Technical reliability of the CSA activity monitor: The EarlyBird Study.

Purpose: To evaluate the technical performance of the CSA accelerometer-based activity monitor.

Methods: Twenty-three CSA monitors were subjected to intra- and inter-instrument variability tests by controlled trials using a motorized turntable. The CSA monitor measures change in acceleration, and precision was tested by producing sinusoidal variations in speed around two fixed baseline speeds (fast and medium).