Athletes looking to log big miles while avoiding injury may naturally be drawn to more cushioned running shoes, which intuitively would seem to offer more protection. The birth of the ‘maximalist’ running shoe, with an immense amount of cushion (and often with a minimal drop), has filled this niche nicely as more runners get into the ultra scene.
Scientists have studied just about every element in running shoes, observing not only speed but injury rates. And while the infinite models of shoes available combined with variations in individual stride can make testing problematic, many studies suggest that more cushion in a running shoe might not always be better.
In June 2018, a study at Oregon State University indicated that super-cushioned, maximalist shoes actually caused a higher rate of peak loading and impact forces—basically the effect of the foot striking the ground. The theory behind the result is that big soft shoes prevent the foot from functioning as it should (like a spring), and instead turn it into a shock absorber. Joints and tissues end up doing the job, which can lead to injury.
A study in 2015 had similar results, showing that a softer shoe increased vertical impact forces and caused more knee joint stiffness, which implied the possibility of increased loading on the tissues. In other words, the squishiness you feel when your foot lands and expands doesn’t necessarily help protect your joints, and may even hurt them—you could be creating more stress instead of less when you opt for the most cushioned shoe.
The midsole of the shoe—the material sandwiched between the upper and the lower (outsole)—is where the cushion resides. Traditionally, this material is one of two types of foam: EVA (ethylene vinyl acetate); or polyurethane (PU). In the past, having more cushion generally meant having more, softer foam and usually more bulk and weight. But in recent years, EVA and PU are often replaced by proprietary materials created by individual shoe companies and tested extensively. Some new foams absorb the shock of a stride and also respond, or give back, putting spring back into your stride.
Nike’s Zoom Vaporfly 4% (4% less energy required to run) boasts a light and responsive midsole with its proprietary foam and carbon plate. As Eliud Kipchoge said after running 2:00:25 in an attempt to break the 2-hour marathon mark in Nike’s controlled experiment, “You feel like flying when you’re running. [There’s] no impact at all, no soreness on the muscles.”
Adidas shoes are equipped with a ‘boost’ foam, made of squishy pellets that absorb impact and spring back into shape, giving you rebound. This effect transfers even to lower-profile shoes, like the Boston, which is light and svelte, allows you to feel the road, and provides a springy response with each foot strike.
Brooks has a DNA midsole made up of a foam that adapts to your stride, weight, pace, gait and is said to give twice as much return no matter what kind of runner you are. On, a Swiss shoe company, uses what they call Cloud-Tec technology, featuring hollow pods that cushion for a soft landing and then become firm for an explosive take off. Again the idea is that you are cushioned for your landing but get a spring for takeoff.
There are a lot of other characteristics in running shoes not covered here, and no single style of shoe will work for every runner. Remember that if you are using a shoe that doesn’t feel right, it probably isn’t right for you. Your body will be most efficient, and your stride will feel most comfortable, when you find a shoe that works for your particular geometry and running stride.
A good running store will give you 30-90 days to try shoes, as will most running shoe online ordering platforms. My recommendation is always to buy a relatively light shoe and to look for one with good materials that absorb and respond. Of course, you should always have more than one pair of shoes in your quiver, especially if you run the same roads every day. Adding a little diversity keeps you and your shoes fresh!
References
Baltich J, Maurer C, Nigg BM. Increased Vertical Impact Forces and Altered Running Mechanics with Softer Midsole Shoes. Garcia Aznar JM, ed. PLoS ONE. 2015;10(4):e0125196. doi:10.1371/journal.pone.0125196.
Pollard, Christine D. et al. “Influence of Maximal Running Shoes on Biomechanics Before and After a 5K Run.” Orthopaedic Journal of Sports Medicine 6.6 (2018): 2325967118775720. PMC. Web. 12 Oct. 2018.
