The first of these benefits, the release of tension, is immediate .* Tension builds in the body because of an overaccumulation of adrenaline produced by stress, anxiety, or fear. * Doctors agree that performing calisthenics or participating in an active sport such as tennis or volleyball for thirty minutes releases tension. If a person swims, jogs or rides a bicycle for half that time, he or she should sleep better at night and have a better temperament the next day. In addition, after the release of tension, petty irritations and frustrations should be less troubling. * For example, an employee upset by the day's work and by traffic congestion may rush home, argue with the family, and eat excessively. Taking about thirty minutes to release frustrations through physical exercise could help him or her to avoid this behavior. Planned physical exercise, therefore, can eliminate, or at least control, tension.*