ABSTRACT
Objective To observe the effect of elbow support on muscle activity and subjective feelings of comfort during typing.Methods Ten college students voluntarily participated in this experiment.They typed the same text using elbow supports of five different heights.The distance between their elbows and the desk was supported at 3 cm below,0 cm,and-3 cm and-6 cm above the desk.There was also an unsupported condition.Myoelectric readings were recorded from the right splenius,trapezius,biceps,extensor carpi radialis,flexor digitorum superficialis,flexor carpi radialis,and extensor digitorum muscles.Perceptions of comfort of the neck,shoulder,hand and forearm,and hand using the different supports were surveyed using a questionnaire.Results One way ANOVA shows that the height of the elbow significantly affects the activity of the trapezius,the extensor carpi radialis and the extensor digitorum muscles.Trapezius muscle activity was higher with 3 cm high elbow support than without support,and the value was smaller when using-6 cm elbow support.The activity of the carpi radialis longus extensor was least when using-6 cm and-3 cm elbow support,and greatest with 3 cm support.Extensor digitorum activity was least when using-3 cm high elbow support and again greatest with 3 cm support.The different elbow support heights had no significant relationship with comfort perceptions for any body part.Conclusion The height of elbow support can change the average myoelectric signals from muscles during typing,but there is no significant difference in the typist's perception of comfort.This could be due to a change of typing position and neuromuscular motion control mode in response to the height of elbow support.