A. Bruns, D. Heil, FACSM

Montana State University, Bozeman, MT

Body segment muscle mass symmetry refers to the distributions of skeletal muscle mass across opposite appendages. Interestingly, there is no published research evaluating muscle mass symmetry trends across different athletic populations. PURPOSE: This study sought to characterize and compare the degree of muscle mass symmetry between select collegiate athletes. METHODS: This early phase of the study utilized convenience samples of collegiate athletes who were either recreationally resistance trained (RRT: 9 men (Mean±SD: 21±1 yrs; 25.7±4.2 BMI) and 3 women (20±0 yrs; 20.1±1.0 BMI) or competitive cross skiers (XC: 12 men (22±2 yrs; 22.6±1 BMI) and 11 women (21±2 yrs; 21.6±2.1 BMI)). Each athlete visited our lab in the early morning before breakfast and after voiding their bladder to have body composition evaluated using a whole-body bioimpedance analyzer (BIA). Outcomes of interest from the BIA included relative measures of fat mass, muscle mass, and bone mass as a percent of body mass (FMPerc, MMPerc, BMPerc), as well as absolute measures of FM and MM for left and right arms and legs. Relative measures were compared between athletes (RRT vs XC) using paired T-tests (α=0.05), while left- and right-side absolute measures were compared using a multivariate 2-factor (Side x Athlete) RMANOVA (α=0.05). RESULTS: The RRT athletes tended to have slightly higher FMPerc (Mean±SE: 16.2±1.6% vs 13.0±1.3%), lower MMPerc (79.6±1.5% vs 82.6±1.2%), and lower BMPerc (4.1±0.1% vs 4.4±0.1%) when compared to the XC athletes, but none of these differences were significant (P=0.36-0.41). Further, there were no differences between left and right arms, or left and right legs, within or between the athletic groups evaluated (P=0.07-0.45). CONCLUSIONS: Our findings indicate that there were no significant differences in muscle mass symmetry amongst XC and RRT athletes. These findings are most likely due to the symmetrical nature of the training utilized by both athletic groups (both groups utilize similar types of resistance training). Future research should focus on the same outcomes for different collegiate athletes and non-athletes where training (or lack thereof) may not be as symmetrical.

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