Benefits of Hot and Cold Contrast Therapy Baths
How Contrast Baths Are Used in Physical Therapy
Medically reviewed by Eva Umoh Asomugha, M.D.
Contrast therapy involves submerging an injured body part or your entire body into a hot bath and then a cold bath, switching back and forth, to improve circulation and muscle recovery. It is commonly used by physical therapists and sports medicine specialists, as a form of whirlpool hydrotherapy.
Research has shown that contrast therapy can reduce muscle fatigue, spasms, pain, swelling, and lactic acid buildup following intense exercise. It may help improve the range of motion and functional mobility of joints like the knee, elbow, or hands.
This article describes how contrast therapy works, including the benefits and risks. It also explains how to perform contrast therapy at home to recover from injury or manage conditions like arthritis.
Verywell / Danie Drankwalter
How Contrast Therapy Works
Contrast therapy works by triggering physiological responses to heat and cold. It operates on the same principles of thermotherapy (heat therapy) and cryotherapy (cold therapy) wherein exposure to warmth causes blood vessels to dilate (widen) and exposure to cold causes them to constrict (narrow).
Switching back and forth between warmth and cold creates a pumping action that may help decrease inflammation. This, in turn, can help alleviate pain and improve joint mobility.
Contrast therapy is commonly used to recover from a soft tissue or joint injury but is also used by performance athletes to enhance post-exercise recovery. It can also be used to speed healing following orthopedic surgery.
Injuries that benefit from contrast bath treatments include:
Contrast therapy is typically performed in temperature-controlled whirlpool baths. The whirlpool action is thought to further promote muscle relaxation and ease pain.
Related: Benefits of Whirlpool Therapy
How Contrast Therapy Is Performed
Depending on the facility, contrast therapy may involve two whirlpool baths, one hot and one cold, or one hot whirlpool bath and a cooling tub.
Once both tubs are at the correct temperature, the injured body part will be submerged in the heated water for three to four minutes. The physical therapist may also ask you to perform gentle-motion exercises (like wrist rotations or knee extensions) to increase joint mobility.
You will then submerge the body part in a cold whirlpool bath or tub for one minute. For this portion of the therapy, you will let the joint relax without movement.
This sequence is repeated back and forth for 20 to 30 minutes. Upon completion, you will be asked to rest for several minutes before evaluation by the physical therapist.
Takeaway
This video has been medically reviewed by Laura Campedelli, PT, DPT
Benefits of Contrast Therapy Baths
The goals of contrast therapy differ based on whether you are recovering from an injury or surgery or using it to improve recovery during rigorous sports training.
Irrespective of the reason, contrast baths work by:
Decreasing muscle pain
Decreasing joint stiffness and improving joint mobility
Reducing swelling and edema (fluid overload in tissues)
Promoting circulation that can speed healing
For athletes, contrast baths can reduce delayed onset muscle soreness (DOMS) caused by the buildup of lactic acid in muscles. By doing so, athletes can continue strict training programs without interruption.
The current body of research tends to support the benefits of contrast therapy in physical therapy and sports medicine:
A 2018 study in the Journal of Athletic Training examined the effects of contrast therapy using infrared spectroscopy and other tools, and confirmed that it promotes healing by increasing tissue oxygenation and decreasing tissue swelling and edema.
A 2014 study in the Journal of Clinical Diagnosis and Research reported that contrast baths may be as effective as steroid injections in reducing pain associated with plantar fasciitis.
A 2022 review of studies in Cureus suggests that contrast therapy is more effective in easing arthritis pain and stiffness than a hot bath alone. It also suggests that gentle vibration, such as that involved in whirlpools, blocks pain signals by stimulating mechano-receptors in the skin.
A 2022 case study in Spinal Cord Series and Cases reported that a 54-year-old male with severe nerve pain due to multiple myeloma had a greater than 50% reduction in pain after daily contrast therapy, allowing him to sleep at night. This suggests that contrast therapy may have benefits in easing neuropathic pain.
Related: 8 Common Physical Therapy Treatments
Risks of Contrast Therapy
While generally considered safe, contrast therapy poses certain risks if performed incorrectly or inappropriately. These include:
Scalding burns from water that is too hot
Increased bleeding if there are ruptured blood vessels on or inside the wound
Intense nerve pain in people with peripheral neuropathy from cold exposure
Increased pain from cold exposure in people with peripheral vascular disease
At-Home Contrast Therapy Treatment
Contrast therapy can be performed at home with relatively simple tools, including two receptacles (like a bucket or tub) and a water thermometer to ensure the ideal, safe temperatures.
To keep the hot and cold baths at the correct temperatures, have a kettle of hot water and some ice to add if needed.
To start:
Fill one basin with hot water (100 to 104 degrees F).
Fill the other basin with cold water (46 to 50 degrees F).
Dip the affected area in the hot water basin for 3 to 4 minutes.
Immediately switch to the cold water basin for 1 minute or as long as long as it can be tolerated.
Repeat the process three or four more times for a total of 20 minutes.
If the water in the cold basin gets above 50 F, add some ice.
If the water in the hot basin drops below 100 F, add a little hot water but do not continue if it goes above 104 F. Either allow it to cool down or add some ice.
You do not need special water for contrast therapy; plain tap water will do just fine.
Summary
Contrast therapy is used in physical therapy to reduce pain, improve joint mobility, and speed healing after a joint or soft tissue injury. It can also be used to enhance post-exercise recovery.
Contrast therapy involves submerging a body part in warm water for three to four minutes and then submerging it in cold water for one minute. The process is switched back and forth for a total of 20 to 30 minutes.
Contrast therapy is considered safe but may not be appropriate if there is bleeding on or below the skin or if you have severe peripheral neuropathy or peripheral artery disease.
Related: Benefits of Ice Bath: What Could They Help With?
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