Take the plunge to elevate your recovery with contrast therapy

Contrast therapy is the latest recovery approach dominating social media feeds, with the trend already evolving into a significant social phenomenon, with specialised “contrast clubs” and communal bathhouses replacing traditional nightlife as a sober, health-focused way to bond.

Turning up the heat is often coupled with ice bath immersions in a practice known as hot-cold contrasting, or contrast therapy, which research¹ shows can improve post-exercise recovery by reducing muscle damage, fatigue, and soreness. 

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Contrasting results

Contrast therapy works by promoting vasodilation from heat (thermotherapy) and vasoconstriction from cold (cryotherapy) to create a “pumping action” that helps to improve circulation, manage swelling, and aid lymph drainage and exercise metabolite removal¹. The therapy also helps to improve joint range of motion¹.

By cycling through vasodilation in the heat and vasoconstriction in the cold, the practice aims to flush metabolic waste, reduce inflammation, and accelerate muscle repair, making it a favourite among athletes and “biohackers” alike.

Available evidence² shows that contrast therapy is superior to using passive recovery or rest after exercise, with greater effects among serious and elite athletes who are subjected to higher training loads. 

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Bring the heat

Studies³ show that thermotherapy can support muscle recovery by increasing blood flow, promoting healing, and reducing muscle soreness through mechanisms like vasodilation and increased heat shock protein (HSP) expression. 

Thermotherapy is effective when used before exercise to prepare muscles and after exercise to speed recovery, with some research indicating it may be more beneficial than cold therapy immediately after intense activity.

There are also potential benefits associated with regular sweating, such as better natural detoxification. The skin is technically the body’s largest elimination organ, supporting the kidneys and liver by bringing certain toxins to the skin’s surface for removal. However, the skin’s contribution to removing toxins is minor compared to the kidneys.

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The cold, hard truth

Cryotherapy (specifically whole-body cryotherapy, or WBC) acts directly on muscles, particularly the extremities, causing vasoconstriction. As the body reacts to the extreme cold, it diverts peripheral blood flow to internal organs.

This promotes the removal of exercise metabolites and other by-products from muscle tissue, where they travel in the bloodstream and are more effectively expelled through the kidneys and liver.

Cryotherapy also works indirectly on the autonomic nervous system (ANS)⁴ and endocrine (hormonal) systems to more rapidly restore homeostasis and improve function.

Cryotherapy supports recovery primarily by modulating the ANS, shifting it toward a state of rest and repair. The initial, brief exposure to extreme cold, such as in whole-body cryotherapy, is an acute stressor that triggers a “fight-or-flight” response, which is mediated by a branch of the ANS – the sympathetic nervous system (SNS).

This initial stress triggers the release of stress hormones and neurotransmitters, like norepinephrine and adrenaline, which can lead to a temporary increase in alertness and mood elevation.

The key to cryotherapy’s recovery benefit lies in the subsequent, compensatory response, which is a shift toward the other branch of the ANS, the parasympathetic nervous system (PNS), which triggers the “rest-and-digest” state. This elevated parasympathetic response accelerates recovery following intense physical exertion.

The indirect impact also stems from the release of powerful hormones that aid the recovery and rebuilding process, such as noradrenaline (which helps reduce inflammation)⁴ and testosterone (which boosts strength and anabolism)⁵.

Cryotherapy’s hormonal benefits include:

• Increased release of noradrenaline⁴
• Increased release of testosterone⁵
• Reduces cortisol levels with prolonged use ⁶

Cold plunging

 Without access to a WBC chamber, cold water therapy requires immersing your body in water that is 15°C or colder. This can include ice baths, cold showers or outdoor swimming in cold or icy climates.

How to prepare an ice bath at home:

1. Add cold water to a bathtub or a large plastic drum, leaving room for ice.
2. Slowly add ice to the water while stirring to distribute the cold evenly.
3. Use a thermometer to ensure the water reaches your target temperature (7-10°C). This can take around 10-20 minutes.
4. Set a timer: Limit your time in the ice bath to 10-15 minutes for safety. Use a timer to keep track.
5. Enter slowly: Step into the ice bath gradually, allowing your body to adjust to the cold. Avoid sudden plunges.

Added benefits

There is also evidence to suggest that cryotherapy has a positive impact on your immune system, which can also support recovery.

Results from a study⁷ published in the Journal of Applied Physiology indicated “that acute cold exposure has immunostimulating effects” that increase the production of immune cells known as natural killer (NK) cells.

A team of researchers from the University of Portsmouth also found that taking daily cold showers increased the number of disease-fighting white blood cells⁸.

Other studies have revealed that acute cold exposure stimulates the production of immune cells, such as natural killer cells. For instance, one study⁹ proved that six weeks of six-minute cold water immersions at 14°C, repeated three times a week, improved the immune system.

Researchers determined that the cold initiated a “fight or flight” response, which triggered an immune response – a “small, but significant, increase in the proportions of lymphocytes”, which are infection-fighting cells.

References

1. Leonardi G, Portaro S, Milardi D, Bonanno F, Sanzarello I, Bruschetta D, Sconza C, Tisano A, Fontana JM, Alito A. Mechanisms and Efficacy of Contrast Therapy for Musculoskeletal Painful Disease: A Scoping Review. J Clin Med. 2025 Feb 21;14(5):1441. doi: 10.3390/jcm14051441. PMID: 40094855; PMCID: PMC11900007.
2. Bieuzen F, Bleakley CM, Costello JT. Contrast water therapy and exercise induced muscle damage: a systematic review and meta-analysis. PLoS One. 2013 Apr 23;8(4):e62356. doi: 10.1371/journal.pone.0062356. PMID: 23626806; PMCID: PMC3633882.
3. Kim K, Monroe JC, Gavin TP, Roseguini BT. Local Heat Therapy to Accelerate Recovery After Exercise-Induced Muscle Damage. Exerc Sport Sci Rev. 2020 Oct;48(4):163-169. doi: 10.1249/JES.0000000000000230. PMID: 32658042; PMCID: PMC7492448.
4. Louis J, Theurot D, Filliard JR, Volondat M, Dugué B, Dupuy O. The use of whole-body cryotherapy: time- and dose-response investigation on circulating blood catecholamines and heart rate variability. Eur J Appl Physiol. 2020 Aug;120(8):1733-1743. doi: 10.1007/s00421-020-04406-5. Epub 2020 May 30. PMID: 32474683; PMCID: PMC7340648.
5. Naylor AS, Edwards BJ, Robertson CM. Effects of treatment dosage of whole-body cryotherapy upon post-match recovery of endocrine and biochemical markers in elite rugby league players: An experimental study. Health Sci Rep. 2023 Apr 19;6(4):e1227. doi: 10.1002/hsr2.1227. PMID: 37091363; PMCID: PMC10114078.
6. Lombardi G, Ziemann E, Banfi G. Whole-Body Cryotherapy in Athletes: From Therapy to Stimulation. An Updated Review of the Literature. Front Physiol. 2017 May 2;8:258. doi: 10.3389/fphys.2017.00258. PMID: 28512432; PMCID: PMC5411446.
7. Immune changes in humans during cold exposure: effects of prior heating and exercise. J App Physiol. 1 August 1999. https://doi.org/10.1152/jappl.1999.87.2.699.
8. Habituation of the initial responses to cold water immersion in humans: a central or peripheral mechanism? Journal of Physiology (1998), 512.2, pp. 621628 621
9. Activation of NK Cells in Subjects Exposed to Mild Hyper- or Hypothermic Load. Journal of Interferon Research. Published Online: 4 May 2009. https://doi.org/10.1089/jir.1988.8.393