Break-technique handheld dynamometry: relation between angular velocity and strength measurements.
OBJECTIVES: To determine whether the muscle strength, as measured with break-technique handheld dynamometry (HHD), is dependent on the angular velocity achieved during testing and to compare reliability at different angular velocities. DESIGN: Repeated-measures study. Participants underwent HHD by using make-technique (isometric) and break-technique (eccentric) dynamometry at 3 prespecified angular velocities. Elbow movement was recorded with an electrogoniometer. SETTING: Inpatient spinal cord injury unit. PARTICIPANTS: Convenience sample of 20 persons with tetraplegia with weakness of elbow flexors or extensors. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Elbow angular velocity and muscle strength recorded during HHD. RESULTS: With the break technique, angular velocities averaging 15 degrees , 33 degrees , and 55 degrees /s produced 16%, 30%, and 51% greater strength measurements, respectively, than velocities recorded by using the make technique (all P < .006 for comparisons between successive techniques). The intraclass correlation coefficient for intrarater reliability was .89 or greater for all testing techniques. CONCLUSIONS: Greater strength is recorded with faster angular velocities during HHD. Differences in angular velocity may explain the wide range previously reported for break- versus make-technique strength measurements. Variation in angular velocity is a potential source of variability in serial HHD strength measurements, and for this reason the make technique may be preferable.