Forget playgrounds. How often do you see playgrounds that are empty? Quite often. You’ve already mentioned it. Gyms! Your ccck measuring contest aside, If I can power a flashlight by shaking it or a radio by by twisting a lever, should there be a way for a whole gym full of sweaty people be able to produce enough energy to power the building it is in (or least the lighting in it)? Have you ever taken a spinning class? You’d be amazed at the consistently high heart rate some people are able to keep. So what if it is “only” able to provide enough energy to offset its own footprint. That is huge! A carbon neutral gym. Brilliant.