This study proposes a new calculation method for the anomaly score of repetitive tasks based on singular spectrum transformation (SST) that accounted for a longterm history of human motion. To validate the efficacy of the proposed method, the calculated anomaly score was compared with movement variability computed by a traditional method and to its SST-computed score. Eleven male participants performed repetitive lightweight material handling tasks under different work conditions and an electromagnetic tracking system measured their working posture. Movement variability and anomaly score on the shoulder and elbow joints were calculated based on measured working postures. The movement variability on the elbow flexion angle increased with time. In contrast, the anomaly score of the elbow flexion angle decreased with time, but shoulder flexion and inner rotation angles showed increased scores with the passage of time. These findings are similar to those of previous studies that stated that movement variability increased from redundant degrees of freedom available for performing multi-joint movements; this occurred due to the development of muscle fatigue on the shoulder joint from performing repetitive tasks. On comparing this to the anomaly scores calculated by conventional SST, it was observed that the score computed by the proposed method reflected the whole trend of human motion in repetitive tasks and did not depend on local problems in working posture. Therefore, it was concluded that the new method of calculating the anomaly score is more suitable to detect changes in movement variability in repetitive tasks.
The number of industrial accidents in social welfare facilities in 2019 had increased by 15% from that in 2017. Responding to increasing those numbers in social welfare facilities in recent years, the Ministry of Health, Labour, and Welfare (MHLW) established the 13th occupational safety & health program and has promoted various schemes to prevent industrial accidents in social welfare facilities. Using the reports about industrial accidents occurring in social welfare facilities provided by MHLW, this study investigates the trend of industrial accidents associated with awkward movement and falls. Moreover, this study categorizes the facilities providing similar services into service series uniquely defined and explores the trend of indus-trial accidents in each service series. Based on a sample survey by simple random sampling, this study ex-tracted items characterizing industrial accidents in social welfare facilities, such as age, experience term, working situation, and cause of accidents, from the industrial accident reports in 2019. As a result, this study provided the following perceptions: (1) the occurrence ratio of industrial accidents in social welfare fa-cilities was high among the older and non-expert workers; (2) industrial accidents associated with the awk-ward movement almost consisted of low back injuries and were frequently occurred by transfer tasks of the care recipient with single-person; (3) industrial accidents associated with falls were frequently occurred in which are slipping on wet surface and in tripping on obstacles; and (4) the trend in the type of occurring acci-dents, work situation, cause of accidents, etc. were varied by differing service series.
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