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Fatigue rate of the external anal sphincter
Author(s) -
Nockolds C. L.,
Hosker G. L.,
Kiff E. S.
Publication year - 2012
Publication title -
colorectal disease
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.029
H-Index - 89
eISSN - 1463-1318
pISSN - 1462-8910
DOI - 10.1111/j.1463-1318.2011.02901.x
Subject(s) - medicine , external anal sphincter , fecal incontinence , sphincter , anal sphincter , muscle fatigue , anorectal manometry , urology , anal canal , surgery , defecation , electromyography , rectum , physical medicine and rehabilitation
Aim Studies of skeletal muscle show that fatigue rate corresponds to the proportion of fast‐twitch and slow‐twitch fibres that are present in the muscle. Limited work has been done on the fatigue rate of the external anal sphincter. We have prospectively studied fatigability of the external anal sphincter in women with faecal incontinence and women with normal bowel control. Method Anorectal manometry was measured by a station‐pull technique using a water‐filled microballoon. Fatigue rate was calculated from anal pressure measurements taken every 0.1 s over a 20‐s squeeze. Results Women with faecal incontinence ( n = 88, median −12 cmH 2 O/min) were less susceptible to fatigue than women with normal bowel control ( n = 36, median −43 cmH 2 O/min) ( P < 0.01). The external anal sphincter was less susceptible to fatigue with increasing age ( P < 0.01, r = 0.499). In women with normal bowel control and in women with faecal incontinence fatigue rate was negatively correlated with maximum squeeze pressure ( P < 0.01, r = −0.287; P < 0.01, r = −0.579). Conclusion The external anal sphincter was less susceptible to fatigue with increasing age. Women with faecal incontinence have a weaker but more fatigue‐resistant external anal sphincter. This might correspond to a higher proportion of slow‐twitch muscle fibres. Histological studies are needed to examine this hypothesis.