Quantifying Arm Movements And Grasps To Support End-users' Needs During Prosthetic Limb Development

Abstract

PURPOSE: To quantify arm movements and common grasps among blue collar workers (BCW) and white collar workers (WCW) over the normal course of daily activities. Data will guide scientists when designing a prosthetic arm with an ample energy source and sufficient degrees of motion and strength to enable users to perform real-life arm functions. METHODS: Participants were videotaped at their workplace during an entire workday. Videos were analyzed to determine dominant arm movement observations including: 1) total arm movements, 2) total and specific type of shoulder, elbow and wrist movements (e.g. shoulder abduction/adduction), 3) total loaded (object grasped in hand during movement) versus unloaded movements, and 4) total compliant (pliable) versus non-compliant (rigid) object grasps. Movements were recorded if any action was observed, regardless of the range of arm movement. Commonly observed grasps during the workday were also recorded. RESULTS: Four men with a mean (±SD) age of 40±8 yrs were studied, consisting of two BCW (machinist and auto-mechanic) and two WCW (engineer and researcher). Total arm movements observed for the workday were: machinist = 15,700, auto-mechanic = 16,103, engineer = 9,130, and researcher = 9,305. Sixty-three percent of movements for BCW were loaded (object grasped in hand during movement) compared to 21% for WCW. The BCW had more than twice the amount of observed object grasps compared to WCW (combined totals: 4,806 for BCW vs. 2,236 for WCW). Eighty-two percent of grasps for BCW were for non-compliant objects, whereas 29% were observed in WCW. Common grasps included the tip, cylindrical and spherical grasp for the BCW and spherical, palmar and lateral grasps for the WCW. Objects commonly grasped by the BCW were tools and drill bits, while WCW grasps included paper and a computer mouse. CONCLUSIONS: BCW exhibit a common pattern of grasps of non-compliant objects with loaded arm movements; in contrast, WCW exhibit a pattern of compliant object grasps with non-loaded arm movements. To optimize function and use, prosthetic limbs should be designed considering the movement/grasp patterns and strength needs of the end-user. This work was sponsored by the DARPA Revolutionizing Prosthetics Program, Contract N66001-06-C-8005 (abstract is approved for public release, distribution unlimited).