Abnormal isokinetic time-to-peak torque of the medial rotators of the shoulder in subjects with impingement syndrome

The time-to-peak torque (TPT) and the peak torque ratio of the lateral to medial rotators (LR/MR) during isokinetic lateral and medial rotation of the shoulder were evaluated in patients with shoulder impingement and in healthy subjects. Fifteen patients with shoulder impingement on the dominant side and 9 healthy subjects were evaluated. TPT and LR/MR were measured bilaterally during isokinetic concentric lateral and medial rotation at 60°/s and 180°/s. The impingement group showed a bilateral decrease in the TPT during medial rotation for both 60°/s and 180°/s. No differences were found in the LR/MR between the groups. It is proposed that decreased (TPT) of the medial rotators can be used as a tool for early detection of shoulder impingement. Notably, the decreased tim- to-peak torque of the medial rotators may occur before the alteration in the peak torque ratio.