Influence of the assistive torque of knee joint on the strength of lower limb muscles
Objective Aiming to reduce the knee joint force during walking,the required assistive torque was assessed based on the calculated knee joint force and torque of subjects during normal walking. The effect of the assistive torque on lower limb muscle strength during different walking speeds was investigated. Methods The kinematics and kinetics data of human subjects at three walking speeds were collected by using 3D optical motion capture system and force plates. The knee joint force,knee joint torque and lower limb muscle strength were calculated based on OpenSim biomechanics software. The assistive torque was calculated by using the global optimization algorithm in MATLAB and used to achieve the purpose of reducing knee joint force by 5％,10％,15％ and 20％,repectively. The influence of the assistive torque on the lower limb muscle activities was analyzed. Results The assistive torque increased with the decrease of knee joint force,and the average correlation coefficient of assistive torque at different walking speed was 0.87,and the highest correlation coefficient was 0. 96. After applying the assistive torque,muscle strength of hamstring,quadriceps femoris and gastrocnemius decreased the most in the early, middle, late and pre-swing phases. The average ratio of muscle strength of the three muscle groups decreased the most at the slow speed, with the decrease of 31％, 26％ and 23％, respectively. Conclusions Assistive torque of knee joint mainly reduces the resultant force of knee joint by decreasing the lower limb muscle strength. It is therefore suggested that the assistive knee joint torque with suitable amplitude and profile might be one of the solutions to prevent the knee joint overload. Furthermore,it provides insights on the driving strategy of assistive equipment such as active mechanical exoskeleton.
万方数据
维普
