Summer's on its way out, and the change of seasons is also a good time to switch up your exercise routine. Some trends you may see: Yoga Nidra is the "definition of deep relaxation," says FitSugar, which is not that surprising since you're in Savasana pose--aka lying on the floor. Oh, and "nidra" means "sleep." If you've been wishing your gym had naptime, this could be a good class for you. Portland's Green Microgym is America's first human-powered gym, reports Pop Goes Green.  Also, its toilet seat covers are made from "recycled content" of some sort. Kettlebells are these big scary black things with handles. "They look just like a twee purse. If your purse weighs 20 pounds, that is," reports Charlotte at The Great Fitness Experiment. She'll be experimenting with them throughout the month and posting her workouts. If a month isn't enough for you, Nathan's Russian Kettlebell Blog is all kettlebells, all the time, with LOTS of videos. Nathan recommends starting kettlebell workouts at age 12. Finally, winter's not here yet, and you don't live in Alaska, but: Sarah Palin says that often goes for midnight runs and tones her upper body by snowmobiling with her family. "It's the best upper body workout you could ever have. You're maneuvering through hundreds of pounds of powder," she tells WSJ.com's Washington Wire.