Activity-related energy expenditure (AEE) is difficult to quantify, especially under sedentary conditions. Here, a model was developed using the detected type of physical activity (PA) and movement intensity (MI), based on a tri-axial seismic accelerometer, with energy expenditure for PA as a reference. The relation between AEE (J/min/kg), MI, and the type of PA was determined for standardized PA's as performed in a laboratory, including: lying, sitting, standing, and walking. AEE (J/min/kg) was calculated from total energy expenditure (TEE) and sleeping metabolic rate (SMR), as assessed with indirect calorimetry ((TEE × 0.9) − SMR)[1].


According to Van Hees et al., the type of physical activity improved the prediction of energy expenditure. A tri-axial seismic accelerometer is a valid tool for estimating energy expenditure related to sedentary physical activities. This is the first study to show a significant relationship between PA monitor output and energy expenditure during sedentary conditions [1].


Basal Metabolic Rate (BMR)

Together with the closely related Resting Metabolic Rate (RMR), the BMR is the minimum amount of energy that a body requires when lying in physiological and mental rest. In many people BMR represents around 60-75% of total EE. The main determinant of BMR is body weight and body composition.

Diet Induced Thermo Genesis (DIT)

The amount of energy utilized for digestion, absorption and transportation of nutrients. DIT accounts for about 10% of total energy intake for a mixed western diet.

Activity-Related Energy Expenditure (AEE)

Physical Activity is the most variable component of EE in humans and, after BMR, the second largest component of daily energy expenditure. It includes the additional EE above BMR and DIT due to muscular activity and increased cardio respiratory function.

Total Energy Expenditure (TEE)

The total amount of energy a person uses is calculated by the sum of BMR, DIT, and AEE. To prevent weight gain or weight loss, energy intake must be balanced with Total Energy Expenditure.

Physical Activity Ratio (PAR)

Values are commonly used to convert subjects’ physical activity recalls into estimates of Daily Energy Expenditure (DEE). A PAR is defined as the ratio between energy expenditure corresponding to a sedentary or a physical activity (kJ/min) and basal metabolic rate [(BMR) kJ/min].

Physical Activity Level (PAL)

A person’s total energy expenditure based on a 24-hour period, divided by his Basal Metabolic Rate (BMR). The physical activity level can also be estimated based on a list of the (physical) activities a person performs from day to day. Each activity has its own PAR. The physical activity level is the time-weighted average of the PARs. A chair- or bed-bound lifestyle corresponds to an average PAL value of 1.2, while a lifestyle of strenuous work or highly active leisure corresponds to a PAL value of 2.0-2.4 [2].

1. van Hees, V. T., van Lummel, R. C., & Westerterp, K. R. (2009). Estimating Activity-Related Energy Expenditure Under Sedentary Conditions Using a Tri-Axial Seismic Accelerometer. Obesity, 17(6), 1287-1292. doi:10.1038/oby.2009.55.
2. Food and Agriculture Organization of the United Nations. (n.d). ENERGY REQUIREMENTS OF ADULTS. Retrieved from