It’s really exciting to see those calories add up, whether it’s on your wearable fitness tracker, a fitness tracking app or a cardio machine, but are they really accurate?
It’s extremely common to hear things like, “I’m eating a cupcake tonight, so I’m going to run 2 extra miles today.” Or “Going to the gym to burn off all that BBQ I ate last night.” Or “My FitBit says I burned 3200 calories today, so I get to eat more!!”
There are many issues with this way of thinking and rationalizing, but let’s focus on the point of this article and that is, those calories may be wildly inaccurate and if you’re basing your caloric intake or indulgences on these estimated total caloric expenditures, this could be what is hindering your weight loss or progress!
Cardio Machines
Take a look at this extensive list of variables that can be a factor when it comes to machines:
Body size
Body Composition
Fitness History and Level
For a treadmill - The speed at which walking becomes running differs from person to person
Workout type - High Intensity Interval, Steady State, etc
Whether or not you hold the hand rails
When the machine was manufactured
Wear and Tear on the machine
Manufacturers use different algorithms, some validate them, some do not.
Those are A LOT of variables!!
The writer of this article says, “Some formulas are based on the principle that during exercise, heart rate has a linear relationship with oxygen consumption, which can be easily converted to determine the number of calories burned. However, heart rate is influenced by a number of things such as temperature, body position, food intake, muscle groups exercised, some medications, and whether the exercise is continuous or intermittent.“(3)
As well, this article further explains, “According to the makers, calorie counting software doesn't adjust to machine wear and tear. Also, machine resistance can change overtime, which skews the calculation. And none of the machines can calculate a user's metabolism rate, health history and fitness level, all of which affect calorie counters.(1)
Wearable Heart Rate Based Activity Trackers
When it comes to wearable heart rate based activity trackers, many of the same variables come into play.
In an article published by Stanford Medicine(2), Euan Ashley, DPhil, FRCP, professor of cardiovascular medicine, of genetics and of biomedical data science at Stanford, and his team studied 7 different types of fitness trackers on their ability to accurately measure heart rate and energy expenditure. When it came to heart rate, most were accurate within 5%. However, when it came to measuring energy expenditure, even the most accurate was still off by 27%, on average. With the least accurate being off an alarming 93%!! Euan Ashley states that, “People are basing life decisions on the data provided by these devices. But consumer devices aren’t held to the same standards as medical-grade devices, and it’s hard for doctors to know what to make of heart-rate data and other data from a patient’s wearable device.” He further explains, “The heart rate measurements performed far better than we expected, but the energy expenditure measures were way off the mark. The magnitude of just how bad they were surprised me.” Graduate student and part of Ashley’s team, Anna Shcherbina, offers, “My take on this is that it’s very hard to train an algorithm that would be accurate across a wide variety of people because energy expenditure is variable based on someone’s fitness level, height and weight, etc. Heart rate,” says Shcherbina, “Is measured directly, whereas energy expenditure must be measured indirectly through proxy calculations.”
References
Noll, Eric. “Don't Get Burned by Calorie Counters.” ABC News, ABC News Network, 28 Feb. 2010, abcnews.go.com/GMA/Weekend/exercise-calorie-counters-work/story?id=9966500.
Shcherbina A, Mattsson CM, Waggott D, Salisbury H, Christle JW, Hastie T, Wheeler MT, Ashley EA. Accuracy in Wrist-Worn, Sensor-Based Measurements of Heart Rate and Energy Expenditure in a Diverse Cohort. Journal of Personalized Medicine. 2017; 7(2):3.
Valentour, Author Julia Valentour Contributor Julia. “Are the Calorie Counts on Exercise Machines Accurate?” ACE, www.acefitness.org/education-and-resources/lifestyle/blog/1571/are-the-calorie-counts-on-exercise-machines-accurate.
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