By Podiatrist Rob Dallimore

Whilst helping out at some recent training sessions, I came across some good and bad examples of running shoes. I have noticed experienced triathletes seem far more open to, and willing to adhere to, professional advice on footwear and biomechanics than those new to the sport - perhaps a sign of the commitment and attention to detail this sport demands.

However, I am unfortunately finding (whether your shoes are suitable or unsuitable) that most of you tend to wear your shoes past their useful life. This may cause problems/injuries if left for a period and matters will only be hastened or made worse if you begin to increase your fitness or build up for targeted events, such as ½ Ironman, Ironman and Marathons. As you increase your mileage and intensity, you may notice a rapid return of an old injury or even signs of a new one when wearing poor footwear. If allowed to progress for too long, the stresses on your body may be significant enough to develop into a more serious injury in the body and put you on the side line - not a nice place to be when you want to be out exercising.

Most shoe companies state that their shoes will last longer than 800km. This is a lot of running, and for some of you it may take a long time to reach this amount. However I certainly do not recommend running in shoes as old as this - for some very pertinent reasons.

The following few points will help you determine when your shoes are past their "use by date":

Outsole Wear

Most of the shoes on the market today are made of very hard-wearing carbon rubber soles, which in some brands, seem to last for ever. Saucony for example probably have the hardest wearing outsoles with their XT900 compound. In the past, the compromise for having a harder outsole is that you lose some traction in the wet, however this issue seems to have been alleviated. Blown rubber is often used to improve traction and this is a lighter compound than the carbon. Shoe companies are now placing hard carbon rubber on high wear areas and blown rubber on areas of low wear - to keep the weight down. So with these new hard wearing compounds most of your shoes outsoles last longer than they ever used to. This means that the old tried and true method of wearing your shoes until the black bits are gone is obsolete. If you can see areas of the midsole poking through, then you have worn your shoes way past their use by date and that may explain the onset of your injury.

Midsole wear

In the past, shoes midsoles were made out of Ethyl Vinyl Acetate (EVA), which broke down very quickly and had poor cushioning, or Polyurethane (PU) which was hard wearing, heavy and smelt like cat wee if left wet. Today every shoe company has its own patented midsole material. Some brands will work better for you and other people, and unfortunately trial and error may be the best way to determine what works best for you - your Podiatrist or shoe shop staff will be able to give good advice as to what may suit you too. Keep an eye out for creases in the midsole unit of your shoes around the heel and the forefoot. If they appear very early in the life of the shoe then it would suggest you are compressing them down too much and that they may not be suited to your biomechanics. Also, be cautious of creases in the dual density (grey coloured) section of the medial aspect of the midsole as this is where the shoe provides its support - if this isn't holding up then the shoe isn't working. My personal feeling is that when you run in the wet the shoes midsole will squeeze like a sponge and therefore draw in a lot of moisture. However, it is unlikely that all the moisture will be expelled the next time the sole is compressed (the next step), so there will be a residual amount held within the midsole. If this moisture is not allowed to dry out completely before the next use, then the cycle will be repeated, bringing more moisture in. Over a longer period of time the midsole material will probably breakdown quicker than desired. It is often a good idea to have a second pair of shoes and let the wet ones dry naturally - not in the dryer!!

Heel Counter / Fabric

The heel counter is the hard section of the shoe that cups the heel and is a classic tell tale area for a worn out shoe. The stiffness of the counter itself is by virtue a strong plastic which is designed to prevent lateral slippage of the heel in the shoe and to provide prevention of excessive supination and pronation. The nature of this part of the shoe is such that it is under constant strain when running and will eventually conform to the pressure the foot is placing on it - this results in a steadily less effective support mechanism the older the shoe gets - this doesn't start happening before a long period of continuous wear over a season or so. It is important to check your old shoes are not taking on this shape by placing them on a flat surface, looking at them from behind and determining that a bisection line up the back of the heel maintains an upright position. Once the counter appears to be pushed towards a medial (turned in) or lateral (turned out) direction then it is time to replace your shoes. Another good indicator is the amount of wear on the fabric lining the heel counter. The more a foot shifts and pronates inside a shoe, the more it will wear the material down. This is a fairly self-explanatory alarm for replacing your shoes as the torn fabric feels uncomfortable and may cause blistering.

Innersole wear

The innersoles from your running shoes also have a limited life span and these can indicate when shoes are worn out. Simply remove the liner from your shoes and feel how flimsy or firm it is. If it barely holds its existing shape and the rubber is being worn through then replace your shoes. These liners do provide a small amount of cushioning and if they are worn out then the shoe will feel very uncomfortable in the forefoot.

Upper wear

Keep an eye out for any cuts or tears in the shoes upper, either in the creased areas of the forefoot or about the toe box. Any loss in integrity of the upper will affect the way the shoe fits around the foot and the overall comfort and function of the shoe.

Forefoot and Rearfoot Cushioning

All shoe brands have their own patented cushioning system. They all have their benefits for different types of runners and therefore wear in different patterns and durations. You will probably notice when the shoes cushioning gives up the ghost, as the shoe will all of a sudden feel uncomfortable. Some people even describe a sudden 'giving out' of the cushioning. This is particularly applicable to the forefoot cushioning unit as these tend to be less resilient that the rear foot. In the past, shoes with visible cushioning units had a history of 'blowing or popping' prematurely, however the shoe companies are wise to these faults now and seem to be able to prevent this happening to their technical running shoes.

Midfoot Shank

I will always bend a shoe in the middle to determine the strength of the midfoot shank. This is not a useless habit, but in fact, a very reliable way to determine the stability and strength of a shoe. If the shoe flexes transversely across the middle when the forefoot is bent back towards the heel counter then it is likely that it has been worn heavily. In the majority of running shoes this aspect is required to be stiff as it prevents collapse of your midfoot when running. For the most part though, a shoe should only flex at the forefoot where the toes bend and longitudinally when the forefoot is twisted on the rear foot.

So keep an eye out that your shoes are in fact working for you. Just because at first glance they still seem like you could wear them to a barbecue with pride, they may be affecting your form so take a closer look. And remember, if you're ever in doubt pop into your local running shoe shop or make an appointment for a professional biomechanical and gait assessment with a reputed Sports Podiatrist.

Click here to return to the Articles page