Dr. Mark Harper recalls his first cold-water swim 20 years ago. It was August, but the initial jolt took his breath away. The shock to his system lasted a minute or two, until he was "recombobulated and able to think about something other than the cold," Harper says. A surprise sensation replaced discomfort. "I remember getting out of the water the first time and feeling so good," says Harper, an anesthesiologist who has since researched the risks and rewards of taking a nippy dunk. Claims about the benefits of cold-water immersion date back centuries, reports the AP, with Thomas Jefferson having written about using a cold foot bath daily for 60 years.
While evidence is building around the positive health effects of a dunk in chilly water, scientific confirmation is still lacking. But Harper, who became a regular cold-water swimmer, began wondering if the brief bodily shock had clinical uses for treating depression. He cites the biological phenomenon of hormesis, in which a low-dose stressor creates a positive response. In the case of cold-water immersion, the benefits may also come from meeting people, the exercise itself, or simply taking on a challenge, he says. "I think it's all of those things, and the cold has an additive effect," Harper says. Harper says first-timers often say "the fact that I've done this means I can do anything."
Dr. Mike Tipton, a physiologist at the University of Portsmouth in England, authored a paper with Harper several years ago. One finding: The activity presents dangers, and deaths aren't uncommon. The shock of frigid water can cause people to hyperventilate and drown. But Tipton says risks can be managed:
- How cold, how long? You don't need to go to extremes to get a payoff. Entering water at a temperature between 59 degrees and 68 degrees Fahrenheit and staying for a few minutes is sufficient. Tipton says if the water is colder than that, you may see more benefit—but limit your exposure. "I wouldn't go in water much below [54 degrees], and I wouldn't stay in for much more than two minutes."
- Be safe: Tipton says he's not trying to be the "fun police" but suggests caution and a medical screening. Humans are "tropical animals" whose resting body temperature is about 97.7 degrees to 99.5 degrees. Because of that, cold-water immersion is stressful and carries risks for the cardiovascular and respiratory systems. "We don't want to stop people doing it, but we want to make sure they do it in a way that maximizes the benefits and minimizes the risks," Tipton says.
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