When Conner Mantz recently broke the American record in the marathon, the shoes he wore made him faster. Super shoes improve running economy, a measure of the energy cost to run at a specific speed, by about 4%, leading to a 2% performance improvement in distance events. Super shoes have a curved carbon-fiber plate embedded in a thick midsole of bouncy, light foam. Runners have broken all world records in distance events since super shoes were released in 2016. How do super shoes make runners faster?
Plate:
The carbon-fiber plate makes the shoe stiffer. A stiffer shoe makes the runner’s toes bend less, so less energy is lost. Researchers found the ankle performed less work in super shoes. Super shoes make runners’ lower leg muscles use less energy.
Furthermore, scientists compare the plate to a lever or teeter-totter. When a runner pushes off the ground, the curve and stiffness of the plate shifts the vertical forces in the foot forward, propelling the runner’s heel upwards and forward. This shifting of forces creates a longer, more efficient lever arm, similar to how it is easier to close a door by pushing farther from the hinge.
Foam:
The foam is like a spring. The thick layer of foam returns 87% of its stored energy, which is an improvement from previous foams that returned 75% of their stored energy. Since the foam stores more energy, the calf has to store less energy. Runners don’t have to use the calf muscles as much when wearing super shoes. The high stack height makes a runner have longer legs, which makes runners more efficient.
Injury Risk:
The running community has observed anecdotally common injury locations shifting when runners started using super shoes. As previously stated, super shoes decrease loading at the ankle, which decreases the chance of injury to the lower leg. However, new demands arise on the knee and hip as a result of the decreased loading in the calf and ankle. Consequently, if a runner’s body isn’t adapted to these demands, she could suffer an overuse injury. Runners wearing super shoes had stride characteristics correlated with lower injury risk to the shins. Researchers also measured increases in stride characteristics associated with knee and hip injuries in female runners wearing super shoes. Runners also experience higher forces in their knees and hips while wearing super shoes. Runners may face decreased injury risk in their lower legs, but increased injury risk in their hips or knees when using super shoes because of the changes in their biomechanical patterns. Studies have also shown a correlation between super shoe use and bone stress injury or injury risk in a bone in the foot called the navicular. Biomechanical changes caused by super shoes improve performance, but may also change the locations runners get injured.
The combination of a thick layer of foam and the stiff, curved plate results in more efficient biomechanics and performance improvements. Future research can explore how biomechanics and shoes affect running performance and how shoes affect injury risk.
Featured image taken by Arianne Olson