The goal of this proposed research is to determine which interventions, such as alternative keyboard designs, workstation arrangements, and typing styles lead to reduced static and dynamic loading of the tissues of the upper extremity, hence reducing the risk of computer related musculoskeletal disorders. The approach of this research project is as follows: (1) Develop a dynamic, EMG-driven musculoskeletal model of the finger and wrist, to predict the forces of, as well as to elicit the specific coordination of the finger and wrist muscles balancing the wrist and finger joint dynamics. This multilink model will incorporate Hill type muscle models and EMG to drive the distribution of forces across the muscles to determine role of finger and wrist muscles during tapping and typing. Experimental kinematic, kinetic and electromyographic (EMG) data will be used as inputs into these models. Using repeated measures experimental design, we will use the model to examine the effect of non-vertical keyswitch designs, non-neutral wrist postures, use of wrist rests, and co-contraction of finger and hand muscles on the static and dynamic loading of the wrist and fingers during tapping and typing tasks. (2) Measure and characterize the biomechanical demands of upper extremity during single finger tapping and multi-finger typing and determine how specific ergonomic interventions reduce biomechanical demands associated with these activities. We will measure the kinematics of the finger, wrist, forearm, elbow, upper arm and shoulder, the muscle activity of prime wrist, elbow and shoulder muscles, and the forces applied at the fingertip and at any forearm and/or wrist supports. Joint torques will be estimated using a link-segment model of the upper extremity and joint coordination will be determined through graphic and correlation analyses of the EMG with the segment kinematics and kinetics. We will determine which type of forearm support configurations, motor control strategies and typing styles lead to lower mechanical loading. Public Health Relevance: We will address unresolved questions about risk factors for musculoskeletal disorders among computer users, namely key angle, forearm, wrist, and palm support, wrist posture, and typing style. These biomechanical studies are a critical step in testing the effectiveness of these interventions for reducing work-related musculoskeletal disorders
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