PNF and Movement 2024; 22(3): 465-472
https://doi.org/10.21598/JKPNFA.2024.22.3.465
An Effect of the Muscular Activity of Lower Limbs During Smith Machine Squat Exercise According to Foot Position
Jeong-Wook Kim, P.T., M.S. 1⋅Min-Chull Park, P.T., Ph.D.2†
1Department of Physical Therapy, College of Health Sciences, Graduated School, Catholic University of Pusan
2Department of Physical Therapy, College of Health Sciences, Catholic University of Pusan
Correspondence to: †Min-Chull (mcpark@cup.ac.kr)
Received: November 16, 2024; Revised: November 26, 2024; Accepted: November 26, 2024; Published online: December 31, 2024.
© 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 aim of this study was to determine muscle activity, depending on foot position, during Smith Machine squat exercises.
Methods: For three kinds of Smith Machine squat positions, the participants adopted a foot position with the lateral malleolus placed in a straight line with the bar, another foot position with the lateral malleolus placed at the one-half point of the femur, and a further foot position with the lateral malleolus extended forward as long as the femur. Electromyography data were collected from the biceps femoris (BF), semitendinosus (SM), vastus lateralis (VL), and vastus medialis (VM). In addition, the ratios of hamstrings and quadriceps (HQ) and VM/VL were measured using electromyography during the Smith Machine squat exercises.
Results: The HQ ratio was significantly higher for the foot position in a straight line with the bar than for the foot position with the lateral malleolus extended forward as long as the femur. The VL and VM were significantly higher for the foot position with the lateral malleolus extended forward as long as the femur than for the foot position in a straight line with the bar.
Conclusion: To increase the muscle activity of the quadriceps femoris, is to place the lateral malleolus forward as long as the femur from a point in a straight line with the bar. Intervention considering the HQ ratio is to place the lateral malleolus in a straight line with the bar.
Keywords: Co-activation, Squat, Electromyography

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