INCREASED BODY FAT TO LEAN MASS RATIO RESULTS IN LARGER DECREMENTS IN QUADRICEPS STRENGTH FOLLOWING DOWNHILL RUNNING

Abstract

1888 The purpose of this study was to determine if the added mechanical load of bearing body fat would result in greater muscle damage and decrements in leg strength following downhill running. The relationship between percentage body fat and strength decline caused by a bout of downhill running was investigated in 26 male runners (23.4±0.7 yr). Quadriceps strength was measured isokinetically one hour before and 48 hours after 30 minutes of downhill running (−11% grade). Quadriceps strength was reduced 3.8±0.5% after downhill running. Body fat was 13.4±2.1%, and was negatively correlated with the change in strength due to downhill running (r= −0.64, P<0.001). There was no relationship between body mass and the decrement in strength following downhill running. These data indicate that an increased ratio of fat mass to muscle mass places an increased load on the muscle during downhill running, possibly resulting in increased muscle damage. The ratio of fat mass to muscle mass is therefore a determinant (accounting for nearly 40% for the reduction in strength) of losses in muscle strength following downhill running. It can be concluded that individuals with increased body fat mass relative to muscle mass are at greater risk of developing muscle weakness, and potential muscle injury, following eccentric weight-bearing activities. Supported by a Grant from Experimental and Applied Sciences