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 The demands of the 50 cm DVJ may have superseded the effectiveness of VPAC.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.

The purpose of this study was to examine the effects of increased SW on GRF and lower limb joint motion in healthy older adults during stair descent.Eight healthy older men (52.1 ± 7.4 years, 75.7 ± 10.0 kg, 1.75 ± 0.09 m) were recruited for the study. An instrumented 3-step staircase (FP-stairs, AMTI) mounted independently to two force platforms (1200 Hz, AMTI) with two additional customized wooden steps (4th and 5th steps) was used to collect GRF data during stair descent trials. Participants performed five stair descent trials at their pre-established self-selected speed at self-selected, wide, and wider SW. Loading rate of impact peak vertical GRF and peak medial GRF were greater with wider SW compared to normal and wide SW. Peak ankle eversion angle was reduced with increasing SW and peak ankle inversion moment was smaller in wider SW compared to normal and wide SW. Peak hip adduction angle was greater in wider SW while peak hip abduction moment was smaller in wider SW compared to normal and wide SW. More healthy participants will be tested to increase sample size. Older adults with medial compartment knee osteoarthritis (OA) are also currently being tested to compare the effects of increased SW on GRF, and lower extremity joint variables to healthy adults during stair descent.

The lateral ankle sprain is the most common athletic injury, and many people who suffer an ankle sprain develop chronic ankle instability (CAI). The purpose of this study was to examine the ground reaction force during a simulated lateral ankle sprain among participants with no history of ankle injury and those with CAI. Twelve participants, which included six with CAI, and six with no history of ankle sprain performed 14 repetitions of a vertical drop down off a 27 cm box, landing on an AMTI force platform. Seven trials were completed with a fulcrum outer sole strapped to the bottom of the participant’s shoe, which caused 25° of inversion upon landing, and seven trials were performed with a flat outer sole. Outer sole assignment was randomized. Peak vertical, anterior/posterior, and medial/lateral ground reaction force, normalized to multiples of body weight (BW), were measured for each participant. Results revealed that the no injury group landed with significantly greater (P< .05) peak vertical and peak anterior/posterior force than the CAI group. These differences in force between the two groups may be an attempt by the CAI participants to change loading of the unstable ankle, and the altered landing kinetics potentially increase future risk of injury.