Ankle Rocker and Ankle Stiffness: Can they Coexist? Anyone who has been around this site for a while knows we have spent a lot of time on the feet. Recently I began thinking about the impacts of improved ankle rocker on running speed. It started with the simple question that is the title of this article. Why is this a dilemma? Well, ankle stiffness is the bodies ability to lock the ankle in a position minimizing the eccentric heel dip towards the ground. This heel drop utilizes ankle rocker. So a stiff ankle uses less ankle rocker. The idea being that as the heel dips the tissues deform and leak energy. As the calf eccentrically elongates the force from the hip is not being transferred to the ground it is getting lost in the eccentric contraction. Ok, then why should the athlete or sprinter develop ankle rocker? This question popped into my head when I was watching some videos of Chris Korfist's sprinters online. In the video Dr. Shawn Allen was commenting on how poor their ankle rocker was. This is because so much time was spent training ankle stiffness. I was thinking "duh, but who do we need the ankle rocker while sprinting?" Here is my take: Athletes need ankle stiffness and a competent ankle rocker despite them seeming to be diametrically opposed. First upon forefoot strike the athlete utilizes ankle stiffness preventing the heel to dip to the ground and energy leakage. Now once the forefoot is planted and locked the tib/fib rocker over the ankle while the heel is still elevated. Using the ankle rocker allows more horizontal force to be applied to the ground. While we do know much of the force required to maintain a top speed sprint is vertical, during the acceleration phase horizontal force plays a much larger role. By rockering over the ankle you can maintain a better acceleration position and utilize more of the horizontal pulling forces of the glutes and hamstrings. This is very advanced and requires solid coordination. The athlete is using ankle stiffness and ankle rocker simultaneously. As the athlete rockers over the ankle this requires an eccentric contraction of the gastroc/soleus and a concentric contraction of the dorsiflexors in a specific balance that allows the heel to stay elevated while rockering over the ankle. So in higher level sprinters ankle stiffness and ankle rocker exists and function simultaneously in a precise and delicate dance between the two opposing functions.