Old School Rules Don’t knock Jane Fonda! According to a study in the Journal of Strength and Conditioning Research, you can scorch as many calories in an aerobics class as you can on a treadmill.

Researchers calculated the calorie burn of 28 women ages 18 to 34 during hour-long step, Tae-Bo, spinning, and pump (aerobic weight-training) classes.

They compared those numbers with what the women burned in an hour running at 5 mph. The results: Women in the pump class burned only 480 calories, but steppers, Tae-Boers, and spinners torched 576, 584, and 593, respectively.

That’s better than running at 5 mph, which burns 552 calories, and comparable to running at 5.2 mph, which singes 606, says study coauthor Michael Bemben, Ph.D. So pull on that leotard with pride. [source: Women's Health]