In his autobiography, Bolt reveals that he has suffered from scoliosis, a condition that has curved his spine to the right and has made his right leg shorter than his left. A result of this is that his left leg remains on the ground 14 percent longer than his right leg, with left leg striking the ground with a force of and right with . Biomechanics researchers have studied, with no firm conclusions, whether this asymmetry has helped or hurt Bolt in his sprinting career.