Research on the required coefficient of friction and muscle force during recovery from unexpected slip

The required friction coefficient (RCOF) and muscle force are significant of exploring the human body recovery strategy after an unexpected slip. This paper quantitatively studied the muscle force distribution and response characteristics after an unexpected slip in conjunction with the variation of the required coefficient of friction (RCOF). Twenty healthy subjects were recruited for this research. Ground reaction force and gait motion data were collected by using the Vicon Motion System and AMTI force platforms. The required friction coefficient was calculated based on the ground reaction force. A musculoskeletal model was built in the Any Body Modeling System to determine the muscle forces. The results show that the RCOF changes significantly (p < 0.001) and approaches 0 at 12% of the gait cycle when a slip occurs, compared to non-slip conditions. During the recovery process, the values of semitendinosus, tibialis anterior, medial gastrocnemius, and lateral gastrocnemius increase by 27%, 103%, 34% and 61%, respectively. After successful recovery, there is no substantial change in muscle force in the selected muscles except for biceps femoris, medial gastrocnemius, and lateral gastrocnemius. This research suggests that biceps femoris, medial gastrocnemius, lateral gastrocnemius, tibialis anterior, and semitendinosus are with a greater impact on recovery after an unexpected slip. The paper will assist in rehabilitation training, developing effective anti-slip strategies, and conducting bipedal robot stability studies.