorable alterations in indices of plasma glucose homeostasis.