Shin splints are small tears in the area where the lower leg muscle attaches to the tibia, aka the shinbone. The tears result from overuse, and since the pavement taxes your muscles more than a treadmill, many runners complain of shin pain when they first begin outdoor runs. Shin splints often occur because the calf muscle becomes stronger than the tibialis anterior, the muscle on the outside of the shin. Even if the ache isn't that bad, it's still a minor injury. Pushing through the pain could result in more severe tears — an injury that could sideline your running routine altogether.