A Biomechanical Study On The Movement Of "Tiger Crawling",Imitated Tortoise Crawling And "Cat Crawling"

Human beings have various kinematic patterns when crawling at different speeds.It is proved that human take similar gait patterns as animals due to the coordination of motoneurons between the lumbosacral segment and cervical segment of the innate neural circuits in their spinal cord.Based on that,the purpose of this study is to explore the features of range of motion,muscle activity and body load intensity by collecting and analysis kinematical data,main surface EMG signals and heart rate data when human are crawling with high,middle and low gravity centers and to compare differences of those features under the condition of upright walking and animal crawling.Therefore,this study mainly takes following procedures: Standardize crawling motions by consulting literature.In the experiment,the physiological and biomechanical data of 8 male subjects have been collected with the help of three-dimensional dynamic capture of American Motion,BTS FREEEMG300 wireless surface electromyography of Germany Physiomed and RS400 team movement heart rate monitor of Finland Polar.After processing and analyzing those data,we made conclusions.The main conclusions of this study are as followed:1)Human kinematics / dynamics: The heights of gravity center at low,medium and high levels are 0.43m-0.48 m,0.49m-0.60 m and 0.61m-0.68 m respectively.When human are crawling at high and middle gravity center,the swing ratio of hand is far higher than that of foot while the figures are similar during low gravity-center crawling.With the decrease of the height,the subjects tend to take a diagonal mode(IPL ~ 50%,r =-0.926).The range of motion of upper limbs shoulder and elbow joint gradually reduce while that of lower limb hip,knee and ankle gradually increase.The main function of upper limb is to consume energy in order to speed down during crawling.2)Muscle activation characteristics: The activation of muscle showed different sequences when crawling with different gravity centers.However the core muscle activation happened earlier(not the first one),and the activation process of upper limbs and the coremuscle groups turned out very similar.As the declining of gravity center height,the amplitude of posterior deltoid(r = 0.697,r: the correlation between the height of the center of gravity and the amplitude of the EMG),erector spinae(r = 0.684),multifidus(r = 0.570)and gluteus maximus(r = 0.726)gradually decreased while that of biceps femoris(r =-0.648)increased gradually.The co-activation degree of shoulder and knee joints kept going up with the decreasing of gravity center,on the contrary,the degree of elbow and hip joints gradually reduced.3)Load intensity characteristics:Generally speaking,the beginner could keep crawling for about 5 minutes.Human's heart rate increased significantly by about 20%-25% of the maximum heart rate when crawling witin 1 minute.The load intensity is impacted by the height of gravity center during crawling: The load intensity gradually goes down with the increase of gravity center,and the average load intensity amounts to around 61%-74% of the maximum heart rate.However,subjects with better aerobic endurance showed a lower-than-average exercise intensity when crawling.The main conclusions:1)The main joints have a wider range of activity when doing crawling than walking upright,the height of gravity center is an element that affects the joint range of activity and the myoelectric activity of muscle groups.The deltoid and triceps of upper limbs show different EMG features when crawling compared with upright walking.This conclusion verifies that neural signals of cerebral cortex have covered the spinal motor neuron and also provides evidence for segmental control of spinal neural signal output in the muscles.2)The conclusions of this study demonstrate that human tend to feel partial muscle fatigue when crawling.The beginner's heart rate increases significantly within 1 minute,which indicates that the beginner's duration of crawling should not be too long and 4 minutes would be appropriate.Normally crawling is an exercise of small or nearly moderate intensity.A lower exercise intensity will be found from those who have a better aerobic capacity.