Ergonomics is defined as the study of the interaction between workers and the equipment being used and the environments in which they function. Ergonomics is centered on the person. The equipment itself can be important if the person must operate, service, install, and/or repair that equipment. The same holds true for the environment which can be important if the person works in it. The application of this knowledge to the workplace is essential in order to enhance productivity and to increase the social responsibility of the firm. The significance of this benefit is getting more attention and interest from the industrial sector in Thailand. Laboratory for Ergonomics Research was invited by Johnson and Johnson (Thailand) Co., Ltd. to conduct an ergonomic study in its factory in Lard-Krabang Industrial Estage. Total Ergonomic Approach was promised to be the main methods to employ in the study. The objectives of the study were to 1) investigate muscular load of workers who perform a heavy work and a repetitive work, 2) compare responses of EMG measurement and heart rate record on different works, 3) study effects of work factors on muscles, and 4) propose solutions to the problems. The measurements of workspace dimensions and of workers anthropometry were collected. Interviews were done using standard interviewing forms to find an abnormal index. Nine test subjects were selected, i.e., five from repetitive work (sanitary napkin packing department), four from heavy work (two each from sack carrying work and hauling cart of sacks in and out of oven). Electromyogram (EMG) levels of deltoid and trapezius muscles and heart rate were measured together with observation of work conditions. Force required to push cart of sacks in and out of oven was also recorded. It was found that the average EMG values of deltoid and trapezius muscles for heavy work were higher than 35% of maximum value (from the MVE), which was considered dangerous by most previous reported works. After suggestions to use lifging aid for sacks and toinstall anti-slip floor sheets, EMG values were reduced. For sanitary-napkin packing, a repetitive work, it was found that EMG values were lower than those of heavy work. However, when comparing EMG values of sanitary-napkin packing for the beginning of the week against the end of the week, it was found that fatigue accumulation was existed in packing work. Job rotation was recommended as a solution to this accumulation problem. In every case, the statistical relationship between EMG and heart rate was not confirmed. From this study, it was concluded that factors affecting muscular activity are 1) type of work, 2) work shift (beginning-end of week), and 3) work environment.
