Laterality And Asymmetry Of Body Composition And Handgrip Strength In Collegiate Baseball Players

PURPOSE: 1) To assess asymmetry in upper (arms) and lower (legs) whole-body composition and handgrip strength in collegiate baseball players and 2) examine changes in body composition over a 31-week baseball season. METHODS: NCAA D2 baseball players completed both pre-season (September 2023) and post-season (May 2024) testing. Total and regional body composition (fat mass/FM; lean mass/LM; and bone mineral content/BMC) were measured using a Hologic dual-energy x-ray absorptiometry scanner. Handgrip strength was measured, per hand, using a Handexer dynamometer. Statistical significance set at p < 0.05. RESULTS: Data were combined (N = 25; 12 pitchers; 2 lefties) for both total and regional asymmetry analyses (right limb vs. left limb, respectively). For total mass, both the right arms (6.11 ± 0.78 vs. 5.61 ± 0.75 kg; p < 0.001) and legs (16.32 ± 1.65 vs. 15.98 ± 1.76 kg; p = 0.003) were significantly higher than the left limb. For LM, the right arms (4.69 ± 0.63 vs. 4.31 ± 0.59 kg; p < 0.001) and legs (12.08 ± 1.18 vs. 11.77 ± 1.31 kg; p = 0.002) were higher than the left limb. The right arms had significantly more FM (11.33 ± 0.31 vs. 1.05 ± 0.31 kg; p = 0.001) and BMC (0.29 ± 0.033 vs, 0.25 ± 0.04; p < 0.001) than the left limb. However, no significant (NS) differences were found between the legs for FM (3.62 ± 1.01 vs. 3.57 ± 1.04 kg; p = 0.12) and BMC (0.65 ± 0.05 vs. 0.64 ± 0.05 kg; p = 0.39). Handgrip was similar between the right vs. left hands (55.6 ± 6.0 vs. 54.6 ± 7.4 kg; p = 0.35). For changes in total body composition, there were trivial (NS) decreases in total mass (-0.32 ± 3.8 kg) and LM (-0.86 ± 2.1 kg) along with increases in FM (0.21 ± 2.5 kg). Total handgrip strength increased NS (6.3 ± 14.4%). For regional results, and expressed as a percent change, NS decreases in LM were seen in the right arms (-1.2 ± 6.5%) and legs (-0.32 ± 3.4%). Trunk LM also decreased (-1.3 ± 4.3%) while FM increased (1.8 ± 16.1%). CONCLUSION: Asymmetries were noted in body composition between the left and right arms. However, in the legs, regional differences were seen only in total mass and LM. There were no differences in handgrip strength, between the left and right limbs. Across the season there were no significant changes body composition or handgrip strength. Whether statistical significance translates into performance advantages or injury risk remains unclear.