This is an excerpt from Beth Shaw's YogaFit 3rd Edition by Beth Shaw.
Because of the repetitive motion of the legs, running creates tightness in the hip flexors, hamstrings, and quads, often leading to low-back pain. Running also fails to strengthen the upper body or the abdominal muscles. The YogaFit poses here serve as counterposes to offset runners' lower-body strength and to provide supplemental work to increase total body strength, endurance, and flexibility. After a run is a great time to add in some fun arm balances and then move to the floor for increasing upper-body and core strength. Many runners find that yoga keeps them running longer and faster, without the nagging injuries.