Vincent's Curtsy is a squatting technique often used by people (children, in particular) as a "holding maneuver" when they need to urinate. It involves squatting so that your heel pushes up against the perineum. A variant involves energetically crossing the legs. These maneuvers are known colloquially as the "pee dance."
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The technique is named after Dr. S.A. Vincent of Belfast City Hospital who first described it in a Sep 17, 1966 article in The Lancet
("Postural Control of Urinary Incontinence: The Curtsy Sign"
). Vincent learned of the technique from the mother of an 8-year-old girl. He wrote:
In April, 1965, an eight-year-old girl who had nocturnal enuresis and also gross diurnal frequency and urgency was being examined in the outpatient department when her mother volunteered the information that the child squatted when she had the urge to micturate. She would remain squatting for as long as twenty minutes; after this she could sometimes reach the lavatory without an "accident," but her companions at school had learned that if they pushed her over when she was in this posture she would immediately wet herself.
Source: The Lancet - Sep 17, 1966
Vincent then went on to hypothesize that children have been using this pee-holding technique for as long as kids have had a need to hold their pee, without formal recognition by the medical community, and he suggests that it may have been the inspiration for a classic yoga pose, the Maha Bandha, or "Great Binding"
Koestler had described a "Hatha Yoga technique called the Maha Bandha, or 'Great Binding,' for control of the anal and urethral canals through perineal pressure by the heel of the left foot. This well-conceived disposition of the left foot is an integral part of the classic Lotus Posture adopted by Oriental contemplatives for the past thousand years, and perhaps much longer."...
Of all the children exhibiting the "curtsy" posture only one had had instruction in the posture (from an older sister). Since all the rest learned it entirely by chance experience or by deliberate experiment, this posture may well have originated long before Hatha Yoga technique was evolved and may have been adopted since urge-incontinence first became a problem — whenever that was. Indeed, the contemplatives may have learned it from children, and the discovery, or re-discovery, may itself have taken place much longer than a thousand years ago when the "marvellous new lotus posture" was introduced.