Calculating Daily Energy Expenditure using a Pedometer
You can use a pedometer, which is a device for counting the number of steps you take, to estimate the amount of activity that you perform. From the number of steps taken, the walking distance and the number of calories burned, or energy expenditure, can also be calculated.
Measuring how many calories you have burned each day is helpful if you are counting calories, trying to maintain or lose weight by matching this energy expenditure to the amount of food eaten.
Using a pedometer is a simple way to estimate your daily energy expenditure, and this method of directly measuring your activity may be accurate than some of the formulas available to calculate energy expenditure, though there are still some calculations involved, as well as a few assumptions. The advantage of using a pedometer to measure energy expenditure is that it can objectively assess activity levels, they are relatively simple to operate, it is low cost, and are small enough not to restrict the physical activity.
Accurately Measuring Steps and Distance
The primary data measured by a pedometer is the number of steps taken. Some pedometers are more accurate than others at doing this. If you are using the step count for calculating your energy expenditure, you want to first make sure it is measuring that correctly.
It is easy to check if the pedometer is accurately measuring the right number of steps when you are walking or running. Simply walk for some time and manually count the number of steps you take, and compare this to the number that is displayed on the pedometer.
Energy expenditure may also require a measure of the distance walked or run. To convert the number of steps to a distance, without the use of a GPS, the pedometer must know the average length of your stride. You can calibrate your stride length by walking a set distance and counting the number of steps taken. Then it will be a simple process of dividing the distance by the number of steps. Just be aware your stride length can vary, it will be longer when you are running than it is when you are walking. Also, your stride is likely to be shorter when going uphill as opposed to walking on a level surface.
Accurately Measuring Energy Expenditure
Step counting itself is not enough for estimating energy expenditure (Kumahara et al. 2009). The step count measure says nothing of the intensity and duration of the exercise, and does not account for body size and composition. Also, age and gender have an effect on energy expenditure.
The problem with using the pedometer to estimate total energy expenditure is that there is no measure of the volume of work done, that is, there is no measure of the intensity and duration of the activities. Unless you indicate if you are walking or running, the pedometer can not discriminate between the two.
There is also the problem of different exercise modes. A pedometer can be used to crudely measure your daily activity by counting steps. However, this is going to miss some activity as you do not always take 'steps' when doing some activities, for example, if the pedometer is on your wrist it may not record cycling exercise very well.
In conclusion, a pedometer itself is not sufficient to measure daily energy expenditure. Fortunately, there are not many such simple pedometers, often they are associated with other sensors so the electronic devices use GPS and accelerometers to also record distance, speed and intensity. With this additional information, plus factoring in age, gender and body weight, the energy expenditure can be more accurately calculated.
Things to Consider
Pedometers do not ...
- always accurately count all steps
- perform well during some activities (e.g. swimming)
- measure exercise intensity or duration
- measure stride length and distance covered
- Kumahara, H., Tanaka, H. & Schutz, Y. Are pedometers adequate instruments for assessing energy expenditure?. Eur J Clin Nutr 63, 1425–1432 (2009).
- Nielson R, Vehrs PR, Fellingham GW, Hager R, Prusak KA. Step counts and energy expenditure as estimated by pedometry during treadmill walking at different stride frequencies. J Phys Act Health. 2011 Sep;8(7):1004-13.
- About Energy Expenditure — methods, formula and calculators.
- Daily Calorie Counter — determines how many calories you need each day.
- Power output and energy expenditure for running and walking
- Calories Burned Running — determines how many calories you have burned based on your weight and distance run.
- Walking for weight loss — an argument for why you shouldn't do it.