Physical Activity Assessment with the ActiGraph GT3X and Doubly Labeled Water

Abstract

Purpose To compare the degree to which four accelerometer metrics—total activity counts per day (TAC/d), steps per day (steps/d), physical activity energy expenditure (PAEE, kcal/kg/day), and moderate- to vigorous-intensity physical activity (MVPA, min/d)— were correlated with PAEE measured by doubly-labeled water (DLW). Additionally, accelerometer metrics based on vertical axis counts and triaxial counts were compared. Methods This analysis included 684 women and 611 men aged 43 – 83 years. Participants wore the Actigraph GT3X on the hip for seven days twice during the study and the average of the two measurements was used. Each participant also completed one DLW measurement, with a subset having a repeat. PAEE was estimated by subtracting resting metabolic rate and the thermic effect of food from total daily energy expenditure estimated by DLW. Partial Spearman correlations were used to estimate associations between PAEE and each accelerometer metric. Results Correlations between the accelerometer metrics and DLW-determined PAEE were higher for triaxial counts than vertical axis counts. After adjusting for weight, age, accelerometer wear time, and fat free mass, the correlation between TAC/d based on triaxial counts and DLW-determined PAEE was 0.44 in women and 0.41 in men. Correlations for steps/d and accelerometer-estimated PAEE with DLW-determined PAEE were similar. After adjustment for within-person variation in DLW-determined PAEE, the correlations for TAC/d increased to 0.61 and 0.49, respectively. Correlations between MVPA and DLW-determined PAEE were lower, particularly for modified bouts of ≥10 minutes. Conclusion Accelerometer measures that represent total activity volume, including TAC/d, steps/d, and PAEE, were more highly correlated with DLW-determined PAEE than MVPA using traditional thresholds and should be considered by researchers seeking to reduce accelerometer data to a single metric.

Volume of Light Versus Moderate‐to‐Vigorous Physical Activity: Similar Benefits for All‐Cause Mortality?

“…The application of device-based measures of PA is evolving 17 ; our estimates of light and moderate-to-vigorous intensity activity duration have been evaluated and found to be reasonably accurate in comparison to a range of criterion measures. 15,16,18 To determine the volume of PA, we estimated intensity-specific activity counts-a metric demonstrated to be a good proxy for total volume of PA. 13 We also chose a widely accepted threshold to distinguish sedentary behavior from PA (100 AC) 19 and a light/moderate-tovigorous threshold designed to capture a broader range of lifestyle and ambulatory activities in adults (760 AC). 14 There are a variety of published cut points, 18 and NHANES studies have commonly used 2020 counts/min, which is based on ambulatory calibrations, to define moderate-to-vigorous PA.…”

“…The devices were initialized to collect activity counts (AC) in 1‐minute epochs. Accumulated AC provide an accurate estimate of the duration and intensity of body movement at the waist and were summed across the whole day to assess total PA volume . Using established cut points, we summed the accumulated volume of activity as AC in nonsedentary light (100<AC<760) and moderate‐to‐vigorous activity (≥760 AC).…”

“…Accumulated AC provide an accurate estimate of the duration and intensity of body movement at the waist and were summed across the whole day to assess total PA volume. 13 Using established cut points, we summed the accumulated volume of activity as AC in nonsedentary light (100<AC<760) and moderate-to-vigorous activity (≥760 AC). We also summed nonsedentary total activity counts (TAC; AC>100).Thesecutpointsprovide useful approximationsof time spent in light and moderate-to-vigorous activity in a variety of free-living studies.…”

Free‐Living Responses in Energy Balance to Short‐Term Overfeeding in Adults Differing in Propensity for Obesity

“…A Bland‐Altman analysis showed that the mean bias between measurements was −5 kcal/d (95% CI: −109 to 99 kcal/d). This method of estimating TDEE has similar accuracy compared to with other types of PA monitoring devices .…”

Using Accelerometer/GPS Data to Validate a Neighborhood-Adapted Version of the International Physical Activity Questionnaire (IPAQ)

“…With the exception of vigorous-intensity physical activity, the day-to-day intraclass correlation for accelerometer counts estimated for at least three valid consecutive days was .80 (Supplementary Material [available online]). ActiGraph ® wGT3X-BT is a tri-axial accelerometer that has been found to be reliable in free-living situations (Aadland & Ylvisåker, 2015) and has been validated in adults using indirect calorimetry (Santos-Lozano et al, 2013) and doubly labelled water (Chomistek et al, 2017) as criterion measures.…”