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Updated: May 27, 2026

Measuring the Motor Aspect of Cancer-Related Fatigue using a Handheld Dynamometer
Published on: February 20, 2020
Fatigue rate of the external anal sphincter
C L Nockolds1, G L Hosker, E S Kiff
1Colorectal Surgery, South Manchester NHS Trust, UK. clairenockolds@btinternet.com
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.
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