Effect of two seating positions on upper limb function in normal subjects

Abstract

Many upper limb functions are performed in a sitting position. However, if seating is inadequate and poorly designed, back pain and reduced upper limb control may result. This study investigates pelvic posture and performance in an upper limb task. In total, 15 normal healthy volunteers (aged 18–30 years) were seated in posterior and anterior pelvic tilt positions and performed a simple upper limb task. The parameters measured were electromyography of the lumbar paravertebral muscles, time taken to complete the task and the task error rate. The data were analysed by repeated measures analysis of variance (ANOVA) and post-hoc t tests. The results indicate that, when seated in an anterior pelvic tilt position, the error rate decreased (P=0.013) and the electrical activity increased (P=0.008). The time taken to complete the task was not significantly different. Since the error rate decreased when seated in the anterior pelvic tilt position, it might be concluded that this posture facilitated task skill. It is suggested that the increase in electrical activity is related to the increased load on the lumbar muscles in maintaining the posture. This study's generalizability is limited, with small subject numbers and the use of a non-functional task. It is, however, a beginning in addressing the interrelationship between the seated posture and skilled upper limb performance.