Sensitivity and reliability of force tracking and joint-movement tracking scores in healthy subjects.

The purpose of this study was to examine the sensitivity and reliability of two tracking tests designed to measure control of handgrip force and finger movement. In one test, the subject exerts careful control of handgrip force on a dynamometer, which is interfaced with a computer, and attempts to guide a cursor as accurately as possible along a stationary target track displayed on the computer screen. In the second test, the subject attempts to trace a different target track by precise flexion-extension movement of the metacarpophalangeal joint of the index finger to which an electrogoniometer is attached. For both tests, the computer quantifies the subject's performance with an accuracy index. Fourteen healthy subjects participated in the force tracking test (FTT), which involved three pretest tracking trials, a 20-minute inactivity period, and three posttest trials. Thirteen different healthy subjects participated in the joint-movement tracking test (JMTT) using the same testing format. One-tailed, paired t tests of the pretest-posttest tracking scores showed significant (p less than .01) improvement in tracking accuracy for both the FTT and the JMTT. Additionally, intraclass correlation coefficients for both the pretest and the posttest trials showed acceptable reliability in the FTT and the JMTT. We concluded, for healthy subjects, that 1) these tracking tests are sensitive to small changes in force control and joint-movement control, and 2) the tracking scores are reliable. We believe that these tests could be very useful in documenting objectively the effects of treatment applied to the hand.