It Depends - The Shoe Edition

It’s not uncommon to hear someone say that they ‘need’ cushioned shoes or a certain millimeter drop. 

Let’s be clear, they don’t say they ‘like the feel’ of a cushioned high-drop pair of runners -  they say ‘I need’ them. So do you really ‘need’ a certain drop and cushioned shoes? Well, it depends!

First, let’s explore drop. The drop of a shoe is the difference in height between the heel and forefoot. The greater the drop, the steeper the angle between your heel and forefoot.

Based on a heel drop, shoes are typically split into 4 categories: 

• Zero drop (0 mm), 

• Low drop (1-4 mm), 

• Mid drop (5-8 mm), and

• High drop (8+ mm) shoes. 

Heel drop should not be confused with stack height (or cushioning), the amount of material between feet and the ground. They are completely independent of each other.

The effects of a heel drop

Heel drop influences running kinematic and kinetic patterns (as explained in this study) and summarized below:

Zero to Low Drop

• The lower the drop, the greater the potential to improve cadence.

• Lower and zero drop shoes promote midfoot and forefoot strike.

• Lower heel drop can help with ITB, (anterior) knee pain, gluteal overuse syndrome.

• Low-drop shoes allow for more ankle flexion during landing. The ankle absorbs the impact and works as a spring. These shoes can place greater stress on the foot, ankle, lower leg.

Mid to High Drop

• Ground contact time is longer.

• A higher drop promotes a rearfoot strike because the elevated heel helps with high impacts when the heel hits the ground.

• Higher heel drop can help with plantar fasciitis, Achilles tendinopathy (stiff Achilles), and calf injuries.

• High drop has a higher knee flexion moment. This means it has the potential to load hips and knees more, similar to heel strike.

If you are running on the track there’s a reason that track spikes are zero (or very low) drop and there’s a reason why racing flats were flat. This is to make full use of the stretch reflex on the Achilles calf complex to occur. It’s like fully stretching a spring to allow for maximum recoil.

So do you need drop? I say no. Below I summarize my case. The first set of arguments are based on my beliefs and research conclusions, and as such, you can choose to ignore them, but then wait for the kicker:

I believe: 

• In adaptation over protection. Protecting your feet (too much) with cushioned shoes unlearns your brain from optimal running biomechanics. Running with the correct technique (even in prepared bare feet) on any surface is injury-free.

• That all additions to the body damage running skill. Evolution didn’t make us born to run without reason. Running is a movement skill.

Research proves:

• That cushioning protects (but weakens) your feet, and also magnifies the forces to the joints.

• That overpronation doesn’t cause common overuse injuries; a weak kinetic chain is the primary catalyst of those ailments.

• That stability and motion control shoes don’t fix pronation; instead, they weaken and limit the natural motion of the feet, lower legs, knees, and hips, causing an unnatural gait pattern.

• That good running form is facilitated by strong feet, ankles, and lower legs as well as lower limb agility, allowing knees and hips to track consistently in the sagittal plane.

• That an efficient running gait results in a foot hitting the ground below the body and not far out in front of it in a heavy heel-striking fashion.

But even if you have different beliefs or decide to make different conclusions on the research data, here is the kicker. 

Swimrun races are predominantly trail races. When we are running on a trail the ground is uneven. The discussion of 0 mm versus 10 mm drop is irrelevant. When you are running trails the offset between your forefoot and heel through contact can be several centimeters either way. 

Your Honor, I rest my case.

So let’s move on to cushioning. 

If you told me that you like the feel of soft, bouncy moon boots, or like the feeling that the shoe is doing the work for you. Okay. Fine. But why do you ‘need’ that feeling, especially when highly cushioned shoes are not actually linked to lower levels of impact than more minimal running shoes?  In fact, they come with a higher vertical average load rate and vertical instantaneous loading rate; both of which promote overuse injuries like stress fractures and plantar fasciitis. 

How is it possible that more cushioning can result in a harder impact? There are 200,000 receptors on the bottoms of the feet, and they’re screaming for awareness and activation. When we put more cushion and stack underneath the bottom of the foot, we start to disrupt the way the foot is designed to feel the ground and that can show up in your gait via overstriding and other movement inefficiencies. 

High cushioning can also lure you into running more than your connective tissues are ready to handle.  In addition to creating distance from the ground, the foam’s density affects your interaction with the surface and your stride. If your foot and ankle are working harder inside the shoe to stabilize your gait, generally that’s going to create some extra rotation at the knee and extra work at the hip.

If you have lower leg stress issues you may wish to put some cushioning into your rotation. But this is more an argument to build a robust running body rather than for cushioning per se. You need to be careful not to just treat a symptom and move the imbalance somewhere else.

However, there is one good reason!

This said, I can think of one reason you would need cushioning, but it is certainly not to do with feeling nice, protection or good running biomechanics. It is to do with performance.

Carbon plated super shoes have made an impact on run times since the Nike Vaporfly 4% shoes were introduced in 2016.  The performance advantage isn’t purely the carbon plate (or rods), it is the synergistic interaction of the carbon structure with the specialty midsole super foam. This is why it took the other brands so long to catch up. It wasn’t because they couldn’t create the carbon plate, it was that their foam midsoles were initially inferior to Zoom X. So if you need a thick layer of foam for performance benefits you have to accept cushioning. I’ve been in minimal shoes for more than a decade but for key races on the road I’m lacing up the fastest pair of supers I can find! Vanity is a great motivator.

Although more relevant to sub-elite marathoners than swimrunners. In a somewhat related performance theme, if you’re someone who likes to get lots of kilometers in, then the reduced muscle fatigue that comes from using “super shoes” can be a handy tactic.

The combination of advanced foams and the carbon plate means some of the “pounding” is taken away from the muscles, and less muscle damage results from eccentric (braking) muscle contractions. By keeping a lid on the leg fatigue, high mileage weeks are more attainable.

Running 120+ km isn’t necessary for most of us, and even those looking to run sub 2:30 often won’t need to reach this mileage, but some runners prefer to go down this route. This kind of weekly mileage in “normal” running shoes can be brutal, especially when you’re sustaining that for 10-14 weeks in a marathon block.

Conversely, if you are on a lower milage routine the reduction in muscle work being done to achieve your desired paces means the muscles don’t get as much stimulus to adapt and become stronger, so some benefits of running are lost.

How about the trail?

When it comes to trail it is a little less black and white. The Altra Mont Blanc Carbon and the Adidas Terrex Agravic Speed Ultra are examples of brands bringing this super shoe performance formula to the trails. I name these two examples as the respective Vibram and Continental soles give good grip for swimrun. Whereas I’m sure Tom Evans has the running form, fatigue resilience, strength, and stability to use them on tough trails, I do not believe most weekend warriors do. I have tried, but when the trails get technical I revert to lower stack heights and more ground feel.

Final words

You don’t need stack, cushioning, or drop. What you need is a strong kinetic chain, superior foot strength, and great running biomechanics on which to build running fitness. You need to be elastic, fluid, connected, and synergistic. Moving better takes time but is a celebration of what it means to be human. Embrace natural movement, if you do, you’ll get more out of your cushioned shoes when you do need them.