I opened my eyes, looked around the studio. So much muscle power peddling these machines!—yet, we weren’t going anywhere. If we were on real bikes, just think of the places we could go.

Or the things we could be generating energy for! Small things, like the light in the spinning studio, or the sound system we were listening to. How could we capture, harness, and store the energy created from all this movement?

Modern gyms waste a lot of electricity during off-peak hours (and arguably, even during peak hours). It’s crucial, I thought to myself, between beats and breaths, that we find a way to do it better.

Some gyms already have found a way. A number of gyms have popped up that generate their own power from elliptical machines, recumbent and upright bicycles, and other cardiovascular equipment. The machines are specially designed to convert the energy generated from their spinning fly-wheels into electricity. The electricity is then circulated back into the gym’s power outlets or into a central battery that can store energy for later use.

According to website The Green Microgym, an average workout creates 37.5 watt hours (Wh), while a vigorous workout produces 50 Wh of electricity. Fifty Wh is enough to power 10 smart phones, five netbooks, five CFL lightbulbs, two LCD screens of the kind found on exercise machines, or one stereo.

Unfortunately, this much energy still isn’t enough to go carbon-neutral—these gyms still need to utilize electricity powered from local power plants, which are typically coal burning.

To reverse the effects of climate change, we need to work to reduce our own contributions to carbon emissions. Meaning, if you’re going to have a gym membership, you’ve got to do your best to create a greener workout. I do it by avoiding the plugged-in equipment. There’s still yoga, boot camp, weights, and spin class to keep me in good shape.