Lower Body Lean Mass Asymmetry Is Not Associated With Performance Asymmetries In Collegiate Baseball Players

Taylor Parmentier1, Isabelle Farm1, Evan Semonis1, Jadon Konkel1, Chris Carter1, Kelly Laurson1, Samantha McDonald1, Dale Brown1, Michael Torry1, Marcel Lopes dos Santos1 1Illinois State University, Normal, IL Asymmetry in lower body lean mass has been linked to potential deficits in performance and increased injury risk. Countermovement jumps (CMJ) are commonly used as a readiness indicator for athletic performance. However, there is a paucity of data examining the relationship between asymmetry in lower body lean mass and jump performance, particularly in single-leg CMJs (SLCMJ). PURPOSE: To examine whether lower body lean mass asymmetries align with performance asymmetries in SLCMJs. METHODS: Data was collected using bilateral force plates during SLCMJs in 34 Division I male baseball players (body mass (BM) = 91.48 ± 8.62 kg, height (H) = 1.85 ± 0.05 m, age = 21.29 ± 1.45 years). Performance data included jump height (JH), flight time (FT), peak force (PF) reactive strength index (RSI), time-to-take-off (TTO), take-off velocity (TOV), braking impulse (BI), propulsive impulse (PI). Lean mass was assessed via dual-energy X-ray absorptiometry (DEXA). Percent asymmetry was calculated for the variables, using the Bilateral Asymmetry Index-1 (BAI-1) equation. Kappa coefficients were calculated to determine levels of agreement between lower body lean mass and performance variables. RESULTS: Asymmetry levels for all variables were low: lower body lean mass (-0.55%), JH (-4.36%), FT (-1.36%), TTO (1.77%), TOV (-1.12%), RSI (-3.79%), PF (-1.81%), BI (2.33%), and PI (1.47%). Kappa coefficients ranged from slight (JH = 0.15, TTO = 0.08, TOV = 0.15, PF = 0.09, BI = 0.03) to fair (RSI = 0.21, FT = 0.21, PI = -0.21) agreement. CONCLUSION: Lower body lean mass asymmetries are not associated with SLCMJ performance asymmetries. Interestingly, the negative fair agreement level suggests that lean mass distribution may be inversely related to propulsive impulse in SLCMJs.