Are you legs starting to feel tired & heavy when your run? Getting niggles? Sore, hots spots in your feet that you didn't have before? Maybe it's time for some new shoes...
A general rule of thumb has always been when you’ve run in the vicinity of 800 k’s, it was time for some new shoes. The heavier the runner, or even the light runner with a heavy foot strike might only get 500k’s out of a pair of running shoes.
Usually it's the midsole of the shoe that fails first. The midsole, funnily enough, is the middle part of the shoe, the bit between the upper and the outsole and in most running shoes is made from a viscoelastic material called EVA (ethylene vinyl acetate) As the shoe ages, the air content of the EVA foam decreases. You can start to see wrinkles and collapses in the side walls of the EVA, the midsole becomes stiffer, thinner and loses its capacity to dissipate energy. This can lead to changes in the way you run with increase pressure on the heel, increasing vertical loading and potential increase risk of injuries. One study has suggested that you increase your risk of injury if your shoes are 4 months or older!
But things have changed - and not necessarily for the good.
There has been a recent trend towards softer midsoles in running shoes across many of the popular shoe manufacturers. Super, marshmallow soft. And yes, the first feel of a running shoe with a soft midsole is a pillow of cushioning goodness but unfortunately the softer material doesn’t have the same durability as a firmer midsole. The softer midsole absorbs 83% more energy initially but degrades 49% faster than a firmer midsole!!
How can you check the midsole of your shoes?
Look at them - If you see a crinkle cut patterns in the midsole material then they have started to compress. The dead shoe test is also quick and simple to do. Grab your shoe and see if you can bend the forefoot back down towards the heel of the shoe. If it feels firm and doesn’t shift, awesome. If it easily bends, then the midsole has deteriorated and you probably need new shoe.
So, if your shoes are older than 4 months or if you wear them for everything not just running and they fail the dead shoe test, then now is a perfect time to get yourself some new running shoes.