The objective of this study was to evaluate the effect of different walking speed on the range of motion, angular velocity, and angular acceleration of the shoulder and elbow during walking. An optical motion capture system was used to capture the walking motion on the treadmill system. The independent variable of this study was set as four levels of walking speeds including 3.6, 5.4, 7.2 km/h, and preferred walking speed. Seven dependent variables were analysed as follows: maximum joint angle, minimum joint angle, range of motion (ROM), maximum joint angular velocity, minimum joint angular velocity, maximum joint angular acceleration and minimum joint angular acceleration. The subject walked according to the randomized walking speed during 90 seconds on the treadmill. Twenty gait cycles of motion capture data from each experiment condition of each subject were extracted. In the shoulder joint, the mean of ROM and the mean of maximum angular acceleration were the highest at 5.4 km/h walking speed. It can be considered that the arm swing was sufficiently performed to maintain the walking stability. At the walking speed 7.4 km/h, the gait pattern of one cycle was too short due to fast walking. It indicated that the time of motion for sufficiently swinging the arm was short. At the walking speed 7.2 km/h, the ROM and angular velocity of the shoulder joint decreased but those of the elbow joint were increased. It could be related to maintain the walking balance by swinging the elbow to compensate the reduction of the shoulder movement during a fast walking. We suggest that the ergonomic threshold walking speed of the wearable robot is limited to 5.4 km/h. In addition, the fast walking speed can cause biomechanical load and discomfort in the arm movement.

The purpose of this study was to evaluate the legibility of one-syllable Korean characters with the participation of sixteen subjects. The experiment considered nine factors including age (young and old), gender (male and female), illuminance (150lx and 600lx), viewing distance (50cm and 200cm), material type (paper and LCD), typeface (Ming and Gothic), thickness (plain and bold), color contrast (black letter/white background and white letter/black background), and complexity (simple, complex, and number) to examine main effects with a 2 6-3 ×3 fractional factorial design. The dependent variables were minimum character size of 100% correctness, maximum character size of 0% correctness, and minimum character size of comfortable reading preference. The results of analysis of variance (ANOVA) revealed that age, illuminance, viewing distance and complexity were significant for all dependent variables, except gender which was significant only for the minimum character size of comfortable reading preference. In general, the young could see twofold smaller size letters than the elderly. The subjects could see smaller sized letters with the illuminance of 600lx and viewing distance of 50cm than 150lx and 200cm, respectively and also with numbers, simple characters, and complex characters in that order. The findings of this study could be characterized about the legibility of Korean characters and be good resources for developing its standard.

The objective of this study was to determine the relaxed hand postures in degree from a total of 14 finger joints including the thumb, index finger, middle finger, ring finger, and little finger without force exertions and constraints. Fifteen male students fully relaxed their right hands in 9 combinations of the hand positions of pronation, neutral, and supination at the shoulder flexion angles of 0 degree, 45 degrees, and 90 degrees. Vicon MX system was utilized to measure the joint angles with 8 cameras and 26 reflective markers. The hand position had more effects on the finger joint angles than the shoulder flexion angles. Overall, the fingers flexed with supination approximately 20% and 27% more than with neutral and pronation, respectively, due to the mass of the phalanges. For the same reason, the fingers were more flexed at the shoulder flexion angle of 90 degrees with the most hand positions except with the hand position of pronation because of the tensile force of the extensor muscles and connective tissues in the forearm.

Industrial grating has been widely used the work surface of manufacturing, plants, and shipyards due to excellent drainage and durability. The purpose of this study is to evaluate the localized muscle fatigue in lower limb by the grating type during walking. Six subjects were male industrial workers who participated in this study. This study considered four independent variables which were grating type, bar type, spacing and muscle. Surface electromyography signals from tibialis anterior (TA), peroneus longus (PL), gastronemius medialis (GM), and gastrocnemius lateralis (GL) were recorded to determine muscle fatigue. To assess fatigue, mean power frequency (MPF) drop rate of each experimental condition was obtained by using initial MPF (the initial 10 second) and last MPF (the last 10 second) and defined by percent decrease. As a results of Friedman test, grating type showed statistically significant difference (p = 0.0317). The MPF drop rate of steel grating analyzed significantly higher 1.5%p than top grating. There were not significantly differences in bar type (p = 0.0758), spacing (p = 0.7630), and muscle (p = 0.2803). It means that top grating evaluated low muscle fatigue than steel grating. That is why top grating should be not only having higher walking stability but also psychological safety due to a firmly structure and less exposed under grating. This study could be recommended to ergonomic work surface by grating to improve walking stability and safety.

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