Abstract
Background: It is important that the load of the repaired rotator cuff tendon must not be heavy. The purpose of this study was to quantify the electromyographic activities of supraspinatus (SSP) and infraspinatus (ISP) muscles in elevating the shoulder, and to select proper rehabilitaion for the repaired rotator cuff muscles.
Methods: We examined wire EMG of SSP and surface EMG of ISP of dominant side in 5 asymptomatic males. Their average age was 26.8 years old. We examined the integration of EMG by manual muscle test of elevation and external rotation. The peak of it reached for one second was defined as the maximal voluntary contraction (MVC). The active elevating positions were supine, sitting, and supine with sling. The elevating speed was 30 degrees / sec. The EMG activities of each active elevation divided by MVC. This was %MVC.
Results: The averaged %MVC of each elevation : at 30 degrees, 60 degrees, 90 degrees, 120 degrees was as follows. A, Sitting flexion. SSP : 4.9, 7.3, 15.6, 25.4. ISP : 5.8, 13.9, 19.4, 20.1. B, Sitting scaption. SSP : 12.5, 18.5, 25.6, 43.4. ISP : 5.8, 13.9, 19.4, 20.1. C, Sitting abduction. SSP : 16.0, 29.1, 38.8, 54.5. ISP : 7.8, 11.5, 16.5, 17.7. D, Supine flexion. SSP : 2.8, 2.5, 3.3, 3.5. ISP : 12.0, 14.5, 12.4, 12.2. E, Supine scaption with sling. SSP : 0.8, 0.7, 0.9, 3.6. ISP : 2.0, 2.6, 2.5, 2.8, respectively.
Conclusion: Sling was under 5%MVC and the most suitable rehabilitation for early days after surgery. Supine flexion was under 5%MVC of SSP and under 15%MVC of ISP. It was safe. Sitting flexion under 90 degree was safe, but sitting abduction was risky.
