[quote]You oversimplified wrote:
What science demonstrates that running on springs would be beneficial? Basically the runner and his or her shoes is a closed energy loop. Without an external source of energy, shoes cannot create extra energy for the runner.
So if the spring returns more energy, it also requires the runner to produce more energy.
Not really. Animals that run faster than us use springs so we're essentially trying to alter our conformation to duplicate their advantage. I[/quote]
I am no expert in biomechanics or physics, although I do have an engineering degree, so I would love to understand more about how a spring would work to "create" energy. Not trolling, I really am interested.[/quote]
If you're a mechanical engineer or an engineer who understood dynamics fairly well, draw a free body diagram of the whole foot as it contacts the ground. This will show you that all this "spring" nonsense about saving energy is more of a publicity thing than working technology.
Running shoes have always been about shock absorption so that your legs don't break down as quickly while running. The only spring-action taking place while running is from the calves (and hamstrings i guess but that's not important for this rant) during ankle flexation, while pushing off the ground. So that piece of carbon fiber in the sole is really only a fancy shoe support, unless runners have been generating force by bending their foot in half somehow...
And before anybody approximates the foot as a single point, just remember that the ankle is a joint, which means, any "extra energy" produced by these shoes is then transferred to the calf muscle which means more atp spent to resist a larger load.