EFFECTS OF 3 PROLONGED SITTING POSTURES ON TRUNK MUSCLE ACTIVATION AND BODY PERCEIVED DISCOMFORT IN OFFICE WORKERS

Abstract

The purpose of this study was to quantity body perceived discomfort and trunk muscle activities experienced during three prolonged sitting postures (i.e. forward leaning, upright, and slump sitting postures). A study with a repeated-measure design was conducted in 10 healthy office workers. Each subject sat for an hour in three sitting postures (i.e. upright, slump, and forward leaning sitting postures). Two-way analysis of variance (ANOVA) for repeated measures was employed to determine the effects of sitting posture, time and their interaction on the EMG activity of trunk muscles. The Borg scores (discomfort scores) after 60 minutes of sitting were compared among three sitting postures using a one-way analysis of covariance (ANCOVA). Regardless of sitting posture, the Borg scores in the neck, upper back, low back and hip/thighs were significantly increased after 60-minute sitting compared with at the beginning. Forward leaning sitting posture led to higher the Borg scores in the low back than those in upright (p = 0.002) and slump sitting postures (p < 0.001). The Borg score in the low back in upright sitting posture was higher than that in slump sitting posture (p = 0.021). For trunk muscle activity, forward leaning posture was significantly associated with increased ICL and MF muscle activity compared with upright and slump sitting postures. Upright sitting posture was significantly associated with increased IO/TrA and ICL muscle activity compared with slump sitting posture. Thus, sitting in an upright posture is recommended because it increases IO/TrA muscle activation and causes only relatively moderate ICL and MF muscle activation.