Accelerometer‐based estimation of oxygen uptake in adults with Down syndrome: vector magnitude vs. vertical axis

Abstract

Background Triaxial accelerometer output [vector magnitude (VM) counts] may better estimate physical activity intensity as reflected in the rate of oxygen uptake (V ˙O2 ) than the traditional vertical axis (VA) counts in adults with Down syndrome (DS). This study examined the accuracy of VM vs. VA counts in estimating V ˙O2 in adults with and without DS across different physical activities and sedentary behaviours. Methods Sixteen adults with DS (10 men and 6 women; 31 ± 15 years) and 19 adults without DS (10 men and 9 women; 24 ± 5 years) performed 12 tasks. V ˙O2 was measured by portable spirometer (K4b 2 , Cosmed) and VM and VA with an accelerometer (wGT3X-BT, Actigraph). Results Vector magnitude and VA were significant predictors of V ˙O2 in adults with DS (P < 0.001; R 2 = 0.74 and 0.65, respectively) and adults without DS (P < 0.001; P < 0.001; R 2 = 0.75 and 0.61, respectively). Absolute error of prediction was significantly smaller for VM than VA for sitting, playing app, drawing, sweeping, standing and basketball (P ≤ 0.005), but smaller for VA than VM for walking at 0.8 m•s À1 (P = 0.005). Bland-Altman plots for adults with and without DS indicated narrower limits of agreement for VM than VA (À5.57 to 5.57 and À6.44 to 6.44 mL•kg À1 •min À1 ; À6.21 to 6.17 and À7.75 to 7.74 mL•kg À1 •min À1 , respectively). Conclusions Vector magnitude and VA are significant predictors of V ˙O2 in adults with and without DS, yet VM more accurately estimated V ˙O2 than VA for most tasks. Development of accelerometer-based prediction of physical activity levels in adults with and without DS may improve by utilising VM counts.

Calibration of hip accelerometers for measuring physical activity and sedentary behaviours in adults with Down syndrome

“…Utilising population-specific cut-points in future research may yield more accurate assessment of the levels and patterns of sedentary behaviour and MVPA of adults with DS. Furthermore, the present results add credibility to utilising VM cut-points as opposed to vertical axis cut-points in classifying sedentary behaviour and physical activity intensity based on accelerometer output in adults with DS as past research has indicated (Leung et al 2021;Ballenger et al 2022). Of course, application of the present cut-points should be done cautiously by considering the limitations of the present research outlined below.…”

“…2021; Ballenger et al . 2022). Of course, application of the present cut‐points should be done cautiously by considering the limitations of the present research outlined below.…”

“…The causes of this altered relationship are possibly due to DS-associated higher metabolic rates or altered and more variable movement patterns during walking (Ulrich et al 2004;Agiovlasitis et al 2014;Mendonca et al 2018). However, vector magnitude-an index of triaxial accelerations-has stronger association with oxygen uptake during walking but also other physical activities and sedentary behaviours than vertical axis accelerations in adults with DS (Leung et al 2021;Ballenger et al 2022); this result has been derived for the ActiGraph triaxial accelerometer-one of the most frequently used accelerometers in physical activity research. Taken together, past research findings indicate that accelerometer output cut-points for MVPA and sedentary behaviour for adults with DS may be different from previously published cut-points for adults without DS and should be derived from vector magnitude rather than the single vertical axis.…”

“…2021; Ballenger et al . 2022); this result has been derived for the ActiGraph triaxial accelerometer—one of the most frequently used accelerometers in physical activity research. Taken together, past research findings indicate that accelerometer output cut‐points for MVPA and sedentary behaviour for adults with DS may be different from previously published cut‐points for adults without DS and should be derived from vector magnitude rather than the single vertical axis.…”

Analysis of sedentary behaviour levels and patterns in adults with Down syndrome

“…Accelerometer data were validated for wear time with the Choi algorithm (Choi et al, 2011) and scored using a sedentary cut‐point based on vector magnitude developed specifically for adults with DS: ≤236 counts/min (Agiovlasitis et al, 2022). Accelerometer measurement using vector magnitude has shown to more accurately estimate energy expenditure compared to vertical axis in adults with DS (Ballenger et al, 2022). The following SB variables were obtained: (a) total daily sedentary time (min day −1 ); (b) percentage of wear time spent sedentary; (c) number of sedentary bouts per day; (d) average duration of bouts in min; (e) number of sedentary breaks per day; (f) average duration of breaks in min.…”