ACOFP Family Physicians Practice Test 2026 – Comprehensive Exam Prep

When the body's weight is positioned with the center of gravity in front of the sacral promontory, gravity creates a forward bending moment at the lumbosacral junction. To maintain an upright posture, the lumbar extensors—primarily the erector spinae and nearby paraspinal muscles—must stay chronically active to pull the spine back into extension. This sustained contraction leads to chronic tension in the lumbar muscles. The abdominal muscles, thoracic muscles, and gluteal muscles are not the primary groups counteracting this specific forward load at the lower spine, so they are less involved in maintaining this posture.