Nonpharmacological management strategies for acute musculoskeletal (MSK) injuries focus on pain reduction and the promotion of tissue healing to facilitate a return to normal function and activity. Thermotherapy (heat therapy) and cryotherapy (cold therapy) are a very common modalities used to encourage this outcome; however, there is significant confusion about which modality (heat vs. cold) to use and when to use it. Most recommendations for the use of heat and cold therapy are based on empirical experience, with limited evidence to support the efficacy of specific modalities.
Thermotherapy is the use of heat in therapy, such as for pain relief and health. It can take the form of a hot cloth, hot water bottle, ultrasound, heating pad or whirlpool baths. Heat therapy is most commonly used for rehabilitation purposes.
Cyrotherapy is the local or general use of low temperatures in medical therapy. It is widely used to relieve muscle pain, sprains and swelling either via soft tissue damage or postoperative swelling. In MSK injuries, the most common method of applying cryotherapy is the use of cold packs. While cryotherapy is widely used, there appears to be little evidence for its effectiveness that has been replicated or shown in large controlled studies.
How does it work?
Heat creates higher tissue temperatures, which produces vasodilation (i.e., widening of the blood vessels), which increases the supply of oxygen and nutrients and the elimination of carbon dioxide and metabolic waste. The increased blood flow also encourages the transmission of proteins, nutrients, and oxygen for improved healing. The therapeutic effects of heat therapy include increasing the extensibility of collagen tissues; decreasing joint stiffness; reducing pain; relieving muscle spasms; reducing inflammation, oedema, and aids in the post acute phase of healing; and increasing blood flow.
In MSK injuries, an ice pack is placed over an injured area and is intended to absorb heat of a closed traumatic or inflammatory injury by using conduction to transfer thermal energy. The physiologic effects of cold application include immediate vasoconstriction (narrowing of blood vessels) with reflexive vasodilation, decreased local metabolism and enzymatic activity, and decreased oxygen demand. As a general rule, it is recommended that patients use ice packs for no longer than 10 minutes at a time: this is because its known to cause adverse effects on muscle force production and balance if left for 20 minutes.
When should I use ice or heat?
Generally speaking, ice therapy is used immediately post-injury and forms part of the ‘POLICE‘ principle (i.e., Protect, Optimal Loading, Ice, Compression, and Elevation). The effect of ice is basically to reduce inflammation and reduce pain via numbing the area; therefore, in acute (0-48 hours) MSK injuries, ice therapy is an appropriate method for recovery purposes. It is important to note that the quicker ice therapy is applied to the injury, the better the outcome will be.
The effect of heat is to basically improve blood flow, remove metabolites and encourage proteins and nutrients to the injured tissue. Heat is generally prescribed when there is little to no swelling. The exact time to begin heat therapy is somewhat unclear and depends on the severity of swelling in the acute injury. It is, however, used as part of the rehabilitation process to reduce pain in MSK injuries.
So, if ice therapy is for a new injury and heat therapy is to relax muscles, what happens when you injure a muscle? This is where the literature is very unclear. If the muscle injury causes severe, sudden muscle pain after a trauma, you may have to use a combination of the two therapies. Start with ice for the first few days to help decrease the inflammation and then switch to heat to help relieve the muscle soreness.
A recent systematic review of 9 randomised clinical trials (RCT) found that there is limited evidence from RCT supporting the use of cold therapy following acute MSK injury and delayed-onset muscle soreness (DOMS). Similarly, there is also limited overall evidence to support the use of topical heat therapy in general; however, there is moderate-quality evidence that heat-wrap therapy provides short-term reductions in pain and disability in patients with acute low back pain and provides significantly greater pain relief of DOMS than does cold therapy. Follow the link for more information on sprains and strains of the low back.
There remains an ongoing need for more robust, high-quality RCT on the effects of cold and heat therapy on recovery from acute MSK injuries.
- Ice is to reduce inflammation and pain in acute MSK injuries (0-48 hours). Get ice on as soon as the injury occurs! Use the POLICE principle.
- Heat is to improve tissue healing via increasing blood flow, proteins and nutrients and also removing metabolites in effected tissues. Use heat when no swelling is present as part of the rehabilitation process to reduce pain.
- In acute muscle injuries, you may have to use a combination of the two. Use ice first, then heat.
- There is little evidence for the use of heat and cold therapies for MSK conditions. More research is required.