A California gym is harnessing human workout energy and turning it into electricity to power the facility.
Sacramento Eco Fitness has installed a non-motorised treadmill and several upright cycles made by Washington-based equipment manufacturer SportsArt, with built-in inverters, similar to those found on solar panels and wind turbines.
The equipment turns the watts generated during a workout into electricity to power the gym.
Any excess electricity is sent to a battery to keep the lights on during off-peak hours.
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"We're harnessing the human power to produce clean energy," says owner Jose Antonio Avina, a former US marine who opened his gym in 2016.
A spin class on stationary cycles will produce anywhere between 1,000 and 2,500 watts, he says, which is enough to power a refrigerator.
But even a short workout can make a difference.
"On average, you at least produce 20 watts, you know, with a 20-minute workout."
The gym's self-powered treadmill uses an electromagnetic and mechanical braking system to generate power, according to SportsArt.
It uses no power at all and doesn't move until someone steps on it and pushes the belt around, either walking, running or using the toughest setting 'sled pushing', which has even the fittest gym members sweating in a few minutes.
Avina says many of his members joined the gym purely because they liked the eco cardio machines.
Nicole McCabe, a 24-year-old project manager for an environmental testing company, says reducing her carbon footprint is a vital part of her life.
"It's really important to me that everything is environmentally conscious, so combining fitness, something that's, of course, really good for you and the environment is probably one of the best ideas that anybody could ever come up with," she says.
For Avina, his self-powered gym is only the beginning.
"I would like gyms to be able to power an entire city block on their own, right? Produce enough energy to power their own needs within the facility and then have the excess energy to power a city block. That would be my goal," he says.