What's Happening?
A recent study has characterized the post-void shudder (PVS) as a distinct type of involuntary physiological reflex event, common in up to 30% of the population and affecting both genders. This phenomenon, previously described anecdotally by comedian
George Carlin and in a newspaper column, involves a brief, patterned, paroxysmal tremor predominantly in the axial upper body, occurring immediately after bladder emptying. The event typically lasts about one second and may include rotatory oscillations of the neck and torso, and quick elevations or isometric contractions of the upper body. The study, based on a 12-question survey distributed to faculty, fellows, and residents at Baylor College of Medicine, received 413 responses. It found that PVS is more common in men (58.8%) than women (22%) among respondents. Most individuals experience PVS weekly to annually, though some report daily occurrences. Similar sporadic shudders without a known trigger are also common.
Why It's Important?
The formal characterization of post-void shudder in medical literature is significant because it moves a previously anecdotal phenomenon into the realm of scientific study. This legitimization can pave the way for further research into its underlying neuroanatomic and neurophysiologic basis, potentially leading to a better understanding of involuntary reflex events in humans. The finding that PVS is more prevalent in men than women, even after adjusting for age, highlights a potential physiological difference that warrants investigation. Understanding such common, yet unstudied, bodily functions can contribute to a more comprehensive knowledge of human physiology, potentially informing future medical research or even clinical observations, especially concerning bladder function and neurological responses. This research also underscores the value of exploring everyday, seemingly minor, bodily experiences that have largely been overlooked by the scientific community.
What's Next?
The study proposes that post-void shudders are triggered by visceral sensory information from the bladder or urethra as voiding concludes, with patterned motor output mediated reflexively by brainstem and autonomic pathways. Future research is needed to elucidate the precise neuroanatomic and neurophysiologic mechanisms behind this phenomenon. Researchers plan to conduct prospective studies with more diverse and balanced populations, including pertinent medical and family histories, and objective measures of the events' duration, frequency, and somatic distribution. The study also invites further discussion and input from the medical community to advance this research. Understanding the differences in frequency between men and women, beyond anatomical variations, will be a key area of focus, potentially exploring factors like standing versus seated urination positions.
Beyond the Headlines
The formal study of post-void shudder highlights a broader trend in medical research: the increasing interest in common, yet previously uncharacterized, physiological phenomena. This approach can demystify everyday bodily experiences, moving them from folklore or anecdotal observation into scientific understanding. The comparison of PVS to other seemingly purposeless involuntary reflex events like contagious yawning or emotional piloerection suggests a potential evolutionary or vestigial objective that could offer insights into human neurological development and survival mechanisms. Furthermore, the study's acknowledgment of imprecise language surrounding 'shudder,' 'shiver,' and 'chill' in English vernacular points to the importance of precise terminology in scientific discourse, which is crucial for accurate research and communication in medicine.
