TIP: if you have problems running, i.e bad knees, shin splints, bad ankles. Then try running on the grass or somewhere with a softer surface. 

If you were injured at one time in your life, and you are trying to rebuild your muscles, run on the sand. You are forced to use your stabilizer muscles and it may hurt a little, but you are strengthening them at the same time. 

Tell me what works for you!