Accelerometers Maria Canino Leah Wagner Leah 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 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 Caltrac TM 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 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, 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), 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), 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), 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,