The normal S-shaped curvature in the vertebral column that increases its strength, resilience, and flexibility. Viewed from the side, there are three principal curvatures that give the back its normal S-shape. The cervical and lumbar curvatures are concave posteriorly; the thoracic curvature and the sacrum are convex posteriorly. See also kyphosis, lordosis, scoliosis.
Subjects: Sports and Exercise Medicine.