IN THE GYM

Fill and Repeat
Remember the water bottle you tossed after Spinning class last night? It may behoove you to know it will take about 1,000 years to biodegrade. A better bet: Pick up a water-filter pitcher or a filter that attaches to your faucet, as well as a refillable aluminum bottle from Sigg (from $16; mysigg.com).

Throw in the Towel
The next time you grab a stack of towels while showering at the gym, remember that coal is required to run every load of laundry, which pumps CO 2 into the air. Limit yourself to a single towel at the gym, or carry a small one in your bag so you won't need to crank out paper from the dispenser to wipe down equipment or your sweaty face.

Give Old Kicks a New Life
Donate any brand of athletic shoes to Nike's Reuse-a-Shoe program and the company will recycle them into materials that will be used in sports surfaces, such as playgrounds, basketball courts, and running tracks, for underserved communities around the world. Go to letmeplay.com/reuseashoe for the drop-off location nearest you.

Head Outdoors
Fresh air and a new view aren't the only benefits of hitting the pavement for a run or walk-you'll save $6 and 45 kilowatt hours of electricity a month by not operating that treadmill (based on an average of 15 hours of use).