Study On Mechanical Properties Of Human Lower Limbs Under Normal Gravity

The manned space technology represents the scientific and technological level of a country,a key part of the manned space technology is to keep astronauts healthy during long term spaceflight.In microgravity,the bone loss in main load-bearing sites occurs at a rate of 1% to 2% per month,especially in the lower extremities such as proximal femur,and is associated with muscle atrophy.The main courses are the lack of mechanical loading induced by gravity and the decrease of mechanical stretch generated from muscle contraction.The bone loss cannot be prevented completely despite a lot of countermeasures including physical exercise in the international space station,because people don't know how much load is needed for sustaining bone structure and strength for astronaut in space beside of hardware limitation.Human being evolved in gravitational environment on earth,and the structure and function of bones have been fully adapted to the Earth's gravity environment.If the amounts of the daily load on bones and minimum stimulus to maintain the structure and function of bones are not clear,it is difficult to counter accurately bone loss in space.Therefore,it is very important,for improving and developing countermeasures against bone loss,to determine the forces in the major load-bearing joints of the body in the daily life and to clarify the amount of stimulus needed to maintain the structure and function of the bones.This study focuses on the forces of the hip,knee and ankle joint in normal gravity environment,so as to provide some information for the development of such countermeasure.This study includes two parts:(1)Monitoring the daily activities of 30 healthy volunteers engaged in research work in the normal gravity environment through the ActivPAL3 CVT equipment.The monitoring results show that the daily activities can be divided into: Sitting and lying,standing,low-intensity slow walking,moderate intensity brisk walking,high-intensity running,the conversion action between sitting and standing,analysis from the perspective of daily activity behavior habits,researchers sit and lie and other static movements occupy 70% of the day,standing status accounted for 21%,the corresponding walking and running and other actions accounted for only 9%,and in the rest day,Standing and walking and other dynamic action to occupy the time has been reduced;analysis from the level of daily activities,whether it is working days or rest days,are mainly low-intensity exercise,and the highest level of exercise at least;(2)Based on the Opensim human modeling technology to establish a specific human body model of 10 volunteers,and the other through the VICON optical motion acquisition system to capture the definition of the action after the simulation data,in Opensim completed 10 volunteers hip,knee,ankle joint forces Analysis,which can be calculated human joint average strength of the hip,knee and ankle in the standing state were 3.13 N/Kg,3.99 N/Kg,4.47 N/Kg;in a gait cycle,joint average strength of the hip,knee and ankle were 4.61 N/Kg,4.47 N/Kg,4.90 N/ Kg when low-intensity walking;joint average strength of the hip,knee and ankle were 4.75 N/Kg,4.93 N/Kg,5.00 N/Kg when moderate intensity of fast walking;joint average strength of the hip,knee and ankle were 5.22 N/Kg,5.38 N/Kg,5.43 N/Kg when running at high intensity,respectively;the average force of the hip,knee and ankle joint were 2.50 N/Kg,2.81 N/Kg,3.81 N/Kg in the action cycle of sitting to standing.After the human joint forces of hip,knee and hip under all kinds of actions were calculated,and further combined with the enhanced daily load stimulation theory to calculated,find out the daily load of the hip was about 13.48 N/kg,and the daily load of the knee was about 14.10 N/kg,and the daily load of the ankle was about 14.06 N/Kg.Finally,according to the calculated hip,knee,ankle joint daily load to stimulate the amount of micro-gravity environment in the corresponding anti-exercise measures,and can be applied to stimulate the amount of daily load,such as wearable low load on the outside Bone design,used to enhance the effectiveness of weightlessness protection.