The Effect of Prolonged Sitting on Different Unstable Chairs on Trunk Muscles Activity and Posture for Individuals with Sedentary Work

BACKGROUND: Sitting nowadays is typical working position and causes various harmful effects which could be minimized by regular changes of position implemented due to periodical activation of corresponding muscles. OBJECTIVE: To determine changes of trunk muscles activity and posture after prolonged sitting on unstable chairs. METHODS: 20 office workers participated in the study. Posture and movements of their torso and pelvis were measured by 3D MoCap system and four trunk muscles activities - by electromyograph. Three different unstable chairs were tested when performing three different tasks while sitting on teach of them. RESULTS: Trunk muscles activity significantly increased after 6 weeks sitting on unstable chairs: Multifidus muscles - 8.88 %, Transversus abdominis muscle - 5.19 %. Measurements of C7, Th7, L3 spine angle showed that it increased by 2 degrees when sitting on Back app and Human Tool unstable chairs. CONCLUSIONS: Sitting on unstable surfaces for 6 weeks significantly increased Multifidus and Transversus abdominis muscles activity, which are responsible for spine stabilization. Unstable chairs, especially Back app and Human Tool, have positive influence on the posture of participants. It means that chairs, mentioned above, it is proper for prolonged sitting position at workplace due to improvement of the posture and muscles activity.