Ready to take the plunge?

As you prepare for that annual icy plunge into a lake, river or ocean, Dr. Chris McMullen has this advice: Enjoy the water for a few minutes, with as many people as possible. Then get out. Warm up.  

“Don’t go off by yourself and cut through the ice and jump in,” said McMullen, a UW Medicine rehabilitation medicine doctor who specializes in sports medicine.  He also suggests you check with your doctor first if you have any underlying conditions. 

New Year’s Day will see gatherings large and small stepping out from the heated comfort of their cars, shedding their heavy coats, shirts and pants, and wearing only bathing suits and towels to fight off the cold.  

Some come to wash away the old year and jump or splash into the new. Others come to take advantage of reported health benefits of a cold plunge, which range from reducing blood sugar to easing depression. 

Immersion in cold water has been well-studied in athletes and shown to reduce physical pain, said McMullen. But jumping once a year into the bay is another matter.  

“There have been these proposed health benefits to how it might help someone with their mental health and physical health,” he said. “Some of the potential benefits include reduction in stress (and) reduction in anxiety. There have been some thoughts that it might help with blood sugar regulation.” 

It’s possible that cold plunges boost immune system health, he added.   

“Repeated cold water immersion has been shown to increase the circulating concentration of certain immune system cells and proteins,” McMullen said. “The limited studies we have on the health benefits from cold immersion suggests that the people who are doing it more on a repetitive basis might see more of those benefits.”  

All this said, McMullen stresses that People with a history of heart problems, high blood pressure, hypothyroidism and Raynaud’s phenomenon (where blood flow is severely restricted to the hands or feet) should check with their doctor before taking a polar plunge. 

As for once-a-year plungers, the research slips into thin ice research-wise. 

“There may be some benefits, but we need to study this a bit more,” he said. 

Still, McMullen encourages people to give it a try, with a few precautions.  

“As benign as it may seem, in some cases, cold water immersion can be dangerous,” he said. “We know that people are more likely to drown in colder water than warmer water.” 

There's a physiological response to such immersions called "cold shock" that can affect the heart and blood pressure. Your heart rate jumps. Stress hormones spike. You gasp suddenly and may breathe erratically. Then you start to shiver. 

The body is trying to keep its core and trunk warm, McMullen said. The peripheral blood vessels constrict to shunt blood to the vital organs. This can increase heart rate and blood pressure and cause the release of hormones and neurotransmitters like cortisol and dopamine and adrenaline. All of these physiological responses happen almost immediately, McMullen added.  

Stay in the frigid water only a few minutes, McMullen emphasized, especially if you’re a first timer.  

More people have embraced the idea of plunging into cold water in recent years. Thousands of social groups report doing so on a weekly or daily basis.  

“We’ve really seen this kind of explosion on social media and influencers kind of promoting these potential benefits,” he said. “It’s a little surprising to see how popular this has become.” 

Access downloadable video files of McMullen discussing the pros and cons of a cold plunge on New Year's Day. 

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