Are the Calorie Counters on Cardio Machines Accurate?

I have often wondered whether the calorie counters on the treadmills, bikes or eliptical machines at my gym are accurate. Why do I burn so many calories on the eliptical machine as compared to the bike or treadmill – where I feel I am working so much harder?

I have many clients who gleefully report they burned off 600 calories in their morning eliptical session. I bet in the back of their minds, they are giving themself permisson for some extra “nourishment”. But I always left wondering if they are really burning this amount of calories. So the question is, are these calorie counters accurate???

I had planned on picking “Julia the fitness trainer’s” brain over cocktails at my birthday party, but happened to receive her newsletter that day answering my question. We still talked shop, amoung other things (you probably guess what that was) over cocktails. (Pic is of Martha and Julia at my bday party discussing calories burned)

So here is an excerpt from Julia’s newsletter:

 Question from Jennifer: Hi, my name is Jennifer and I’m a 36-year-old travel agent. About five times a week I come to the gym and do a cardio machine. Sometimes I use the elliptical and sometimes I use the stationary bike. The calorie counter on these machines give me different readings even though I spend about the same time on each (30-40 minutes). The elliptical says that I have burned 450 calories and the bike says usually around 300. It feels to me as though I’m working out with the same intensity on both machines. So how can it be different? Is one more correct than the other?

 
Answer from Julia: Jennifer, thanks for this great question! I often get this question and used to wonder about it myself in the early days of my career. I’m going to answer your last question first, if the calorie counters are correct or not. It might surprise some people to hear this, but they are actually quite correct – as long as there are features attached to the counter (and you use these!) such as age and weight, and you use the machine the way it was designed. For example, you’re not supposed to use the handles of the machine to lean on, only to lightly grasp in order to maintain your balance. I assume that you do use the machine’s features because if you don’t, the counters are not accurate. Weight bearing machines like the elliptical and the treadmill are more accurate than non-weight bearing machines like the stationary bike as these machines takes the pressure of your body weight into account. These machines also measure the speed you’re going, unlike the stationary bike, which only includes the distance and time of your workout in calculatinng calories burnes. The formula that bikes and ergometers use depends on an “average rpm cycling speed,” usually 70 rpm (revolutions per minute). So the only variables in the equation are the level of intensity — meaning the resistance you are pedaling against — and the time you spent working out. With most stationary bikes you will find that if you ride for 10 minutes at 50 rpm, 70 rpm and then 90 rpm, the number of calories you burned at each of the different speeds are all the same or very close.
It’s important to keep in mind that most cardio machines over estimate calories burned by about 10-15%, in some cases up to 25%. Generally, the newer the machine, the less it will over estimate as its calibration won’t be set off by time and use. Keep this mind when you look at the calorie counter afterwards. Another important factor to keep in mind is that the machine doesn’t take your body composition into account. A woman weighing 140 pound with 18% body fat will have burned more calories than a 140-pound woman with 30% body fat. The reason for this is because muscles use up more energy (calories) than body fat. To get the most accurate reading, make sure a person with experience in using the caliper method, usually an experienced trainer, measures you. Unfortunately, this method doesn’t work well for people with a lot of belly fat (think beer guts of aging men). People who carry most of their body fat in one area are better off going to a facility that measures people’s body fat under water. This is considered the most exact body fat measurement. Of course, if you have so much fat around your belly that it is impossible for the calipers to grip it, it’s quite clear that you are not mostly muscle and therefore can safely assume that your body fat percentage will be high…

You need to also be aware of that if you use the same machine over and over the same way, you’re most likely burning less and less calories even though the calorie counter stays the same. This is because your body gets used to the motion and intensity and becomes a more effective energy expender, effective as in using up fewer calories.

Take home message: Weight-bearing cardio machines such as treadmills and ellipticals are more likely to accurately account for calories burned. The newer the machine, the more accurate the reading. If your body fat is low (you are very lean) and you put in your personal data correctly, the reading is probably almost dead on accurate. If not, subtract 15 % of calories burned. Last, switch machines often to avoid getting used to one machine! 

********* Martha will be asking Julia a very perplexing question regarding the comparison between heart rate monitors and the calorie counters on the machines. SO JULIA – GET YOUR THINKING CAP ON. I THINK WILL ALSO ASK SAL, EN EXERCISE PHYSIOLOGIST AND NEW CONTRIBUTOR TO MY BLOG THE SAME QUESTION.  Boy this is “Julia week” on my blog – she has been featured this week on some level 3 times!