Date of Award

2007

Document Type

Scholarly Project

Degree Name

Doctor of Physical Therapy (DPT)

Department

Physical Therapy

First Advisor

David Relling

Keywords

Electromyography; Muscle Contraction; Muscles -- physiology

Abstract

Purpose: The purpose of this study was to determine if an isometric hip adduction contraction and varied foot positions during a wall squat results in increased muscle recruitment of the lower extremity.

Subjects: Eleven healthy female adult volunteers without a prior history of knee pathology participated.

Methods: Surface electromyography (EMG) data were collected from the adductor longus (AL), vastus medialis oblique (VMO), vastus lateralis (VL), biceps femoris (BF), gastrocnemius (GN) and anterior tibialis (AT) muscles of the dominant leg for each individual during six wall squats with different treatment conditions. Experimental trials included three different rotation positions with or without simultaneous isometric hip adduction. The rotation positions included 30° internal rotation, neutral rotation, and 30° external rotation. Raw EMG data was rectified, smoothed, and normalized to a freestanding squat to 90° of knee flexion. All exercises were performed to a position of 45° knee flexion. Subjects perfonned three repetitions for each trial condition with a six second hold in the squat position and five seconds between reps. Each trial was separated by two minute rest periods. A one way repeated-measure analysis of variance (ANOVA) was performed to determine if the position or adductor contraction altered the EMG response.

Results: The repeated measures ANOV A revealed a significant difference in EMG activity in five of the six muscles: AL, VMO, VL, BF, AT (p<.05) with adduction and rotation. In comparison to the neutral without position, muscle activity was significantly increased in neutral with and external rotation with adduction. The GN was the only muscle that did not show a significant difference in muscle activity (p=.056). Notably, all muscle activity was lower when compared to the free standing squat.

Discussion/Conclusion: The recruitment of the muscles under varied foot positions with an adduction component proved to be considerably increased when compared with the control position of a wall squat in neutral without adduction. Our data suggests that to recruit VMO, an adduction component in neutral or external rotation is beneficial. These results are important for clinicians who implement a rehabilitation program with a wall squat as an exercise to facilitate strengthening in the lower extremity. It is important to consider using the wall squat as a preliminary exercise to the freestanding squat due to the decrease in muscle activity demonstrated throughout our study.

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