Winner: Simmons (Undergraduate)
Abstract (click to view)
It is common thought that structural asymmetries result in a running disadvantage, and that anatomical and mechanical symmetry is the preferred condition. Our opposition to this stance began in observation of Usain Bolt, who exhibits a 13% force difference in striking with his right versus left leg due to a leg length difference. But there are few studies on gait asymmetries to explain this phenomenon: how can the fastest man in history be asymmetrical? To investigate this, we have created a study in which we lengthen the right leg of athletes and observe the response of both legs. We propose that the body compensates by altering vertical force and contact time in the opposing limb, resulting in an adjustment to both legs. Our subjects ran a control and experimental condition where an 27mm insert was attached to the right shoe at 3, 4, 5, and 6m/s. We hypothesized that the lengthened leg would have a decreased vertical ground reaction force and increased contact time and the unlengthened leg would have an increased vertical ground reaction force and decreased contact time. We further hypothesized that the two-leg average would not change between conditions. We determined both hypotheses to be correct. These findings show that asymmetries are not an inherent disability, but rather, functional asymmetries can increase the body's effectiveness in motion.
Sara Hatcher
Major: Applied Physiology and Health Management
Faculty mentor: Peter Weyand
Sara-
This is great! Nicely done. I see applications for your work in the brain-machine interface field. One question I would have asked you if we were able to be in person: Do you think the results would change if the subject was given more time to habituate to the lengthening insert? I.e., What would happen if the subject was able to wear the insert for a week or two?
Great question! We have tested a number of different habituation times, and have found that ten minutes is a sweet spot. Anything less does not give the subject enough time to adjust, but beyond ten minutes, no further changes are obvious. I do think that wearing it for days or weeks has the potential to solidify the adaptation better, and this would be a great next step in our project. My hunch is that it would increase the effect further and the data would be even more significant.
Thank you for this informative talk! I enjoyed this particularly because I am a runner with uneven legs. Good to know I am not dysfunctional 🙂
I’d also like to know if leg injuries are related to uneven leg lengths and if so, which leg sustains more injuries? I know that’s not within the scope of your work but I’d be interested to know.
Thank you for your comment! You are certainly not dysfunctional. My research has not shown an increased risk of injury with an LLD, but my guess is that should an injury occur, it would more likely be the shorter leg. This is because that leg has a farther distance to travel and therefore exerting more force. This higher force of impact would increase the likelihood of injury as compared to the longer leg.
Thank you!