We often get asked what to do when injured. Do you use heat or ice as a first level treatment. Ice is always your friend when injury strikes, and this is why. When you injure a muscle Inflammation and swelling occur. They need to occur as the swelling supports the injured area, much like a bandage would, limiting movement. Inflammation is an increase in blood flow, which is important as it brings lots of useful things to the injury site to allow the healing process to start. A bit like a truck bringing materials to a building site.
So inflammation is useful, without it you can't heal. But we want to control that inflammation so the materials get to the area to heal it, but too much inflammation can delay healing. So to control it we use ice, we allow inflammation, but control how much inflammation arrives. You don't want all your materials on site on day one of a build project clogging up the roads etc.
So we ice for a max of 10mins per hour, it calms but doesn't freeze the area, allowing lots of healing to occur but not overloading the area. If you were to put heat on it you would add to the inflammation, effectively inviting more materials onto your building site and slowing the healing process. After a couple of days of regular icing the first stage of healing should be well under way and the area is ready for stage two.