Validity and reliability of a hand-held dynamometer with two populations.

Research supported by a grant from Nicholas Institute of Sports Medicine and Athletic Trauma. With the trend in our society toward mainstreaming persons with mental retardation, there is a need to evaluate the efficacy of rehabilitation procedures for this population. The purpose of this study was to examine the validity and reliability of measurements determined with the Nicholas Manual Muscle Tester (MMT) and with the Cybex II isokinetic dynamometer using a sample of 20 adults without mental retardation and 10 adults with mental retardation. Utilizing stabilization techniques, knee extension and elbow flexion were measured with both dynamometers. The Nicholas MMT manifested excellent discriminatory function among subgroups. Correlational analyses between the dynamometers yielded coefficients of .74 and .77 for knee and elbow actions. Significant differences between dynamometers for the subgroups were found in three of the six analyses. Intrarater and interrater reliability coefficients were all greater than .90 for subjects with mental retardation. In conclusion, measurements of muscle strength obtained with the Nicholas MMT from subjects with and without mental retardation were reliable. The validity of this dynamometer assessed by construct and criterion processes was not conclusively established. This dynamometer, which is portable and relatively inexpensive, appears to be suitable as an assessment tool in clinical settings for persons with mental retardation. J Orthop Sports Phys Ther 1992;16(5):229-234.