Comparison of two objective monitors for assessing physical activity and sedentary behaviors in bariatric surgery patients.

Background: Objective quantification of physical activity (PA) is needed to understand PA and sedentary behaviors in bariatric surgery patients, yet it is unclear whether PA estimates produced by different monitors are comparable and can be interpreted similarly across studies.

Methods: We compared PA estimates from the Stayhealthy RT3 triaxial accelerometer (RT3) and the Sensewear Pro(2) Armband (SWA) at both the group and individual participant level. Bariatric surgery candidates were instructed to wear the RT3 and SWA during waking hours for 7 days. Participants meeting valid wear time requirements (≥4 days of ≥8 h/day) for both monitors were included in the analyses. Time spent in sedentary (<1.5 METs), light (1.5-2.9 METs), moderate-to-vigorous (MVPA; ≥3.0 METs), and total PA (TPA; ≥1.5 METs) according to each monitor was compared.

Results: Fifty-five participants (BMI 48.4 ± 8.2 kg/m(2)) met wear time requirements. Daily time spent in sedentary (RT3 582.9 ± 94.3; SWA 602.3 ± 128.6 min), light (RT3 131.9 ± 60.0; SWA 120.6 ± 65.7 min), MVPA (RT3 25.9 ± 20.9; SWA 29.9 ± 19.5 min), and TPA (RT3 157.8 ± 74.5; SWA 150.6 ± 80.7 min) was similar between monitors (p > 0.05). While the average difference in TPA between the two monitors at the group level was 7.2 ± 64.2 min; the average difference between the two monitors for each participant was 45.6 ± 45.4 min. At the group level, the RT3 and SWA provide similar estimates of PA and sedentary behaviors; however, concordance between monitors may be compromised at the individual level.

Conclusions: Findings related to PA and sedentary behaviors at the group level can be interpreted similarly across studies when either monitor is used.