Validity of three accelerometers during treadmill walking and motor vehicle travel.
OBJECTIVE
To determine the relative accuracy during treadmill walking and motor vehicle travel of the ActivPAL, PALlite and Digi-Walker accelerometers.


METHODS
Forty healthy volunteers wearing all accelerometers undertook either five treadmill walks (n=20) at speeds ranging between 0.6 and 1.4 m/s or a 15 min motor vehicle journey (n=20). Step counts recorded by each accelerometer were compared with the actual step count determined by video analysis (treadmill walking) or with an actual step count of zero (motor vehicle). Mean percentage measurement error was calculated and compared between devices by one-way ANOVA and Student t test.


RESULTS
For treadmill walking, the measurement error was lowest for the ActivPAL, with no significant differences between the ActivPAL and the PALlite monitors. The measurement error was significantly higher for the Digi-Walker at speeds of < or =1 m/s. During vehicle travel erroneous steps were recorded by the PALlite (254 steps) and Digi-Walker (25 steps), but not the ActivPAL monitor (0 steps).


CONCLUSIONS
The ActivPAL accelerometer accurately measures step count over a range of walking speeds and, unlike the other accelerometers tested, is not falsely triggered by motor vehicle travel.
Maddocks
Matthew
M
Division of Physiotherapy Education, University of Nottingham, Nottingham NG5 1PB, UK. matthew.maddocks@nottingham.ac.uk
Petrou
Andrea
A
Skipper
Lindsay
L
Wilcock
Andrew
A
D000054:Acceleration; D000328:Adult; D005080:Exercise Test / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D018670:Monitoring, Ambulatory / Q000295:instrumentation*; D018986:Motor Vehicles / Q000706:statistics & numerical data*; D014195:Travel; D016138:Walking / Q000502:physiology* / Q000706:statistics & numerical data