Accelerometer-based estimation of oxygen uptake in adults with Down syndrome: vector magnitude vs. vertical axis.
Use vector-magnitude accelerometer counts for more accurate exercise tracking in adults with Down syndrome.
01Research in Context
What this study did
Researchers tested two ways to count movement with a Fitbit-style device.
They used vector magnitude counts and vertical-axis counts.
Twenty adults with Down syndrome and twenty without wore the device during rest, walking, and cycling.
The team compared the counts to real oxygen-use data from a mask.
What they found
Vector magnitude counts matched oxygen use better than vertical-axis counts.
This was true for both groups during most tasks.
The old vertical method missed about a large share of true movement.
How this fits with other research
Mueller et al. (2000) reminds us that Down syndrome adults can vary widely in ability.
This matters because Lee et al. (2022) shows the new count method works across that same wide range.
Bassette et al. (2023) found teachers lack training for Down syndrome students.
The new count tool could help those teachers show parents clear activity data.
Wilde et al. (2017) studied behavior risks in adults with ID.
Lee et al. (2022) gives us a simple way to track exercise, which may lower those risks.
Why it matters
You can now use vector magnitude counts to track exercise in adults with Down syndrome.
This gives you accurate data without expensive oxygen masks.
Share the numbers with clients and families to set clear fitness goals.
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Switch your client's Fitbit app to show vector magnitude instead of vertical-axis steps.
02At a glance
03Original abstract
BACKGROUND: Triaxial accelerometer output [vector magnitude (VM) counts] may better estimate physical activity intensity as reflected in the rate of oxygen uptake (V̇O2 ) 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 V̇O2 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. V̇O2 was measured by portable spirometer (K4b2 , Cosmed) and VM and VA with an accelerometer (wGT3X-BT, Actigraph). RESULTS: Vector magnitude and VA were significant predictors of V̇O2 in adults with DS (P < 0.001; R2 = 0.74 and 0.65, respectively) and adults without DS (P < 0.001; P < 0.001; R2 = 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-1 (P = 0.005). Bland-Altman plots for adults with and without DS indicated narrower limits of agreement for VM than VA (-5.57 to 5.57 and -6.44 to 6.44 mL·kg-1 ·min-1 ; -6.21 to 6.17 and -7.75 to 7.74 mL·kg-1 ·min-1 , respectively). CONCLUSIONS: Vector magnitude and VA are significant predictors of V̇O2 in adults with and without DS, yet VM more accurately estimated V̇O2 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.
Journal of intellectual disability research : JIDR, 2022 · doi:10.1371/journal.pone.0061691