Construct validity of the Actiwatch-2 for assessing movement in people with profound intellectual and multiple disabilities.
Helena J M van Alphen, Aly Waninge, Alexander E M G Minnaert and 2 others
PMID 32725667WHAT IT FOUND
The Actiwatch-2 accurately detects the presence of upper body movement in people with profound intellectual and multiple disabilities, distinguishing it from stillness.
However, it fails to identify body position or the specific type of activity, such as massage versus active play. Individual calibration is required.
Key findings
01The Actiwatch-2 significantly distinguishes the presence of upper body movement from its absence, with movement yielding higher activity counts.
02The device does not significantly detect differences in body position (lying, sitting, standing), making it unsuitable for determining posture.
03While the device detects involvement in an activity versus being present, it cannot distinguish between specific types of involvement, such as passive participation versus active participation.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTsWhat it means for SLPs
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What it does not show
The study only assessed upper body movement via wrist acceleration; leg movements were not measured. Small involuntary movements (e.g., tremors, stereotypies) and subtle head movements were not reliably distinguished from purposeful movement. The device failed to detect body position, limiting its utility for postural analysis. There is high variability in counts between participants, meaning group averages are misleading. Some participants (11.5%) were excluded because they could not tolerate wearing the wrist device. The study did not validate the device against a gold standard for energy expenditure, only against video observation of movement presence/absence.
Declared interests
There are no conflicts of interest declared by the authors.
The easy way to misread this
Do not assume the Actiwatch-2 can distinguish between different types of movement activities (e.g., massage vs. active play) or determine the patient's body position (e.g., sitting vs. lying). It only confirms whether the upper body is moving or still. Additionally, do not use standard population cut-off values for activity intensity; these must be individually calibrated for people with PIMD.