Running is a popular sport – there are 2 million runners in the U.K. and an estimated 10 million runners in the U.S.[1] In Hong Kong, almost 110,000 runners registered for the most anticipated marathon race in 2017 while only 74,000 of them could partake in the event[2] Its popularity isn’t that hard to explain. You just need a pair of running shoes to start your routine, without spending more on renting courts and pitches, or buying rackets and other equipment. You can run alone and that makes it a lot more accessible than team sports. It’s also tempting to think that everybody can run without taking a lesson. Yet, this claim is up for discussion – running the wrong way for long distances increases the risk of injury substantially. Dr Roy T. H. Cheung, Associate Professor, Department of Rehabilitation Sciences, is a dedicated runner himself. While there are many apps on the market to track pace, distance and speed, he couldn’t find an affordable method to monitor his foot landing pattern. Thus, he worked with his research team on inexpensive ways to do it and the end-product is the footstrike-sensing insoles. The technology has been licensed to a leading sports brand in the Chinese mainland and for an affordable price, runners will soon be able to run without adding unnecessary pressure to their knees or calves.
Footstrike patterns and risk of injury
The risk of injury among runners is partly related to their footstrike patterns, that is how their feet land on the ground. “According to a research, only 1% of long-distance runners can be spared from any kind of sports injury in three years. Many injuries are related to footstrike pattern. Running with forefoot strike for long distances tends to increase the risk of calf injury and Achilles tendinitis. Conversely, running with rearfoot strike may pose extra loading to the knees and shank, which may result in patellofemoral pain and stress fractures. The optimal way to run is to use a midfoot strike, but it’s hard for runners to maintain midfoot strike by self-adjustment,” said Dr Cheung.
Traditionally, runners have to run in a lab to determine their footstrike patterns. It involves expensive pressure sensors and high-speed motion capturing devices that cost over HK$100,000. “There are also smart insoles in the market with numerous built-in pressure sensors. But they cost over HK$10,000 a pair. Worse still, they don’t last very long. For long-distance runners who run for at least 15 km a week, those smart insoles only last for one year at most,” Dr Cheung added.
Sensing insoles and app for real-time footstrike adjustments
To let average runners have access to their own footstrike patterns and thus, prevent injuries, Dr Cheung and his team worked on a simplified version of the steeply priced smart insoles. Only two pressure diodes are put under the heel and ball of the foot. Forefoot strike triggers the switch under the ball of the foot first. Rearfoot strike triggers the switch under the heel first. Perfect midfoot strike should trigger both switches at almost the same time. But it should still be considered a midfoot strike if the time difference between the heel and the ball of the foot hitting the ground is short enough. The sensing insole is wirelessly connected to a smartphone app. When midfoot landing is detected, the runner would hear a beep sound in the earphones. The concept is for the runners to adjust their landing pattern continuously real-time by listening to the beep. Rehabilitating runners may also use the insoles to avoid further overloading the injured body parts.
The technology is licensed to a Chinese sports brand and runners will have an affordable way to monitor their footstrike pattern while reducing the risk of injuries.
In March 2017, the Sensing Insole for Footstrike Pattern Detection in Runners won a silver medal and a special merit award in the 45th International Exhibition of Inventions of Geneva, Switzerland.
