Treadmills are a versatile piece of exercise equipment. Most treadmills display the speed, distance, time and calories burned during a workout but the accuracy of the calories burned is often debated. Determining how the calories are being calculated can offer insight into how accurate that number will be for you.
Most treadmills calculate calories burned by plugging your weight, speed, time, distance and elevation into a mathematical equation. When you are not required to enter your weight, the calories are based on a 154-pound person known as the "reference male". The reference male is a model composed of the average measurements of people and it is often used as a tool for comparison or baseline measurements. Depending on how your weight compares to the reference male, the calorie prediction on the treadmill may be greatly over or underestimated.
The largest factor determining how many calories you will burn for any activity is body weight. The more mass you have to move, the more calories you will burn. Many treadmills ask the user to enter body weight, which is then incorporated into the calorie equation. This provides a more accurate estimate of the calories burned compared to using the reference male, but can still have a fairly large margin of error. Entering your weight correctly is important. Even a small error in your weight will skew the calorie estimate.
Heart rate is another valuable tool for estimating the number of calories you burn. There is a linear relationship between heart rate and oxygen consumption, meaning as your heart rate increases so does your oxygen consumption and, similarly, the amount of calories you burn. Being able to include your heart rate into the treadmill's prediction equation improves the accuracy of the calorie estimate. Heart rate may be measured by either wearing a heart rate monitor or by holding on to pulse sensors that are built into the treadmill.
Other Factors that Impact Calories
While weight and heart rate and strong predictors of the calories you burn, other issues may cause the estimate of calories to be incorrect. Holding onto the handrails on the treadmill reduces the number of calories you are burning but that reduction isn't reflected in the caloric output display. New treadmill users may feel uncomfortable at first, causing walking or running gait to be less efficient than it would be on the ground. Inefficiency would cause the user to burn more calories than predicted because their movement pattern would less coordinated than a regular user.
- American Council on Exercise: Are the Calorie Counts on Exercise Machines Accurate?
- American College of Sports Medicine: Consumers Should Exercise Caution on Fitness Machine Claims, Expert Says
- Exercise Physiology: Energy, Nutrition and Human Performance; William D. McArdle et al.
Wendy Fryer holds a Master of Science in exercise physiology from the University of Illinois at Urbana-Champaign. She has more than 15 years of experience managing health clubs and working with clients.