Perineal neuromuscular fatigue.
OBJECTIVE
The physiology of urinary continence during stress is complex and the role of passive and active mechanisms remains unclear. Coughing leads to a contraction of urethral rhabdomyosphincter and pelvic floor muscles leading to a positive urethro-vesical gradient and continence. Neuromuscular fatigue can involve all striated muscles, including rhabdomyosphincter, peri-urethral and pelvic floor muscles. This article reviews results of studies assessing perineal muscular fatigue in urinary incontinence.


METHODS
A systematic review of the literature (Medline, Pascal and Embase) with use of the MESH keywords fatigue, stress, urinary incontinence, pelvic floor, urethra, urethral pressure, and muscle.


RESULTS
Animal models have shown that the pelvic muscles (iliococcygeus and pubococcygeous) exhibit more neuromuscular fatigue than classical skeletal striated muscles (i.e. soleus muscle). Although the human external urethral sphincter is considered to be a highly fatigue-resistant muscle with its high proportion of slow muscle fibers, repeated coughing seems to lead to decreased urethral pressure in numerous women affected with stress urinary incontinence. In this case, "urethral fatigue" might be a possibility.


CONCLUSIONS
Although few studies have focused on perineal muscular fatigue, such increased fatigue in pelvic floor muscles may play a role in the pathophysiologic features of stress urinary incontinence in women.
Deffieux
X
X
Laboratoire d'Urodynamique et d'Explorations Neurophysiologiques du Périnée, Service de Rééducation Neurologique, Hôpital Rothschild, APHP, 75012 Paris, France. x.deffieux@free.fr
Hubeaux
K
K
Damphousse
M
M
Raibaut
P
P
Sheikh Ismael
S
S
Thoumie
P
P
Amarenco
G
G
Lapeyre
E
E
Jousse
M
M
D004576:Electromyography; D006801:Humans; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000503:physiopathology*; D010502:Perineum / Q000503:physiopathology*; D014549:Urinary Incontinence / Q000503:physiopathology