Validity of the Polar M430 Activity Monitor in Free-Living Conditions: Validation Study

Abstract

Background Accelerometers, often in conjunction with heart rate sensors, are extensively used to track physical activity (PA) in research. Research-grade instruments are often expensive and have limited battery capacity, limited storage, and high participant burden. Consumer-based activity trackers are equipped with similar technology and designed for long-term wear, and can therefore potentially be used in research. Objective We aimed to assess the criterion validity of the Polar M430 sport watch, compared with 2 research-grade instruments (ActiGraph and Actiheart), worn on 4 different locations using 1- and 3-axis accelerometers. Methods A total of 50 participants wore 2 ActiGraphs (wrist and hip), 2 Actihearts (upper and lower chest position), and 1 Polar M430 sport watch for 1 full day. We compared reported time (minutes) spent in sedentary behavior and in light, moderate, vigorous, and moderate to vigorous PA, step counts, activity energy expenditure, and total energy expenditure between devices. We used Pearson correlations, intraclass correlations, mean absolute percentage errors (MAPEs), and Bland-Altman plots to assess criterion validity. Results Pearson correlations between the Polar M430 and all research-grade instruments were moderate or stronger for vigorous PA (r range .59-.76), moderate to vigorous PA (r range .51-.75), steps (r range .85-.87), total energy expenditure (r range .88-.94), and activity energy expenditure (r range .74-.79). Bland-Altman plots showed higher agreement for higher intensities of PA. MAPE was high for most outcomes. Only total energy expenditure measured by the hip-worn ActiGraph and both Actiheart positions had acceptable or close to acceptable errors with MAPEs of 6.94% (ActiGraph, 3 axes), 8.26% (ActiGraph, 1 axis), 14.54% (Actiheart, upper position), and 14.37% (Actiheart, lower position). The wrist-worn ActiGraph had a MAPE of 15.94% for measuring steps. All other outcomes had a MAPE of 22% or higher. For most outcomes, the Polar M430 was most strongly correlated with the hip-worn triaxial ActiGraph, with a moderate or strong Pearson correlation for sedentary behavior (r=.52) and for light (r=.7), moderate (r=.57), vigorous (r=.76), and moderate to vigorous (r=.75) PA. In addition, correlations were strong or very strong for activity energy expenditure (r=.75), steps (r=.85), and total energy expenditure (r=.91). Conclusions The Polar M430 can potentially be used as an addition to established research-grade instruments to collect some PA variables over a prolonged period. However, due to the high MAPE of most outcomes, only total energy expenditure can be trusted to provide close to valid results. Depending on the variable, the Polar M430 over- or underreported most metrics, and may therefore be better suited to report changes in PA over time for some outcomes, rather than as an accurate instrument for PA status in a population.

Polar Vantage and Oura physical activity and sleep trackers: A validation and comparison study

“…Correlations for MVPA on previous Polar validation studies varies, but our findings are similarly high compared to findings from Polar M430 [28] and Polar V800 [29]. Similarly, strong correlations for step counting is in accordance with previous studies on Polar V800 [28,29] and Polar M600 [30]. For Oura, we could not find any previous studies on steps, MVPA, or TEE.…”

“…While correlations for EE in the present study are higher than most previous Polar studies [27], it is lower compared to a lab-setting study on Polar Vantage [8] and a free-living study of Polar M430 [28]. Correlations for MVPA on previous Polar validation studies varies, but our findings are similarly high compared to findings from Polar M430 [28] and Polar V800 [29]. Similarly, strong correlations for step counting is in accordance with previous studies on Polar V800 [28,29] and Polar M600 [30].…”

Succeeding with prolonged usage of consumer-based activity trackers in clinical studies: A mixed methods approach

“…In a systematic review of Polar activity trackers [47], we have previously reported that Polar activity trackers show mixed results depending on activity tracker, study setting, and study sample. Furthermore, compared to ndings in a previous Polar M430 validation study [29], with a wider range of weight, height, and age, correlations were lower and MAPEs were higher in the present cohort.…”

“…It is waterproof, weighs 51 grams, has up to 20 days of battery life, and cost 150 USD. In a previous study we have shown that the Polar M430 gives valid results for TEE in a wider age-and weight-range, when compared to a hip-worn ActiGraph wGT3X-BT accelerometer (ActiGraph, Pensacola, FL, USA) [29].…”

Complex lifestyle intervention among inactive older adults with elevated cardiovascular disease risk and obesity. A mixed-method, single-arm feasibility study for RESTART- a randomized controlled trial

“…This indicate that the AT was mostly well tolerated and provided valuable data regarding participants' PA intensity levels and daily activity (77). In a previous study, we have also shown that Polar M430 is valid to measure total energy expenditure (78).…”