Mary Beth McCullough1, Nicole Bordelon1, Kenzie Friesen2, Anthony Fava1, Katherine Everhart1, Gretchen Oliver, FACSM1. 1Auburn University, Auburn, AL. 2University of Saskatchewan, Saskatoon, SK.

BACKGROUND: Kinematic differences exist between baseball live pitching and machine hitting; however, the differences between common hitting practices are unknown. The purpose of this study was to compare kinematics between tee and front toss hitting. METHODS: 21 baseball players (13.9±3.1yrs; 167.1±17.4cm; 64.7±20.1kg) performed three maximal effort swings using front toss and a stationary tee. The tee was adjusted to the middle of the strike zone, and front toss was pitched underhand (9.14m away). Kinematic data (pelvis and trunk rotation, trunk flexion, and lateral flexion) were averaged across three trials and collected using an electromagnetic tracking system. Front and back-side were defined as the participant’s left and right sides, respectively. Hitting variables were analyzed at foot contact (FC), ball-contact (BC), and follow-through (FT). A 2(condition)x3(event) within-subjects RM·MANOVA was used to determine kinematic differences between tee and front toss. RESULTS:The RM·MANOVA was significant for condition (Wilks’ Λ=.248; p<.001), event (Wilks’ Λ=.003; p<.001), and interaction between condition and event (Wilks’ Λ=.215;p<.001). Univariate ANOVAs showed a significant condition effect for pelvis [F(1, 20)=12.3; p=.002] and trunk rotation [F(1, 20)=52.0; p<.001]. Event effect was significant for pelvis rotation [F(1.6, 32.2)=841.5; p<.001], trunk rotation [F(2.0, 39.3)=1439.7; p<.001], trunk lateral flexion [F(1.9, 38.7)=19.9; p<.001], and trunk flexion [F(1.4, 29.0)=12.8; p<.001]. There was a significant interaction for pelvis rotation [F(1.6, 31.3)=11.9; p<.001], trunk rotation [F(1.6, 31.4)=24.2; p <.001], trunk lateral flexion [F(1.3, 25.5)=14.1; p<.001], and trunk flexion [F(1.7, 33.9)=7.2; p=004]. Simple effects showed significant differences between conditions for pelvis rotation at FC (p<.001), trunk rotation at all events (all p-values <0.014), and trunk lateral flexion at FC (p=.026) and BC (p=.008). Specifically, there was greater pelvis rotation toward the front-side at FC, greater trunk rotation toward the front-side at all events, and greater trunk lateral flexion toward the back-side at BC during front toss, and greater trunk lateral flexion toward the back-side at FC during tee hitting. CONCLUSIONS: Kinematic differences exist between baseball tee and front toss hitting. Hitters display a more closed pelvis and trunk position when hitting off a tee compared to front toss.

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