Few of us today have time to do all the types of exercise we need to stay fit.  Not only should aerobic exercise be an integral part of our daily routines, but strength training is also very important.  Fitness experts advise you to focus your strength training on upper body or lower body, rotating them on different days and, further, on large muscle groups and small muscle groups. If you can't spend a few hours at the gym every day, here's at least one exercise machine that works several muscle groups and gives you an aerobic workout too: The Low Impact Fitness Trampoline.