Abstract
Ten male subjects performed four methods of setting a vertical boxcar hand brake. Muscle activity was recorded in arm, leg, and back muscles. Each method was rated in terms of adherence to principles of work design and rated by subjects in order of comfort. Maximum braking force was recorded for each method and the subjects were videotaped to analyze postures. Biographical and strength data were recorded. The study found that as equipment arrangements allowed the operator to assume a more upright posture, braking force tended to increase, comfort ratings improved, EMG signals tended to decrease, and the task adhered to more principles of physiologically sound work design. Strength of the left arm was the major predictor of braking force, and back muscle activity tended to increase as braking force increased.
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