Biomedical subjects

Dohyung Kee

Publications and source records attributed to Dohyung Kee.

5 recordsLinked to original sources

PubMed2005

Quantitative postural load assessment for whole body manual tasks based on perceived discomfort.

Many Korean workers are exposed to repetitive manual tasks or prolonged poor working postures that are closely related to back pain or symptoms of musculoskeletal disorders. Workers engage in tasks that require not only handling of heavy materials, but also assuming prolonged or repetitive non-neutral work postures. Poor work postures that have been frequently observed in the workplaces of shipbuilding shops, manufacturing plants, automobile assembly lines and farms often require prolonged squatting, repetitive arm raising and wrist flexion and simultaneous trunk flexion and lateral bending. In most manufacturing industries, workers have to assume improper work postures repetitively, several hundreds of times per day depending on daily production rate. A series of psychophysical laboratory experiments were conducted to evaluate the postural load at various joints. A postural load assessment system was then developed based on a macro-postural classification scheme. The classification scheme was constructed based on perceived discomfort for various joint motions as well as previous research outcomes. On the basis of the perceived discomfort, postural stress levels for the postures at individual joints were also defined by a ratio scale to the standing neutral posture. Laboratory experiments simulating automobile assembly tasks were carried out to investigate the relationship between body-joint and whole-body discomfort. Results showed a linear relationship between the two types of discomfort, with the shoulder and low back postures being the dominant factor in determining the whole body postural stresses. The proposed method was implemented into a computer software program in order to automate the procedure of analysing postural load and to enhance usability and practical applicability.

Humans↗

PubMed2004

Joint angles of isocomfort for female subjects based on the psychophysical scaling of static standing postures.

This study investigated the joint angles of isocomfort (JAIs) for females based on the psychophysical scalings for static standing postures held for 60 s, which were obtained in a laboratory experiment. The subjects were instructed to rate their comfort levels for varyious joint postures by using the free modulus method of magnitude estimation. The comfort scores for the joint postures and the related verbal comfort categories were subjected to regression analysis in order to obtain the JAIs corresponding to verbal categories. The results showed that the JAIs were significantly different depending upon the joints and joint postures investigated (p < 0.01), and that the JAIs for female subjects were significantly different than those for males (p < 0.01) which had been obtained in an earlier study (Kee and Karwowski, 2001). Compared to the corresponding range of joint motion values, the JAIs for hip postures were the smallest of all joint postures dealt with in this study, while those for the neck were the largest of all postures, which means that hip postures are more stressful than any other joint posture. Based on this study, it is recommended that the gender-based JAI values should be used for design applications.

Adult↗

PubMed2003

Ranking systems for evaluation of joint and joint motion stressfulness based on perceived discomforts.

This study aims to develop ranking systems for evaluation of the stressfulness of joints and joint motions based on perceived discomforts measured through an experiment. Twenty healthy male subjects participated in the experiment, where discomforts for varying joint motions in the sitting and standing postures were measured using the magnitude estimation. The results showed that the perceived discomforts were affected by the type of joint motions, size of joint motions, and joints. The joints and joint motions were classified into several distinct classes according to perceived stresses. Three ranking systems based on the perceived discomforts were developed, including classification by the joint motions and joints, by types of joint motions, and by the joints only. The ranking systems revealed that while hip and back motions exhibited higher discomfort ratings than any other joint motion, elbow motions were the least stressful of all joint motions. The ranking systems can be used as a valuable design guideline when ergonomically designing or evaluating workplaces, or as a helpful tool for understanding adverse effects of poor working postures.

Adult↗

PubMed2002

A method for analytically generating three-dimensional isocomfort workspace based on perceived discomfort.

The purpose of this study was to develop a new method for analytically generating three-dimensional isocomfort workspace for the upper extremities using the robot kinematics. Subjective perceived discomfort scores in varying postures for manipulating four types of controls were used. Fifteen healthy male subjects participated in the experiment. The subjects were asked to hold the given postures manipulating controls for 60 s in the seated position, and to rate their perceived discomfort during the following rest of 60 s using the magnitude estimation. Postures of the upper extremities set by shoulder and elbow motions, types of controls, and left right hand were selected as experimental variables, in which the L32 orthogonal array was adopted. The results showed that shoulder flexion and adduction-abduction, elbow flexion, and types of controls significantly affected perceived discomfort for postures operating controls, but hand used for operating controls did not. Depending upon the types of controls, four regression models predicting perceived discomfort were presented. Using the models, a sweeping algorithm to generate three-dimensional isocomfort workspace was developed, in which the robot kinematics was employed to describe the translational relationships between the upper arm and the lower arm/hand. It is expected that the isocomfort workspace can be used as a valuable design guideline when ergonomically designing three-dimensional workplaces.

Adult↗

PubMed2002

Analytically derived three-dimensional reach volumes based on multijoint movements.

The main objectives of this study were to quantify the range of reaching for the upper body with eight degrees of freedom (the trunk and shoulder, elbow, and wrist joints) and the lower body with six degrees of freedom (the hip, knee, and ankle joints). A sweeping algorithm that included trunk and foot motions was used to generate the analytical total reach volume of the human body for young men. Three types of reach volume--unconstrained arm reach, shoulder-restricted arm reach, and foot reach--were generated depending on the joint involved in reach activities. The robot kinematics methodology was employed to represent the human body as a multilink system, which was needed for calculating three-dimensional coordinates of the involved joints. The statistical test results showed that the total reach volume analytically generated in this study was nearly identical to that obtained from the direct human body measurements. Applications of this research include generating the human body's reach volume for the purpose of designing work spaces and products.

Adult↗