The Monday Shakeout: The Variability of Shoe Drop
By Matthew Klein
This week we talk about the static measurement of heel drop doesn't tell the true story and why a dynamic understanding will help runners (and walkers) best understand this commonly reported specification.
Along with weight, "Shoe Drop" is a commonly reported number in the description of many running shoes. Heel-Toe Drop, Heel Drop or Shoe Drop is defined as the static difference in height between the back (heel) and the front (forefoot) of the shoe. This changes the relative position of the foot within the shoe. A higher heel drop will put the foot in a more plantarflexed position (pointed foot). A lower heel drop will put the foot in a more neutral or relative level of dorsiflexion. Several years ago, the average drop was 10-12 mm. Since the minimalist movement and the current progressions of the maximal movement, that number now averages in the 5-8mm range. A higher drop is known to reduce the range of motion required at the ankle and from the calf muscles. Those with stiff ankles or calf muscles may benefit from a higher drop shoe, although it does place more load into the anterior shin muscles, quadriceps/knee muscles and the gluteal/hip muscles. A lower drop requires greater range of motion and muscle activity from the ankle and calf muscles. Those with good ankle motion, adequate dorsiflexion, good calf strength/power/flexibility and those looking to shift work away from their knee and hip may benefit from a lower drop shoe.
Drop is Dynamic
What many people do not realize is that the listed drop is a static measurement and shoes are dynamic structures when loaded during activity. The high forces during running, which can be anywhere from 4-6x your body weight with each step, will deform all but the most minimal shoes during the stance phase of running gait (foot on the ground loading the shoe). Additionally, different midsole and outsole combinations will compress more or less depending on their cushioning/compliance. Softer materials will compress far more while firmer materials will compress less (although sometimes a shoe can feel firm despite having a lower compliance foam due to the shoe "bottoming out" or you pushing through all the foam too quickly and compressing it). Some shoes now have different densities of foams in different parts of the shoe that may compress differently, further changing the dynamic drop of the shoe. Depending on several factors, the actual dynamic drop of a shoe can vary greatly not only throughout a person's footstrike, but also between different people.
The Impact of Footstrike
Initial footstrike is one thing that will impact the heel drop. A heel strike will compress the rear portion of the shoe, lowering the drop as the rear foam compresses relative to the front. A forefoot strike will compress the front portion of the shoe, raising the drop as the front foam compresses relative to the back. A midfoot strike should theoretically compress both the front and back at the same time depending on whether you actually load them equally. As the body transitions over the shoe, regardless of where you land first, there will be a transition of load to the front of the shoe. Therefore, as your foot travels under and behind you and the forefoot of the shoe is more compressed, the dynamic or relative drop will increase.
It is for the above reasons that shoes can feel like they have a different drop than what is listed. The listed drop is a static measurement and may not be reflective of what the shoe does or feels like under load. This can make low drop shoes feel like they have a negative drop (heel strike) or a moderate drop (forefoot strike) or high drop shoes feel like they have a moderate drop (heel strike) or extremely high drop (forefoot strike).
How Does Shoe Wear Play a Role
The last factor is shoe wear. As shoes wear down, the foams/materials begin to compress more and lose their resilience (reforming) ability. Depending on where you land and load, that part of the shoe may compress more. This can also make a shoe feel higher or lower drop than listed with time. This is also why drop can feel so different once you get a new pair of the same shoe after wearing out the old one. For all of these reasons and more, this is why we talk about what the heel drop of the shoe actually feels like. It is also why we encourage you not to obsess about this number given its range and variability.
PAST MONDAY SHAKEOUTS
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Challenges with Large Toe Spring
Phases of the Swing Gait
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The Best Shoes of 2023 for Highly Specific Reasons
Andrea's Favorite Shoes of 2023
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Matt's Favorite Shoes of 2023
My Favorite Flat Feet Shoes of 2023
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How Forefoot Rockers Help Toe Mobility
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The Importance of Heel Bevels in Shoe Design
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NEXT: Science of Sole Width in Shoes