Running shoes are designed to help protect our bodies from the impact force of each footfall. These forces are proportional to a runner's weight, so a 15-stone person, for example, produces 50 per cent more force with each running stride than someone who weighs 10st. Not every shoe handles these forces the same way.

Lighter, softer neutral-cushioned and performance shoes get crushed under the heels of heavier runners. On the other end of the scale, lighter runners don't land with enough force to effectively compress a firm stability or motion-control shoe.

The cushioning tests done by the RW Shoe Lab can give you a pretty good idea of how soft or firm your shoe should be based on your weight. A high cushioning score results from a midsole that requires less force to compress and is soft underfoot. A shoe with a low score generally has a firm midsole that takes more force to compress. However, it can offer the same impact reduction to a heavier runner as a softer sole does to a lighter runner.

The chart above provides a general idea of the heel- and forefoot-cushioning scores that your running shoes should have based on your body weight.

Along with weight, the shape and flexibility of your arch plays a major role in determining what kind of shoe you need. While arches vary widely, there are two types worth noting - low and flexible, and high and rigid. These define the extremes of how much your feet are inclined to roll inward - or pronate - when you land. Pronation is one way the body absorbs shock, but too much or too little can lead to aches and pains.

Taking a wet test will help diagnose your foot type and determine which shoes are likely to provide the appropriate arch support. Once you know this, you can narrow the search based on your weight and your cushioning requirements.