A Knee Brace You Want to Keep On
If the nuclear powered backpack doesn't work out, there's always going to be knee power. Imagine flocks of runners with LEDs powered by these.
Taking People Power to a New Level - NY Times - 08 Feb 08
"The generator does not capture the motion throughout the entire stride, since that would subject the user to a dragging feeling with each step. Instead, the gearwork disengages at the beginning of the step and re-engages as the leg swings back from a stride. This means that the only drag occurs at the tail end of the stride, when muscles are actually working to slow the leg down."