The midsole of a running shoe is where the magic happens. If there is one thing to take away from this writing today, it’s that all that stuff positioned between the ground and your foot is very, very important. I bet you didn’t think about the anatomy of your running shoe, did you?
The “sole unit” of your shoe is made up of the outsole and the midsole stuck together. The outsole is the bottom surface that is in touch with the ground. Its job is to be durable because we pack on the miles and has to make the shoe last. The midsole is the material between the bottom of the inside of the shoe and the outsole. And this is what I want to talk about.
Why is it so important? Why should you care?
Basically, the midsole dictates how the shoe is going to feel to you and how the ground affects your foot. When you read about high cushion, responsiveness, motion control, stability, etc. you are reading about how the midsole for that shoe is designed and structured in that shoe.
Traditionally the midsole is a foam material. Think of a big marshmallow or pillow. They can be used to cushion a fall or contact of sorts. This is the same idea for the shoe. And in the past, the more cushion the better but that made shoes heavy. Heavy is not necessarily a good thing. (because increased shoe weight decreases running efficiency while decreased shoe weight increases running efficiency). So the ever-present game of balance was providing sufficient midsole cushion without adding too much weight. This is why elite runners would race in flats but train in more cushioned shoes. It was not always possible to train and race in minimal cushion, so they would “save” their low-weight (and low-cushioned) options for the day it really counted.
Enter the early 2010’s and running shoe companies have made some massive strides in shoe technology. And yes that pun was most definitely intended! Traditional midsoles are a thing of the past as the new research and development started turning out new materials and new technology that allowed more cushion with less weight. From a physics standpoint, that is the golden ticket. This is often why you see these “super shoes” look like moon boots with high stack heights. Yet they are surprisingly light. And this is why they have been shodding the feet of runners everywhere. …shod is a unique word to mean “wearing shoes” and I possibly just used it incorrectly, but it sounded good.
Increased cushioning without increased weight means increased efficiency.
That’s all that matters. Nike, Hoka, Saucony, Asics, Adidas, etc. are all companies revamping their running shoe lineups and offering models with improved midsoles for runners. Some use generic materials and some companies have their own proprietary materials that they keep close to their chest. But you’ll see it in the names of the shoes or the descriptions. Don’t go crazy trying to decipher it all, just understand that the midsole matters, and it can have an impact on your running and training life.
That’s the true take-home message. The midsole is important, and it’s where the magic happens. When you’re wondering which model to get, and why some cost more, chances are the materials and technology have been a worthwhile investment and it’s possible your feet may thank you later. Understanding what the midsole does may help you understand the shoe lineups a bit better and maybe even help you make a better choice next time you’re opening up some boxes with that new shoe smell.