WRITTEN BY WOODSIDE DIRECTOR OF TRAINING, JOHN BEANE
The Science of Hot and Cold for Recovery
As we have discussed in a few previous articles, recovery is often the missing link in a well-rounded training program. While training, nutrition and sleep receive the most attention, targeted recovery strategies can make a significant difference in performance, longevity and overall well-being. Among these strategies, contrast therapy, the practice of alternating between hot and cold exposure has been used for centuries by various cultures and is still widely employed by athletes, rehabilitation professionals and wellness practitioners. The rationale behind contrast therapy is straightforward: by rapidly shifting between hot and cold, the body experiences vascular, neurological and metabolic changes that may accelerate muscle recovery, reduce inflammation and promote overall resilience. But while contrast therapy is commonly used, its effectiveness is still debated. Does it truly enhance recovery, or is it just another wellness trend?
In this article, we will take a deep dive into the mechanisms of contrast therapy, exploring the physiological effects of heat and cold, its potential benefits, common misconceptions and evidence-based protocols for its application. Our hope is that the evidence-based protocols included at the end of this article will help answer any questions you have regarding time spent in hot vs. cold temperatures and free up some time for other components of your program. As is the case with many other wellness interventions, it is easy to fall into the “more is better” trap.
Understanding Contrast Therapy
Contrast therapy is fundamentally based on temperature-induced changes in blood circulation and nervous system activity. The application of heat leads to vasodilation, expanding blood vessels and increasing blood flow to muscles and tissues. Conversely, cold exposure induces vasoconstriction, restricting blood flow and directing circulation toward the body’s core. When alternating between these two extremes, the body undergoes a pumping effect, where blood flow rapidly shifts, enhancing circulation and possibly aiding in the removal of metabolic byproducts and inflammatory markers.
Imagine your blood circulation as a highway system, responsible for delivering oxygen and nutrients and removing waste from your muscles just like highways transport goods and clear debris from a busy city.
- Heat is like a green light at every traffic signal. When you apply heat, your blood vessels dilate (expand) like a city opening all its roads. Traffic flows freely, and delivery trucks (oxygen and nutrients) can get to where they’re needed quickly, while garbage trucks (waste products like carbon dioxide) can easily remove debris.
- Cold is like a red light. When you apply cold, your blood vessels constrict (narrow), momentarily slowing down circulation and directing blood to the body’s core just like a traffic system stopping cars temporarily to clear congestion.
Now, imagine alternating between heat and cold this is like a traffic light changing rapidly between green and red, creating a pumping effect. Blood rushes in during the “green light” (heat) and then gets squeezed out during the “red light” (cold), helping to flush out metabolic waste and bring in fresh nutrients more efficiently. This pumping action is why contrast therapy feels rejuvenating. It flushes the system, refreshes your muscles and resets your body’s circulation much like an efficient traffic system keeps a city running smoothly. This method has been practiced for centuries in different cultures. Scandinavian countries have long incorporated sauna and cold plunge cycles as part of their wellness traditions, while Japanese bathhouses often include alternating hot and cold baths. Similarly, in the realm of sports recovery, contrast baths have been a staple in athletic training rooms for decades, often used after high-intensity training or competition. However, while anecdotal evidence and traditional practices support the benefits of contrast therapy, modern research has provided a more nuanced perspective, revealing both its strengths and limitations.
The Physiology of Heat and Cold Exposure
Physiological Effects of Heat
Heat therapy, commonly applied through saunas, hot water immersion, heating pads or infrared light, induces a cascade of physiological changes aimed at enhancing circulation, reducing muscle stiffness and promoting relaxation. One of the most immediate effects of heat is vasodilation, where blood vessels expand, increasing oxygen-rich blood flow to peripheral tissues. This increase in circulation facilitates the delivery of essential nutrients to muscles while promoting the clearance of metabolic waste products, such as carbon dioxide and hydrogen ions, which accumulate during exercise.
Heat also has a profound impact on the nervous system and hormonal response. It stimulates the parasympathetic nervous system, leading to a relaxation effect that can reduce stress and promote a sense of well-being. Additionally, heat exposure triggers the release of heat shock proteins (HSPs), which play a crucial role in cellular repair and protection against oxidative stress. These proteins help fortify cells against damage and have been studied for their role in longevity and disease prevention.
Physiological Effects of Cold
In contrast, cold exposure elicits an entirely different set of physiological responses, primarily centered around vasoconstriction, metabolic activation and inflammatory control. When the body is exposed to cold, blood vessels constrict, redirecting circulation away from the extremities toward the vital organs to conserve heat.
This process, known as peripheral vasoconstriction, helps reduce swelling and tissue inflammation, making cold therapy particularly useful for managing acute injuries and muscle soreness. Cold exposure also has a profound effect on the nervous system, specifically by increasing levels of norepinephrine, a neurotransmitter associated with heightened focus, mood elevation and pain reduction. Studies have shown that cold water immersion can increase norepinephrine levels by two- to five-fold, leading to enhanced alertness and cognitive function.
The Benefits of Contrast Therapy
Enhanced Circulation
By cycling between vasodilation and vasoconstriction, contrast therapy helps drive oxygen-rich blood deeper into tissues while simultaneously flushing out metabolic waste. This increased circulation delivers essential nutrients to recovering muscles and supports tissue repair. Over time, this process can also improve vascular health, benefiting not only athletes but individuals managing circulatory issues.
Reduction in Muscle Soreness
DOMS is a common post-exercise issue, often leaving athletes feeling stiff and fatigued. Contrast therapy may alleviate soreness by promoting muscle relaxation (heat) while controlling excessive inflammation (cold). Some studies suggest that contrast therapy may reduce post-exercise recovery times, allowing for higher training frequency.
Modulation of Inflammation
While acute inflammation is necessary for adaptation, excessive inflammation can prolong recovery. Cold exposure suppresses inflammatory markers, while heat promotes nutrient transport and tissue repair. This balanced inflammatory response can help athletes recover faster without completely blunting their physiological adaptation.
Nervous System Regulation
Alternating between cold-induced sympathetic activation and heat-induced parasympathetic activation creates a powerful reset for the nervous system. This is beneficial for individuals experiencing chronic stress, training fatigue, or nervous system dysregulation, as it helps recalibrate autonomic function.
Limitations + Misconceptions
It Does Not “Flush Out” Lactic Acid
Lactic acid is cleared naturally within an hour after exercise, making the idea of contrast therapy “flushing it out” a persistent myth. While contrast therapy can improve circulation, it does not directly impact lactic acid removal.
Cold May Blunt Muscle Growth
Several studies have found that immediate cold exposure post-strength training can suppress muscle protein synthesis, which is crucial for hypertrophy. For those focusing on muscle growth, delaying cold exposure for at least 4-6 hours post-workout is recommended. Cold therapy reduces muscle temperature, which slows down enzymatic reactions and cellular activity that drive muscle protein synthesis (MPS). Studies have shown that cold water immersion (CWI) immediately after resistance training can significantly reduce MPS compared to passive recovery.
- A study by Roberts et al. (2015) found that cold water immersion reduced long-term strength and muscle hypertrophy in resistance-trained individuals by impairing MPS and satellite cell activation.
- Cold therapy inhibits the mTOR pathway, a crucial regulator of MPS and muscle growth.
Since muscle protein turnover is temperature-dependent, rapidly cooling the muscles after training slows down the entire repair and rebuilding process, which can negatively impact long-term adaptations.
Individual Responses Vary
Not everyone experiences the same benefits from contrast therapy. Factors like genetics, training type and personal tolerance play a significant role. While some individuals report enhanced recovery, others find it unnecessary or even counterproductive.
More Research is Needed
Although contrast therapy is widely used, long-term studies are still lacking. While current research supports short-term benefits, more robust studies are needed to determine its effectiveness for injury prevention and overall performance enhancement.
Science-Backed Contrast Therapy Protocols
While contrast therapy can be a powerful recovery tool, it’s important to ease into it gradually, especially if you’re new to extreme temperature exposure. Just like you wouldn’t jump into an advanced workout without proper preparation, your body needs time to adapt to the alternating heat and cold stressors. Starting too aggressively such as jumping straight into an ice bath after a long sauna session can be overwhelming for your nervous system and may lead to dizziness, excessive fatigue or even a stress response that negates the benefits of recovery. A good rule of thumb is to begin with shorter exposure times and milder temperatures, then gradually increase intensity as your body acclimates.
Additionally, it’s crucial to avoid spending excessive time in either temperature extreme. Prolonged heat exposure especially in high-temperature saunas or hot tubs can lead to dehydration, overheating and an increased risk of heat exhaustion. On the other hand, staying in cold immersion too long can cause a dangerous drop in core body temperature, excessive vasoconstriction or even hypothermia. The goal of contrast therapy is balance—exposing the body to enough temperature variation to stimulate beneficial adaptations without overloading the system. Pay close attention to how your body responds and always prioritize safety over intensity.
Protocols
- A standard contrast therapy protocol involves 3-4 minutes of heat (100–104°F) followed by 1 minute of cold (50–60°F), repeated for 3-5 cycles.
- For sauna and cold plunge, a common approach is spending 10-15 minutes in a sauna, followed by 2-3 minutes in a cold plunge, repeated for 2-3 rounds.
Please take a cleansing shower when transitioning between different spaces.
To wrap up, Contrast Therapy is a powerful and time-tested recovery method that leverages the physiological effects of heat and cold exposure to enhance circulation, reduce muscle soreness and regulate the nervous system. While research supports its benefits, it’s not a magic bullet. Rather, it should be used as one tool in a well-rounded recovery strategy alongside proper training, sleep and nutrition. Ultimately, the best recovery method is the one that supports your specific goals and allows you to perform at your best over the long run.
Our team of Trainers can help you create a plan for incorporating contrast therapy into your fitness routine. To learn more click here or email us.
References
Bleakley, C. M., Costello, J. T., & Glasgow, P. D. (2013). Contrast water therapy and exercise-induced muscle damage: A systematic review and meta-analysis. Physical Therapy in Sport, 14(3), 144-153. https://doi.org/10.1016/j.ptsp.2012.05.002
Sellwood, K. L., Brukner, P., Williams, D., Nicol, A., & Hinman, R. (2007). Ice-water immersion and delayed-onset muscle soreness: A randomized controlled trial. British Journal of Sports Medicine, 41(6), 392-397. https://doi.org/10.1136/bjsm.2006.033985
Higgins, T. R., Cameron, M. L., & Climstein, M. (2011). Acute response to hydrotherapy after a simulated rugby match. Journal of Strength and Conditioning Research, 25(3), 696-702. https://doi.org/10.1519/JSC.0b013e3181cc237e
Versey, N. G., Halson, S. L., & Dawson, B. T. (2013). Effect of contrast water therapy duration on recovery of cycling performance: A dose-response study. European Journal of Applied Physiology, 113(1), 27-38. https://doi.org/10.1007/s00421-012-2400-0
Peake, J. M., Roberts, L. A., Figueiredo, V. C., Egner, I. M., Bastiani, Y., Cameron-Smith, D., & Markworth, J. F. (2017). The effects of cold-water immersion and contrast water therapy on recovery following resistance exercise. Journal of Strength & Conditioning Research, 31(8), 2083-2095. https://doi.org/10.1519/JSC.0000000000001760
Ihsan, M., Watson, G., & Abbiss, C. R. (2016). What are the physiological mechanisms underlying post-exercise cold water immersion for recovery? A systematic review. Sports Medicine, 46(8), 1095-1109. https://doi.org/10.1007/s40279-016-0477-6
Merrick, M. A., Jutte, L. S., & Smith, M. E. (2003). Cold modalities with different thermodynamic properties produce different surface and intramuscular temperatures. Journal of Athletic Training, 38(1), 28-33. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC164401/
Yamane, M., Ohnishi, N., & Matsumoto, T. (2015). Post-exercise leg and arm cooling impairs gains in whole-body muscle mass and strength training adaptations. European Journal of Applied Physiology, 115(7), 1515-1526. https://doi.org/10.1007/s00421-015-3149-4
Dupuy, O., Douzi, W., Theurot, D., Bosquet, L., & Dugué, B. (2018). An evidence-based approach for choosing post-exercise recovery techniques to reduce markers of muscle damage, soreness, fatigue, and inflammation: A systematic review with meta-analysis. Frontiers in Physiology, 9, 403. https://doi.org/10.3389/fphys.2018.00403
Leeder, J. D., Gissane, C., van Someren, K. A., Gregson, W., & Howatson, G. (2012). Cold water immersion and recovery from strenuous exercise: A meta-analysis. British Journal of Sports Medicine, 46(4), 233-240. https://doi.org/10.1136/bjsports-2011-090061
