Injury occurs most often in the first month. Adherence to a gradual increase toward your goal reduces chances of injury. Increase your time or mileage by 10 percent per week. If you're running three times a week, make no single run greater than 50 percent of your weekly mileage. If you're running five times a week, make no single run greater than 33 percent of your weekly mileage.
Injuries occur when repetitive running is performed too intensely, too frequently or too long.
Even the most biomechanically inefficient people can avoid injury if they are careful to advance their training changes slowly. A medical practitioner should evaluate pain that does not improve with a few days rest. The most significant equipment decision for a runner is shoes. Shoes become the protective barrier between the runner and the road. Do not retrieve the decades old shoes from the closet for your new program.