The question I probably come across most in my practice is: When do I useheatand when is it better to useice? Although the answer is somewhat complex depending upon symptoms and condition, one rule of thumb applies: Do not use heat on any fresh injury! During physical trauma blood vessels are broken and consequently blood will leak into surrounding soft tissue. Heat increases circulation, causing even more blood to flow into injured area. This will create more swelling and pain, as well as increased scar tissue formation down the road.