Abstract
BackgroundThe use of physical activity (PA) monitors is commonly associated with an increase in habitual PA level in healthy and clinical populations. The PiezoRx is a medical-grade PA monitor that uses adjustable step rate thresholds to estimate moderate-to-vigorous physical activity (MVPA) and is a valid indicator of free-living PA in adults. Laboratory validation of step count derived MVPA in adults is needed to justify the use of these monitors in clinical practice to track individuals’ progress toward meeting PA guidelines that are based on MVPA, not steps.ObjectiveThe objective of our study was to assess the validity and interinstrument reliability of the PiezoRx to derive step count and MVPA in a laboratory setting compared with criterion measures and other frequently used PA monitors in a diverse sample of adults.MethodsThe adult participants (n=43; 39.4 years, SD 15.2) wore an Omron HJ-320 pedometer, an ActiGraph GT3X accelerometer, and four PiezoRx monitors during a progressive treadmill protocol conducted for 6 minutes at speeds of 2.4, 3.2, 4.0, 5.6, 6.4, and 7.2 km/hour, respectively. The four PiezoRx monitors were set at different MVPA step rate thresholds (MPA in steps/minute/VPA in steps/minute) 100/120, 110/130, height adjusted, and height+fitness adjusted.ResultsThe PiezoRx was more correlated (intraclass correlation, ICC=.97; P<.001) to manual step counting than the ActiGraph (ICC=.72; P<.001) and Omron (ICC=.62; P<.001). The PiezoRxs absolute percent error in measuring steps was 2.2% (ActiGraph=15.9%; Omron=15.0%). Compared with indirect calorimetry, the height-adjusted PiezoRx and ActiGraph were accurate measures of the time spent in MVPA (both ICC=.76; P<.001).ConclusionsThe PiezoRx PA monitor appears to be a valid and reliable measure of step count and MVPA in this diverse sample of adults. The device’s ability to measure MVPA may be improved when anthropometric differences are considered, performing at par or better than a research grade accelerometer.
Highlights
Regular physical activity (PA) and exercise are associated with a reduced risk of developing cardiovascular diseases, cancer, and diabetes mellitus [1]
The height-adjusted PiezoRx and ActiGraph were accurate measures of the time spent in moderate-to-vigorous physical activity (MVPA)
Step count prescriptions provided by physicians increased the daily step count by 20% and improved the glycemic control of patients with type 2 diabetes and hypertension after 1 year compared with the control group [5]
Summary
Regular physical activity (PA) and exercise are associated with a reduced risk of developing cardiovascular diseases, cancer, and diabetes mellitus [1]. Most Canadians do not engage in a sufficient level of daily activity with only 15% meeting the PA guidelines of 150 minutes of moderate-to-vigorous aerobic physical activity (MVPA) per week and 35% achieving 10,000 steps per day [2]. Health care providers may not use PA monitors as a measurement tool because of their accuracy and reliability, owing to the different capabilities of popular commercial grade PA monitors in measuring step count and MVPA [7]. The use of physical activity (PA) monitors is commonly associated with an increase in habitual PA level in healthy and clinical populations. The PiezoRx is a medical-grade PA monitor that uses adjustable step rate thresholds to estimate moderate-to-vigorous physical activity (MVPA) and is a valid indicator of free-living PA in adults. Laboratory validation of step count derived MVPA in adults is needed to justify the use of these monitors in clinical practice to track individuals’ progress toward meeting PA guidelines that are based on MVPA, not steps
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