Restarting Fitness For Net Energy Gain

Before we bought our house, we'd gotten into the habit of exercising almost daily. There was a gym (AllStar Fitness) very close to where Kris works, so we'd get up at O-God-Thirty and walk over there fore whatever class they were having. We got a nice mix of spinning, weightlifting (...under some cool name like "BodySculpting", but whatever!), and yoga. We were looking pretty good and feeling great! Also we made some good friends ... there's nothing like sweating and hurting just a little together!
The only real downside to buying a house is that we had to completely change our exercise routine. We tried to stay at the same place, but it just didn't work out; it made no sense to drive out of our way even though the classes were just as good. We soon found many excuses to take off a day or two, and then all of them.
Nature took its course: weight up, tone down, creaking increasing!
Recently, we restarted by joining the West Seattle YMCA. It's on the way to Kris' work and has classes early enough that she can get to work on time. It seems to be a nice bunch of people and the price is right. In fact, the price is so right that we can afford to chip in a little extra for scholarships; it just feels good to be a contributing member of our community!
We're starting slow and easy with yoga classes. Getting injured because we cranked up the weights too soon after a year or more off didn't seem smart. From the very first class, we felt better: looser, more energetic. We'll add some of the more intense stuff as we get back to trim, but at least we've started; as they say, half of life is just showing up!
I'm writing about this because this week's Change The World Wednesday Challenge is

"This week unplug your exercise routine by using no power. No treadmills, ellipticals, gyms, TV, music, or anything powered to assist in exercise. Make your workout Eco-friendly ... and, as always, let us know all about it."

This lead me to see that one minor benefit of our preferred exercises is that they are energy-efficient. Yoga, spinning and weights take no energy except our own - and I just don't like treadmills! I don't know whether it's because of the risk to being flung off when you put your foot where the belt meets the frame (yes, I've done this!), or  just because an endless treadmill is too much like a metaphor for life. I've stepped off the office treadmill, so why step back on at the gym?