pISSN 2288-6982
eISSN 2288-7105


Original Article

Phys. Ther. Korea 2021; 28(4): 256-265

Published online November 20, 2021

© Korean Research Society of Physical Therapy

Immediate Effects of Flexi-bar Exercise With Knee Push-up Plus on Shoulder Joint Position Sense and Muscle Activity in Subjects With Scapular Winging

Seok-hyun Kim1 , PT, BPT, Heon-seock Cynn1 , PT, PhD, Seung-min Baik1,2 , PT, BPT

1Applied Kinesiology and Ergonomic Technology Laboratory, Department of Physical Therapy, The Graduate School, Yonsei University, Wonju, 2Department of Physical Therapy, Division of Health Science, Baekseok University, Cheonan, Korea

Correspondence to: Heon-seock Cynn

Received: September 17, 2021; Revised: October 2, 2021; Accepted: October 6, 2021

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.


Background: Individuals with scapular winging may have proprioceptive dysfunction which is important for motor control and causes shoulder instability. Reduced serratus anterior (SA) and lower trapezius (LT) muscle activity accompanied by over-active upper trapezius (UT), and pectoralis major (PM) may be contributing factors. Flexi-bar (FB) exercise may be used to increase joint position sense (JPS) and alter the target muscle activities.
Objects: This study aimed to investigate the immediate effects of flexi-bar exercise prior to knee push-up plus (FPK) versus knee push-up plus (KPP) on JPS and muscle activity of SA, LT, UT, and PM in subjects with scapular winging.
Methods: Eighteen subjects with scapular winging were recruited. JPS was investigated at baseline, after KPP and after FPK. Passive and active JPS errors were calculated by isokinetic equipment. Surface electromyography was used to record muscle activities during KPP and FPK. One-way repeated-measures analysis of variance and post hoc analyses were used to analyze the JPS error measured at baseline, after KPP and after FPK. Paired t-tests were used to compare muscle activities between KPP and FPK.
Results: Passive JPS error was significantly decreased after KPP (p = 0.005) and after FPK (p = 0.003) compared to the baseline. Active JPS error was also significantly decreased after KPP (p = 0.016) and after FPK (p = 0.012) compared to the baseline. There was no significant difp <ference in the passive and active JPS errors between KPP and FPK. SA activity during FPK was significantly increased (p = 0.024), and LT activity during FPK was significantly increased (p = 0.006). There were no significant differences in the UT and PM activity.
Conclusion: FB might be recommended to immediately improve passive and active JPS and to selectively increase SA and LT muscle activities during KPP in individuals with scapular winging.

Keywords: Flexi-bar, Joint position sense, Knee push-up plus, Lower trapezius, Scapular winging, Serratus anterior