Further tests of the activity-set hypothesis for warm-up decrement.

An alternative to the set hypothesis for warm-up decrement (WU) is proposed which states that WU is due to the loss over rest of an activity-set consisting of proper adjustment of activation, attention to relevant sources of feedback, etc. Force estimation (Exp. 1) and arm positioning (Exp. 2 and 3) were used as criterion tasks. During an interpolated rest period, activities were introduced which were intended to reinstate the lost activity-set but which would not contribute habit strength to the criterion task. WU on subsequent criterion task performance was nearly eliminated in one task (Exp. 1) and greatly reduced in another (Exp. 2 and 3), and the evidence strongly supported the activity-set hypothesis.