Break-technique handheld dynamometry: Relation between angular velocity and strength measurements

Objectives: To determine whether the muscle strength, as measured with break-technique handheld dynamomety (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. (c) 2005 by American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation.