Along with the obvious mobility issues faced by athletes who are unable to walk, they also face another challenge – if they're unable to feel their legs, that means they can't always tell when they've been hurt. Severe bruises or broken bones can simply go unnoticed, until they develop into even more of a problem. That's why a group of students at Imperial College London have invented a set of "bruise trousers" that show such athletes when and where they've received a serious impact below the waist.

The trousers were created by engineering students Lucy Jung, Elena Dieckmann, Dan Garrett and Ming Kong as part of the Rio Tinto Sports Innovation project, which is aimed at fostering the development of Paralympic sporting equipment.

They're made of breathable white Lycra, that's lined with pockets containing strips of a pressure-reactive film – the pockets are strategically located over the thorax, pelvis and leg bones. Commonly used to measure pressure distribution in industrial applications such as newspaper printing presses, that film releases a magenta dye from embedded microcapsules when it receives a hard impact – the stronger the impact, the more intense the color of the resulting stain in the film, which can be seen through the Lyrca.

The students wrapped animal bones in the trouser material, then subjected those bones to impacts of varying levels using a droptower. By observing how the shape and intensity of the stains varied with different impact loads, they were able to produce a chart that could be used by coaches or other people, to determine the severity of an athlete's injuries based on the stains on their bruise trousers.

They now hope to develop an entire bruise suit, and to commercialize the technology into a line of sports apparel.