What Science Says About Protocols, Adaptations, Safety

No matter how much we’d like to convince ourselves that we can skip the ice bath (or even just the ice bucket) and sip on a hot cup of coffee instead, we can’t stop hearing whispers about the potential benefits for the endurance athlete who dares to lower themselves into an icy tub.

From reduced inflammation to enhanced immunity to an all-natural mood boost, there’s been plenty of hype (and commerce) surrounding cold water immersion in recent years, under a variety of names: cold plunging, ice baths, and cold water therapy, to name a few. But is the science there to support it?

Cold water immersion (CWI) is the scientific term encompassing techniques such as ice baths (in which the water is at an implied zero degrees C) and cold plunges (which vary in length, but are often very short). To better understand if, why, and how it’s worth coaxing ourselves into such chilly water, we spoke to Dr. Aaron Petersen, Associate Professor of Exercise Physiology at Victoria University. He helped us understand the scientific consensus on CWI and provided a few tips for folks just dipping their toes into the ice-bath world.

What the science says (and doesn’t say) about cold water immersion

Beginning in the early 2000s, scientific research around CWI began to blossom. However, studies didn’t paint a clear picture of how endurance athletes should incorporate such procedures into their training schedules.

Initial studies mostly focused on the short-term recovery benefits of CWI after singular exercise sessions rather than long-term repetition. Plus, not all the studies indicated CWI to be beneficial (in fact, some reported the opposite). Over the past few decades, more research has been conducted on the long-term use of CWI, which we’ll get into momentarily.

As it stands today, the scientific literature around CWI mostly focuses on moderately active males who train two to four times each week, Petersen says. There’s not much for athletes to glean regarding how disparities in body size and composition (not to mention hormones) might alter CWI’s efficacy.

It’s therefore clear that while the research around CWI is not exactly in its nascent phase, more studies are needed to better inform endurance athletes about CWI’s benefits and optimal techniques. Moving forward, studies will need to focus on specific demographics, such as the female population, as well as athletes who are training every day at high intensity and require more finely tuned recovery techniques. Additionally, factors like the frequency and timing of CWI relative to exercise must be examined more deeply.

Admittedly, CWI’s efficacy for athletes is still rather ambiguous, so as you try it out, treat your body as a laboratory and pay close attention to what works (and doesn’t work) for you.

Short-term recovery vs. long-term training adaptations

Petersen said that if we’re talking about the short-term recovery benefits after a single exercise session, CWI appears to offer promising benefits after both resistance and endurance training. In other words, you can draw yourself an ice bath after a weights session in the gym or a long run, and you’ll reap the benefits…or will you?

“Short-term” was the key word there. “The evidence is fairly clear that frequently engaging in CWI immediately after resistance training can impair the normal adaptations to that training,” Petersen says. His own research backs this up, with findings indicating that regular CWI after resistance training lessens one’s ability to gain strength and increase muscle size. Following endurance training, however, frequent CWI seems to have a rather neutral effect.

But what is the definition of “frequent”? How often is too often? There aren’t answers to those questions yet, Petersen said. Studies on CWI’s long-term effects have usually had participants implement this recovery technique after each training session. There’s not yet substantial evidence showing whether an athlete using CWI once or twice a week will benefit from physiological adaptations.

Furthermore, research suggests that using CWI at different times of the day (and not immediately post-exercise) could alter its efficacy, but there’s not enough data to come to any conclusive theories there, either.

Your cold plunge protocol: Temperature, time, and setup

“There is currently no clear consensus on an optimal CWI recovery protocol, and there probably never will be,” Petersen says. That’s because those highly personal factors mentioned earlier – such as body size and composition, sex, age, and training patterns – all influence the working definition of “optimal.”

That’s not to say that researchers haven’t tried to wrestle an answer out of those icy waters. “For improving recovery from endurance exercise, water temperatures of 9 to 12 degrees C seem to be best when combined with immersion times of 10 to 15 minutes,” Petersen stated. That’s approximately 48 to 54 degrees F.

Petersen’s lab sets the water temperature to 10 degrees Celsius (50 degrees F) and keeps participants in the water for 15 minutes. In his words, this is “tolerable for most people.” Nevertheless, some folks need to start with smaller chunks of time, and that’s nothing to be ashamed of. Who knew that sitting still for 15 minutes could be considered a feat of endurance?

No special equipment is necessary to practice CWI, Petersen says. Simply fill a bathtub with cold water and add ice if needed to bring down the temperature (speaking from experience, it would be wise to buy bags of ice rather than spend all day emptying and refilling your freezer’s ice trays). Of course, keep a towel and some warm clothes on standby for when you’re ready to pull the plug.

Petersen also emphasized the need to adopt a positive frame of mind. It’s useful not only for cajoling yourself into the tub, but also because multiple studies indicate that CWI’s placebo effect is quite powerful. “So if you believe that CWI will be beneficial for you, then it probably will be,” he concluded.

Safety first: Risks of cold water immersion and how to start slow

As you might expect, CWI doesn’t come without its share of risks. “Immersion in cold water causes a cold shock response and results in rapid breathing and gasping, as well as elevated heart rate and blood pressure,” explained Petersen. Any athlete would do well to start with baby steps – for instance, by submerging only the legs, adding smaller amounts of ice, and staying in for shorter durations.

After getting over the initial shock, the average athlete may manage to regain control of their breath and synergize their mind and body to reap the benefits of CWI. However, those at risk for cardiovascular disease should consult their doctors before sinking into an icy tub.