Been doing a full-body circuit at the gym over the last several months. Just about always start with the elliptical to warm-up. Low-impact on my joints, done right, it gets the heart going, breaks a sweat, and motivates me. Of late to lengthen my workout and keep it fresh, I have been throwing in some hard 10-15 minute intervals on the elliptical in the middle and at the end of my workout. The elliptical is my favorite cardio machine next to a bicycle.