Running a marathon can temporarily shrink your spine by up to 0.5 inches due to fluid loss in your spinal discs.

When runners complete a marathon, their spine experiences intense physical stress. The human spine contains 23 intervertebral discs that function as shock absorbers between vertebrae. Each disc has a gel-like center called the nucleus pulposus, which is approximately 80% water.During a 26.2-mile marathon, a runner typically takes 25,000 to 50,000 steps. Each footfall generates a force of three to four times the runner's body weight through the skeletal system. This repetitive loading triggers disc dehydration, where fluid is squeezed out of the spinal discs and into surrounding tissues.Research published in the Journal of International Medical Research documented that marathon runners lost an average of 1 centimeter (approximately 0.4 inches) in height by the finish line. This loss occurs primarily in the lumbar and thoracic regions of the spine, where disc compression is most pronounced. While everyone loses small amounts of height daily due to gravity, marathon running dramatically accelerates this process.Recovery happens naturally within 24 hours through a process called osmotic swelling. As the body rehydrates and vertical pressure decreases—especially during sleep—the discs reabsorb fluid and return to their original volume. This remarkable phenomenon demonstrates the elasticity and resilience of the human musculoskeletal system, even under extreme endurance stress.