Now this isn’t an easy question that can be put in a box and wrapped up. It depends on what injury or condition we are discussing. There are many situations that ice would be the best remedy and there are others that heat reigns supreme.
Ice
Ice constricts blood vessels, causing the numbing sensation; this will in time relieve inflammation and limit bruising. Ice is best for new injuries occurring within 72 hours.
Examples:
Chronic inflammatory arthritis (Gout)
Acute strains or pulled muscles
Acute tendinitis
Heat
Heat is great for arthritis and chronic injuries. Moist heat is best, but heat helps increase blood flow and circulation, allowing the natural healing pathways to occur faster. Heat will also relax tight muscles and relieve aching joints.
Examples:
Worn away joints or arthritis
Headaches
Pulled muscles and sprains after inflammation resolves
Tendinitis after inflammation resolves