Hot vs Cold: A Tepid Response From a Physical Therapist

One of the most common questions that are often asked of physical therapists is “when should I use heat and when should I ice an injury?”  The answer you get will be different, depending on who you ask and the particular situation. Every therapist has their opinion that has been sculpted largely based on their personal experiences, education, and the most recent research.

In order to understand why a therapist chooses either heat or cold as a modality, it is important to know what the underlying problem that the therapist is addressing.  Both heat and ice each bring their individual benefits to the table. Depending on what the issue is, it is important to pick the correct modality.

The primary effect that heat has when it is being applied to a body part is that it increases blood flow to an area.  This is primarily achieved by dilating, or widening, the blood vessels in the area that it is being applied to. With the increase of blood to the area, more nutrients, oxygen, inflammatory agents, and other compounds flood the area. This increase can help relieve symptoms of stiffness and discomfort.  

Ice is a bit more complex in its’ action.  Upon application of a cold modality, the body’s immediate response is to constrict blood vessels and muscles in the immediate area.  This is done in order to help prevent additional heat loss. This decrease in blood flow, helps slow the arrival of various blood-borne inflammatory agents and also helps control swelling to a localized area. This also has the benefit of calming down inflamed nerves by decreasing the amount of signal that is being transmitted by nerves in an area.  After 10-15 minutes of application of a cold modality, the opposite effect begins to start. The blood vessels in the area begin to dilate and muscles relax and release. This is the inhibitory effect of cold modalities. The important warning at this point is to remind people to not apply ice for more than 20 minutes at a time. This is because, after twenty minutes, the opposite of this desired effect starts to happen.  The body sends more blood to the area, thinking that hypothermia is imminent. This is called Hunter’s Reflex.

So it is really the individual mechanisms of action that dictate which modality to use. I often tell my patient, that if your problem is too much inflammation, I advise using ice because it is the modality with greater anti-inflammatory properties.  

Many times a patient will ask me concrete questions. The answer I give is based on my experiences as a physical therapist and mediocre athlete. And based on my experience, I generally give a simple rule; only use heat when you have a stiff muscle or a longstanding soreness. For every other situation, use ice for the recommended time.  

As always, it is a good idea to consult your physician or physical therapist to answer questions about your particular situation. This information is for general purposes and is meant to be purely educational.