This dataset contains inertial sensor and optical motion capture data from a trial of 20 healthy adult participants performing various upper limb movements. Each subject had an IMU and cluster of relfective markers attached to their sternum, right upper arm, and right forearm (as in the image attached), and IMU and marker data was recorded simultaneously. This trial was carried out with the intention of investigating alternative sensor-to-segment calibration methods, but may be useful for other areas of inertial sensor research. CAD files for the 3D printed mounts are also included.