Electromyographic activities of the abdominal muscles during 30% and 75% of maximum expiratory pressure

The aim of this study was to quantify the activities of the rectus abdominis (RA), external oblique (EO), and internal oblique (IO) muscles during 30% and 75% of maximum expiratory pressure (PE max). Fifteen healthy male university students participated in this study. Electromyographic (EMG) activities of the RA, EO, and IO muscles were measured during 30% and 75% of PE max and then normalized relative to maximum voluntary contractions (%MVC). All muscles during 75% of PE max showed significantly higher %MVC compared to that during 30% of PE max (P < 0.01). The EO and IO muscles showed significantly higher %MVC compared to the RA muscle during 30% and 75% of PE max (P < 0.05). Muscle endurance and strength induced by expiratory muscle strength training might be different in each abdominal muscle.