Try Cross-Country Skiing (500–643 calories)
Riding the stationary bike will get you nowhere—except for to the last page of a celebrity tabloid magazine. But cross-country skiing will take you over hills and dales through a winter wonderland. It's not only one of the most pleasurable ways to enjoy the outdoors but also an intense cardio workout that strengthens the entire lower body as well as the shoulders, chest and the bedeviling, hard-to-tone triceps. If you're stuck inside or live in a place where snow is a rarity, hop on the Nordic ski machine (500 calories) to practice for your next trip north. The machine isn't quite as exciting as an outdoor tour, but at least it provides a break from the bike.