Magnetic resonance imaging evaluation of muscle usage associated with three exercises for rotator cuff rehabilitation.

Horrigan JM, Shellock FG, Mink JH, Deutsch AL.  Medicine and Science in Sports and Exercise, 1999, Volume 31, Number 10:1361-366

Purpose: Methods of determining muscle usage for exercises involving rotator cuff muscles are limited.  Therefore, this investigation used magnetic resonance imaging (MRI) to evaluate the effect of three different exercises used for rehabilitation of the rotator cuff.

Methods: Five normal volunteer subjects (3 men, 2 women, mean age 31.4 yr) were studied.  The exercises were scaption with internal rotation (SIR), military press (MP), and sidle-lying 45 degree abduction (SLA).  MRI imaging was performed immediately before and after exercise using a  “fast” spin echo STIR sequence and an oblique coronal plane imaging.  Changes in signal intensity pre- and post-exercise were measured at comparable section locations for the MR images of the supraspinatus, infraspinatus, teres minor, subscapularis, deltoid and trapezius.

Results:  The SLA showed the greatest increase in signal intensity in all the muscles (percent change, P<0.01) except for the trapezius, which was used more the MP and SIR.  None of the exercises activated the teres minor (percent change, P = not significant).

Conclusion: Theses findings have important implications in efficacy of physical rehabilitation of the rotator cuff and avoidance of subacromial impingement exercise motions.