Electromyographic study of the anterolateral abdominal wall muscles during ejaculation.
BACKGROUND
The anterolateral abdominal wall muscles (AAWMs) are composed of the external and internal oblique, transversus abdominis, and the rectus abdominis muscles.


OBJECTIVE
We investigated the hypothesis that the AAWMs contract reflexly during ejaculation.


METHODS
Effect of coitus on AAWMs was tested in 16 healthy men (mean age 37.2 +/- 9.7 years). The intra-abdominal pressure was measured by a manometric catheter introduced into the rectum. The response of the AAWMs to erection and ejaculation was recorded before and after penile and AAWMs' anesthetization by a needle electrode inserted into each of the muscles.


METHODS
Electromyographic (EMG) activity of AAWMs and rectal pressure increased at ejaculation.


RESULTS
A few seconds before and during ejaculation, the rectal pressure and motor unit action potentials (EMG activity) of each of the AAWMs increased; this effect was abolished by anesthetization of the penis and AAWMs.


CONCLUSIONS
Increased AAWMs' EMG denotes contraction of the said muscles. AAWMs' contraction at ejaculation, the resulting increase of the intra-abdominal pressure, and the presumably increased pelvic venous congestion seem to augment the penile venous congestion and rigidity. This effect is suggested to be mediated through a reflex which we call "ejaculation-abdominal wall reflex."
Shafik
Ahmed
A
Department of Surgery and Experimental Research, Faculty of Medicine, Cairo University, 2 Talaat Harb Street, Cairo 11121, Egypt. shafik@ahmedshafik.com
Shafik
Ismail A
IA
El Sibai
Olfat
O
Shafik
Ali A
AA
D034861:Abdominal Wall / Q000502:physiology*; D000328:Adult; D004542:Ejaculation; D004576:Electromyography; D006801:Humans; D008297:Male; D008365:Manometry; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D010812:Physical Stimulation; D012016:Reference Values