A Kinematic Study on the Use of Overhead Squat Exercise with Elastic Resistance on the Shoulder Kinetic Chain Approach

<b>Background:</b> The overhead squat movement involves various bodily structures, but the interaction with three-dimensional elastic resistance along the kinetic chain approach requires further understanding. <b>Objectives</b>: We aim to describe and compare scapular and trunk kinematics during an overhead squat under different external resistance conditions. <b>Methods</b>: The three-dimensional shoulder and trunk kinematics of 19 male participants were captured at 15-degree intervals, from 30 to 120 degrees, during the overhead squat movement and analyzed by phase. <b>Results</b>: Scapular posterior tilt was significantly affected by resistance during the UNLOAD phase (<i>p</i> = 0.005, η²ₚ = 0.26). Significant resistance-by-arm elevation interactions were found for scapular upward rotation during the LOAD phase (<i>p</i> = 0.003, η²ₚ = 0.19) and UNLOAD phase <i>(p <</i> 0.001, η²ₚ = 0.24); for scapular internal rotation during both the LOAD (<i>p</i> < 0.001, η²ₚ = 0.37) and UNLOAD phases (<i>p</i> = 0.006, η² = 0.19); and for scapular posterior tilt during both the LOAD (<i>p</i> = 0.003, η²ₚ = 0.26) and the UNLOAD phases (<i>p</i> = 0.006, η²ₚ = 0.21). Trunk flexion/extension showed a significant effect on resistance during the LOAD phase (<i>p</i> = 0.008, η²ₚ = 0.24). <b>Conclusions</b>: Increasing resistance through elastic resistance significantly improves scapular kinematics via the trunk during arm elevation. This underscores the potential of the overhead squat movement as a valuable tool for assessing and treating scapular and trunk dysfunction.