When to Use: If you have a tender or tight spot that's been bothering you for a little while, applying heat before you run or do another form of exercise can help loosen your muscle and relax the area.
What to Use: Use a heating pad (available at most drugstores) or a towel soaked with hot water.
How Long: Before you head out for a run, apply heat for 5 to 10 minutes.
When to Use: Use ice immediately after sustaining an acute injury, such as a sprain. Ice should also be used when you've re-aggravated a chronic injury, such as plantar fasciitis or shin splints. An ice bath can also help with muscle recovery after running a marathon or long-training run.
What to Use: You can use an ice pack (a plastic bag filled with ice; a bag of frozen vegetables; or even a frozen water bottle, which is especially good for pain on the bottom of the foot). Make sure that you place a towel between the ice and your skin -- don't apply it directly.
How Long: Ice for 15 to 20 minutes for three to five times a day, if possible. For acute injuries, ice the first 24 to 48 hours after the injury. For chronic injuries, ice when you've re-aggravated the injury and are feeling pain.
More: VIDEO: How to Ice a Running Injury