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Phys. Ther. Korea 2023; 30(2): 160-168

Published online May 20, 2023

https://doi.org/10.12674/ptk.2023.30.2.160

© Korean Research Society of Physical Therapy

Effect of Isometric Horizontal Abduction on Scapular and Shoulder Muscle Activity During Knee Push-up Plus With Different Shoulder Angles in Individuals With Scapular Winging

Jung-Hoon Choi1,2 , PT, MSc, Heon-Seock Cynn1 , PT, PhD, Seung-Min Baik1 , PT, PhD, Seok-Hyun Kim1 , PT, MSc

1Applied Kinesiology and Ergonomic Technology Laboratory, Department of Physical Therapy, The Graduate School, Yonsei University, Wonju, 2Department of Rehabilitation Team, Yongin Severance Hospital, Yongin, Korea

Correspondence to: Heon-Seock Cynn
E-mail: cynn@yonsei.ac.kr
https://orcid.org/0000-0002-5810-2371

Received: March 16, 2023; Revised: March 29, 2023; Accepted: March 30, 2023

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

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Background: Individuals with scapular winging have a weak serratus anterior (SA) muscle, and to compensate, the pectoralis major (PM) and upper trapezius (UT) muscles excessively activate, which can cause upper extremity dysfunction. This study aimed to compare the effects of isometric horizontal abduction (IHA) on SA, PM, and UT muscle activity, as well as the SA/PM and SA/UT muscle activity ratios during knee push-up plus (KPP) at 90° and 120° of shoulder flexion. Objects: This study aimed to compare the effects of IHA on SA, PM, and UT muscle activity, as well as the SA/PM and SA/UT muscle activity ratios during KPP at 90° and 120° of shoulder flexion.
Methods: This study, conducted at a university research laboratory, included 20 individuals with scapular winging. Participants performed KPP with and without IHA at 90° (KPP90) and 120° (KPP120) of shoulder flexion. SA, PM, and UT muscle activity were measured using surface electromyography.
Results: PM activity in KPP90 with IHA was significantly lower than KPP90 and in KPP120 was significantly lower than KPP90. UT activity was significantly greater with IHA than without IHA and at 120° than 90° of shoulder flexion. SA/PM muscle activity ratio was significantly higher in KPP90 with IHA than without IHA and in KPP120 than in KPP90. SA/UT muscle activity ratio was significantly lower with IHA than without IHA.
Conclusion: KPP90 with IHA and KPP120 are effective exercises to reduce PM activity and increase SA/PM muscle activity ratio. However, applying IHA in KPP90 also reduces SA/UT muscle activity ratio, implying that it would be preferable to apply KPP120 in individuals overusing their UT muscles.

Keywords: Muscle weakness, Pectoralis muscles, Scapular winging, Shoulder blade, Trapezius muscle

Article

Original Article

Phys. Ther. Korea 2023; 30(2): 160-168

Published online May 20, 2023 https://doi.org/10.12674/ptk.2023.30.2.160

Copyright © Korean Research Society of Physical Therapy.

Effect of Isometric Horizontal Abduction on Scapular and Shoulder Muscle Activity During Knee Push-up Plus With Different Shoulder Angles in Individuals With Scapular Winging

Jung-Hoon Choi1,2 , PT, MSc, Heon-Seock Cynn1 , PT, PhD, Seung-Min Baik1 , PT, PhD, Seok-Hyun Kim1 , PT, MSc

1Applied Kinesiology and Ergonomic Technology Laboratory, Department of Physical Therapy, The Graduate School, Yonsei University, Wonju, 2Department of Rehabilitation Team, Yongin Severance Hospital, Yongin, Korea

Correspondence to:Heon-Seock Cynn
E-mail: cynn@yonsei.ac.kr
https://orcid.org/0000-0002-5810-2371

Received: March 16, 2023; Revised: March 29, 2023; Accepted: March 30, 2023

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background: Individuals with scapular winging have a weak serratus anterior (SA) muscle, and to compensate, the pectoralis major (PM) and upper trapezius (UT) muscles excessively activate, which can cause upper extremity dysfunction. This study aimed to compare the effects of isometric horizontal abduction (IHA) on SA, PM, and UT muscle activity, as well as the SA/PM and SA/UT muscle activity ratios during knee push-up plus (KPP) at 90° and 120° of shoulder flexion. Objects: This study aimed to compare the effects of IHA on SA, PM, and UT muscle activity, as well as the SA/PM and SA/UT muscle activity ratios during KPP at 90° and 120° of shoulder flexion.
Methods: This study, conducted at a university research laboratory, included 20 individuals with scapular winging. Participants performed KPP with and without IHA at 90° (KPP90) and 120° (KPP120) of shoulder flexion. SA, PM, and UT muscle activity were measured using surface electromyography.
Results: PM activity in KPP90 with IHA was significantly lower than KPP90 and in KPP120 was significantly lower than KPP90. UT activity was significantly greater with IHA than without IHA and at 120° than 90° of shoulder flexion. SA/PM muscle activity ratio was significantly higher in KPP90 with IHA than without IHA and in KPP120 than in KPP90. SA/UT muscle activity ratio was significantly lower with IHA than without IHA.
Conclusion: KPP90 with IHA and KPP120 are effective exercises to reduce PM activity and increase SA/PM muscle activity ratio. However, applying IHA in KPP90 also reduces SA/UT muscle activity ratio, implying that it would be preferable to apply KPP120 in individuals overusing their UT muscles.

Keywords: Muscle weakness, Pectoralis muscles, Scapular winging, Shoulder blade, Trapezius muscle

Fig 1.

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Figure 1.KPP with or without IHA at 90° and 120° of shoulder flexion. (A) KPP90, (B) KPP120, (C) KPP90-IHA, and (D) KPP120-IHA. KPP, knee push-up plus; IHA, isometric horizontal abduction.
Physical Therapy Korea 2023; 30: 160-168https://doi.org/10.12674/ptk.2023.30.2.160

Fig 2.

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Figure 2.Comparison of SA activity during KPP with and without IHA at 90° and 120° of shoulder flexion. SA, serratus anterior; %MVIC, percentages of the mean maximal voluntary isometric contraction; KPP, knee push-up plus; IHA, isometric horizontal abduction.
Physical Therapy Korea 2023; 30: 160-168https://doi.org/10.12674/ptk.2023.30.2.160

Fig 3.

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Figure 3.Comparison of PM activity during KPP with and without IHA at 90° and 120° degree of shoulder flexion. PM, pectoralis major; %MVIC, percentages of the mean maximal voluntary isometric contraction; KPP, knee push-up plus; IHA, isometric horizontal abduction. *p < 0.0125, significant simple effect.
Physical Therapy Korea 2023; 30: 160-168https://doi.org/10.12674/ptk.2023.30.2.160

Fig 4.

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Figure 4.Comparison of UT activity during KPP with and without IHA at 90° and 120° of shoulder flexion. UT, upper trapezius; %MVIC, percentages of the mean maximal voluntary isometric contraction; KPP, knee push-up plus; IHA, isometric horizontal abduction. (A) Significant difference in the main effect for IHA condition, (B) significant difference in the main effect for shoulder flexion angle. *p < 0.05, significant difference in main effects.
Physical Therapy Korea 2023; 30: 160-168https://doi.org/10.12674/ptk.2023.30.2.160

Fig 5.

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Figure 5.Comparison of the SA/PM muscle activity ratio during KPP with and without IHA at 90° and 120° of shoulder flexion. SA, serratus anterior; PM, pectoralis major; KPP, knee push-up plus; IHA, isometric horizontal abduction. *p < 0.0125, significant simple effect.
Physical Therapy Korea 2023; 30: 160-168https://doi.org/10.12674/ptk.2023.30.2.160

Fig 6.

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Figure 6.Comparison of the SA/UT activity ratio during KPP with and without IHA at 90° and 120° of shoulder flexion. SA, serratus anterior; UT, upper trapezius; KPP, knee push-up plus; IHA, isometric horizontal abduction. *p < 0.05, significant difference in the main effect for IHA.
Physical Therapy Korea 2023; 30: 160-168https://doi.org/10.12674/ptk.2023.30.2.160