Background and Purpose
Shoulder impingement syndrome is a common complaint of shoulder pain in overhead athletes such as bodybuilders. Shoulder exercises and overhead movements with heavy weights, which are usually accompanied by high stress and strain, occupy a significant part of the bodybuilding training program. Impingement is associated with altered muscle activity of the shoulder complex. However, the pattern of muscle activity in these patients is controversial and inconsistent. Functional training is one of the methods used in preventive and rehabilitation interventions in scapular stabilization. It is believed that functional training in a closed kinetic chain can contribute to the clinical treatment and recovery of athletes with shoulder impingement syndrome. However, there is a need to investigate different aspects of functional training in overhead sports, especially sports that place high stress and strain on the shoulder, such as bodybuilding. The aim of this study was to determine the electromyographic activity of selected muscles of the shoulder complex during some functional movements in female bodybuilders with shoulder impingement syndrome.
 
Methods
Ten healthy female bodybuilders and ten athletes with unilateral shoulder impingement syndrome of the dominant hand participated in this quasi-experimental study. Electromyography activity of the anterior deltoid, pectoralis major, serratus anterior, posterior deltoid, and upper and lower trapezius muscles during the performance of three functional movements common in bodybuilding in a closed-chain motion namely, Australian chain-up, push-up, and parallel bar dip, was recorded with an eight-channel biometric system (DataLink) at a sampling rate of 2000 Hz. Surface electrodes were placed on the muscles according to the European SENIAM protocol. Raw electromyographic signals were analyzed with DataLog software with a bandpass filter of 8 to 500 Hz. Then, the root mean square (RMS) of the filtered data was taken with a time window of 100 ms. One second of each data (the highest plateau of the curve) was separated and its data was extracted. It was determined by dividing the activity obtained for each muscle by MVIC and multiplying the obtained number by 100% of the activity of each muscle. The normalized activity of the studied muscles was extracted and used for statistical analysis. Also, directional co-contraction was calculated by dividing the mean of the RMS values ​​of the antagonist muscle by the mean of the RMS values ​​of the agonist muscles minus one. After ensuring the normality of the data distribution with the Shapiro-Wilk test, analysis of variance with repeated measures was used for data analysis (p<0.05).
 
Results
In comparing muscle activity in three functional movements in the individuals with shoulder impingement syndrome, it was shown that the activity of the anterior deltoid muscle in the parallel bar dip movement was significantly higher than the Australian chain-up and the push-up. Also, the activity of this muscle in the push-up was higher than the Australian chain-up. The posterior deltoid muscle in the parallel bar dip movement was significantly higher than the Australian chain-up and the push-up. Also, the activity of this muscle in the Australian chain-up was higher than the push-up. The pectoralis major muscle in the parallel bar dip movement showed significantly higher activity than the Australian chain-up and the push-up. Also, the mean activity of this muscle in the push-up movement was higher than the Australian chain-up movement. The serratus anterior muscle was significantly higher in the parallel bar dip movement than the Australian chain-up movement and the push-up movement. However, the activity of this muscle in the Australian chain-up movement was not significantly different from the push-up movement. The activity of the upper part of the trapezius muscle in the Australian chain-up movement and the parallel bar dip movement was significantly higher than the push-up movement. However, the activity of this muscle was not significant in the Australian chain-up movement and the parallel bar dip movement. The mean activity of the lower part of the trapezius muscle in the parallel bar dip movement was significantly higher than the push-up movement and the Australian chain-up movement. Also, the activity of this muscle in the Australian chain-up movement was higher than the push-up movement. The results showed that directional co-contraction in the push-up movement was higher in the healthy group than in the shoulder impingement syndrome group (p=0.01). No significant difference was observed for directional co-contraction in the Australian chain-up and parallel bar dip movements (p=0.13 and p=0.64, respectively).
 
Conclusion
According to our findings, it can be concluded that the anterior shoulder muscles, including the pectoralis major and anterior deltoid, of bodybuilders with shoulder impingement syndrome are more active than healthy individuals when performing closed-chain movements, including parallel bar dip, push-up and Australian chain-up. This action can create a compensatory mechanism for other muscles of the shoulder complex and ultimately speed up the injury cycle. It is better for female bodybuilders with shoulder impingement syndrome to avoid closed-chain exercises until recovery. If bodybuilders with shoulder impingement need to use closed-chain exercises to strengthen shoulder muscles, it is suggested to use the Australian chain-up exercise, which has the least amount of variation compared to the other two methods and may be safer for these individuals. Further study is warranted.
 
 
Article Message
Choosing the right type of exercises for rehabilitation and designing a training program for athletes with shoulder impingement syndrome can prevent aggravation of the injury. It is recommended that fitness trainers use safe closed-chain exercises for this group of athletes, which place less pressure on the anterior shoulder joint.
Ethical Considerations
This research received ethical approval from the Biomedical Research Ethics Committee at Bu-Ali Sina University, with the assigned Ethics Code: IR.BASU.REC.1401.017.
Authors’ Contributions
Conceptualization: Mehrdad Anbarian, Gita Babal-Moradi
Data Collection: Gita Babal-Moradi
Data Analysis: Gita Babal-Moradi, Mehrdad Anbarian
Manuscript Writing: Mehrdad Anbarian, Gita Babal-Moradi
Review and Editing: Mehrdad Anbarian
Conflict of Interest
The researchers confirm that there are no conflicts of interest.
 
Acknowledgments
This study is extracted from Master degree of Sports Biomechanics at Bu-Ali Sina University. The authors would like to thank all subjects who participated in this study.