Think about what your body is doing when you run. As you move through a stride, the joints in your lower leg and connective tissue become tighter. This creates the power you need to propel yourself forward while, at the same time, braces your joints for the oncoming impact. If your joints, muscles, and connective tissues are inflexible, they are more prone to injury. Some must-do exercises include: Hamstring stretches, which improve flexibility in the back of the thigh, reducing the risk of strains, Hip flexor stretches, which increase the range of motion in the hips, Calf stretches, which loosen tight calves to prevent Achilles tendon injuries and increase push-off strength, IT band stretches, which reduce tension in the iliotibial band, protecting against knee pain