Figure 2From: The feasibility of measuring the activation of the trunk muscles in healthy older adults during trunk stability exercises Motion capture. The Flock of Birds Motion Captureâ„¢ sensor was placed on the antero-superior portion of the left lateral iliac crest. Note that the z-axis is positioned perpendicular to the sensor. This sensor records motion with respect to a fixed global reference and not an anatomical reference.Back to article page