Muscle force analysis for cart-pushing motion: Examination of push-start operation

According to a survey conducted by the Ministry of Health, Labour and Welfare in Japan in 2023, the numbers of fatalities and injuries at factories and other production sites have been decreasing, but the numbers of injuries have been increasing. For this study, musculoskeletal model analysis was used to elucidate the starting motion of cart pushing as a factory task. For 10 healthy male study participants, body coordinate data and floor reaction force data were obtained using a three-dimensional motion analysis system and two floor reaction force plates during cart pushing without a weight and with a 100 kg weight. Then, lower limb joint angles, lower limb joint moments, lower limb muscle forces, and lumbar muscle forces were evaluated using OpenSim musculoskeletal model analysis software. The following results were obtained. The amplitudes of the pelvis list moment and pelvis rotation moment were significantly higher when pushing the weight. The maximum values of muscle force in the gluteus maximus muscle and tibialis anterior muscle of the left leg were significantly higher. Also, the integral value of the rectus femoris muscle was significantly higher. The maximum and integral values of the external abdominal oblique muscle right were significantly higher. Results demonstrated that moving a cart with a 100 kg weight on it required greater force in the hip and knee joint extension muscles, the ankle joint dorsiflexion muscle, and the external abdominal oblique muscle right.