Reliability assessment of isometric knee extension measurements with a computer-assisted hand-held dynamometer

Objective: To assess clinically relevant indexes of measurement error of hand-held dynamometer measurements using a computer-assisted hand-held dynamometer (CAHN-DY). Design: In separate sessions, different physical therapists performed repeated measurements of maximal isometric knee extension. Setting: Four physical therapy practices and outpatient departments. Patients: Consecutive samples of 30 male and 28 female patients aged 13 to 77 years, with isolated orthopedic knee disorders participated in this study. Main Outcome Measures: For intrarater and interrater applications, the standard error of measurement (SEM) and related 95% confidence intervals and minimal detectable changes were assessed. Results: Sixty percent of the patients performed within the therapist's upper force limit. Variance between sessions performed by the same or different therapists accounted for a large percentage of the measurement error (70% to 81%). For single measurements, the standard error of measurement was assessed not to exceed 10N . m. Minimal detectable changes for different designs varied from 13.8 to 28.2N . m. Conclusions: The CAHN-DY facilitated standardization of test performance in a satisfactory manner, resulting in less measurement error compared with simple hand-held dynamometry. (C) 1998 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation.