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"Non-neutral wrist posture is a risk factor of the musculoskeletal disorders among computer users. This study aimed to assess internal loads on hand and forearm musculature while tapping in different wrist postures. Ten healthy subjects tapped on a key switch using their index finger in four wrist postures: straight, ulnar deviated, flexed and extended. Torque at the finger and wrist joints were calculated from measured joint postures and fingertip force. Muscle stresses of the six finger muscles and four wrist muscles that balanced the calculated joint torques were estimated using a musculoskeletal model and optimization algorithm minimizing the squared sum of muscle stress. Non-neutral wrist postures resulted in greater muscle stresses than the neutral (straight) wrist posture, and the stress in the extensor muscles were greater than the flexors in all conditions. Wrist extensors stress remained higher than 4.5 N/cm² and wrist flexor stress remained below 0.5 N/cm² during tapping. The sustained high motor unit recruitment of extensors suggests a greater risk than other muscles especially in flexed wrist posture. This study demonstrated from the perspective of internal tissue loading the importance of maintaining neutral wrist posture during keying activities."

This report examined different perspectives of upper extremity (UE) rehabilitation outcome in order to critically analyze various approaches to effectiveness evaluation. The impact of the patient's perspective and expectations on the outcome of treatment was discussed. Contributions made to classification bias from etiologic and anatomic heterogeneity were outlined. A conceptual framework was developed which relates the impact of interventions on the disease, impairments, the person and the environment. The worker's own perceptions of UE dysfunction and the expectations that person has were explored using various individual based designs of outcome quantification, including an illustration of the tension between individual and group perspectives on outcome. A model for population based outcome evaluation was presented which addresses diagnosis specific as well as individual goal specific evaluation. The authors suggest that to successfully measure the outcome of the rehabilitation process, one must take into account the achievement of individual goals as well as the objective scalar quantification of impairments, disabilities, and handicaps that are comparable between groups.