Note: [*] University of Virginia, Charlottesville, VA.
Note: [**] Address reprint requests to David H. Perrin, PhD, ATC, Memorial Gymnasium, University of Virginia, Charlottesville, VA 22903.
Note: [***] University of Virginia, Charlottesville, VA.
Note: [****] University of Virginia, Charlottesville, VA.
Note: [*****] George Fox College, Newberg, OR.
Abstract: This study examined the effect of gravity correction on concentric and eccentric average force of the right and left side shoulder rotator muscles and on the external/internal rotation reciprocal muscle group ratios. Thirty-three males were tested on a Kinetic Communicator dynamometer at 150 deg/sec from a seated position with the shoulder abducted to 90 deg and positioned along the frontal plane. Gravity correction procedures were followed prior to testing, and both the gravity-uncorrected (GU) and gravity-corrected (GC) values were obtained from the dynamometer's software. Paired t-tests indicated the gravity correction procedure increased every value obtained during external rotation and decreased all values obtained during internal rotation. Also, the concentric and eccentric external/internal rotation reciprocal muscle group ratios were all higher as a result of the gravity correction procedure. These findings were consistent with previous reports on the effect of gravity correction on lower extremity muscle groups. In particular, gravity correction significantly added to the muscle group opposed by gravity (external rotators) and detracted from the muscle group assisted by gravity (internal rotators). Therefore correction for the effects of gravity is recommended during isokinetic assessment of the shoulder internal and external rotator muscle groups.
Keywords: External/internal rotation ratio, concentric and eccentric average force, gravity correction
