Curves features a 30-minute circuit-training workout that combines weight-training and cardiovascular exercises. The calories burned at Curves depend in your fitness level and the intensity with which you exercise. For instance, unfit women working at 80% of their maximal heart rate burn 164 - 238 calories in 30 minutes, while very fit women can burn 500 calories in the same amount of time. The bottom line: As you become more fit, your capacity to burn calories increases. When you log a Curves workout, use Health Club Exercise if you are not particularly fit.