If you are in the midst of training for a marathon or half marathon, or thinking about running one in the future, you will inevitably be faced with the task of increasing your weekly running mileage in preparation for race day. Currently, there are many commercial training programs readily available online, with varying degrees of progression, at various costs to the consumer. But how do you evaluate a training program and select the right one for you? An important consideration is how much should you be increasing your running mileage each week. Research suggests increasing your running mileage no more than 10% per week in order to minimize your risk of injury, while still improving performance. Anything more and you are significantly increasing your injury risk. Contrary to popular belief, the leading cause of running-related injury is overuse or improper training progression, not running form, shoe selection, or running on pavement. Too much, too soon, and/or too fast can lead to situations where tissue breakdown exceeds the ability of the tissue to regenerate. This is the primary mechanism of an overuse injury. Common overuse injuries seen in runner's include patellofemoral pain syndrome (runner's knee), median tibial stress syndrome (shin splints), Achilles tendinopathy, and plantar fasciitis. So if you are experiencing any nagging aches and pains while running, assess your training program and see how much your running mileage is increasing each week.