AccelerometersMaria CaninoLeah WagnerLeah Sanders

What is it? How does it work?

• A small device “that measures acceleration forces such as movement.” (Actigraph sheet)

• It contains a sensor to detect changes in movement and produces an electrical signal directly linked to speed of the movement. The signals are then converted into numbers and stored on the device.• Worn at wrist or hip• Recorded as “counts”• Two- or three- axis options (anterior/posterior, medial/lateral,

vertical)• Caloric expenditure and algorithms• Epoch(s) measurement(s)

Broderick, J.M. et al 2013

Uploading/Analyzing Data

• We used the ActiGraph accelerometers (GT3X).

• Initialization period (name, epoch selection, time period, etc.)

• Data is uploaded to the software to be examined after use.• Demographics added at this time

• Step count, caloric expenditure, sleep patterns can be evaluated

• Epoch, axis movement and steps can be converted into a excel file.

Homescreen

After Plugging Device In…

Cost

• Software license for ActiGraph costs around $1,500.• Newest monitor (with Bluetooth) costs $225

Device Uses

• Most studies use accelerometers to assess current physical activity behaviors on a variety of populations.• Children, older adults, etc.

• Device comparisons for accuracy and reliability.

• Professionals can monitor and prescribe physical activity and exercise in order to enhance one’s health.

Accelerometers in Research

Accelerometer Placement• Purpose: Accelerometer optimal sensor location and type

of mounting

• 10 subjects participated in the following tasks while wearing five ProMove2 sensors at different placements at the hip held by an elastic belt.• Walked/Jogged at various speeds on treadmill

• Performed deskwork tasks

• Walked on level ground

• Most lateral position on waist• If sensor interferes with free movement, it may be placed

slightly anterior to the body.

• Must be fitted as “tight to the body as possible” to avoid any unwanted movement.

Boerema, S. et al 2014

Findings

Device Usage Across Ages

• Purpose: Describe physical activity in children (6-11 yr), adolescents (12-19 yr) and adults (20+ yr) through the use of an accelerometer.

• Data obtained from 2003-2004 NHANES, cross-sectional• 6,329 provided at least 1 day of data

• 4,867 provided at least 4 or more days

• Participants were interviewed (1-2 hrs) prior to the start of the study as well as had a medical examination.

Findings

• Males are more physically active than females.

• Physical activity and age had an inverse relationship. • Age increased, physical activity decreased

• 42% children met recommended 60 minutes of PA a day

• 8% adolescents met the recommendation of 60 minutes of PA a day

• < 5% adults met the recommendation of 30 minutes of PA a day

• Physical activity was overestimated when given the self-report tool.

Troiano, R. et al 2007

Device Usage in Specific Populations• Purpose: Examine the relationship between exercise and

fatigue over the first three cycles of chemotherapy in women receiving one of the four specified treatments for breast cancer.

• 72 newly diagnosed women with breast cancer participated• They were instructed to perform home-based moderate-intensity

exercises.• Assigned a CaltracTM accelerometer to wear to measure physical

activity• Pre- and Post-Variables measured: functional ability (i.e. 12-

minute walk), EE and fatigue • Subjects recorded daily fatigue (i.e. self-report diary), exercise

duration, intensity, and type.

Findings• Exercise significantly reduced all four levels of fatigue in all 4

types.

• As duration of exercise increased, intensity of fatigue decreased.• When exercise >60 minutes, fatigue levels increased.

• Authors mentioned that the use of accelerometers wasn’t the most valid method to measure exercise intensity. However, heart rate monitoring was not ideal for the subjects due to “anemia caused by chemotherapy.”

Schwartz. et al 2001

Our Mini Study

• Pedometers vs. Accelerometers• Step comparisons

• Consumer-targeted Devices vs. Accelerometers• Step comparisons

• Energy expenditure comparisons

Pedometers Comparison Day 1

Pedometers Comparison Day 2

Day 2 continued…

Pedometer Overall Findings

• Pedometers were consistently under recording steps.

• Accelerometers were inconsistent across all subjects.• Location

• Hip/Wrist Placement

• Mode of exercise

• Not practical during cycling activity for both devices

Consumer-Targeted Devices Comparison

* Cycling not an optimal choice for either device.

*Accelerometers have the option of 5 different algorithms to estimate energy expenditure.*Direct calorimetry is necessary for true comparison.

FitBit Overall Findings

• Steps between both devices were fairly close.

• Caloric expenditure dramatically varied.• Dependent on device location, placement and algorithm

choice

Accelerometer Advantages• Distinguishes between walk and run• Measures METs for choosing various activities• Can be used in large sample sizes• Stores data for extended periods (up to 21 days)• User-friendly• Great for older population and kids• Measures overall activity for health and current behavior patterns• Uses epoch for time (i.e. 1-240 seconds options)• 3-axis • Non-invasive• Cost?

Disadvantages

• Cost?• Not optimal for athletic performance assessment or

enhancement• Endurance weight-supporting activities (i.e. cycling, rowing)• Not water friendly• Location and placement is crucial• Non-instantaneous feedback• Possible difficulty measuring upper body movement and

weight lifting• Not ideal for assessing non-exercise activity

thermogenesis (NEAT)• Caloric expenditure

References• ActiGraph. (n.d.). Retrieved September 23, 2014.• Boerema, S., VanVelsen, L., Schaake, L., Tönis, T., & Hermens, H. (2014).

Optimal sensor placement for measuring physical activity with a 3D accelerometer. Sensors 2014, 14(2), 3188-3206.

• Broderick, J., Ryan, J., O'Donnell, D., & Hussey, J. (2014). A guide to assessing physical activity using accelerometry in cancer

patients. Support Care Cancer, 22(4), 1121-1130.• Schwartz, A., Mori, M., Gao, R., Nail, L., & King, M. (2001). Exercise

reduces daily fatigue in women with breast cancer receiving chemotherapy.  Medicine & Science in Sports & Exercise,  33(5), 718-23.

• Troiano, R. (February 24, 2005). Physical activity assessment using accelerometers. Active Living Research Annual Conference. Lecture conducted from Coronado, CA.

• Troiano, R., Berrigan, D., Dodd, K., Mâsse, L., Tilert, T., & Mcdowell, M. (2008). Physical Activity In The United States Measured By Accelerometer. Medicine & Science in Sports & Exercise, 40, 181-188.