Generalizability of grip strength measurements in patients with tennis elbow.

The purpose of this study was to determine the interrepetition and interoccasion generalizability of grip strength measurements in patients with the diagnosis of proximal extensor carpi radialis brevis tendinitis. Thirty-five consecutive patients (mean age = 44.5 +/- 8.6 years; mean duration of symptoms = 3.9 +/- 3.5 months) fulfilling the eligibility criteria participated in the study. Measurements of pain-free grip strength and maximum grip strength for the involved limb and maximum grip strength for the uninvolved limb were taken on two test dates within seven days of each other. We calculated the variation between measurements within a test session and the variation from one session to the next using generalizability coefficients based on the mean of the six measurements. The coefficients for interrepetition, interoccasion, and overall generalizability were .99, .97, and .96, respectively. The clinical implication of these findings is that the overall generalizability can best be enhanced by averaging grip strength measurements recorded from multiple test sessions rather than by increasing the number of repetitions during a single test session.