PNF and Movement 2020; 18(1): 65-75
https://doi.org/10.21598/JKPNFA.2020.18.1.65
The Effect of Squat Exercise According to Ankle Angle-Toe 0°, Toe In 10°, Toe Out 10°-on Muscle Thickness and Ground Reaction Force of Vastus Medialis Oblique and Vastus Lateralis Oblique Muscles
Su-Hong Ahn, P.T., M.S⋅Su-Kyong Lee, P.T., Ph.D1†
Department of Biomedical Health Science, Graduate School, Dong-Eui University
1Department of Physical Therapy, College of Nersing and Healthcare Sciences, Dong-Eui University,
The Research Institute Health for Functional Material
Correspondence to: Su-Kyong Lee (ptlsk@deu.ac.kr)
Received: December 20, 2019; Revised: January 14, 2020; Accepted: January 22, 2020; Published online: April 30, 2020.
© Korea Proprioceptive Neuromuscular Facilitation Association. All rights reserved.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
Purpose: The purpose of this study was to investigate the differences in muscle thickness and ground reaction force of the vastus medialis oblique and vastus lateral oblique muscles during squats at ankle angles of toe 0°, toe in 10°, and toe out 10°.
Methods: In this study, 9 male and 17 female students in their 20s participated in a randomized controlled trial and were compared according to the ankle angles of toe 0°, toe in 10°, and toe out 10°. To determine the reliability and measurement of muscle thickness according to ankle angle using ultrasound equipment and muscle thickness, the participants’ ankle angles-toe 0°, toe in 10°, and toe out 10°-were measured three times at the vastus medialis oblique and vastus lateralis oblique muscles during squats. At the same time, the maximum vertical ground reaction force was measured with a force plate. A total of three measurements were taken and averaged, and two minutes of squat movements were assessed between ankle angles to prevent target action.
Results: The results of this study illustrated that the reliability of the vastus medialis oblique muscles and vastus lateralis oblique muscles in ankle angle was high. The difference in muscle thickness was significantly greater in comparing the toe out10° angle with the toe 0° angle than between toe in 10° and toe out 10° in vastus medialis oblique and vastus lateralis oblique (p < 0.05). There was no statistically significant difference between the ankle angle of toe 0° and toe in 10° (p > 0.05). The maximum vertical ground reaction force was significantly greater at toe out 10° than at the ankle angle of toe 0° and toe out 10° and between toe in 10° and toe out 10° (p < 0.05). There was no statistically significant difference in the comparison between toe 0° and toe in 10° (p > 0.05).
Conclusion: Squatting at an ankle angle of toe out 10° increases the dorsi flexion; thus, the stability of the ankle and the thickness of both oblique muscles increased to perform more effective squats. In addition, as the base of support widens, it is thought that the stability of the posture increases so that squat training can be performed safely.
Keywords: Squat, Ankle angle, Muscle thickness, Ground reaction force


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