Unraveling a Mystery: Why Do You Need to Pee After Swimming?

Have you ever experienced the sudden urge to pee after spending about 20 minutes in the water? 

Curious about what causes this phenomenon?

👋🏼 Hi!  It's me, Dr. Kelly Sadauckas.  Double Board Certified Pelvic PT to the stars, and YOUR go-to pelvic health expert on the internet. 

Today, I'd like to "dive into the details" about why swimming makes us have to pee!!

Are you ready? Me too!  Let's start, of course...with physics 🥰
 

Hydrostatic Pressure: The Aquatic Squeeze

Did you know that being submerged in water acts like a giant compression stocking for your entire body? This is due to the effect of hydrostatic pressure—the force exerted by fluid due to gravity...that gets greater the deeper the water gets (it’s why you ears hurt if you try to dive down to the bottom of a 12-foot pool). 

As we immerse yourself in water, the water's compression forces squeeze fluids back towards your torso...with the feet and ankles (or parts of our body that are in the deepest water) having the greatest “squeezing force”, our midsection having “middle compression”, and our shoulders (or the parts of our body in the shallowest water) having least compression. 

This hydrostatic pressure is fantastic for reducing swelling, and the buoyancy of the water reduces pressure on our joints, making aquatic exercise FABULOUS for all of life’s stages. But…with that amazing compression comes a shift in ‘where’ our body holds fluid…which puts the kidneys at the center of the “why we pee after swimming” mystery.

The Kidneys’ Quick Response

With your feet usually deeper than your head, they experience the most compression, pushing fluids back into your torso, resulting in a net “change in blood volume” so that our torso (midsection) now has more blood volume than it usually does (because the water is pushing it out of the limbs). 

Your kidneys, detecting this rapid increase in perceived blood volume in the midsection, kick into action, thinking you've just consumed a significant amount of water. They speed up filtration, to make more pee to clear out this ‘extra” fluid, which in turn fills up our bladder swiftly. This whole process takes about 20 minutes, leading to the initial urge to pee after being in the water for about 20 minutes.

Swimming and Peeing Mystery Solved!  

We need to pee after being in the water for 20 minutes due to our kidneys managing our changing blood volume distribution. But don’t stop reading/learning now, there’s more to understand about the intriguing effects of water immersion on multiple body systems.

Positive Side Effects: Improved Heart Function and Lower Blood Pressure

The increase in central fluid volume from water immersion benefits your heart. By having more fluid to fill up the chambers, it pumps more effectively, and your blood pressure decreases for about 2-3 hours after just 20 minutes in chest-deep water. If only we could bottle this effect for treating high blood pressure!

But the Reduced Blood Pressure & Frequent Pees Come with a Risk…

While this natural response is fascinating and generally fabulous, we do need to be cautious that our blood pressure doesn’t drop TOO fast, as we leave the pool (or hot tub).  Those of us on blood pressure medication, or with a history of lower blood pressure, should take our time exiting the water, to allow our blood vessels and heart to adapt to having to “work” to pump the blood out of the limbs again. 

Furthermore, the frequent pees, from the kidney adjustments, will also last 2-3 hours after water immersion, and can lead to dehydration if not managed. As your kidneys process liquids faster, it's crucial to stay hydrated during and after water activities. Remember to adjust your fluid intake based on factors like exercise, breastfeeding, and climate.

Key Takeaway

Getting the urge to pee in the water is entirely normal—it's your body efficiently managing blood volume and pressure. So, next time you feel the call, take a break, relieve yourself, and dive back into the fun.

Final Note:

If you frequently experience strong urges to pee in or outside the pool—like when you arrive home, hear running water, or wake up—this might indicate bladder hypersensitivity or other pelvic dysfunction. In such cases, Pelvic PT can often help, even where medications (and heaven forbid trying to cut down on your water intake) hasn’t!  Consult a Pelvic PT one:one in person or online, for bladder retraining, or consider Vag Lab, which is like a condensed version of Pelvic PT, or The Signature Series, which is a 12-week curated online course in Pelvic Wellness Info & Exercises, to learn about your pelvic muscles.  

Remember that while online or in person PT is amazing, online streamable courses allow you to approach info at your own pace, from the privacy of your own home.  And with new technology, all Pelvic Floored Courses are seamlessly streamable from your computer, phone or tablet, meaning I can always be with you, to keep you on your pelvic toes!  Just download the FREE Kajabi App (Blue K, wherever you get your apps from), and you'll have easy transition from computer to phone to tablet!

Thanks for Diving In!

xoxo, Dr. Kelly

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