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2013 Abstracts

Wrist Forces and Torques during Activities of Daily Living

Autumn Pando, Brigham Young University

Mechanical Engineering

The wrist is one of the most common sites for joint injury. Over two-thirds of 75,000 annual repetitive joint injuries occur at the wrist. Excessive or abnormal wrist forces are thought to be one of the main contributing factors, yet no characterization of normal wrist forces exists. The purpose of this research is to fill this lack by creating a systematic, quantitative characterization of wrist forces and torques experienced in daily life. This database will aid further research in developing better and more personalized treatments as well as improving design considerations for human-machine interfaces. Ten healthy subjects participated in the experiment. Subjects performed 25 activities representative of daily life (e.g. hygiene maintenance, food preparation, using technology). Electromyographic (EMG) sensors recorded wrist muscle activity and electromagnetic motion sensors recorded wrist kinematics. Each subject performed a calibration task prior to the experimental protocol to determine the proportionality constant between EMG activity and torque. Wrist force and torque were determined from EMG activity using a constant of proportionality (identified by calibration), muscle length, and muscle velocity. Co-contraction was computed from torque. Wrist muscle usage, forces, torque magnitudes, torque angles, and percentage of co-contraction at varying levels of contraction were characterized. The results indicate muscle use, forces, and torques are unevenly distributed.