['Recent studies have indicated that maximum expiration could be a useful way of performing challenging exercises that include coactivation of the deep and superficial abdominal muscles. However, little is known about the effect of maximum expiration on the activity of the abdominal muscles during lumbar stabilizing exercise.', 'The purpose of our study was to quantify changes in the activities of the abdominal muscles during side bridge exercise in combination with maximum expiration.', 'Experimental laboratory study.', 'The activities of the rectus abdominis (RA), external oblique (EO), and internal oblique (IO) muscles were measured using electromyography in 12 healthy men performing 3 tasks: holding the breath after maximum expiration in the supine position, holding the breath after resting expiration during side bridge exercise, and holding the breath after maximum expiration during side bridge exercise.', 'Significant increases in the activities of the abdominal muscles (RA, EO, and IO) occurred with maximum expiration when compared with resting expiration during side bridge exercise (P <0.05).'] Does maximum expiration activate the abdominal muscles during side bridge exercise?