Its winter and your runs are becoming harder and harder.  Is it because you don’t want to get out of your warm bed and go jog in the frigid morning air? Or are you like me and struggle to breath in cold weather? Maybe you feel like your muscles just can’t get loose?  All of this leads to aches and pains that lead you to dreading one of your most beloved activities. Although we are able to feel all the changes the cold is making on us, we usually don’t acknowledge how it affects our most important tool … Our shoes.

For years, the soft cushy foam you have felt under your foot has been EVA (ethylene-vinyl acetate) foam. This has been the preferred cushioning material because it is versatile, soft, flexible, and, importantly, cheap. This makes an optimal material for manufacturers to make their midsoles out of.  EVA foam does have 2 major flaws though, 

  1. Degrades relatively quickly
  2. Loses much of its softness in cold temperature

I experienced this second issue while I was camping in Utah; At night the temperature was around 15 degrees Fahrenheit. In the morning when I put on my EVA shoes , they felt like bricks under my feet.  However, in recent years a new cushioning material has entered the running shoe arena, TPU. TPU (thermoplastic polyurethane) is made from plastic pellets that are fused together using heat and pressure. Originally, TPU was controlled entirely by Adidas, and was the secret to their “ultraboost” cushion.  The Adidas Ultra and Pureboost became incredibly popular in both the running and casual shoe community, due to their incredible comfort and High energy return. Runners were seeing improved performance, and the adiZero adios Boost was the shoe of choice for many of the marathon champions across the world.  TPU foam offered many benefits including

  1. Increased energy return
  2. Increased durability 
  3. An ability to maintain its elastic(cushion properties) in extreme temperatures, both warm and cold.

This last point is something that becomes very important in the winter, as this shoe will maintain its cushion feel much better than a traditional EVA foam shoe. In recent years there has also become much more of a market for TPU shoes.  It is no longer just the Adidas boost line.  But instead there are also the Brooks Levitate, Mizuno Wavesky and Wave Horizon, Saucony Triumph etc. This is why, while working at the running store, I suggest TPU shoes in the winter months, especially for individuals who come in complaining of pains they are beginning to experience in the winter months. The one downside of TPU shoes was the heavier weight and lack of options.  Gradually there are becoming more and more options and the weight issue has also begun to improve.  Many companies have started using expanded thermoplastic polyurethan (eTPU) which thermoplastic polyurethane particles are expanded to form closed cells around tiny pockets of air.

So should you switch to TPU shoes for the winter months?

The answer is the most Physical Therapy answer, it depends!  I do believe that TPU shoes do offer some benefits of maintaining softness during the winter months compared to their EVA counter parts.  However, if you don’t notice this change and are not experiencing any issues, then it is probably not worth the change.  Money is another factor to consider, TPU shoes typically are more expensive.  Finally, we have to acknowledge that there are many other factors that will affect our runs in the winter including, attire, warmups, surfaces, etc.  I hope you found this article interesting

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