Movement times of different arm components

Data for ballistic and visually controlled movement times of different arm components are presented. Ballistic movement times gave strong support to the theoretical model that movement time is linearly related to the square-root of movement amplitude, for all arm components. It was found that there was a significant effect on movement time of the arm component being used. A scaling analysis showed that this time was linearly related to the product of the square-root of amplitude and the one-tenth power of limb mass moment of inertia. This relationship was found to be approximately true in the experiment. For visually controlled movements, movement time showed a significant interaction between Fitts' Index of Difficulty and arm component. The effect of arm component on movement time was stronger in visually controlled movements than in ballistic movements and did not allow the simple modelling in terms of limb mass moment of inertia as was possible with ballistic moves. STATEMENT OF RELEVANCE: Different arm components take different times to move the same distance, dependent on their mass moments of inertia and muscle strength. The work investigated times for finger, wrist, forearm, and full-arm movements that are relevant to tasks such as manual assembly where there are alternative movement methods available for an operator.