Monthly Archives: August 2016

Kinesiology doctoral student Amanda Hickey publishes results of studies on utility and validity of physical activity monitors

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Kinesiology doctoral student Amanda Hickey is the lead author on two recent publications examining the utility and validity of physical activity monitors. Hickey, along with faculty mentor Patty Freedson, reviews the existing literature on the usefulness of consumer activity trackers in an article appearing in the current issue of Progress in Cardiovascular Diseases, a special issue devoted to the examination of the use of technology for cardiovascular disease prevention and treatment.

In an article titled “Utility of Consumer Physical Activity Trackers as an Intervention Tool in Cardiovascular Disease Prevention and Treatment,” the authors note that the increasing popularity of consumer activity trackers, which provide users with information about physical activity measures such as steps taken and energy expenditure along with easily monitored physical activity tools and goals, provides a potentially powerful tool for use in populations with cardiovascular disease (CVD).

“Wearable devices may provide opportunities to overcome limitations of self-reported activity and also provide a driver for physical activity behavior change,” the authors note. Due in part to the limited data on the accuracy of the devices, opportunities for future research abound. “For example, these devices could be used to track free-living physical activity behavior as an outcome after different treatments,” they write, “and/or used to encourage individuals to be more active as a preventive or management tool for CVD. However, before they are implemented broadly into the clinical health field, more research is needed to evaluate their performance accuracy in the free-living environment. This is necessary to determine which features of the devices and/or associated apps will be most effective in changing behavior and to overcome privacy and security concerns regarding transmission data from these devices in order to help heath care professionals to promote physical activity throughout the health care system and to the general public.”

Their review follows on the completion of a recent study by Hickey and colleagues on the validity of professional-grade activity monitor step detection. In an article titled “Validity of Activity Monitor Step Detection Is Related to Movement Patterns” that appeared in the February issue of the Journal of Physical Activity and Health, Hickey, with colleagues Dinesh John of Northeastern University and Jeffer E. Sasaki, Marianna Mavilia, and Patty Freedson of UMass Amherst, assessed the step-counting accuracy of these devices during different types of movements.

In the study, the researchers compared different activity monitor results during treadmill and simulated free-living activities to manually counted steps using the StepWatch (SW). Hickey and colleagues recruited fifteen participants to perform laboratory-based treadmill exercise at varying speeds and simulated free-living activities, such as cleaning a room, while wearing different activity monitoring devices (including activPAL, Omron HJ720-ITC, Yamax Digi- Walker SW-200, two ActiGraph GT3Xs in “low-frequency extension” and in “normal-frequency” mode, an ActiGraph 7164, and an SW). Participants also wore monitors for a day in their free-living environment.

The researchers conducted linear mixed model analyses and identified varying levels of discrepancies between activity monitor steps and the results from the free-living settings. Most monitors performed poorly during treadmill walking at its slowest speed; cleaning a room had the largest errors of all simulated free-living activities. The accuracy was highest for forward rhythmic movements for all monitors.

“Our study improves upon previous investigations that were limited to examining the accuracy of different monitors only during treadmill and/or free-living conditions,” writes Hickey et al. “This is the first study to assess the accuracy of many pedometers and accelerometers during treadmill activities, simulated free-living activities, and the free-living environment. The inclusion of the simulated free-living activities, categorized by movement type and direction, is of critical importance to understanding the source of errors in step measures during free-living conditions. The activities we chose included movement with unpredictable start and stop times, which is typical in a free-living setting. In addition, these activities induce much more individual variability than treadmill activities where a rhythmic activity like the gait cycle is further constrained by treadmill speed.”

“Based on the findings from the current study, pedometers and accelerometers are accurate in detecting steps at normal walking speeds. However, at very slow treadmill walking and during running, the errors in step estimates are large and variable among monitors. An important finding of our study is that with the exception of the SW pedometer, pedometers and accelerometers were less accurate in detecting steps from non-rhythmic and multidirectional movements such as those that take place during activities of daily living. This has implications for studies using monitor-based step estimates to characterize physical activity and relating this physical activity metric to health. Substantial underestimation of daily steps may occur if participants spend a higher proportion of their day in activities of daily living.”

They conclude, “This study highlights the need to verify step-counting accuracy of activity monitors with activities that include different movement types and directions. This is important to understand the origin of errors in step-counting during free-living conditions.”