If you've decided that joining the gym is the best way to go (at least for the winter) you can still encourage your local health club to make some green changes: restrict the use of towels, invest in energy-efficient machines, offer recycling bins for water bottles (or, even better, stop selling them altogether), set up the televisions to shut off when the machines aren't in use.
Some gyms are even harnessing human power to supply energy and reduce bills. Every little bit helps. Then talk to your workout partner about switching indoor workouts for weekend hikes or bike rides. You'll be able to switch up your routine and get a better workout while making everyone a little greener.
More great ways to show how much you care about our planet