Heat Pads vs Cold Compressions

Many I've worked with have said that they never know which to use: heat or ice?
Knowing how this impacts the body physiologically can shed light on any confusion out there.   Be prepared for some 10 cent biological terms...ok, ok 5 cent.

Heat acts as a vasodilator, it widens the blood vessels by relaxing the smooth muscles cells within the cell walls.  This allows blood to flow with less vascular resistance.  (Thank you Wikipedia!)
Generally speaking remember: muscles, particularly stiff and rigid ones, love heat and typically respond very well to it.  In fact, muscles that are more chronically rigid and stiff often suffer from impeded blood flow (ischemia) and heat pads can be a very beneficial intervention.  Although, reduced blood flow is usually more of a result of something else and less of a perpetuating or causative factor.

If you decide to break out your heating pad to address your next stiff area, do not exceed 20 minute applications.  Generally, 20 minutes on and 20 minutes off is the most accepted cycle.  I use 10-15 minutes on and the same amount of off-time for my cycles.  Once heated (vasodilated) having a brief time-off allows the tissue to "normalize" (return to a homeostatic state).  When this on-off cycle is repeated it can pump blood through the area, thusly removing debris that could have developed in the ischemic, rigid tissue.
Like I said, remember: stiff muscles love heat.

Ice or cold compresses act as a vasoconstrictor, it narrows the blood vessels by contracting the muscular wall of the vessels.  Blood flow is restricted, thus retaining body heat and increasing vascular resistance (Thanks again Wikipedia!)
In addition, the cold application also slows the signals being sent to the central nervous system particularly the nociceptors (specialized receptor cells that transmit information about pain).  For this last reason, cold compresses act as a natural analgesic and are very helpful interventions for acute pain.

Our bodies are very adept at producing inflammation.  Once the inflammatory response is triggered, the body can easily become overzealous in its production.  Because of its vasoconstrictive properties, cold compresses can help corral and contain the inflammation to the tissues that are in need of its services.  The next time you twist your ankle and it swells up and becomes very painful, you may want to use a cold compress.  Follow the same general rules for time applications as heat, don't apply for longer than 20 minutes at a time and cycle as desired.  Also know that the inflammation stage for most acute injuries is the 48-72 hours period following the injury.  During this time, stay with cold applications; heat is not recommended (you want to contain the inflammation) and if the inflammation stage lasts longer than 72 hours, seek medical intervention.
So remember: if the pain is acute and there's inflammation or swelling, use a cold compress.

Keep in mind, these are physiologic generalities, your case may be different, there are always exceptions.  Both temperature applications are not long standing interventions; they address a more immediate concern and not the perpetuating factor.
Be well and stay healthy!
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