Both aerobic step and a stair stepper machine can give you a mean cardio workout, as long as you're willing to put in the necessary sweat factor. Although there are some differences between the two, the main difference is the personal factor. That is, which one will you do on a regular basis to maintain your weight and health.
To get the most out of your cardio, you need to reach your target heart rate -- anywhere from 50 to 85 percent of your maximum heart rate depending on your health and fitness level -- and maintain it for at least 20 minutes. Because many gym machines, including stair steppers, come with a readout, monitoring your intensity level may be easier than with a step aerobics class where you have to stop what you're doing, find your pulse and count the beats. In addition, having the readout right in front of you won't allow you to convince yourself that you're working harder than you are. On the other hand, you may find it easier to reach and maintain your target rate in a group step aerobics class with great music, a motivating instructor and classmates you want to keep up with.
The number of calories you burn in a step aerobics class or on the stair stepper will depend on the intensity level -- heart rate -- duration and your weight. Assuming you did both for 30 minutes and weighed 125 pounds, Harvard Health Publications estimates that you'd burn about 180 calories on the stair stepper versus about 210 with low-impact aerobic step. Up your aerobic step workout to high impact, meaning a lot more jumping around, and you could burn as many as 300 calories. Of course, you can always up the intensity level on the stair stepper, while the intensity level of your aerobic step class may be somewhat controlled by the instructor or the fitness level of your fellow members. Opting for the "seniors" class may make you look better in comparison, but you'll reap fewer benefits.
The impact of your workout is the amount of force you put on your joints. Although this may not matter much to you right now, you don't want to be a candidate for knee replacement once you reach your mom's age. Worse, impact can affect your back, and there's no way to replace that. Cardio workouts with the least impact are those where your feet stay in contact with the ground or pedals, meaning the stair stepper is low impact. Although aerobic step classes will be slightly higher impact because of the stepping up and stepping down, the impact can still be fairly low. But if you get into what the American Council on Exercise calls "propulsion" steps, where both feet leave the floor, you're getting into high-impact territory.
Because the stair stepper and aerobic step involve pretty much the same movement -- stepping -- you'd probably assume they work the same muscles. But you'd be wrong. In fact, the muscles worked is the biggest difference between these workouts. Cardio machines, including stair steppers, provide some assistance and give. That means work for your quads and calves, but it's less of a workout for your hamstrings and butt. Aerobic step requires lifting your entire body and incorporates your quads, hamstrings, calves and glutes. In addition, you can include other moves in step aerobics, such as traveling, A-steps and side-kicks to emphasize the glutes or inner and outer thighs.
Nancy Cross is a certified paralegal who has worked as an employee benefits specialist and counseled employees on retirement preparation, including financial and estate planning. In addition to writing and editing, she runs a small business with her husband and is a certified personal trainer with the Aerobics and Fitness Association of America (AFAA).