When to Ice or Heat an Injury?
After an injury there is often a question of whether to apply heat or ice to help with the recovery process. There are some basic principles to identify which method is appropriate for an injury. Cryotherapy (ice) and thermotherapy (heat) are both effective and easy ways to manage pain after an injury helping to speed the recovery process. These two forms of therapy have very different reasons and effects on the point of injury so it is important to know which one to use in order to maximize its effects.
This article with explain the physiological effects of heat and ice so that you can better manage your injury quickly.
Cryotherapy & how it works
Essentially ice removes heat from the body through conduction, body heat is transferred to the cold pack/ice or evaporation, moisture created by the ice on the surface of the skin vaporizes taking heat with it, much in the same way sweat helps cool the body during exercise.
To what extent does it cool the tissue within the skin, muscle and joint structure?
The degree of cooling depends on the type of tissue, the method of cooling and the duration of application.
The more superficial the injury the less time it takes to cool the tissue to a meaningful level. Remember the body tissues are constantly producing heat, so a joint such as the shoulder under the thickness of the large deltoid muscle may take upwards of an hour to produce any meaningful temperature change at the joint level.
Physiological effects of cryotherapy
There are three main physiological effects of ice to promote therapeutic effects on the tissue.
1) Circulation effects - Ice causes vasoconstriction of the blood vessels, effectively reducing blood flow to the area. Now this might sound like a bad idea reducing blood flow to an injured area but its actually very helpful. Blood vessels by nature are "leaky" and fluid in our blood is constantly seeping from vessels. After an injury this process is increased substantially leading to the swelling you can see after injury. Swelling and inflammation = pain and can be significantly reduced using ice.
2) Metabolic effects - When an injury occurs often the delivery system of oxygen and nutrients to that tissue is also damaged. This can further compromise the injured tissue if it can not get adequate levels. Ice can effectively lower the metabolic activity of cells, reducing its oxygen requirement so that it can better survive with a compromised delivery system.
Studies have shown an ice pack to the knee for 20 minutes after injury can reduce metabolism levels up to 19.3%.
Lowering tissue metabolism is also helpful to prevent healthy tissue around the injury site from suffering inadequate oxygen delivery, known as secondary hypoxic injury, minimizing the size of the injury.
3) Neuromuscular effects - Cryotherapy reduces nerve conduction velocities of sensory and motor nerves, effectively reducing pain and muscle spasm.
Heat & how it works
Heat therapy essentially transfers energy from one source to another.
To what extent does it heat the tissue within the skin, muscle and joint structure?
As with ice, the degree of heating depends on the type of tissue, the method of heating and the duration of application.
Generally with heat application for every 10 ⁰C increase in cutaneous tissue (skin) there is a 1 ⁰C increase in deeper tissue.
Physiological effects of thermotherapy.
The same three main physiological effects of ice also apply to heat but promote a different set of therapeutic effects on the tissue.
1) Circulation effects - Heat causes vasodilation, increasing blood flow to deeper tissues of the body, bringing more oxygen to tissues improving tissue healing.
2) Metabolic effects - Improved tissue healing achieved by increasing the metabolic activity of cell (cell growth). Studies have shown an increase of 1⁰C is approx 15% increase in cellular activity.
3) Neuromuscular effects - Heat application increases nerve conduction velocities of sensory and motor nerves, effectively reducing pain and muscle spasm. Increases the extensibility of tissues to reduce muscle pain and spasm.
What is the appropriate dosage of ice and heat application?
For ice and heat there are no standardized guidelines of frequency, intensity and duration defined through research.
For both ice and heat the most common recommendation of 20 minutes as tolerated is recommended.
Remember the deeper the injured tissue to longer time required to make meaningful temperature change. With heat there is the added guideline when using a temperature of 45⁰C used for a maximum of 1 hour before tissue damage could occur.
Are there any risks or adverse reactions to using ice or heat on an injury?
It is possible to experience an ice or heat burn if left for too long. It is advised to avoid direct contact with the ski by wrapping the ice/heat bag in a moist thin towel acting as a barrier protecting the skin. It is recommended to check the condition of the skin frequently. Those with compromised sensation should monitor this very closely.
When to use ice or heat on an injury
Ice is typically used for acute injuries like sprains and strains. Used in the first 48-72 hours after an injury to reduce inflammation, swelling and pain. Heat is used for chronic injuries, where muscle stiffness and soreness is the primary source of pain. There are excepts to the rules and some injuries may even respond better with a combination of the two.
