Running does not cause permanent height loss, but it does cause a temporary, measurable reduction in stature. This transient change is a normal physiological response to the physical stresses of activity and is quickly reversed. The slight compression observed during and immediately after a run is merely a temporary fluctuation, similar to the natural height changes that occur throughout any given day.
The Biomechanics of Temporary Spinal Compression
The spine is composed of vertebrae cushioned by structures called intervertebral discs. These discs have a tough outer ring and a soft, gel-like center consisting primarily of water, functioning as shock absorbers. When a person runs, repetitive vertical impact forces travel up the kinetic chain to the spine. This mechanical loading, combined with gravity, momentarily squeezes the discs, causing a temporary loss of fluid and volume within the disc’s center. Studies show this can lead to a measurable spinal shrinkage, with some runners losing up to 7 to 8 millimeters of height after a long run. This temporary height reduction is most noticeable in the lumbar spine, where the discs absorb the greatest load.
Running Impact Compared to Daily Activities
Spinal compression is not unique to intense exercise; it is a normal part of daily life. Simply standing or sitting upright subjects the intervertebral discs to constant gravitational forces, causing them to gradually lose fluid throughout the day, meaning individuals are naturally tallest in the morning and shortest by evening. While running accelerates this fluid loss due to the added impact, the spine is specifically designed to handle these forces. For example, a 30-minute run can cause a spinal shrinkage ranging from approximately 3.37 mm to 7.69 mm, depending on the running pace. This temporary compression is completely reversible, as the discs rehydrate and regain their full volume when the spine is unloaded, primarily during sleep.
Long-Term Effects on Skeletal Structure
Running is a weight-bearing activity that provides significant long-term benefits to the skeletal system. The mechanical stress stimulates cells called osteoblasts, which build new bone tissue, increasing bone mineral density and offering protection against conditions like osteoporosis later in life. Regular running also improves the health and resilience of the intervertebral discs themselves. Studies comparing long-term runners to non-runners often find that runners exhibit healthier and thicker discs, suggesting that the cycles of compression and rehydration make the discs more robust. Furthermore, a strong running regimen often includes core strengthening, which improves posture and spinal alignment.