### 1. What is a MET_{y}?

In adults, 1 MET represents an oxygen uptake of 3.5 mL·kg-1·min-1 or 1 kcal·kg-1·hr-1. Due to metabolic differences in children and adolescents, adult MET values are not applicable to children. Youth have higher basal metabolic rates per unit body mass than adults, and typically expend more energy per kilogram of body mass for physical activities than adults. In this new Youth Compendium, physical activity energy expenditures are reported in multiples of metabolic equivalents or youth METs (MET_{y}). One MET_{y} represents the basal metabolic rate. For this compendium, BMR was calculated using the Schofield equations accounting for sex, age-group and body mass of the child. Additionally, the MET_{y} values for specific activities are presented for four age groupings. MET_{y} values for each physical activity were derived from literature reviews, data analysis, and imputation.

### 2. How should information from the Youth Compendium be used?

Youth Compendium information should be used to convert time spent in different activities to units of MET scores. Values are best used to represent group-level estimates for energy expenditure. In cases where individual estimation is desired, users should realize that energy expenditure can be influenced by many factors not represented by values in the table (e.g., body size, economy of movement). Thus, users should understand that these values are truly estimates and are not recommended to be used for precise estimates of individual energy expenditure. Youth Compendium data can also be used to help determine the intensity level (e.g., moderate- or vigorous-intensity) of a specific activity for a specific age group.

### 3. What is the difference between the smoothed and observed/imputed METy values?

Both the smoothed and observed/imputed MET_{y} values come from the same data sources. The observed/imputed MET_{y} values represent the mean value for each activity and age group. The smoothed value is calculated from a linear regression model where MET_{y} is regressed onto age. Smoothing the estimates served to remove some of the natural variability across age groups in the observed MET_{y} values within each activity.

### 4. What do the activity codes mean?

Codes have 6 digits. The first two digits represent an activity category, the next three digits represent a specific activity, and the final digit represents age group. It is important to note that in the web version, age group is represented by an “x” in the activity code, because the 4 age group values are listed across one row in separate columns. However, in the downloadable file, age group is included in each code for each MET_{y} value.

Here is example code for walking at 3 mph for a 13-15 year-old:

Code | Activity Category | Specific Activity | Age Group |
---|---|---|---|

802004 | 80 (Walking) | 200 (Walking 3.0 mph) | 4 (13-15 years) |

### 5. How do I calculate energy expenditure from MET_{y} values?

Total energy cost of a physical activity can be estimated based on the MET_{y} from the Youth Compendium, a measured or computed BMR, and duration of the specific activity, as follows:

** Total energy cost (kcal) = MET _{y} x BMR (kcal/min) x duration (min)**

where BMR for boys is measured or predicted from Schofield equations:

** 3–10y BMR (kcal/min) = [22.706 × Weight (kg) + 504.3]/1440**

** 10–18y BMR (kcal/min) = [17.686 × Weight (kg) + 658.2]/1440**

and where BMR for girls is measured or predicted from Schofield equations:

** 3-10y BMR (kcal/min) = [20.315 × Weight (kg) + 485.9]/1440**

** 10-18y BMR (kcal/min) = [13.384 × Weight (kg) + 692.6]/1440**

*Example:* What is the energy expenditure for a 14-yr-old girl (who weighs 40 kg) walking at 3 mph for 20 minutes?

** Total energy cost = METy x BMR (kcal/min) x duration (min)**

** 4.3 x BMR x 20 where BMR = [13.384 × 40 kg + 692.6]/1440**

** 4.3 x .853 x 20 = 73.3 kcal**

### 6. How do I search the Youth Compendium?

To view the tables, click either MET_{y} values. Next you will need to click on either “View All Categories” or click on an individual category within or “View by Individual Category”. Now, in the upper right-hand corner of the table, start typing your keyword inside the search box. The table will automatically filter for matching results.

### 7. How do I download the data?

To download the data, please visit the Downloads page. Be sure you download the appropriate data for your interests.

### 8. How do I choose an age group if the age of children/adolescents in my sample overlaps two groups?

Whenever possible, assign the MET_{y} value according to appropriate age. For example, if there are 8-12 year-olds in your sample, you would assign 8- and 9-year-olds to the 6-9 age group value and 10-12 year-olds to that group. If this is not possible, use the average of the two age categories that apply.

### 9. What do I do if I cannot find my activity?

If you cannot find the exact activity you are looking for, search the Youth Compendium for a similar activity in terms of sitting/standing or active, and use the MET_{y} value associated with that activity.