Beach J, Feist N, Hiscock M, Stromme R, Jeno S, Mabey R; Department of Physical Therapy, University of North Dakota School of Medicine and Health Sciences, Grand Forks, ND, USA. sujeno@medicine.nodak.edu.

PURPOSE: The purpose of this study was to determine the electromyographic (EMG) activity in the muscles of the lower extremity during a wall squat with the feet in 3 different foot positions. SUBJECTS: Thirty subjects (18 male, 12 female; ages 20-44 years) with no history of knee pathology participated in this study. METHODS AND MATERIALS: Each subject was asked to perform a free standing squat followed by a series of 5 wall slides (to a depth of 45° of knee flexion) in each of 3 different foot positions (neutral rotation, 30° internal rotation, and 30° external rotation). EMG activity was recorded for the rectus femoris, vastus lateralis, vastus medialis, biceps femoris, gastrocnemius, and anterior tibialis muscles of the subject's dominant leg for all trials. ANALYSES: EMG data from the second through fourth repetition of the wall slide in each trial was compared to the EMG data from the free standing squat for each muscle. Data were expressed as a percentage of EMG activity for the muscle. A repeated-measures ANOVA was used to compare the normalized data for the 6 different muscles in the 3 different foot positions. Alpha equals .05 for all tests. RESULTS: The results indicated there was a significant difference in the EMG activity of the anterior tibialis (F(2.58) = 4.159, p = .021), biceps femoris (F(2.58) = 9.671, p = .00), and gastrocnemius (F(2.58) = 7.292, p = .001) muscles. Post hoc analysis revealed that for the anterior tibialis muscle, external rotation produced significantly more EMG activity than neutral rotation. For the biceps femoris muscle, external rotation produced more EMG activity than either neutral or internal rotation. Internal rotation produced more EMG activity than external rotation in the gastrocnemius muscle. No significant difference was noted in EMG activity of the vastus lateralis, vastus medialis, and rectus femoris across foot positions. CONCLUSIONS: There was no impact of foot position on the EMG activity of the quadriceps muscle group, the muscle group targeted for strengthening with the wall squat activity. For the anterior tibialis, biceps femoris, and gastrocnemius, the significance in EMG activity indicated that rehabilitation of these leg muscles may be impacted by foot position. When the wall squat is used to strengthen the quadriceps muscle group, no specific foot position is preferable to another. Rather, patient comfort should be used as a guiding factor during this activity. Foot position does affect leg musculature and should be considered when the rehabilitation program focuses on these muscles. FUNDING SOURCE: None.

Copyright 2004 by the American Physical Therapy Association

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