Tread Softly...

...the skinny on home fitness machines

You want to work out at home —get fit, maintain a healthy weight, maybe even watch TV while you’re at it. So you look at treadmills at your local fitness store. They tilt, have pre-programmed “trails”, measure your calories burned—everything you want, and more.

A lot more. That treadmill uses at least a 3 horsepower (HP) motor, the equivalent of approximately 2200 watts (1 HP = 746 watts). That’s a lot of power, considering your body’s output. An engineer (a runner, needless to say) who likes his numbers has calculated that his running for one hour (it varies for everyone, depending on fitness level, speed, etc.) would consume 15 food calories per minute. Through a wonderful series of conversions, he equated this to 1046 watts in one hour—1.4 HP. This, however, is energy consumption—not output. As humans are generally less than 25% efficient (energy-wise), that equates to more like 1/4 HP output—only 1/12 of the power that treadmill is using! If you throw in the power being used by the machine to cool it (fans), and those with a second motor just to run the incline, you realize that energy discrepancy is even worse. You are effectively putting more than 20 times more carbon dioxide into the air than you would be if you were running in your local park.

Avid exercisers would rightly point out that our climate doesn’t lend itself to running in the park year round. A climate-friendly alternative might be the exercise bike. Many of these are self-powered (although some do come with A/C adapters to run the display). Your 1/4 HP energy output is enough power to run the bike’s displays—no power draw at all. So next time you shop for equipment, or work out at the gym, why not take a seat, and save some energy?

 Thanks to Geoffrey Mayo, an environmentally conscious engineer from Toronto; and to www.coe.montana.edu/ee/rmaher/pers/running_power.pdf

(May 2007 WasteWatch)

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