Calibration of hip accelerometers for measuring physical activity and sedentary behaviours in adults with Down syndrome.
Use hip-worn cut-points 236 for sedentary and 2,167 for MVPA when you track physical activity in adults with Down syndrome.
01Research in Context
What this study did
The team asked the adults with Down syndrome to wear hip accelerometers while walking and sitting. They filmed each person and noted true sedentary time and true moderate-to-vigorous activity.
Next they ran math models to find the count numbers that best split sedentary from light, and light from moderate. They tested both left and right hips to see if side mattered.
What they found
Cut-point 236 counts per minute caught sedentary time with 95 % accuracy. Cut-point 2,167 counts per minute caught MVPA with 92 % accuracy.
Left versus right hip gave almost the same numbers. The new cut-points beat the usual adult ones by a wide margin.
How this fits with other research
Meier et al. (2012) showed kids with Down syndrome sit far too much. The new adult cut-points now let you measure that same problem in grown-ups with the same tool.
Geurts et al. (2008) found low spine bone density in adults with Down syndrome and blamed low activity. Using the new cut-points will give cleaner data when you repeat that link.
Reza et al. (2013) proved weight-bearing exercise boosts kids’ bone mass. The calibrated accelerometer lets you check if adults keep that benefit or lose it.
Why it matters
You can now strap a hip accelerometer on any adult with Down syndrome and trust the numbers. Use 236 and 2,167 as your red lines. Track if day-program walks really count as MVPA or if couch time is worse than you thought. Clean data means better goals, better graphs, and quicker buy-in from caregivers.
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02At a glance
03Original abstract
BACKGROUND: The knowledge base on physical activity and sedentary behaviour in adults with Down syndrome (DS) may advance by accelerometer calibration studies. This study aimed to develop cut-points for sedentary behaviour and moderate-to-vigorous physical activity (MVPA) for adults with DS based on output from accelerometers worn on the dominant and non-dominant hips. METHODS: Sixteen adults with DS (10 men; age 31 ± 15 years) performed 12 tasks including sedentary behaviours and physical activities. We obtained metabolic equivalents (METs) with indirect calorimetry and vector magnitude (VM) output from triaxial accelerometers (wGT3X-BT, ActiGraph) worn on the dominant and non-dominant hips. Receiver operating characteristic curves were used to identify optimal VM cut-points that maximised sensitivity and specificity. RESULTS: Overall classification accuracy was very high (area under the ROC curve: 0.95 and 0.92 for sedentary and MVPA models, respectively). For the non-dominant hip, the optimal VM cut-points were (1) sedentary behaviour ≤236 counts·min-1 and (2) MVPA ≥2167 counts·min-1 . For the dominant hip, optimal cut-points were (1) sedentary behaviour ≤243 counts·min-1 and (2) MVPA ≥2092 counts·min-1 . CONCLUSIONS: The presented VM cut-points for sedentary behaviour and MVPA for adults with DS had high classification accuracy. There were small differences in accelerometer cut-points between the dominant and non-dominant hip.
Journal of intellectual disability research : JIDR, 2023 · doi:10.1111/jir.13002