Shoulder joint strength assessment in people with subacromial shoulder impingment

Recent conservative management of sub-acromial shoulder impingement (SSI) includes general strengthening exercises, especially for internal (IR) and external (ER) shoulder rotators. Despite various studies, so far, there is no directly investigated for indicating the difference in muscle strength between patients with SSI and normal subjects. This study was done to compare the shoulder joint muscles’ strength in male students with and without SSI. This case-control study was conducted on Twenty-four students with SSI as case group and 24 normal students as controls.The subjects in both groups matched for hand dominance and physical activity level, completed isokinetic shoulder IR and ER testing. In the case group, 18 patients had the symptoms in their dominant and 6 patients in their non-dominant side. Both sides IR and ER of shoulder were measured separately using continuous reciprocal concentric and eccentric contraction cycles at speed of 60 and 120 degrees per second, respectively. Values of peak torque were compared between the case and control groups. There was a significant difference between the two groups only when the symptomatic SSI shoulder was the dominant shoulder. Eccentric and concentric ER peak torque at 120 degree per second (22.20±7.01, 11.36±3.36), eccentric ER peak torque at 60 degree per second (20.53±6.15) and eccentric IR peak torque at 60 degree per second and 120 degree per second were significantly lower in the symptomatic dominant shoulder case group in compared to the dominant shoulder control group (P<0.05). Changes in eccentric and concentric peak torque in SSI group may be related to limb dominance, which may have implications for strengthening regimes. Therefore, clinicians and therapeutic exercise expertise may benefit from eccentric isokinetic exercises for shoulder IR and ER rotators in order to design a treatment plan for patients with SSI.