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Science Behind Cryotherapy

Joe Fleming provides an overview of the science behind cryotherapy for injury treatment.

Incur an acute soft tissue injury as an athlete, and within minutes you are guaranteed to be administering cold therapy, or cryotherapy, for relief. For decades, athletes and doctors have seen the positive effects of applying something as simple as an ice pack to an injury like a sprained ankle - a modulation in swelling, temporary pain relief, decreased inflammation, and even a sped-up recovery.

The science behind how the body reacts to the local application of cold, however, is continuing to evolve. Do not miss this essential guide to the physiological effects of cryotherapy:


The local application of cold to the body immediately results in a narrowing of the blood vessels at the site of application. This blood vessel shrinkage, also known as vasoconstriction, quickly cuts down the flow of blood to the affected area. According to research[1], vasoconstriction can effectively lower microcirculation by upwards of 60% and even persist up to 30 minutes after cooling has ceased. Reduced blood flow helps prevent excess blood from circulating into traumatized tissues and accumulating, which can contribute to swelling and bruising.

How do the blood vessels know to constrict? Essentially, cold receptors on the skin trigger the sympathetic nervous system to release neurochemicals, like norepinephrine, a notably strong vasoconstrictive agent, that induce vasoconstriction. The effects of vasoconstriction are so powerful that it has even been shown to help decrease the regional perfusion of chemotherapy drugs and mitigate peripheral neuropathy side effects [2].

Pain Relief

The local anesthetic effect of cryotherapy via the application of an ice pack or cold compress does more than just "numb" the area. On a physiological level, a handful of essential processes are happening. As blood flow is diminished, swelling goes down and reduces the pressure on the soft tissues and skin of the injured area.

At the same time, a sudden drop in the temperature of the nerve receptors and fibres expands the threshold of stimulation for pain fibres. This effectively slows the nerve conductivity down enough to block pain signals and thereby reduce feelings of discomfort. The quick application of cryotherapy tools may also alleviate acute skeletal muscle spasms associated with both the injury itself as well as the reflexive muscle reaction to pain.

Altered Metabolic Rate

Soft tissue trauma is well, just that, trauma. The cell destruction that occurs both during and the acute musculoskeletal injury itself as well as in the period following the injury is significant. An acute injury like a sprain, for example, will immediately result in the stretching and tearing of ligaments, tendons, blood vessels, capillaries, and so forth. The cells which make up those significant anatomical players quickly become shredded and die.

Blood and fluid buildup cut off oxygen and nutrient supply resulting in tissue death. This cell death can cascade to neighbouring tissues as the primary vascular supply becomes impaired by the swelling and reflexive muscle spasms. This secondary hypoxic injury [3], or secondary ischemic injury, is exacerbated by an increase in cell metabolism as intact cells outside of the primary injury site become compromised trying to remove the dead ones in a process known as phagocytosis. The struggle for adequate nutrient and oxygen supply and the spillover from enzymatic digestion washes over adjacent cells unless immediately stymied.

One of the modalities for limiting secondary ischemic injury is a sudden reduction in tissue temperature via cryotherapy. Studies have shown that the local application of cold immediately slows the metabolic processing, which suppresses the cell demand for oxygen and nutrients among the neighbouring tissues. This helps minimize cell destruction [4], enhances coagulation of the blood (clotting), and suppresses the body's natural inflammation process.

Cryotherapy Modalities

Gone are the days of slapping a bag of frozen vegetables on an injured limb. The vast array of cold therapy tools available to athletes and sports medicine specialists continues to grow as advancements in science and technology pave the way. Cryotherapy modalities include:

  • Reusable ice/gel pack or ice bag
  • Disposable (chemical) cold/gel pack
  • Cold compress
  • Coldwater immersion
  • Ice immersion
  • Ice massage
  • Cold whirlpool therapy
  • Cryokinetics
  • Insulated ice therapy machines

In addition to acute musculoskeletal injury treatment, cryotherapy is also implemented regularly for reducing delayed onset muscle soreness [5] and speeding up the recovery of force-generating muscles following intense bouts of exercise. As an anti-inflammatory agent, cryotherapy is believed to help reduce secondary injury damage related to stressful exercise as well as provide analgesic side effects that minimize muscle aches and discomfort.

Safety Tips for the Application of Cold

Because the skin temperature drops rapidly within the first few minutes of applying cold to a local area of the body, it is critical that athletes and treating professionals take precautions to prevent cold-induced tissue damage from excessive icing. Recent research recommends:

  • Applying ice locally in 15 to 20-minute intervals every 2 to 3 hours following an acute injury
  • Use a barrier like a towel or cotton wrap between a cold pack and your skin to prevent ice burn and frostbite
  • Resting and elevating an injured limb or joint while you ice it to help relieve swelling
  • Simultaneously applying light pressure (compression) via an elastic bandage or similar tool to aid swelling and improve microcirculation

Blunting the innate inflammatory response through cryotherapy has also come into question as a potential negative side effect as the body relies on it to activate cell signalling and ultimately trigger tissue repair. However, cold therapy has been found time and time again to be a primary source of pain relief following an acute musculoskeletal injury. Pain relief can mean reduced muscle spasming which can limit swelling and adjacent cell destruction.

One of the most important aspects of cryotherapy is what happens after the local application of cold has relieved pain and swelling. Experts agree muscle activation via movement and exercise as soon as the injured joint can safely support it is vital. Mobilizing the soft tissues through active muscle pumping [6] can help deal with residual swelling, trigger cell reconstruction, and prevent joint stiffening.


  1. BLOCK, J. E. (2010) Cold and compression in the management of musculoskeletal injuries and orthopedic operative procedures: a narrative review. Open access journal of sports medicine, 1, 105-13.
  2. HANAI, A. et al. (2017) Effects of Cryotherapy on Objective and Subjective Symptoms of Paclitaxel-Induced Neuropathy: 5 Prospective Self-Controlled Trial. Journal of the National Cancer Institute, DOI: 10.1093/jnci/djx178
  3. MERRICK, M. A. (2002) Secondary injury after musculoskeletal trauma: a review and update. Journal of athletic training, 37(2), 209-17.
  4. HOWARD, M. E. (2017) The Physiologic Effects of Immediate Cold Therapy.
  5. WHITE, G. E., and WELLS, G. D. (2013) Cold-water immersion and other forms of cryotherapy: physiological changes potentially affecting recovery from high-intensity exercise. Extreme physiology & medicine, 2(1), 26. doi:10.1186/2046-7648-2-26
  6. HAWKINS, S. W., & HAWKINS, J. R. (2016) Clinical applications of cryotherapy among sports physical therapists. International journal of sports physical therapy, 11(1), 141-8.

Page Reference

If you quote information from this page in your work, then the reference for this page is:

  • FLEMING, J. (2019) Science Behind Cryotherapy [WWW] Available from: [Accessed

About the Author

Joe Fleming is the President of Passionate about healthy lifestyles and living a full life, he enjoys sharing and expressing these interests through his writing. To inspire others and fight ageism, Joe writes to help people of all backgrounds and ages overcome life's challenges. His work ranges from articles on wellness, holistic health, and ageing to social narratives, motivational pieces, and news stories. For Joe, helping others is vital.