Influence of expectation of task duration on efficiency of muscular activity.

The purpose of this study was to test the hypothesis that intensity and organization of muscular activity is a function of S's expectation of a task's duration. The electrical activity of the following muscles was measured while S was holding a 19-lb. weight under expectation for short and long tasks: biceps brachii, brachioradials, brachialis, and flexor carpi ulnaris. For the intervals measured, there was less electrical activity in all muscles during the long task. The less appropriate muscle showed the largest relative decrease. The results were interpreted as evidence of superior organization of activity under expectation of a task of long duration of work over expectation of a short duration of work.