The effect of lower limb muscle contractions on the impact acceleration behaviour of medial knee in low-speed pedestrian impact

For accurate analysis in low-speed collisions, roles of muscle in the low extremities are included in a finite element (FE) human model. The impact accelerations were estimated for vehicle-pedestrian collisions with and without muscle activations under 10 km/hour. The predicted acceleration at the medial knee was verified by the actual tests performed at 2.88 km/hour. Then, experiments were performed using a sled to obtain muscle activations, and impact accelerations of the subjects. More analyses were performed using the FE human model at 5 and 10 km/hour to understand effects of muscle activations on impact accelerations. At the lowest impact speed, the reduction of acceleration was 20% when the result with muscle activations was compared to that without muscle activations. The reduction was decreased to 12% at 5 km/hour. At 10 km/hour, the reduction was insignificant but existed to as much as 3%. Therefore, muscle activations in the lower limbs are important when the impact velocity is lower than 10 km/hour.