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Observational Study
, 18 (2), 248-252
eCollection

Muscle Activity Pattern With A Shifted Center of Pressure During the Squat Exercise

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Observational Study

Muscle Activity Pattern With A Shifted Center of Pressure During the Squat Exercise

Tetsuro Kitamura et al. J Sports Sci Med.

Abstract

The squat exercise is a fundamental movement in athletic training and rehabilitation. In this study, we measured muscle activities in a normal squat posture (NSP) and a squat posture with the center of foot pressure (COP) intentionally shifted forward as far as possible (FSP). Ten healthy men performed double-limb squats, adopting the NSP and FSP, with three knee flexion angles (30, 60, and 90 degrees). The muscle activities of the vastus medialis (VM), semitendinosus (ST), tibialis anterior (TA), and gastrocnemius muscle lateral head (GL) were measured using surface electromyography, and activity patterns were analyzed. Compared to that for the NSP, the COP was significantly shifted forward in the FSP by at least 30% of the foot length for all knee flexion angles (p < 0.05). At all knee flexion angles, VM muscle activity significantly decreased, while GL muscle activity increased, in the FSP compared to that for the NSP (p < 0.05). In addition, ST muscle activity increased significantly in the FSP compared to that for the NSP at knee flexion angles of 30 and 60 degrees (p < 0.05). TA muscle activity significantly decreased in the FSP compared to that for the NSP at only 90 degrees of knee flexion (p < 0.05). These results demonstrate that muscle activity patterns vary significantly according to squat posture. Thus, the active control of the COP position during the squat can be a new training approach in targeting specific muscle groups.

Keywords: Body weight squats; forward-shifted posture; rehabilitation; stabilometer; surface electromyogram.

Figures

Figure 1.
Figure 1.
A) The normal squat posture (NSP): The shoulder joint was abducted as an external rotation and the middle finger was placed on the temple. The center of the foot pressure (COP) was between the left and right feet, but the subjects did not focus on the sagittal plane. B) The forward-shifted posture (FSP): Subjects looked at the front monitor, lifted their upper limbs and shifted the COP forward.
Figure 2.
Figure 2.
The differences in the COP location between the NSP and FSP are shown for the three knee flexion angles. A) The mean %COP shifted from 41.8 ± 6.0% to 75.5 ± 8.2% (NSP vs FSP). B) The mean %COP shifted from 46.0 ± 8.3% to 79.9 ± 4.6% (NSP vs FSP). C) The mean %COP shifted from 44.8 ± 12.1% to 76.4 ± 7.5% (NSP vs FSP). * Significant difference (p < 0.05). COP, center of the foot pressure; NSP, normal squat posture; FSP, forward-shifted posture.

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