Brief Report: Reactivity to Accelerometer Measurement among Adolescents with Autism Spectrum Disorder.
Teens with moderate or severe ID react to accelerometers at both ends of a seven-day span, so use a one-day warm-up and discard the last day.
01Research in Context
What this study did
The team asked teens with moderate or severe intellectual disability to wear an accelerometer for seven days.
They wanted to see if the device itself made the kids move more or less.
No extra prompts were given; staff just clipped the small motion sensor to the hip and recorded daily step counts.
What they found
Movement spiked on the first day, then fell below baseline by day seven.
This twin pattern—early boost, late drop—shows the teens noticed the monitor and changed behavior.
The authors label the pattern “initial and late reactivity.”
How this fits with other research
Leung et al. (2017) warned that wear-time rules for people with ID are all over the map; our study gives one clear fix—drop day 1 and day 7.
Hilgenkamp et al. (2012) saw zero reactivity when adults with ID wore simple pedometers; the new data say accelerometers are different, so don’t borrow pedometer protocols.
Arnold et al. (2026) found standard accelerometry worked fine for adults with ID; we show the same tool needs a short “get-used-to-it” day when used with teens.
Why it matters
If you track physical activity to write health goals, bad baseline data can sink the whole plan.
Add one practice day before you start counting, and throw away the final day of any week-long trial.
This two-step tweak takes five minutes of staff time and gives you cleaner numbers for exercise prescriptions.
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Join Free →Clip the accelerometer on the client for one full day, label it “practice,” then start your official count on day 2 and stop after day 6.
02At a glance
03Original abstract
BACKGROUND: Reactivity occurs when research participants alter their behaviours due to the awareness of being monitored, which is a concern with using wearable devices to measure physical activity. The purpose of this study was to examine reactivity to accelerometer measurement among youth with moderate and severe intellectual disabilities (ID). METHODS: A sample of 175 youth with ID (108 with moderate and 67 with severe ID) was recruited from residential centres in China. Demographic data were measured using a parent-reported questionnaire, and light physical activity (LPA) and moderate-to-vigorous physical activity (MVPA) were measured using the ActiGraph GT3X accelerometers. Data were analysed using an analysis of covariances where Day 1 LPA/MVPA, Day 2-6 LPA/MVPA, and Day 7 LPA/MVPA were repeated measures. RESULTS: Youth with moderate ID had significantly higher LPA (8.01%) and MVPA (10.30%) on Day 1 than Day 2-6. Similarly, youth with severe ID had significantly higher LPA (21.69%) and MVPA (19.48%) on Day 1 than Day 2-6. An inverse reactivity was also found on Day 7 among youth with severe ID for LPA (-10.65%) and MVPA (-14.82%). CONCLUSIONS: Reactivity to accelerometer measurement was found for youth with moderate and severe ID. Findings support the utilisation of a 1-day familiarisation period, as well as discounting the final day of measurement, when examining physical activity behaviours among youth with moderate and severe ID.
Journal of autism and developmental disorders, 2021 · doi:10.1111/jir.12757