IMPEDANCE MEASUREMENTS ARE RELATED TO DIETOR EXERCISE-INDUCED CHANGES IN SKELETAL MUSCLE MASS

Abstract

2077 The purpose of this research was to determine whether bioelectrical impedance measurements are related to diet- or exercise-induced changes in whole-body skeletal muscle (SM) mass measured by magnetic resonance imaging (MRI). Fifty-four sedentary obese men were randomly assigned to four groups: control (C, n=9), diet induced weight loss (DWL, n=14), exercise (aerobic) induced weight loss (EWL, n=16), and exercise weight stable (EWS, n=15). Whole body SM was measured by MRI and bioelectrical resistance (BIA-R) by a tetrapolar impedance method (50 kHz, 800uA). The treatment period for all groups was 12 weeks. Weight loss in the DWL (7.4±0.9 kg) and EWL (7.6±0.6 kg) groups was not different (P>0.1). No change in BIA-R or SM was observed within the C group (P>0.1). Within both weight loss groups SM decreased (−4.3±2.5%, P<0.01) while BIA-R increased (0.5±4.6%, P>0.1). Within the EWS group BIA-R decreased significantly (3.3±2.8%, P<0.01) concurrent with a small but non-significant increase in SM mass (1.2±3.1%, P>0.05). Collapsed across group (n=54), SM mass was significantly (P<0.01) correlated to BIA-R before (r=−0.062) and after (r=−0.066) the 12 week treatment period. The slope and intercept of the regression lines between BIA-R and SM did not change (P>0.05) from pre- to post-treatment. These findings indicate that changes in BIA-R are related to corresponding changes in SM mass and thus, impedance shows promise as a method for measuring diet- or exercise-induced changes in SM mass in-vivo. Funded by the Medical Research Council of Canada.