Strength training for runners is crucial! When you run, you put your body through repeated stresses in one set range of motion. Without strengthening, you overload your muscles, ligaments and tendons, increasing chances of injuries. Runners who do not strength train are prone to recurrent injuries and risk long term damage. Idea of strength / resistance training is to train the muscle groups in different movement patterns and planes that improves muscle fatigue during runs and gives you a better control on your form and movement.