Foot strike pattern in running is directly linked to impact production whereby heel strike running is a major source of injury because it produces exponential impact that actually damages the lower back.
A study by Cook et al., in the Journal Sports Medicine found that the heavy impact force produced at heel strike when running caused disc degeneration of the lower back, leading to disc height reduction and lower back pain.
Lumbar (or lower back) disc degeneration is a common condition in aging adults, and is a common cause of lower back pain. The spine is made up of a column of bones called vertebrae. Between each vertebra is a shock-absorbing disc that prevents the bones from rubbing together. Inside the disc is a gel-filled center called the nucleus which is made of about 80% water. As you get older, the discs separating the spine bones slowly lose water and shrink, causing the lower back to become very stiff and painful. These age-related changes don’t happen to everyone, but there are known risk factors for the condition, and heel strike running is verifiably a major one!
The same study found that disk height reduction in heel strike running was due to the cyclic diskal and compressive loading that is always produced when striking heel-first whereby the compressive loads at heel strike exceeded interstitial osmotic pressure of the disk. This caused water to escape through the disk wall, thereby reducing disc height.
Even worse, the study also found that as the heel strike runners increased their running distance, the conditions for disk height reduction were more pronounced! This is not the case in forefoot running, which is why it has gained near universal acclaim as the safest way to run. Read more here!
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