Benefits Of Cold Water Therapy

Introduction

Every year on the morning of New Year’s Day, thousands of Scots gather to continue a tradition that’s been going on since 1986: the Loony Dook. Dressing up in wacky fancy dress, people take a refreshing ‘dook’ (Scottish for ‘dip’ or ‘plunge’) on beaches across the country. Not only does this fun tradition help stave off the New Year’s Eve (or ‘Hogmanay’) hangover and raise money for charity, but it may also have some real health benefits. 

Cold water therapy has been used by humans for hundreds of years as a generic ‘cure-all’ to relieve pain, or just for relaxation. However, recent research suggests cold water therapy offers several health benefits, such as improved cardiovascular health, mental health, weight management, and potentially, enhanced immune function. This article will go through these benefits, and tell you how you can use cold water therapy to improve your health and wellbeing.

Figure 1. Scots taking part in the Loony Dook.  The image above is licensed under Wikimedia Commons, found here.

What is cold water therapy?

Cold water therapy, as the name suggests, uses exposure to cold water to provide health benefits such as: 

• Reducing muscle soreness post-exercise
• Reducing muscle recovery time post-exercise
• Pain relief
• Improving mood
• Improved resilience to stress 
• Increased alertness and energy
• Managing weight

It also has some other less-researched benefits that we will touch on later. Cold water therapy can be implemented through cold showers, cold water immersion (like an ice bath or outdoor swimming), contrast therapy (alternating hot and cold water), cryo chambers, or the Wim Hof method.¹

Physiological responses to cold water

Let’s first discuss how our body normally responds to cold water, before addressing how these changes may benefit our health. 

Improves circulation

When we first get into cold water, our body detects this shock and initiates a stress response. The blood vessels in our skin constrict (vasoconstriction), and the pressure of the water pushes against the vessels, redirecting blood to our core.² Our heart rate also rises, increasing the blood flow to our organs and allowing our blood to pick up more oxygen and nutrients from our lungs and digestive system. We also begin to shiver as our muscles contract rhythmically to generate heat. All these changes ensure our organs receive lots of heat, oxygen, and nutrients, keeping them alive and functioning.³

Once we get out of the water, our peripheral blood vessels relax and open up (or vasodilate). This causes a rebound effect, allowing oxygen and nutrient-rich blood to return to our extremities, improving circulation around our muscles and skin.⁴

Increases metabolism

To stay warm in the cold, the body needs to generate more heat, which it can do by shivering and by using chemical processes inside our cells. To do this the body needs more energy - and cold exposure can increase our metabolism by as much as 350%.⁵ By increasing our metabolism, the body can actively acquire energy from free glucose, stored glucose, or fat cells. We have two types of fat; brown and white fat tissue. Brown tissue is particularly good at producing heat (or ‘thermogenesis’), so the body will start converting white fat cells to brown, which are then used to generate heat.⁶

Stimulates release of signalling molecules

As well as physiological and metabolic changes, cold exposure stimulates the release of signalling molecules like noradrenaline and dopamine. These chemicals function both within the brain and the rest of the body, with different effects. Scientists have shown that cold exposure increases levels of noradrenaline and dopamine in the blood by 530% and 250%, respectively,, and these increases seem to persist for a long time afterwards.⁵ Within the blood, noradrenaline and dopamine are part of the sympathetic nervous system, which controls our ‘fight-or-flight response’, which controls responses to stress. As such, it is responsible for changes like increased heart rate and vasoconstriction, explaining why we see these effects with cold exposure.⁷ While the release of these chemicals in the brain during cold water therapy has not been thoroughly studied, there seems to be increased noradrenaline release in the brain,⁸ and this could explain some of the mental health benefits we will discuss later.  

Pain and exercise recovery

So what do all these changes in the body mean for our health? The most established benefit is improving recovery and reducing muscle pain after exercise. 

Reduces muscle soreness

In the following hours and days after exercise, many people find their muscles are sore and stiff, likely due to muscle damage and inflammation.⁹ Delayed-onset muscle soreness (DOMS) is particularly common, peaking around 24-48 hours after exercise.¹⁰ To combat this soreness, many athletes participate in cold water therapy.

Scientists have suggested a few ways cold water therapy could help, including:

1. The improved circulation to the muscles after we get out of cold water helps to clear out fluid build-up in the muscles more quickly.
2. The improved circulation to the muscles reduces inflammation.¹¹
3. The cold decreases how quickly your nerves signal to your brain, and how sensitive they are to pain. Both of these result in less pain.²

While a few studies found cold water therapy to have no impact in reducing muscle soreness, in general, research supports its use, as shown by a study analysing the results of many other studies (known as a meta-analysis).^12,13,14 

This pain reduction also has clinical applications. For example, rheumatoid arthritis symptoms can be treated with contrast therapy.¹⁵

Speeds up exercise recovery 

As well as soreness, many athletes feel weaker after exercise as their muscles recover. Research suggests cold water therapy may speed up this recovery and allow athletes to return to peak form more quickly. Another meta-analysis found that participating in cold water therapy for less than five minutes increased the recovery of muscle power and the athlete’s perceived recovery. This is likely due to the increased circulation and oxygen supply to the muscles.⁸

While this is useful for athletes, cold water therapy seems to impair improvements in strength, endurance, or muscle growth made during exercise.¹⁶ Waiting 6-8 hours after training could avoid this impairment while still aiding recovery.

Mental health benefits

Mood enhancement

Cold water therapy may also provide mental health benefits. A survey comparing 100 people who took regular paddles in the sea in winter, against 107 who did not, showed that swimmers had significantly lower reported stress.¹⁷ While the cause of this isn’t certain, the increased noradrenaline and dopamine levels in the blood could reflect similar increases in the brain, where dopamine is known to evoke feelings of pleasure as part of our reward system.

Improving resilience 

As well as reducing stress in the short term, cold water therapy may improve our resilience to stressful events in our day-to-day lives. By choosing to expose ourselves to stressful events, we use our conscious mind to fight against our natural reflex to avoid the stressor (i.e. get out of the cold water), practising what some refer to as ‘resilience’ or ‘grit’. In a quote from Professor Andrew Huberman, a neuroscientist at Stanford University, he states:

“[resilience] is a skill that carries over to situations outside of the deliberate cold environment, allowing you to cope better and maintain a calm, clear mind when confronted with real-world stressors. In other words, deliberate cold exposure is great training for the mind.”

Improves alertness and focus

When we get in cold water, our ‘fight-or-flight response’ kicks in. This sets off many different changes in our body to help us deal with a stressful event, including increasing our alertness, focus, and energy. These changes seem to extend to cold water therapy, as those who took a five-minute cold water immersion reported markedly increased alertness in a questionnaire.¹⁸ Taking part in some cold water therapy before a bout of intensive work could help you power through that all-important report for your boss!

Weight and diabetes management

To keep us warm during cold water therapy, our metabolism has to go into overdrive, using our sugar and fat stores to provide heat energy. This has been shown in healthy, obese, and type 2 diabetic humans.¹⁹ Cold water therapy also seems to increase our body’s sensitivity to insulin.²⁰ Insulin is the hormone that causes our cells to take glucose from the blood and use it for energy. The cells of type 2 diabetics aren’t as able to respond to insulin as healthy cells, so using cold water therapy to sensitise our cells to insulin could be a real benefit to these patients. 

While the amount of calories burnt during cold water exposure isn’t significant enough to completely replace your diet or exercise routine, it will still help with weight management and/or weight loss. It MAY lead to a more sustained increase in metabolism, and help convert more of our white fat tissue to healthier brown tissue in the long term.²⁰ However, more research is needed to show if cold water therapy is powerful enough to have a noticeable benefit in helping people lose weight or manage obesity and diabetes. 

Other suggested benefits 

Besides the established benefits we’ve discussed so far, cold water therapy may also lead to better sleep and a stronger immune system.^21,22 However, the evidence supporting these benefits is either limited or contradictory. For example, one study suggested that people who swim outdoors regularly in the winter get fewer respiratory infections than people who don’t.²² However, this study compared swimmers to non-swimmers, so their stronger immune system may have been due to more exercise rather than the cold water.²³ Indeed, many other studies investigating this have shown no benefit.²⁴ 

Summary

Cold water therapy is the practice of exposing yourself to cold water to benefit your health and well-being. While the benefits have historically been anecdotal, research suggests many of these effects have real scientific backing. Here, we’ve outlined how cold water therapy can speed up recovery and aid muscle soreness for athletes, and help manage diseases like obesity, type 2 diabetes and arthritis. It can also improve our mood, make us more resilient to challenges in our day-to-day life, and improve our focus with intensive work. So the next time you’re disappointed that the hot water runs out just before your morning shower, remember - it might actually be a good thing!