Marathon Season Injuries: Part 4

In this latest article on distance running injuries we look at lower limb stress fractures. More specifically we want to discuss the bio-mechanical factors that influence the development of lower leg stress fractures. As discussed in earlier articles on running in this series (see here) training volume and tissue characteristics play a significant role in the development of running injuries, however we will not discuss these further here.

Bone stress injuries are more common in female runners due to the effect of hormone changes that are associated with menstruation and the effects that training can have on hormone balance particularly as training loads increase, commonly seen in long distance training.

What are some of the bio-mechanical risk factors associated with lower limb bone stress?

Research from Pohl et al 2008 and Milner et al 2006 highlight that biomechanical loading patterns are associated with the development of tibial stress fracture injuries. The studies highlighted that in female distance runners in particular tibial stress injuries are associated with increased peak and average vertical loading rates (that is the rate of the ground reaction force, see video below and not the effect of the heavy heel strike on the graph). These studies also indicated that increased hip adduction angles on landing and support, increased rearfoot eversion (see image below). Rearfoot eversion upon landing as also been associated with navicular stress fracture injuries.

Can changing running mechanics alter the loading and injury risk?

Work by Willy et al 2016 and Yong et al 2018 highlights that alterations in landing position, changing from a rearfoot to a forefoot or full foot landing and alterations in cadence can reduce stride length and limit overstriding and thus increased vertical loading rates. These changes are suggested to reduce the likelihood of developing bone stress injuries associated with biomechanics.

With this in mind altering running gait to increase the ability to absorb the load and not collapse through the knee, hip and ankle, as well as creating landing positions that do not create detrimental high vertical loading rates are likely to assist with the development of these injuries. Cues to assist with this include landing on a whole foot, bouncing off the ground to limit collapse through hip, knee and ankle and landing under the hips (or relatively close to) are likely to improve these biomechanical issues.

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