applied sciences  
A Study on the Comfort Level of Standing Chairs Based on Pressure Sensors and sEMG  
[PERSON], [PERSON],*, [PERSON] and [PERSON]  
1 Department of Mechanical Engineering, Xi'an Jiaotong University City College, Xi'an 710018, China;  
2 [EMAIL_ADDRESS] (W.Z.); [EMAIL_ADDRESS] (C.F.)  
2 Engineering Research Center of Robot and Intelligent Manufacturing, Universities of Shaanxi Province, Xi'an 710018, China  
3 Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China;  
4 [EMAIL_ADDRESS]; Tel.: +86-151-9910-8673  
**Featured Application: Most existing research centers on examining the effects of sit-stand desks on sitting and standing positions, often overlooking the influence of the workplace environment and seat tilt angles on comfort. This study develops and constructs a model of a standing desk chair to address this gap and explores how seat tilt angles and various task conditions impact chair comfort. In this article, researchers adopt an innovative approach to evaluate the comfort of standing desk chairs, integrating the analysis of pressure distribution and electromyography signals. This holistic method not only delivers an objective assessment of chair comfort but also sheds light on how chairs affect muscle activity. Through the analysis of pressure distribution, researchers gain insight into how standing desk chairs support different body parts, enabling evaluation of their overall comfort and supportiveness. Furthermore, by incorporating electromyography signal analysis, researchers delve into the impact of chairs on muscle activity, thereby facilitating a more comprehensive evaluation of chair comfort. The distinctiveness of this integrated analytical approach lies in its consideration of both pressure distribution on the seated body and changes in muscle activity, resulting in a thorough and precise assessment of chair comfort. This research methodology provides valuable insights and guidance for the design and enhancement of standing desk chairs, ultimately improving user comfort and satisfaction.**  
This study explores the health consequences of prolonged sitting by introducing a standing chair and examining the effects of seat tilt angles on comfort. Using synchronized pressure distribution testing and surface electromyographic (sEMG) signal analysis, we assessed pressure and sEMG responses at tilt angles of 0\({}^{\circ}\), 20\({}^{\circ}\), and 40\({}^{\circ}\) during tasks such as computer work, writing, and ironing. Initial measurements with body pressure distribution sensors targeted the buttocks and feet, while surface electromyographic equipment captured signals from the bilateral lumbar erector spinae, vastus lateralis, and gastrocnemius muscles. MATLAB processing facilitated the analysis of integrated electromyographic values and mean power frequencies, elucidating the effects of tilt angles on comfort. Our research findings indicate that a 20\({}^{\circ}\) tilt angle significantly enhances comfort during computer and writing tasks and noticeably increases the comfort of the erector spinae muscles during ironing. Conversely, a 0\({}^{\circ}\) tilt angle is more beneficial for the vastus lateralis and gastrocnemius muscles. These results underscore the importance of selecting appropriate tilt angles to improve comfort across various tasks. Furthermore, integrating pressure sensors and surface electromyographic signals enables a comprehensive evaluation of chair ergonomic quality, offering valuable insights for chair design optimization.  
standing seat; human sitting pressure distribution; electromyographic signals; seat comfort