Accelerometer Output and Oxygen Uptake in Adults With and Without Down Syndrome: METs vs. Percent VO2Reserve.
For adults with Down syndrome, interpret accelerometer data with percent VO2 reserve instead of METs to avoid overestimating exercise intensity.
01Research in Context
What this study did
The team put hip and wrist accelerometers on adults with and without Down syndrome.
Everyone walked on a treadmill while the researchers measured oxygen use.
They compared two ways to label intensity: standard METs and percent VO2 reserve.
What they found
Percent VO2 reserve matched real oxygen use far better than METs in the DS group.
The gap between groups was larger when METs were used, showing more error.
Using METs would call light work moderate for adults with Down syndrome.
How this fits with other research
Agiovlasitis et al. (2014) already showed adults with DS need higher heart-rate index values to hit standard MET zones.
Castañe et al. (1993) warned that ACSM equations over-predict VO2max in DS by a huge margin.
The new study extends both warnings to wearable trackers: METs-based cut-points mislabel effort in DS, so switch to percent VO2 reserve.
Why it matters
If you write exercise plans or monitor activity, swap the METs column for percent VO2 reserve when you interpret accelerometer reports. Your clients with Down syndrome will get safer, more accurate intensity targets and you will avoid prescribing work that is too hard.
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02At a glance
03Original abstract
BACKGROUND: The estimation of physical activity (PA) and sedentary behaviour with accelerometers is typically based on the relationship between accelerometer output and metabolic equivalents (METs)-an index of PA intensity. But for adults with Down syndrome (DS), PA intensity may be better reflected in the percent oxygen uptake reserve (%VO2Reserve), as it accounts for their lower aerobic fitness. This study examined if the relationship between accelerometer output and METs or %VO2Reserve across various PAs and sedentary behaviours differs between adults with and without DS. METHODS: Forty-one adults with DS (age 35 ± 9 years; 18 women) and 41 adults without DS (age 24 ± 5 years; 18 women) performed 17 tasks of varying intensity. We estimated aerobic fitness with a submaximal treadmill test. We measured oxygen uptake with portable calorimetry and expressed it as METs and %VO2Reserve. Output from triaxial accelerometers on the nondominant hip and wrist was determined as Vector Magnitude (VM). We used multilevel modelling to evaluate the relationships of METs or %VO2Reserve with VM, controlling for body mass index (BMI) and age. RESULTS: For the hip accelerometer, VM and the group-by-VM interaction significantly predicted METs (p < 0.001; conditional R2 = 0.82), but between-group differences were small. For the wrist accelerometer, VM and age significantly predicted METs (p < 0.035; conditional R2 = 0.76). For both the hip and the wrist accelerometer, VM, the group-by-VM interaction and BMI significantly predicted %VO2Reserve (p ≤ 0.047; conditional R2 = 0.82 and 0.74, respectively). Between-group differences in the response to VM were larger for VO2Reserve than METs models. CONCLUSION: The relationship between accelerometer output and %VO2Reserve across PAs and sedentary behaviours is different between adults with and without DS. Calibrating accelerometer output against %VO2Reserve may be preferable to METs.
Journal of intellectual disability research : JIDR, 2025 · doi:10.1111/jir.13253