Varying the duration of acute exercise: Implications for changes in affect

Acute bouts of aerobic exercise have been associated with modest reductions in self-reported state anxiety. Some have speculated that certain intensity or duration thresholds must be achieved before such reductions in anxiety can occur. Additionally, most of the previous research has focused on anxiety reduction or alleviation of negative affect with little concern for the positive affect enhancing potential of exercise. The purposes of the present study were to (1) determine whether anxiety reduction differs at two levels of exercise duration; and (2) examine both positive and negative responses to exercise. Sixteen males completed two (15 min, 30 min) randomly ordered exercise bouts (treadmill running at 75% VO₂max) on separate days. Affective responses were assessed before, immediately after, and at 5, 10, 20, and 30 min after the exercise bouts. State anxiety was reduced equally for both durations of exercise, positive affect did not change, and 30 min of running reduced negative affect. The results are discussed in terms of implications for delineating mechanisms to explain such effects.