What's the Deal With Heel Drop?
Over the past few years, more and more attention has been drawn to the heel drop a shoe. This is the difference between the height that your heel is off of the ground vs the ball/forefoot. For reference, the average running shoe has a heel drop of 8-12mm, meaning that the heel is 8-12mm higher off the ground than the ball of the foot. One reason this has become a hot topic is the minimalist and barefoot running movement.
Running barefoot is a zero heel drop activity by definition, and many of the minimal or “barefoot” running shoes therefore adopted very small heel drops to help the runner achieve a more natural stride. It didn't stop with minimalist shoes though, as more cushioned shoes such as the pair of Altra's pictured above have also adopted a low heel drop. This was all done in the name of injury prevention and the belief that this was better for you than having your heel much higher than the ball of your foot.
It was theorized and even demonstrated in some studies that the running shoes of the past, which commonly had heel drops in the mid teens, resulted in increased torque and impact forces on landing. This, in turn, could result in increased injuries in the tendons and joints that need to act as shock absorption and convert this extra force into forward movement. It does make sense when it's put this way, but I don't think the added forces are really about the heel drop. Instead, I think it's more about over striding with a heavy heel/rearfoot strike, and my fear is that minimal heel drop shoes won't address this at all.
Traditional stability shoe with a 12mm drop
Minimal heel drops are primarily found in shoes that are more ideal for a forefoot or midfoot strike. Runners with the more common rearfoot strike may unknowingly use these shoes without attempting to change their gait or foot strike. This can result in decreased heel protection in some shoes and a large increase in the strain of the achilles tendon, which is not used to the stretch or range of motion that a zero drop shoe requires. It has been shown that simply wearing a zero drop shoe will not force the runner to adopt the proper form to wear it, potentially increasing injury risk in some runners.
Personally, I’ve tested a pair of Altra’s, a popular zero drop shoe. I liked the shoe for walking around because they have ample cushioning and a wide toe box, but I wasn't a big fan of actually running in them. To me, it felt like I was running uphill because of the zero drop, and it completely threw off my gait to the point that I just didn't feel fluid. As a rearfoot striker, I personally like the way that a higher heel drop acts to keep me moving forward toward my toes, and I just didn't get that feeling with the zero drop shoes. I also noticed that after several miles of running and walking, I began to get some minor discomfort in my achilles that went away after switching shoes. I gave the shoe a few tries but each time I felt the same way, and I refused to adapt my rearfoot striking gait in order to wear a new shoe.
There's nothing wrong with a rearfoot strike if done properly, and there are plenty of professional runners to prove it. I’m a firm believer that unless injuries are directly related to foot strike, then there’s little reason for the average runner to change it. This is especially true when it takes six months to two years of adaptation to completely change and become accustomed to a different strike pattern. Most people just don’t have the time or necessity to do this. I'll admit that it is possible that overtime I'd get used to the shoes, but I didn't feel the need to modify my gait without a real reason, because gait modification can result in injuries as well.
Far more important than foot strike and heel drop is cadence, or steps per minute. When a heel striker is being bothered by shin splints, knee problems, achilles injuries etc, it is more likely a problem inherent to their stride length than it is with which part of the foot is landing first. After all, there are plenty of elite runners and ultra-marathoners who use a heel strike without ever experiencing chronic injuries. The key might just be their cadence. In general, these elite runners are taking greater than 180 steps per minute. The result is that their stride lengths are often slightly shorter, and they land with their heel closer to their center of mass with their knees bent slightly instead of extended. This puts less impact forces throughout the major joints and tendons, likely contributing to lower injury risk. It’s my opinion, and that of many experts much smarter than me, that simply increasing stride frequency through minor gait changes can be very beneficial to the average runner without the need to change strike pattern. Changing cadence, with a goal of greater than at least 160 spm, is much less risky than changing foot strike or other components of the gait. Therefore, it should be attempted before extreme measures should be made. This can be done in many ways, such as with music or wearable devices, but the methods are explained much better here than I could myself:
This is the method I use to check my overall cadence. This happens to be Garmin Connect Mobile's interface, but many other companies and fitness trackers also include cadence. Some even include real time cadence that can be displayed on your watch as you're running.
I know that this may seem like a tangent from heel drop, but in my mind it all ties together. The proponents of zero drop shoes are mostly the minimalists who want a more natural stride. They praise less impact as a major reason, but I believe that this lesser impact is primarily caused by the increased cadence that a forefoot or midfoot strike necessitates. It’s nearly impossible to continually land on your forefoot and have a long stride. It just doesn’t work. Therefore, they have shorter strides and increased frequency of steps for a similar pace, thus lowering their impact forces.
So where does this all leave us? Well, the average running shoe still has a heel drop in the 8-12mm range. This is the range that the majority of heel strikers are going to feel the most comfortable in, as it tends to propel you forward from landing on your heel to pushing off of your toes. Sometimes, I’ll recommend a higher heel drop such as 12mm for individuals with achilles tendon issues, but more often than not I tend to focus more on other foot factors such as arch height, cadence or flexibility rather than the heel drop. Instead, the higher heel drop will be for their walking shoes rather than their running shoe. The heel drop of the running shoe itself may not be as important as other aspects of the shoe such as the firmness of the foam or rocker shape of the midsole, which is also meant to propel you forward. This is why I’m a fan of the Hoka One One Clifton, and other shoes in the hoka line/rocker family. Even though they have a lower heel drop of 5mm, the shape of the midsole helps you move forward no matter where you land, accommodating all types of strides and landing patterns.
Midrange drop of 5mm may be low for people with very tight achilles, although the design of the HOKA pictured actually allows for any foot strike pattern and so is better tolerated than a zero drop shoe.
Less than 4mm drops I reserve for my die hard forefoot and midfoot strikers, as these shoes can be great for them and help them maintain better posture. I tend to suggest novices in these strike patterns to start with minimal shoes that still have some heel padding, such as Altra's, just in case their form devolves over longer runs. This is not to say that a rearfoot striker cannot use these minimal drop shoes. I don't typically recommend it, but if they insist then they need to make sure to stretch regularly and maintain achilles flexibility to reduce injury risk.
As with any new shoe purchase, make sure to test the shoe in the store and find one that assists your running gait and flow rather than hinders it. If you aren’t sure about the heel drop of a shoe, ask the clerk or check online with a simple search.
As always, let me know what your thoughts on this subject are, or if you want me to do any other related topics.