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New Sleep Hack: Contrast Showers, What They Are and How They Improve Sleep

July 14, 2020 | Posted by Caroline McMorrow
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A cold shower before bed to speed the lowering of core body temperature in preparation for a successful night’s sleep? Or rather, a hot shower to relax body tension, improve blood circulation, and induce a stress-free mindset before nodding off for the day? 

I’m sure you’ve heard claims to support both, as we have too. Below is a breakdown of the key benefits of hot and cold showers to help you navigate the information available on the topic.

Hot Showers

Cold Showers

Loosens up stiff muscles

Elevates endorphin release

Reduces anxiety 

Boosts metabolic performance

Clears nasal cavities

Improves circulation

Promotes healthy skin by clearing toxins

Strengthens the immune system

To sum, both cold and hot showers can likely serve you well depending on the time of day and context in which you decide to take them; however, when it comes to preparing for sleep, scientific-based evidence has shown that a combination of both is actually the way to go.

What is Contrast Water Therapy? 

Water as therapy dates back to ancient cultures as various techniques were once used in traditional medicine approaches to remedy conditions such as fibromyalgia, osteoarthritis, insomnia and rheumatoid arthritis. In the modern age, contrast therapy/immersion is recommended in clinical practice to treat symptoms associated with inflammation. Contrast water therapy consists of alternating between cold and warm/hot bath immersion for set intervals. It has been frequently used in elite athletics to delay onset of muscle soreness; it is suggested to reduce swelling by channeling body-wide variance between peripheral vasoconstriction and vasodilation. In other words, the discrepancy between blood vessels constricting and dilating leads to increased blood flow. 

Current theories suggest that swelling is reduced as a result of contrast water therapy because constriction increases pressure in blood vessels, causing fluid to move with the valves in veins, thereby preventing backflow of fluid. This has been validated by Coffey et al. who investigated the use of contrast water therapy after exercise and showed that post-activity lactate was lowered and the subjective perception of recovery improved. An additional study demonstrated that contrast water therapy accelerated the rate at which plasma lactate declined after intense anaerobic exercise.  

So maybe you are…or aren’t an athlete looking to engage in optimal muscle recovery through the use of contrast water therapy. The best implications of this practice go far beyond simply preventing muscle soreness and provide benefits for all individuals—especially those looking to speed their preparation for a strong night’s sleep. 

How Do Contrast Showers Work? 

The concept behind contrast water therapy has been transferred to a place that we all spend time in: the shower. Many people already intentionally take a shower before bed for cleansing purposes, to prepare their mind for rest, or as part of their daily ritual; but what if what was originally thought of as “just part of a routine,” turned out to be much more than that? 

According to the technique developed by Dr. Sebastian Kneipp, one of the founders of naturopathic medicine, the best way to fully grasp the benefits of hydrotherapy is to start with a warm/hot shower, and then diverge to cold; this is what has been popularly coined as a contrast shower. According to his approach, by beginning with a hot shower, blood vessels throughout the body dilate and blood circulates from the internal core to the extremities of the body; a quick shift to cold immersion causes these same vessels to constrict, which pumps blood back toward the center. This fluctuation can also have a healing and detoxifying effect by moving bodily materials where they may have been partially stagnate beforehand. The concept behind this wavering “pumping action” is that more efficient blood flow can occur, allowing for alterations in tissue temperature, and reduction of muscle spasms and inflammation

How Contrast Showers Improve Sleep

For the average individual, a 0.5 to 1° F decline in body temperature is expected to occur roughly an hour before their usual bed time. This drop in core temperature serves as a natural signal for the body to begin to prepare for sleep, and tends to coincide feelings of tiredness, which is suggested to be related to a timely release of melatonin. You can accelerate the decline of your internal temperature with the use of contrast showers. Unlike cold showers alone, contrast showers do not overstimulate the senses or enhance alertness.  

Experts recommend finishing the contrast cycle on hot, as blood will come rushing out of the dilated vessels and toward various muscles and organs, thereby taking heat away from the center of the body. A contrast shower is also more favorable in comparison to an exclusively warm/hot bath or shower before bed as it allows you to avoid becoming overheated. A primary critique on taking hot baths or showers before preparing for sleep is that if you do not allow for enough time (roughly 1-2 hours) to completely cool down, you actually slow your ability to ease into a restful and prolonged sleep. 

In addition to expediting the body’s core temperature decline to align with your ideal circadian rhythm, a 2016 study presented promising results that hot-to-cold contrast showers may support a healthier immune system response; it is meaningful to note that part of this may be potentially linked to improved sleep patterns in general by partaking in the intervention of contrast showers for 30 consecutive days. Needless to say, the results showed a 29 percent reduction in absence from work due to sickness out of a 3,018 participant sample group, ages 18 to 65. 

How to Start Using Contrast Showers

If you’re intrigued by the physiological evidence behind this sleep performance hack, here are the simple steps to successfully execute a contrast shower: 

  • Once entering the shower and reaching a comfortable state, turn the water temperature up to as hot as you can reasonably endure for 60 seconds. When the 60 seconds is up, turn the water temperature down to as cold as possible and wait for another full minute. 
  • Complete this alternating minute rotation between hot and cold for 3-5 full cycles. 
  • It is ideal to finish the rotation on hot. Try to not exceed one full minute on the final hot immersion, since the objective is to not overheat the body. 
  • If you’re looking for more specific guidelines on when to do a contrast shower, researchers in the Cockrell School of Biomedical Engineering at The University of Texas at Austin found that bathing/showering 1-2 hours before bedtime led to improvements in sleep quality, including a decrease in the amount of time that it took to fall asleep. 
  • Make contrast showers a consistent part of your night time routine to prepare the body for sleep and help relax your mind.

The Key Takeaway on Contrast Showers

In sum, contrast showers can be a great way to reap both the benefits of hot and cold showers without overstimulating or overheating our bodies before bed. Contrast showers should be part of a nightly wind down routine for optimal sleep. Try them for at least month, and monitor the impact on your sleep by evaluating your sleep quality in the Eight Sleep app.

Caroline McMorrow is a contributing writer for Eight Sleep. Caroline is a recent graduate of the University of Southern California with a Bachelor’s degree in Health & Human Science, and two minors in Performance Science and Occupational Science and Therapy. While at USC, Caroline was a research assistant at the USC Brain and Creativity Institute, primarily focused on embodied cognition, the contextual effects of empathy and the gut-brain connection.

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