Mechanical engineer David Brown of Vanderbilt University (USA) has developed a concept for a device that removes the main advantage cyclists have over runners. That, because of which a person, who rely only on his legs and the physics of their work, will never be compared with the movement of a car with the simplest pedal drive, working at the expense of the same leg strength. So far, this is only a concept with theoretical calculations, according to which a runner in new equipment is guaranteed to be able to develop a speed of 21 m / s.
The main problem for runners is that when moving, each of their legs is in the air for some time and at these moments does not perform any work useful for movement. On a bicycle with pedals, the opposite is true - at each point of the trajectory the foot presses on the pedal and therefore the efficiency is several times higher. Brown intends to make sure that the energy of the runner's leg movement in the air is not wasted, but accumulated.
To do this, he proposes to design an exoskeleton for the legs, in which a powerful spring will become the main active element. During 96% of the stride time, it contracts to release energy upon contact with the ground and give momentum to the runner. In some ways, her work resembles the principle of a catapult, which shoots a projectile, only instead of it there will be an athlete's leg.
Brown's calculations showed that 21 m / s is not the speed limit for such a device. There is no working prototype yet, but there is no doubt that in the future the device will become even faster and more compact. And it will be able to fit right into the shoes, get a gearshift, an anti-injury system, etc. And it can be applied by a wide range of specialists for whom speed of movement is important - military, police, firefighters, couriers.
David Brown's research has been published in Science Advances.