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Immersion in cold water is not always beneficial

Polar dive

I live very close to Lake Ontario and over the past two years I have noticed that the number of people taking cold dips in the lake in the morning – during the winter – has increased dramatically. It’s no longer an oddity: I see people doing cold dives every day, and some are regulars. Usually I’m walking the dog, bundled up with a coat, hat and gloves, and right next to me people are undressing and taking cold dips, usually in groups.

Cold therapy, which proponents believe can boost the immune system and improve cardiovascular health and is simply hard to do, has become increasingly popular. In 2021, the late Harriet Hall wrote about Wim Hof, the Dutch athlete known for his ability to tolerate extreme cold temperatures, and one of the most well-known proponents of this activity. His Wim Hof ​​Method® says you will be “happier, healthier and stronger” with his method of hyperventilation, cold divers and “commitment”. Harriet’s conclusion at the time was that while this practice might reduce inflammation, it would limit a “normal protective response that promotes healing.” She concluded that most of Hof’s claims were speculation and not supported by evidence.

Since Harriet’s post, cold plunges seem to have increased in popularity, and more evidence has emerged about the benefits of this therapy. When it comes to exercise, its benefits are not so clear-cut.

First of all, it should be clear that you cannot do a double-blind, randomized controlled trial of cold therapy. Although researchers have attempted to examine objective measures, the subjective is more difficult to assess. If you just like it to do cold jumps because it makes you feel good/strong/alive/strong – then do it. There is no evidence I can present that confirms or disproves how cold bathing makes you feeling by doing it.

I should also point out that the studies I found focused mainly on cold baths and did not seem to include the hyperventilation that Hof advocates as part of his method. So this is not so much an overview of Hof’s specific recommendations, but of the act of cold diving/cold water immersion.

It’s worth summarizing what actually happens physiologically when you immerse your body in cold water. A sudden plunge can trigger a cold shock response: a rapid increase in breathing, heart rate and blood pressure, which can put pressure on the heart and even trigger heart attacks. Within minutes, the loss of heat from the body can cause other problems. Blood will flow from the extremities to the core to protect vital organs. Hypothermia can be the result. These effects can be partially mitigated or delayed by training over time – but the heat loss from the body is inevitable – it’s physics. (It should be noted that deaths have been attributed to Hof’s approach and cold plunge therapy.)

Effects on recovery after exercise

Russian and Chinese researchers completed a meta-analysis that looked specifically at fatigue recovery. Twenty studies were analyzed, including some randomized controlled trials (RCTs). Cold water immersion was defined as immersion in water ≤15°C (59℉). Control groups would typically rest, without cold immersion. They looked at the degree of recovery after intensive training (e.g. rugby, football) after 0, 24 and 48 hours. Also examined were ratings of perceived exertion, delayed onset muscle soreness (DOMS), and countermovement jump test results, as well as blood markers of exercise recovery.

The analysis showed that cold water immersion reduced DOMS at 0 hours and 24 hours, but not at 48 hours. Ratings of perceived exertion and countermovement jump improved at 0 h, but not after that. Some laboratory measures improved (that is, they were reduced), but others were unaffected. A subgroup analysis found that colder water (<10°C (<59℉)) was more effective than ≥10°C at improving countermovement jump, but had no effect on other measures, such as recovery from fatigue. There was also no difference noted between partial cleavage (waist) and full cleavage (shoulders). The authors concluded that cold water immersion immediately after exercise improved subjective symptoms such as muscle soreness and could accelerate recovery. However, because the quality of the studies was poor (which was acknowledged by the authors), it is reasonable and prudent to view these findings as interesting but not conclusive.

Effects on muscle growth

Another meta-analysis examined the effects of cold water immersion on muscle growth in subjects doing resistance training. Eight studies were included, with studies lasting 4 to 12 weeks and in adults (almost all men) aged 20 to 26 years. Some studies use untrained volunteers, others use those accustomed to resistance training. Studies looked at various strength measures, including handgrip strength, wrist flexors, as well as lower-body and full-body workouts.

All studies used cold water immersion after exercise – some exposing the upper or lower extremities, and others using full-body immersion. The water temperature was 10–15 ℃ (50–59 ℉) and the immersion time was 10–20 minutes.

Muscle size was assessed using various imaging techniques, as well as biopsy and also limb circumference.

The study found that cold water therapy combined with resistance training caused less muscle growth (hypertrophy), compared to resistance training alone. This supports the hypothesis that cold water immersion may blunt or weaken the inflammatory response, reducing muscle adaptation – and ultimately less gainz.

Inflammation is not all bad

A cold water dip may seem trendy and may even feel subjectively good, but that doesn’t mean the health benefits are certain. For those who exercise, it is important to remember that the benefits of your training are realized during the recovery period. Heavy workouts can be painful, due to damage to tissues that prompt the body to remodel and strengthen itself for the next workout. Inflammation is an expected (and desirable) outcome, even if it is painful. Blocking the inflammatory process, which a cold plunge appears to do, can slow down that recovery and adjustment process. When quick recovery is the priority, cold baths can be worthwhile and subjectively beneficial. When muscle growth is sought, the benefits of cold therapy are less clear.

Photo by Flickr user Andrey Papko used under a CC license.

  • Scott Gavura, BScPhm, MBA, RPh is committed to improving the way medicines are used and examining the profession of pharmacy through the lens of science-based medicine. He has a professional interest in improving the cost-effective use of drugs at the population level. Scott earned a Bachelor of Science in Pharmacy and a Master of Business Administration from the University of Toronto, and completed an Accredited Canadian Hospital Pharmacy Residency Program. His professional background includes pharmacy work in both community and hospital settings. He is a registered pharmacist in Ontario, Canada. Scott has no conflicts of interest to declare. Disclaimer: Any views expressed by Scott are solely his personal views and do not represent the views of current or former employers, or any organizations with which he may be affiliated. All information is provided for discussion purposes only and should not be used as a substitute for consultation with a licensed and accredited health professional.

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