As anyone who has ever used an elliptical machine or treadmill can tell you, it's pretty much impossible not to look at an exercise machine's calorie counter. And why not? Not only do these counters indicate the effectiveness of various workout routines, but they also serve as a sort of morale-booster, informing users about the fruits of their labor. Who wouldn't start to feel good about themselves after burning off, say, 400 calories in 40 minutes?
Unfortunately, those 400 calories are likely just be an illusion. A number of recent tests have gauged the accuracy of popular exercise machines, and have unearthed some disappointing results. Many types of modern equipment, it seems, tend to artificially inflate the amount of calories a user burns off. In other words, there might be a good reason while those "400 calorie" workouts aren't trimming your waistline.
Researchers Weigh In
So how off base are all those stationary bikes, treadmills and elliptical machines? As it turns out, quite a bit. An editor of a popular fitness magazine estimates that, on average, exercise equipment overstated burned calories by a sobering 42 percent. Using the example in the opening paragraph, this would mean that your 40 minute workout only used up 232 of your body's stockpiled calories.
Health and wellness magazines aren't the only news mediums to have examined this issue. A well-known morning news program recently put a number of exercise machines under the microscope, using technology specifically designed to monitor breathing patterns. By closely tracking the breaths of test subjects, this equipment (known officially as a VO2 analyzer) can determine just how hard a subject is working, and therefore calculate the number of calories actually burned.
When the results came in, all the machines tested wound up overstating the number of calories expanded by the test subjects. Below are the results of the study, organized by machine type.
Treadmill: Overestimated calories burnt by 13 percent.
Stationary Bike: Overestimated calories burnt by 7 percent.
Stair Climber: Overestimated calories burnt by 12 percent.
Elliptical: Overestimated calories burnt by 42 percent.
Overall: Machines overestimated calories burnt by 19 percent
It probably comes as a bit of a shock that such trusted (and expensive) equipment can be so off target with its calculations. The reasons for these discrepancies depend on the piece of machinery in question. For elliptical machines, the answer simply has to do with the way people walk. Treadmill machines, for the most part, can replicate the impact walking has on the human body (hence its relatively high accuracy). In contrast, elliptical machines require users to move in a pattern that is foreign to the body, thereby significantly overstating its calorie-burning effects.
Stair steppers allow users to pick a pace that best suits them; as a result, you'll see many people taking short, quick strides instead of using the machine's full range of motion. Additionally, stair machines rely on a "gross energy expenditure" formula to calculate calorie burn off, instead of focusing on "net energy expenditure." In plain English, this means that stair machines factor in calories burned while resting to the total it presents users.
For example, suppose a stair-stepper tells you that you've burnt 300 calories over a 25 minute timeframe. While this might seem impressive, this total includes a large number of calories that would have been used anyway. Using the 12 percent figure from the aforementioned study, this means that you would've consumed at least 36 calories just by watching TV from your living room couch.
Unlike stair steppers and elliptical machines, treadmills enjoy a fairly healthy reputation for accuracy (the results of the above study notwithstanding). Still, those impressive numbers from treadmill runs can be deceptive. Many treadmills fail to take into account the weight of their users, and are often programmed to assume a weight of 155 pounds. This can easily lead to misleading and overly generous results; a 135 pound person might be told that she has expended 300 calories, when the real amount is closer to 250. Additionally, a treadmill user can largely sabotage his or her workout by overusing the machine's handrails. Resting only a slight amount of weight against handrails can decrease calorie burn off by 20 percent; if a user applies even more weight, this figure can climb to as high as 40 percent.
That brings us to stationary bicycles. According to many experts, stationary bikes are among the most accurate exercise machines in determining calorie expenditure. Still, the effectiveness of stationary bikes can be distorted, particularly if only a small amount of resistance is used during a workout session. A user's calorie burn off is also linked to his or her pedaling position; in a 15 minute time span, you'll use about 15 percent more calories standing up than while sitting.
Though these findings might put a damper on your eagerness to exercise, cheer up - these machines are still useful tools for keeping in shape, provided you refrain from taking their calorie counters at face value. To determine if you really are getting a good workout, try using the "talk test" while using your preferred exercise machine. If you find yourself gasping for air while attempting to recite song lyrics, then you're probably getting your time's worth.