Treadmills benefit the lower body most and can be use for light to heavy aerobic exercise. Some let you increase resistance. You will outgrow a rider as you get into shape. Riders benefit the whole body for a light to moderate aerobic workout. Some let you program workouts of varying intensity.
Exercise bikes benefit the lower body and are good for light to heavy aerobic exercise.
Cross country-ski machines benefit the whole body and are good for a light to heavy aerobic workout. Stair climber benefit the lower body and are good for light to heavy exercise. It s a good overall workout, but if you don t position yourself properly, you can put a strain on knees and back. Rowing machines benefit the whole body for a light to heavy aerobic exercise. Guided weights and pulleys make them safer than free weights.