Predicting the rate of oxygen uptake from step counts using ActiGraph waist-worn accelerometers in adults with Down syndrome.
A quick hip-worn step count plus BMI gives a fair estimate of calories burned while walking for adults with Down syndrome.
01Research in Context
What this study did
Researchers put hip-worn ActiGraph monitors on the adults with Down syndrome and 31 without. Each person walked on a treadmill while the team counted steps and measured oxygen use (VO2). They built a math model that turns step rate and BMI into calories burned.
The goal was a simple field tool so you can skip the pricey lab mask.
What they found
The equation (step rate + step rate² + BMI) predicted VO2 within 12–a large share error. It worked the same for both groups. Plug in the numbers and you get a fair guess of energy spent during walking.
That error range is close enough for day-to-day fitness tracking.
How this fits with other research
Wee et al. (2015) first showed adults with Down syndrome hit lower peak VO2 (~25 mL/kg/min) and peak heart rate (~167 bpm). The new equation uses those same lab values to check itself, so the two studies line up.
Leung et al. (2017) warned that accelerometer protocols for people with ID are messy and wear-time is often poor. The current paper keeps the waist belt on only during short lab walks, dodging that compliance problem.
Rieth et al. (2022) also built a quick field metric—hand-grip/BMI for muscle quality—in teens with Down syndrome. Both papers give you easy numbers you can grab without a lab, just different ages and outcomes.
Why it matters
If you support adults with Down syndrome in day programs or group homes, you can now turn their ActiGraph step counts into calorie estimates on the spot. No masks, no treadmills. Use the published formula to set realistic walking goals, show progress to caregivers, or justify more activity funding.
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Join Free →Open the paper, copy the VO2 equation into your Excel sheet, and start converting yesterday’s ActiGraph step files into calorie counts for your clients.
02At a glance
03Original abstract
BACKGROUND: Step rate predicts ambulatory intensity as reflected in the rate of oxygen uptake (VO2 ) - a measure of energy expenditure. Whether step rate as measured by an accelerometer predicts VO2 in adults with Down syndrome (DS) is unknown. We examined whether step rate predicts VO2 in adults with and without DS. We also developed an equation for predicting VO2 and examined its accuracy. METHOD: Sixteen adults with DS (6 women and 10 men; age 31 ± 15 years) and 19 adults without DS (9 women and 10 men; age 25 ± 6 years) performed standing and walking at their preferred speed, 0.8 and 1.4 m·s-1 . We measured VO2 with a portable spirometer and step rate with a triaxial accelerometer (wGT3X-BT; ActiGraph) on the non-dominant hip, using the low-frequency extension filter. We ran multilevel regression for predicting VO2 from linear and quadratic terms for step rate, group (1 = DS; 0 = non-DS), body mass, height, body mass index (BMI), leg length and sex. We estimated VO2 with the resultant equation and calculated the equation's absolute per cent error, which we compared between groups. RESULTS: VO2 was higher in persons with than without DS only at the fast walking speed (P = 0.018). DS did not predict VO2 . Step rate, step rate squared and BMI were significant predictors of VO2 (P < 0.001; R2 = 0.80). Absolute error across walking speeds was 13.5-18.8% and 11.7-13.4% for adults with and without DS, respectively, and did not differ between groups or speeds. CONCLUSIONS: Step rate, step rate squared and BMI predict VO2 in adults with and without DS. Prediction error does not differ between groups.
Journal of intellectual disability research : JIDR, 2020 · doi:10.1111/jir.12755