Curves works. Curves works because it gives you a complete cardio and strength-training workout in just 30 minutes, where you can burn up to 500 calories every time. The circuit is made up of resistance machines that work every major muscle group, two muscles at a time. And with a circuit coach to teach and motivate, you're sure to reach your fitness goals in no time. Whether you want to lose weight and inches, gain energy or tone up, the Curves circuit will work for you.