Is it Better to Have Cushioned Running Shoes? NO!

In taking a hard look at the data, cushioned running shoes are shockingly not in alignment with preventing injury. In fact, thick cushioned running shoes were consistently found to directly encourage a force-intensive heel strike that increases impact loads on the knee as compared with true minimalist running shoes (functional footwear that are completely flat, very wide, fully flexible and are designed to mimic the feel of being barefoot).

Why Thick Cushioned Running Shoes Dont Reduce Injuries — It turns out, cushioned running shoes are a losing strategy in preventing injury. The thicker the cushioning in a running shoe, the more the inability it becomes to land lighter in that these shoes actually causes your heel strike to slam harder onto the ground, resulting in more stressed aspects along the leg, namely causing long-term damage to the knee.

For example, an eye-opening study in the journal Clinical Biomechanics investigated the influence of regular cushioned running shoes and minimalist shoes, such as the Nike Free (which have a lot of cushioning to be considered ‘minimal’, the Vibram Five Fingers (a true minimalist shoe), and the Inov-8 Evoskin (another true minimalist shoe), on knee and ankle loading in runners (all shoes mentioned shown below). Their data showed that the most troubling aspect for the Nike Free (again, a shoe marketed as a minimalist shoe, but has thicker underfoot cushioning than a true minimalist shoe) was the cushioned heel resulted in greater knee-loads, similar to regular running shoes!

Cushioned Running Shoes vs Minimalist Running Shoes — **Fig.1** The shoes in the study: (a) the conventional running shoe, (b) Nike Free, (c) Vibram Five Fingers and (d) Inov-8 Evoskin. As you can see, the Nike Free (b) is equipped with an elevated cushioned heel, like the conventional running shoe (a) whereas both (c) and (d), barefoot running shoes, are flat with no interference under the heel. SOURCE: Sinclair, J. Clinc Biomech (2014).

The researchers found that runners in regular running shoes and the Nike Free had greater patellofemoral joint (knee-joint) force and pressure than the runners in barefoot-inspired footwear (Vibram Five Fingers and Inov-8). Thus, the biggest pay-off of the Vibrams and the Inov-8s was their ability to prevent heel strike, thereby reduce knee-loads.

How did the barefoot-inspired footwear reduce knee loads?

Runners in barefoot-inspired footwear had less knee extensor moments which produces a shorter stride, thereby reducing knee-joint torque.
A shorter stride typically corresponds to the stance limb being close to the center of mass (your hips), which reduces the moment arm of the quadriceps and knee-joint torque.

How to Fix Lower Back Pain From Running: Fix Your Foot Strike! — A shoe with a flat heel (above left) makes it easier to land with a forefoot strike, which is safer than a heel strike (above right) which is typically facilitated by a shoe with a thick cushioned heel. The big clinical advantage to forefoot striking, more easily engaged in a true minimalist running shoe, is it prevents a high-impact over-stride by guiding the foot to land closer to your upper body, resulting in a shorter stride. Why does a shorter stride equate to less net impact? A shorter stride automatically reduces the time spent braking with the ground, resulting a smoother, more glide-like stride.

The only way a runner produces higher-than-normal knee loads is by heel striking, and since the Nike Free runners had greater knee loads, suggests that these runners were heel striking.

Worse still, the researchers found that Achilles tendon engagement was lower in the Nike Free runners than the runners in barefoot-inspired footwear –lower Achilles tendon engagement is indicative of a heel strike running style (shown below)

Heel strike runners tend to have less Achilles tendon engagement` than forefoot strike runners because landing heel-first when running impairs the energy-saving elastic properties of the Achilles tendon, while loading more impact through the tendon

The Achilles tendon is engaged differently in forefoot running, allowing the tendon to store more elastic energy during the loading phase, which was found to reduce muscular demands, thereby saving energy. Read more here on that!

The Take Home Message

In all, a strong connection exists between thick cushioned running shoes and knee injuries due to the stride abnormalities evoked by too much cushioning under the heel as compared with minimalist running shoes. More specifically, the cushioned elevated heel in most conventional running shoes increases knee stress by causing the knee-joint to fully unbend and lock out at touchdown, while increasing a force-intensive heel strike, while hindering the efficient use of the Achilles tendon, resulting in economic consequences, like significantly more muscle energy to lift the body forward up and through each step.

Genesis barefoot-inspired huarache style sandal

Its for these reasons that minimalist shoes have an important value because they prevent rigid heel strike landings and mechanical dysfunctions at the knee, thereby preventing long-term damage to the knee mainly by engaging more functionally ordered mechanics in the form a forefoot strike and better knee flexion at landing.

In that light, here are more evidence-backed reasons minimalist shoes are safer than conventional running shoes by every measure!

References:

Daoud et al. Foot strike and injury rates in endurance runners: a retrospective study. Med Sci Sports Exerc, 2012; 44(7): 1325-34.

Sinclair, J. Effects of barefoot and barefoot inspired footwear on knee and ankle loading during running. Clin Biomech, 2014; 29:395-99.
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