sentences:  Some studies used devices such as a headrest and bite-plate to minimise this contamination, with limited success, and in one case a camera affixed to a motorcycle helmet—weighing nearly 3 kg—which was supported by a system of counterbalancing weights and pulleys attached to the ceiling.In addition to extraneous head movement, researchers faced other physical, bodily problems.The musculoskeletal response required to play a musical instrument involves substantial body movement, usually of the hands, arms and torso.