Individual patient factors include Muscle weakness and inflexibility Joint laxity Previous injury Bone malalignment Limb asymmetries Extrinsic factors include Training errors (eg, exercise without sufficient recovery time, excess load, building one group of muscles without training the opposing group, and extensive use of the same movement patterns) Environmental conditions (eg, excessive running on banked tracks or crowned roads—which stresses the limbs asymmetrically) Training equipment characteristics (eg, unusual or unaccustomed motions, such as those made while on an elliptical trainer) Runners most often sustain injury after too rapidly increasing their intensity or length of workouts.