Muscle Size, Quality, and Body Composition: Characteristics of Division I Cross-Country Runners

The primary purpose was to identify the relationship between muscle cross sectional area (mCSA), echo intensity (EI), and body composition of Division I cross-country runners. The secondary purpose was to examine differences in these variables in athletes stratified based on stress fracture (SFx) history. Thirty-six athletes were stratified based on sex and previous SFx history. A panoramic scan vastus lateralis (VL) was performed using a GE logiq-e B-mode ultrasound (US). Echo intensity and mCSA were determined from the scan by using a grayscale imaging software (Image-J). Body composition measures were determined using dual-energy xray absorptiometry (DEXA). For females, mCSA was significantly correlated with left leg lean mass (LM; R=0.54) and EI (R= −0.57). Lean mass was significantly correlated with bone mineral density (BMD; R=0.58) and content (BMC; R=0.56), while BMC was also correlated with leg LM (R=0.72). For males, mCSA was significantly correlated with leg LM (R=0.66), BMD (R=0.50), and BMC (R=0.54). Leg LM was significantly correlated with BMD (R=0.53) and BMC (R=0.77). Personal best times for males were significantly correlated with FM (R=0.489) and %fat (R=0.556) for the 10 kilometer and 5 kilometer races, respectively. Female and male athletes with previous history of SFx were not significantly different across any variables when compared to athletes with no previous history. These correlations suggest more muscle mass may associate with higher BMD and BMC for stronger bone structure. Modifications in training strategies to include heavy resistance training and plyometrics may be advantageous for preventing risk factors associated with stress fracture reoccurrence