The purpose of this study was to determine whether performance of a volitional preemptive abdominal bracing maneuver (VPAC) during a drop vertical jumping (DVJ) task alters lower extremity (LE) kinematics, kinetics and muscle electromyography (EMG). Subjects performed DVJs with and without performance of the ABM from a 30 cm and 50 cm height. Differences in EMG values before and after landing were compared with and without VPAC using repeated measures t-tests. Differences between each kinematic and kinetic dependent variable were assessed using 2 (abdominal contractile state) X 2 (landing phase) within design ANOVAs using SPSS. At the 30 cm landing height, VPAC resulted in statistically significant increases in: knee internal rotation angle, knee flexion angle, knee internal abduction moment, knee energy absorption, medial hamstring post contact activity, trunk left rotation, and external oblique activity pre- and post-contact. At the 50 cm landing height, VPAC resulted in statistically significant decreases in ankle inversion angle, hip energy absorption, and external oblique muscle activity post-contact. In addition, increases in knee flexion angle at contact, medial hamstring activity pre-contact, hip flexion angle at contact, trunk left rotation angle post-contact, trunk left rotation angle at contact, and greater external oblique muscle activity pre-contact. The use of VPAC altered LE and trunk biomechanics and neuromuscular control when performing DVJ from 30 and 50 cm heights. The demands of the 50 cm DVJ may have superseded the effectiveness of VPAC. These results suggest an enhanced protective knee response and improved trunk stability with VPAC use.
Listed In: Biomechanics, Physical Therapy, Sports Science