You may lie on your back, or you may lie face-down with your chin raised. Once you are inside the scanner, the machine's x-ray beam rotates around you. (Modern spiral scanners can perform the exam without stopping.) A computer creates separate images of the body area. These are called slices.
Circuit training builds muscular and cardiovascular endurance. It alternates intense cardiovascular activities, such as jumping rope and running, with strength-training activities, such as pushups, crunches and squats. With circuit training, you can focus on building endurance for a specific muscle group or your entire body, depending on the strength-training exercise you choose.
The four main types of physical activity are aerobic, muscle-strengthening, bone-strengthening, and stretching. Aerobic activity is the type that benefits your heart and lungs the most. Aerobic activity moves your large muscles, such as those in your arms and legs. Running, swimming, walking, bicycling, dancing, and doing jumping jacks are examples of aerobic activity. Aerobic activity also is called endurance activity.