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J Phys Ther Sci. 2017 Jan;29(1):43-47. doi: 10.1589/jpts.29.43. Epub 2017 Jan 30.

A study on muscle activity and ratio of the knee extensor depending on the types of squat exercise.

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Department of Physical Therapy, Sehan University, Republic of Korea.
Department of Physical Therapy, Sehan University, Republic of Korea; Department of Physical Therapy, Haenam Hankook Hospital, Republic of Korea.
Department of Physical Therapy, Mokpo Mirae Hospital, Republic of Korea.
Department of Physical Therapy, Seonam University, Republic of Korea.
Department of Physical Therapy, Mokpo Jung-Ang Hospital, Republic of Korea.


[Purpose] For preventing the patellofemoral pain syndrome, this study aims to suggest a proper squat method, which presents selective muscle activity of Vastus Medialis Oblique and muscle activity ratios of Vastus Medialis Oblique/Vastus Lateralis by applying squat that is a representative weight bearing exercise method in various ways depending on the surface conditions and knee bending angles. [Subjects and Methods] An isometric squat that was accompanied by hip adduction, depending on the surface condition and the knee joint flexion angle, was performed by 24 healthy students. The muscle activity and the ratio of muscle activity were measured. [Results] In a comparison of muscle activity depending on the knee joint flexion angle on a weight-bearing surface, the vastus medialis oblique showed a significant difference at 15° and 60°. Meanwhile, in a comparison of the muscle activity ratio between the vastus medialis oblique and the vastus lateralis depending on the knee joint flexion angle on a weight-bearing surface, significant differences were observed at 15° and 60°. [Conclusion] An efficient squat exercise posture for preventing the patellofemoral pain syndrome is to increase the knee joint bending angle on a stable surface. But it would be efficient for patients with difficulties in bending the knee joint to keep a knee joint bending angle of 15 degrees or less on an unstable surface. It is considered that in future, diverse studies on selective Vastus Medialis Oblique strengthening exercise methods would be needed after applying them to patients with the patellofemoral pain syndrome.


Squat exercise; Vastus lateralis; Vastus medialis oblique

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