MAXIMUM ACCEPTABLE FORCES FOR REPETITIVE ULNAR DEVIATION OF THE WRIST

The purpose of this experiment was to quantify maximum acceptable forc es for ulnar deviation motions of the wrist at various repetition rate s. Subjects grasped a handle with a power grip and moved it through a 1.40 rad (80 degrees) ulnar deviation wrist motion (similar to a knife cutting task). A psychophysical methodology was used in which the sub ject adjusted the resistance on the handle and the experimenter manipu lated or controlled all other variables. Two series of experiments wer e conducted. Thirteen subjects completed the first series, which inves tigated repetition rates of 15 and 20 motions per minute. Eleven subje cts completed the second series, which investigated 15, 20, and 25 mot ions per minute. Subjects performed for 7 hours per day, 5 days per we ek, for 4 weeks in the first series and 5 weeks in the second series. The subjects were instructed to work as if they were on an incentive b asis, getting paid for the amount of work they performed. Symptoms wer e recorded by the subjects during the last 5 minutes of each hour. The results are presented and compared with maximum acceptable forces for wrist flexion and extension.