Analysis of five tests commonly used in determining the ability to control single motor units.

A correlation regression analysis was used to analyze five individual test and two types of scores in terms of their predictive value in determining overall performance in single motor unit (SMU) control. Fine wire electrodes were inserted into the biceps brachii muscle of twenty-five women subjects. Each subject was tested for electrical silence, motor unit isolation, on-off control, frequency control and rhythm control. A detailed protocol and scoring criteria are described for each test. Ten predictors were analyzed--a time score and an error score for each of the five tests. A correlation regression analysis showed that the On-Off Control, the Rhythm Control and the Motor Unit Isolation tests have greater predictive value than the remaining tests. Furthermore, the error scores obtained from these tests are more reliable than the time scores in predicting overall performance in SMU control. The implications that the present findings may have on future studies are discussed.