Once matter passes through the bowels, the effectiveness of the anal sphincter is also thought to be affected by intense exercise. The sphincter has two rings — first, a less powerful, outer, voluntary ring, and second, a more powerful, inner, involuntary ring. As other parts of the body are prioritised during all-out efforts, this involuntary ring weakens — and triggers the final, messy repercussion of faecal incontinence.
~ Jacob Whitehead via The Athletic

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