The Ergonomic Evaluations of Physical and Psychophysical Responses among Different Carrying Methods

• Main Authors: Wu, Chao-Tin, 吳昭瑩
• Other Authors: Wang, Mao-Jiun
• Format: Others
• Language: en_US
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/10728308115359174481

博士 === 國立清華大學 === 工業工程與工程管理學系 === 104 === Care of pre-weaned infants and transporting goods (or personal belongings) were the two major function of carrying activity. In today’s busy world, using carrying devices could free the hands of the person and help them to manage the daily activities while taking care of their baby or carrying their goods. Studies regarding carrying were mostly focused on backpack weight. There were few study investigated walking speed or baby carrier effects. The purpose of this study was to investigate the physiological and biomechanical responses in men and women while carrying the baby or backpack. The first study compared gender differences using the baby sling and front worn harness carrier in the physiological and psychophysical responses. Ten females (aged 23-32 years) and ten males (aged 23-35 years) were recruited to participate in this study. Each subject was asked to carry two different weighted baby dummies (7kg and 10kg) using 3 different baby carriers and walk for 20 minutes. Body tactile pressures were measured. The physiological responses, which were recorded during walking included average surface electromyography (sEMG), skin temperature change, heart rate change and exercise intensity. Immediately after walking, the Borg’s rating scale of perceived exertion was used to collect the psychophysical responses. The traditional baby sling and the two front worn harness carrier showed little differences in sEMG activities, body tactile pressure and exercise intensity. Carrying two different weighted baby dummies caused significant differences in sEMG and body tactile pressure. Gender differences were found in sEMG activities, where men used more upper back muscles and women used more low back muscles. Based on the findings of this study, recommendations about the improved baby carrier design are proposed. The second study examined the backpack load effect on gender walking gait and speed parameters. Twenty subjects (10 males, 10 females) with ages ranging from 21-28 years were involved in a backpack carrying task. The load was specified at 0%, 10%, 15% and 20% of their body weight. The three walking speed levels included preferred walking speed (PWS), 80% PWS and 120% PWS. The response measures included lower extremity joint motion, surface electromyography (sEMG) activities and ground reaction force (GRF) during walking. The results indicated that the load effect was a dominant factor. The increase in backpack weight produced a decrease in pelvis anterior tilt, hip extension and an increase in pelvis posterior tilt. The rectus abdominis muscle activity increased, but the erector spinae and semitendinosus activities decreased with increasing backpack weight. The vertical GRF component increased with the increase in backpack weight. Shoulder area perceived exertion discomfort was the highest at 20% BW load. Post hoc test results showed less difference between 10% BW and 15% BW, but greater differences between 20% BW and the lower weights. Gender differences were found in pelvic ROM, where women had smaller ROM in sagittal plane but larger ROM in frontal plane. In conclusion, people used different muscles with a change in gait pattern to accommodate a heavier backpack. The results from this study provide very useful recommendations for backpack weight and training recommendations for different gender.