Here are some of the common terms I’ve used in my articles. Let me know if I’ve missed anything and I’ll be happy to include it..
Upper: The upper covers your foot, making it literally the upper part of the shoe. Different materials can be used to improve the breathability, or how much air can get through to the foot. This is important as sweaty feet can rub more against the upper and cause blistering.
Midsole: The midsole is really important for running shoes, because it is the part beneath your feet that cushions your step. Depending on the style of the running shoe the thickness can vary considerably. The material is also really important, and countless resources have been spent finding the next great technology.
Outsole: Beneath the midsole we have the outsole, the layer of material that is normally harder wearing and gives the shoe grip.
Overlay: S ome running shoes have just one layer of fabric for the upper, but some areas wear quicker than others. To prevent this, some shoes have extra material or overlays that reinforce the upper or give more structure.
Toebox: The area that covers the front of your foot and toes is the toebox. There is usually some reinforcement to lift the upper away so your foot can breathe, but performance running shoes can fit much more snugly.
Midfoot: The middle of the upper is the midfoot, and is normally where additional reinforcement is added to make the shoe fit around your foot tighter. This prevents it moving during running, which prevents blisters forming from your foot moving against the upper.
Forefoot: The area between the toebox and the midfoot of the shoe is the forefoot. Depending on the design of the shoe, there can be reinforcement placed here to reduce wear.
Heel counter: Some shoes have extra structure around the heel, either plastic or thicker material, to help stabilise the foot when running: this is the heel counter. This can help prevent your foot rolling to each side when your foot strikes the ground and generally helps keep your foot in place.
EVA: Ethylene-vinyl acetate, or EVA for short, is a polymer commonly used to create cushioning for running shoes. It combines two types of plastic, which then has air injected into it. There are many different ways of doing this, resulting in different levels of cushioning. Sneaker Freaker wrote an excellent article on the history of EVA in shoes that you can find here.
TPU: Thermoplastic polyurethane, or TPU, is the technology behind Adidas’ Boost and Lightstrike cushioning. To make Boost, TPU is expanded to form closed cells around small pockets of air. Adidas found this to be highly responsive, durable and it also worked the same across different conditions.
Pebax: Polyether block amide foam, or Pebax as used by Nike, is the technology that has powered their latest high performance running shoes. While highly responsive it is also quite soft, which is why you will normally find it paired with carbon-fibre plates to stabilise the material.
Stack height: Stack height is the thickness of the midsole. Running shoes tend to have higher midsoles at the back and lower at the front, as that is where more support is needed. Older style running shoes tend to have low stack heights but newer models can have fairly high stack heights. World Athletics have even put in limits for stack heights for shoes used in official competition.
Colourway: A colourway is the term given for one of the colour schemes of a shoe, and there can be many different colourways for a particular model. There is no performance benefit from colourways, but they can definitely help a pair of shoes stand out from the crowd.
Weight: Most shoe manufacturers quote the weight of a US size 9 when talking about how heavy their shoe is. When I refer to shoe weight on this website, this is the number I’m using.