Development of a System Observing Worker's Physiological Responses and 3-Dimensional Biomechanical Loads in the Task of Twisting While Lifting Hyun Mok Son 1† , Hoon Seonwoo 2† , Jangho Kim 2 , KiTaek. Lim 2 , Jong Hoon Chung 2,3 * 1 Field Robot R&D Group, Korea institute of technology, Ansan, 426-910, Republic Of Korea 2 Department of Biosystems & Biomaterials Science and Engineering, Seoul National University, Seoul, Republic of Korea 3 Research Institute for Agriculture and Life Sciences, Seoul National University, Seoul 151-742, Republic of Korea † The first two authors contributed equally to this study Received: March 14 th , 2013; Revised: May 9 th , 2013; Accepted: May 24 th , 2013 Purpose: The purpose of this study is to provide analysis of physiological, biomechanical responses occurring from the operation to lifting or twist lifting task appears frequently in agricultural work. Methods: This study investigated the changes of physiological factors such as heart rate, heart rate variability (HRV) and biomechanical factors such as physical activity and kinetic analysis in the task of twisting at the waist while lifting. Results: Heart rates changed significantly with the workload. The result indicated that the workload of 2 kg was light intensity work, and the workload of 12 kg was hard intensity work. Physical activity increased as the workload increased both on wrist and waist. Besides, stress index of the worker increased with the workload. Dynamic load to herniated discs was analyzed using inertial sensor, and the angular acceleration and torque increased with the workload. The proposed measurement system can measure the recipient’s physiological and physical signals in real-time and analyzed 3-dimensionally according to the variety of work load. Conclusions: The system we propose will be a new method to measure agricultural workers’ multi-dimensional signals and analyze various farming tasks. Keywords: Acute stress index, Bio-information, Lumbar spine workload, Physical activity, Repeated lifting work Original Article Journal of Biosystems Engineering J. of Biosystems Eng. 38(2):163-170. (2013. 6) http://dx.doi.org/10.5307/JBE.2013.38.2.163 eISSN : 2234-1862 pISSN : 1738-1266 *Corresponding author: Jong Hoon Chung Tel: +82-2-880-4601; Fax: +82-2-873-2049 E-mail: jchung@snu.ac.kr Copyright ⓒ 2013 by The Korean Society for Agricultural Machinery This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Introduction Most agricultural works, especially for some crops have been done manually, because process of the agricultural works could not be mechanized due to the characteristics of the specific crops or working envir- onment. Some research have reported that manual labor causes musculoskeletal symptoms which may lead to musculoskeletal diseases or body deformation due to the repetitive use of part of the body, uncomfortable posture, or excessive labor intensity. When farmers lift and load the harvested fruits and vegetables, they should bend and twist the waist, which is the main cause of musculoskeletal diseases. For these reasons, instrumentation system for comprehensive observation of health condition and stress of farmers should be developed. With this instrumentation system for biometric information, more research need be implemented to prevent musculoskeletal diseases of farmers and to improve agricultural work environment (Son et al., 2010; Kraus et al., 1997). According to the survey on the self-perceived musculoskeletal symptoms using Dutch Musculoskeletal Questionnaire (DMQ), the result showed that over 90% of farmers complained of multiple musculoskeletal symptoms. Overall they com- plained of symptom at the waist, shoulder, and knee, but the body part showing symptoms are different according