Before you throw a copy of Born to Run at my head, please hear me out!
There has been endless discussion about which footstrike is best and the types of shoes that promote whatever that footstrike is. However, most evidence points towards having your foot land under your center of gravity as the most important biomechanical cue for stride efficiency and injury prevention, rather than the footstrike itself, so it is useful to better understand the link between biomechanical cues that we can observe, such as footstrike, and whether or not we are over/understriding. Notably less discussed are the mechanisms by which we actually control this positioning in the face of the stride cues we are receiving, which is the subject of this post.
The footstrike obsession arose, and has at least some merit, because for many people, a mid/forefoot strike is correlated with a higher cadence and shorter stride, which themselves are correlated with landing with your foot directly under you (the most important thing for stride efficiency). Whatever our stride actually is, we use the feedback of the feeling of our feet hitting the ground to make adjustments and optimize our stride for efficiency.
This feedback is the reason why running barefoot tends to promote an efficient stride – the harsher landing means that you need to absorb the impact as smoothly and as gently as possible, which means using your ankle as a spring upon landing instead of slamming your bare heel into the ground. (Aside: this is also the reason that making global stride changes doesn’t tend to produce huge efficiency gains – you’re already constantly optimizing for that efficiency given your basic stride pattern). If you are a midfoot striker, you engrain that feeling of your shoes hitting the ground flat, and make adjustments on the fly to maintain that feeling.
Where do shoes enter into the picture? Low drop (the height difference between the heel and forefoot) shoes promote a more forward foot strike in several primary ways, depending on the shoe. Firstly, by removing the heel, they allow for more ankle flexion during landing. This allows you to compress your “ankle spring” upon landing, absorbing the impact and storing more energy to be released during toe-off. Higher drop shoes wouldn’t allow the spring to compress as much because some degree of ankle dorsiflexion (think toes pointing downward) is already built into the shoe. If the shoe has minimal cushioning, the “soft landing” effect seen above with barefoot running also is in play as there isn’t enough heel cushioning to comfortably land heel-first.
However, while a low drop shoe might promote a mid/forefoot strike versus a heel strike, how effective is the footstrike at keeping our landing directly under us and thus keeping us from overstriding? While weaker runners will not be able to tolerate the strain of overstriding with a forefoot strike, for runners with strong feet and calves, is the mid/forefoot strike along with a low drop shoe actually providing sufficient feedback to prevent overstriding? The answer is no. That is to say, the cues provided to runners by lower drop shoes do in fact promote a more mid/forefoot strike, but running with a mid/forefoot strike in low drop shoes is not sufficient to prevent overstriding. Once this is understood, it’s not surprising that the Born to Run movement generated a flood of foot and Achilles overuse issues, despite generating a flood of mid/forefoot strikers.
Why don’t low drop shoes prevent overstriding with a mid/forefoot strike? Runners with this footstrike type land with slightly dorsiflexed ankles. This type of landing is surely softer and doesn’t result in as much breaking as a hard heel strike, so here we see feedback to keep your foot dorsiflexed upon landing. The problem is that there isn’t equivalent feedback to keep your foot directly under you while landing, even if properly dorsiflexed. In other words, once you get used to the feeling of a forefoot strike, the same foot strike an inch farther in front doesn’t feel that different if you are in low drop shoes. This is simply because the heel will never really get in the way and wake you up to the fact that you are overstriding.
To illustrate this point more clearly, consider if you were a forefoot striker running in a high drop shoe. As a forefoot striker, you control your stride to give you a consistent forefoot landing. Now if your form started to get sloppy and you started to land farther and farther in front of your body, at some point, the heel would clip the ground before your forefoot touches down. This would send a signal to your brain that your stride is off, as you deviated from the normal feel of a forefoot strike, and you are forced to shorten your stride in order to clear that heel.
Oddly enough, this means that for overstriding heel strikers, a lower drop or more minimal shoe can give feedback promoting a shorter stride with a footfall directly under the runner’s center of gravity, while for overstriding forefoot strikers, a higher drop shoe can give feedback promoting the same thing!
For this reason, I recommend all runners to mix up the shoes they wear, as the types of biomechanical feedback provided by each shoe actually deliver different benefits to keep your stride from becoming biased towards the particular shoes that you wear. To provide an image illustrating this point, think of every shoe you wear having slack and constraints. The constraints are where the shoe doesn’t allow your stride to deviate because your biomechanical feedback will become too disrupted. The slack is where your stride can deviate from its optimal pattern because the shoe doesn’t markedly affect the biomechanical feedback in that direction. Every shoe will have some constraints and some slack, but these will differ between shoe models so mixing things up will help avoid your stride becoming sloppy in the direction of your favorite shoe’s slack.
A final note is that any runner can run with great form regardless of the shoe (within reason of course). The shoe does not make the stride!!! If you need proof of this, just watch a video of Galen Rupp running with impeccable form in the fairly bulky Nike Zoom Structure or Vomero. After years and years of training and extremely good running economy, stride mechanics of elite runners are engrained by many more cues than just footstrike. Mixing up your shoes forces you to integrate different form cues and types of feedback that will help you engrain your efficient stride and become less sensitive to the quirks of any particular shoe.