Running exerts a force on the body equal to two to three times body weight - and while it is designed to deal with these forces, if they are applied too much or too often, injury could be just around the corner. That's why the Alter-G Anti Gravity treadmill, which enables you to reduce your body weight to as little as 20% of its actual value, is the piece of equipment VargoPT describes as the best investment we've ever made.
While there are less high-tech ways of taking the weight off your feet (such as running in water) the Alter-G uses air pressure as the lifting force, so that you can maintain normal running (or walking) biomechanics without the associated forces. This prevents other tissues deconditioning during injury or rehabilitation and helps you retain good form and function.