Even a little weekly exercise can tame a testy boss.

Just a half-hour of exercise once or twice a week can reduce a manager's tendency to put down, humiliate or snap at underlings, according to a study released by Northern Illinois University's College of Business.

Researchers selected 98 full-time employees from a wide range of professions—including accounting, engineering and banking—and asked them to anonymously rate the verbal abusiveness of their bosses on a seven-point scale. In a separate questionnaire, the bosses were asked to record their level of work-related stress and frequency of exercise. The employees were selected from a pool of part-time M.B.A. students in the fall of 2010.

The merged findings showed a strong correlation between a manager's aggressiveness and frequency of exercise. While exercise didn't necessarily lead to reduced stress, it seemed to temper bosses' reaction to stress, thereby acting as a behavioral "buffer," says James Burton, the study's lead researcher and an associate professor of management. The type of exercise didn't seem to matter, he adds.