Protocol - Total Physical Activity-Objective Measure

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An accelerometer is used to measure the intensity of movements continuously over a desirable study period (for a robust assessment of free-living physical activity, a minimum of 4 days is recommended; 7 days of continuous measurement is the most common). It is generally recommended to select the highest time resolution (or the shortest epoch) possible to last over the entire study period. Most current accelerometers have sufficient memory and battery capacity. The participant is asked to wear the accelerometer during all waking hours of the study period. Most monitors are not waterproof, and are not recommended for activities such as swimming and showering. An additional daily record of wearing the monitor can be taken to identify non-wearing time activity. Data are downloaded from the accelerometer after being retrieved from the participant. Although this is the current standard for objective physical activity measurements, more advanced sensor and processing technologies are rapidly evolving in this field to improve accuracy and expand usability.

Specific Instructions:
The hip placements of the accelerometer (on a belt) have been shown to yield the best prediction of energy expenditure. The absolute accuracy may vary with different accelerometers, placement locations, signal filters used by the devices, and models used for predicting energy expenditure or time spent in certain intensity categories. Follow manufacturers' operation manuals for installation, initialization, downloading and other specific procedures if needed.

Refer to Health ABC Study Operations Manual, Accelerometry Section.

Protocol Name from Source:


Publicly available

Personnel and Training Required
The individual who programs the accelerometer, collects the data from the participant, and downloads the data must be trained. The accelerometer's user manual must be used to complete the procedures properly.
Equipment Needs
Personal computer, accelerometers, download ports or readers (for some), battery chargers (for some) and replaceable batteries (for others).
Requirement CategoryRequired
Major equipment No
Specialized training No
Specialized requirements for biospecimen collection No
Average time of greater than 15 minutes in an unaffected individual No
Mode of Administration

Physical Measurement

Life Stage:

Child, Adolescent, Adult, Senior, Pregnancy


Ages 3+

Selection Rationale

There are several accelerometers that can measure physical activity, but the costs, accuracy, sensitivity, complexity, and research applicability vary widely. Several accelerometers have been shown to be applicable in heterogeneous subject populations. While the cost remains relatively high (around $350), they provide detailed physical activity data registered in good time resolutions (typically minute-by-minute or better). The intensity measures from the accelerometers closely represent energy expenditure, and with high data resolution, patterns of movements can also be studied. Accelerometers have low user burden (lightweight and small size, allowing multiple uses, and with rechargeable batteries), and data can be directly downloaded for research. The GT3X accelerometer (Actigraph) is used as an example of a typical accelerometer protocol.



Common Data Elements (CDE) Physical movements accelerometer measurement 3060825 CDE Browser
Derived Variables


Process and Review


National Institutes of Health. National Institute of Aging and National Institute of Diabetes & Digestive & Kidney diseases. The Health, Aging and Body Composition (Health ABC) Study. Operations Manual. Accelerometry Section. 2009.

Pate, R. R., M. J. Almeida, et al. (2006). Validation and Calibration of an Accelerometer in Preschool Children. Obesity. 14(11): 2000-2006.

General References


Protocol ID:


Export Variables
Variable NameVariable IDVariable DescriptionVersiondbGaP Mapping
Physical Activity and Physical Fitness
Measure Name:

Total Physical Activity-Objective Measure

Release Date:

May 12, 2010


Physical movements measured by accelerometer(s).


Recent physical activity patterns are a predictor of lifestyle, and individuals with sedentary lifestyles are at a greater risk for obesity and chronic disease.


Actigraph, Actigraphy, Accelerometer, Acceleration, Movement, Motion sensing, Epoch, Health ABC Study, Physical Activity, Activity Counts, Energy Expenditure, Activity Intensity, Physical Activity and Physical Fitness