Motor Unit Action Potentials of the Rectus Abdominis Muscle according to Changes of Abdominal Pressure

ABSTRACT

OBJECTIVE: In current urodynamic studies, rectal catheters can cause erroneous result affecting detrusor pressure, and the catheter itself is not comfortable to the patients. To reduce these problems we investigated the relationship between the motor unit action potentials (MUAP) of rectus abdominis muscle and the abdominal pressure measured by rectal catheter. METHOD: Healthy seven men and three women volunteers (mean age 49 years) with no neurological abnormality were enrolled. Possible maximal abdominal pressure (Pmax) was attained by Valsalva maneuver for 5 seconds. The MUAPs of the rectus abdominis muscle were recorded with surface electrodes for analysis. These recordings were done on 100, 80, 60, 40, and 20% of Pmax. The parameters of MUAP such as mean frequency, median frequency, turns, mean amplitude, and RMS (root mean square) were measured. RESULTS: Turns, mean amplitude, and RMS were increased in a proportion to the increment of abdominal pressure in all subjects(R=0.840, 0.879, and 0.984, respectively). CONCLUSION: These findings suggested that the surface MUAP of rectus abdominis muscle might be used indirectly for more convenient measurement of the abdominal pressure.