Over the past several years the use of technology in the running industry has become very advanced, with particular regards to footwear. While the offerings may vary from one manufacturer to another, the end product is generally the same; highly specialized running footwear, for every runner. For many runners, there are still many questions regarding how to minimize the risk of injury. Despite the onslaught of technology, in the running shoe industry, this footwear still breaks down! So, the age old question, "how often should I replace my running shoes?"

The answer is that there is no real answer. Due to a large variety of different running styles, no two shoes will wear in exactly the same way. Along with running styles, running terrain and brand can also be a factor in the way running shoes wear down. Add to that the runner's size and running frequency, and we have developed quite the multivariable equation! Just as any multivariable does, this question has several answers.

But, the real question that we should be considering is why it is important to replace running shoes in the first place? From the moment you slip on those new kicks, throughout the initial few hundred miles put on each pair of running shoes, the stability of the shoe starts to break down. As the shoe breaks down, it is not capable of absorbing the impact the way it was when first purchased. Rather than acting as a protective measure, the shoe allows this impact to be delivered to the joints in your feet, ankles, knees and back. In the end, allowing your body to become accustomed to this protective measure, and then essentially taking it away can result in injury.

So, how do you avoid this? To begin with, you need to track the lifetime of your shoe. This is typically measured by the number of miles logged in the shoes. The average mileage per shoe is typically between 350 and 550 miles. Lighter runners generally get a longer lifespan out of their shoes, while heavier runners are typically forced to change their shoes more frequently, closer to 350 miles. Runners who run less frequently, or rotate shoes, often enjoy a longer lifespan, as the shoe is more able to "heal", after each run. Much of what goes into a shoe's construction is blown rubber. When we run, it compresses the rubber. When we are not wearing them, the shoe attempts to heal, as the rubber expands back towards its natural state. The more worn that a shoe becomes, the less able it is to return to that initial state.

Along with mileage, you can also look for visual signs of wear and breakdown. If you've purchased a pair of running shoes in the past, you'll know what the bottom of a new pair of shoes looks like; they're clean, they have good tread, and when put on a table, they sit flat. One easy way to see the general wear on a pair of running shoes is by placing the shoes on a table. If there is a part of the shoe that isn't touching the surface but was when you first purchased the shoe, chances are, it may be approaching the time for a new pair.

Unfortunately, not all signs of wear on the shoes are visual from the exterior. It is possible that the internal sole of the shoe will break down before you are able to see any external signs of wear and tear. It is important to take the soles of the running shoe out, from time to time, and see how they look. Or, always keep a new pair of the same shoes around the house. If you think your shoes might be worn out, try on the new pair, and see if they feel more supportive. Finally, how do the shoes feel to YOU, on YOUR feet? All athletes needs to learn that the most important indicator for working out is their own perception. If you are a runner who is lucky enough to avoid injury, but are starting to feel more sore than normal, or your joints are beginning to hurt, chances are, its time to replace your existing shoes.

As eluded to earlier, a great way to help prolong the life of a pair of new running shoes, is to rotate between two separate pairs. While not the cheapest option, initially, this route will ultimately help prolong the lifetime of each pair of shoes thus helping you save some money and also stay injury free.

As a final note, remember that it is always important to listen to your body and be aware of the signs of wear and tear of the products you use as you pursue your love of running. Running is much more enjoyable when you are pain free and can purely enjoy the act of the sport.