Green gyms shed pounds, create wattage

At the Green Microgym in Portland, Ore., the stationary bikes and elliptical machines recapture the energy patrons create while pedaling, convert it into electricity and channel it back into power outlets, Time magazine reports.

An average workout there generates 37.5 watt hours, which owner Adam Boesel says can power a phone for a week. The gym does not yet produce enough electricity to be carbon-neutral, but if all the equipment is being used at once, it can produce 10 times the amount needed to run the facility at any given moment.

A gym in Hong Kong has used such equipment since 2007, and there are now converters on exercise equipment in more than 80 locations in North America.

"We have seen a significant increase in interest in the past six months, which is a good sign that fitness centers are ready to invest in green technologies," says Mike Curnyn, co-founder of the Green Revolution, a Connecticut company that wires bikes into a central battery to store energy.