Effects of muscle group and placement site on reliability of hand-held dynamometry strength measurements.

Studies of measuring muscle strength with hand-held dynamometers have produced a variety of results. The purpose of this research was to further investigate the effect of muscle group and placement site on reliability. The purpose of Part I of this study was to examine reliabilities of force measurements generated by four specific muscle groups using a hand-held dynamometer (HHD). Part II's purpose was to determine the effects of HHD placement site on the variability of HHD force measurements. In Part I, two testers obtained measurements of right shoulder abductor, wrist extensor, hip flexor, and ankle dorsiflexor forces in 20 subjects. Two-way analysis of variance indicated a main effect due to tester, but no tester by session interaction and no main effect due to session (p < 0.5). Intraclass correlation coefficients ranged from .76-.93 for within-session, intratester reliabilities, .67-.84, for between-session intratester reliabilities, and .30-.83 for within-session, intertester reliabilities. Reliability tended to be higher when HHD placement sites were farther from joint centers. Part II explored the hypothesis that HHD forces would be less variable if measured distally. One tester measured shoulder abductor forces for 30 subjects at three sites on the upper extremity. Bartlett's Test for homogeneity of variance indicated a lower variability at the distal placement site (p < 0.05). J Orthop Sports Phys Ther 1992;15(5):236-242.