Footwear Science
Footwear technology constantly evolves as running research develops and marketing strategies within large shoe companies change. With each brand trying to distinguish itself from others, selecting footwear has become more confusing than ever. As I explained in my previous post on how to select footwear based on what feels natural to your feet, there are some special features to take into consideration.
Toe Spring: The angle of elevation of the toe box off the ground. An increased toe spring assists with rolling off the big toe during push off phase of running and offloads the metatarsals. Most modern racing shoes have an exaggerated toe spring. From a biomechanical standpoint, an elevated toe spring would help a runner with a smooth transition from midstance to push off phase. Someone with great toe pain, metatarsal pain, and bunion pain should find a shoe with a higher toe spring.
2. Rocker bottom: A shoe with an outsole shaped as a “U” meaning there is an elevated toe spring and the back portion of the heel is elevated off the ground. The forefoot and heel are also made wider. Hoka labels their rocker bottom technology as a “meta-rocker” to create a forward driving effect where the runner’s body weight is transitioned to the forefoot quicker/smoother.
3. Carbon fiber plates: Carbon fiber is a lightweight material with extreme rigidity, which gives it excellent ability to store and release energy. Think about a spring that compresses and decompresses without ever losing shape, similar to a trampoline. You have to load the trampoline by jumping on it, the material stores energy, and returns the same energy to you by releasing you to the air. There is much controversy whether carbon fiber plates in racing shoes should be legal or not as research has shown it can increase the running economy by up to 4-5%.
4. Stack Height: The thickness in the outsole. Typically, the thicker the outsole, the more foam and cushioning materials are present. Thick stack heights provide maximal cushioning and good for easy recovery runs. Shoes with carbon fiber plates need to have a thick stack height to sandwich the carbon fiber plate.
5. Toe box width: Most running shoes come in various widths (narrow, regular, wide, extra wide). It’s important to make sure your shoes are not too narrow. The easiest way to figure this out at home is to trace your foot on a sheet of paper. Make sure you are standing when you trace your foot as weight bearing widens the foot and splays the toes. Take a tape measure and measure the length of your foot (from heel to big toe) and then the width of the foot from big toe joint to pinky toe joint). Follow this universal table of measurements for sizing.
6. Heel to Toe Drop (or offset): The difference between the height of the heel and the height of the forefoot. These values range from 0 mm - 12 mm for running shoes. For centuries, running shoes have always been made with a heel to toe drop of 10-12mm. In the recent decade, lower drop shoes are more appealing as a lower value puts the foot in a more neutral position while running. In contrast, a higher heel drop places the foot in more plantarflexion meaning that runners are more likely to have an exaggerated heel strike and increases the lever arm of tibialis posterior muscle (common culprit of shin splints). If you have chronic calf pain, I recommend trying a lower heel to toe offset. Keep in mind this is relative… if your current shoes are 12mm, try switching to 6-8mm instead of going straight to a zero drop shoe.
