Fat-free Mass is Related to One-Mile Race Performance in Elite Standardbred Horses

This study examined whether body composition was predictive of competitive success in elite standardbreds (STB). Rump fat and muscle thickness (MTH) (vastus lateralis/intermedius [VL], extensor carpi radialis [ECR]) were measured in vivo in male n=6; female n=8 by B-mode ultrasound. Percentage body fat (%fat) was calculated from rump fat. There were no gender differences for age, body mass (males 432±11 kg; females 443±13 kg), fat-free mass (FFM) (males 400±12 kg; females 400±11 kg), ECR MTH (males 61±2 cm; females 60±2 cm) or race time (RT) (males 113±3 s; females 114±2 s). Males had less (P<0.05) fat mass (males 32+4 kg; females 44±3 kg) and %fat (males 7.4±0.9%; females 9.9±0.5%) and larger (P<0.05) VL MTH (males 88±7 cm; females 81±3 cm). RT was correlated to %fat and fat mass in males (r=0.89; r=0.82, P<0.05) not females (r=0.51;r =0.14). FFM tended to relate to RT in males (r=−0.76, P=0.07) and females (r=−0.59, P=0.12). Combined %fat and FFM data were correlated to RT (%fatr =0.70, P<0.01; FFM r=−0.65, P<0.01). RT was not correlated to MTH (VL r=−0.28; ECR r=−0.31). In conclusion, FFM was related to RT in elite STB with %fat negatively related to RT in males.