Biomechanical analysis of primary upper limb muscle contributors to a functional pulling movement

Abstract

Better understanding of the muscles that are dominant contributors to upper limb functional tasks may inform rehabilitation in older individuals at risk for disability. Our aim was to determine the muscles primarily responsible for hand movement during pulling. We used an upper limb musculoskeletal computer model that incorporated upper limb joints, physiologic force‐generating properties for all muscles crossing the shoulder, elbow, and forearm, and delays associated with neural activation. A horizontal pulling task was performed by a 50th percentile adult male (5′11″, 180lbs) against 6lb resistance; joint kinematics and EMG were recorded. In the computer simulation, contributions of 32 individual muscles in the measured movement were determined using induced acceleration analysis, which calculates the effect of each muscle's force, applied in isolation, on hand movement. The simulation successfully replicated experimental kinematics (mean error 0.0003°; max 0.06°) and muscle activations. Of the 12 muscles identified as substantial contributors to pulling, 8 cross the shoulder. Our novel simulations suggest that shoulder muscles play an important role in successful functional pulling and are more influential to this upper limb task than elbow and forearm muscles; they may warrant more attention in strengthening programs in at‐risk groups. NIH #5R24HD050821‐02, NSF CBET‐0828115, WFU SRF and CCCRF.