Muscle performance during isokinetic concentric and eccentric abduction in subjects with subacromial impingement syndrome.

Peak torque (PT), total work (TW) and acceleration time (AT) were measured during isokinetic concentric and eccentric abduction of the shoulder in subjects with subacromial impingement syndrome (SIS) and healthy subjects. The SIS group consisted of 27 subjects (33.48 +/- 9.94 years) with unilateral SIS and it was divided into two groups: (1) SIS with the dominant involved side, (2) SIS with the nondominant involved side. The control group consisted of 23 healthy subjects (32.26 +/- 9.04 years). PT, TW and AT were measured bilaterally at 60 and 180 degrees /s. No significant interactions were found between group and side (P > 0.05), as well as no significant main effects of group and side (P > 0.05) for all variables during concentric abduction of the shoulder at both tested speeds. During the eccentric contractions, lower TW (P < 0.05) was demonstrated by the nondominant uninvolved side of SIS group at 60 degrees /s, and by the uninvolved sides of the SIS groups at 180 degrees /s compared to the dominant side of the controls. At 180 degrees /s, the nondominant uninvolved side of the SIS group demonstrated slower AT (P < 0.05) compared to the dominant side of the control group, as well as the nondominant involved side of the SIS group compared to the nondominant side of the controls. The results showed no alterations in the measured parameters during concentric and eccentric phases of isokinetic abduction in subjects with SIS when compared to a control group. However, alterations may be observed in the contralateral side during the eccentric phase of abduction in subjects with unilateral conditions of SIS.