Do you buy your shoes without knowing what they’re made of? At Shoe Solutions we thrive on educating our customers about footwear composition so they can make knowledgeable footwear decisions. The materials that make up your shoe are often overlooked in footwear shopping. However, this piece of information is crucial; knowing what the shoe is made of tells you what the purpose is and whether it will help you through an 8 hr shift standing at the register, dance like nobody's watching, or frolic through the coulees. So buckle up for a quick Shoe Material 101 lesson with a focus this week on midsoles.
When considering materials, you can break a shoe into three components. First, the upper is the main body of the shoe that houses the foot. Uppers are often made of materials such as leather, vinyl, canvas, or ballistic nylon. Second, is the outsole which is the part of the shoe that contacts the ground directly, providing traction and grip. Outsoles are usually a rubber compound of some sort. Lastly, and our focus today, is the oft-forgotten midsole. The midsole is the main cushioning and support system of the shoe. In the midsole you will find a range of materials from rigid shanks to that amazing feeling memory foam. These materials all fall somewhere on the durometer scale. The durometer is simply a measurement for the hardness of a material. This is mainly determined through the amount of time a material takes to rebound back to its original state after being compressed. If the durometer is very high the material is hard and will return to its original state very quickly, or if it’s low the material is softer and takes longer to return to its original state. There is no ‘one durometer fits all’ for midsoles. It will all depend on what you’re using the shoes for.
A shoe that is made of soft, low durometer material, such as memory foam, typically creates an initial comfort, but the longevity of the shoe is abysmal. If you're walking on concrete all day, the memory foam won’t be able to stand up to the repetitive pounding force. You would need a shoe with a stiffer (higher durometer) midsole such as polyurethane (PU) or a harder EVA, so it will withstand the 10,000+ compressive forces from each of your steps. However if you are running, you would be looking for a shoe to aid in shock absorption. In this case a midsole with a medium durometer compound like thermoplastic polyurethane (TPU) or a softer EVA would be better at absorbing the impact. If you’re going on a nature walk in the coulees, you will want to go back to a stiffer shoe that will provide continuous support. There are occasions when you don’t need to worry about the midsole too much. For example, most people if they’re in and out of their car just running errands, will be able to use a softer, memory foam type of shoe. One thing to be aware of is some shoes are without a midsole entirely, we’re looking at you foam flip flops, fancy boots and ballet flats! This is a good indicator that it is not a shoe for long duration wear.
Each shoe is designed for a different activity and the midsole materials lead the way in that design. Thinking about the activities you’re doing will help you choose the right shoe. Then, when you are making a shoe purchase you can test the durometer of a shoe yourself just by compressing the midsole, or twisting the shoe in your hands. It will give you an idea of what stiffness the shoe is and therefore an idea of its purpose and length of time you could be wearing it.