Trunk Posture Adaptations during Sitting on Dynamic Stool: A Validation Study

Effect of two dynamic seat cushions on postural shift, trunk muscle activation and spinal discomfort in office workers

We investigated the effect of two dynamic seat cushions on postural shift, trunk muscle activation and spinal discomfort. In this repeated-measures study, 30 healthy office workers were randomly assigned to a sequence of three conditions: sitting on a dynamic seat cushion-A, cushion-B and control (no seat cushion). The two dynamic seat cushions had different inflation levels. Participants typed a standard text for an hour and were monitored for postural shift by using a seat pressure mat, transversus abdominis/internal oblique and lumbar multifidus muscles activity by using surface EMG, spinal discomfort by using Borg's CR-10 scale. Two-way repeated ANOVAs showed no statistically significant interaction effects between condition and time on postural shift and muscle activation. Post hoc Bonferroni tests showed that postural shifts and lumbar multifidus activation during sitting on cushion-A were significantly higher (p < 0.01) than in the control and cushion-B conditions. Both cushions reduced spinal discomfort, compared to the control condition (p < 0.05).

Effectiveness of Combined Stretching and Strengthening Exercise Using Rehabilitation Exercise System with a Linear Actuator and MR Damper on Static and Dynamic Sitting Postural Balance: A Feasibility Study

Postural imbalance induced by prolonged sitting can be improved by exercise therapy. The aim of study was to evaluate the influence of combined stretching and strengthening exercise using rehabilitation exercise system with a linear actuator and MR damper on static and dynamic sitting postural balance. Twelve subjects who sit almost 10 h a day participated in this study. The rehabilitation exercise system with a linear actuator and MR damper was manufactured to provide stretching and strengthening exercise. All subjects were asked to perform an exercise program that was designed to enhance postural balance by stretching the tight muscle and strengthening the weakened muscle. Body pressure distributions were analyzed for mean force and mean pressure using a seat sensor system. Trunk muscle activities were measured by attaching surface electrodes to the thoracic erector spinae, lumbar erector spinae, and lumbar multifidus muscle. All data were divided into two regions (dominant and non-dominant side) under four conditions: no pelvic tilt, lateral pelvic tilt, anterior pelvic tilt, and posterior pelvic tilt. Body pressure distributions and trunk muscle activities were compared between before and after performing exercise under static and dynamic sitting conditions. Both in static and dynamic sitting conditions, there were significant differences in body pressure distributions and trunk muscle activities between the DS and NDS before performing the exercise (p < 0.01). After performing exercise, the body pressure distributions increased on the dominant side while those decreased on the non-dominant side significantly (p < 0.01). In addition, the activities of all trunk muscles on the non-predominant side increased significantly (p < 0.01 and p < 0.05). These results showed that postural balance was improved by decreasing the differences in body pressure distribution and trunk muscle activity between the dominant and non-dominant side after performing exercise. From the results of this study, we concluded that the rehabilitation exercise system with a linear actuator and MR damper is suitable for providing combined stretching and strengthening exercise, and it could be helpful to maintain correct posture by enhancing postural balance during sitting.