Because of the inherent differences between human individuals, everyone's gait pattern is unique. However, because everyone's anatomy and physiological structure are basically the same, healthy people walk in a series of similar processes [3]. In this periodic and highly automated exercise mode, the body and limbs change rhythmically and dynamically. In the process of continuous walking, the difference between gait cycles is very subtle [4].
Walking is an integral exercise that is repeated the most times in human daily life. Walking upright is the result of long-term human evolution. With the development of modern measurement technology, it is possible for us to make a dynamic quantitative analysis of the movement and stress of all parts of the human body, especially the lower limbs. This work gradually developed into a special branch of biomechanics and was named gait analysis. Gait analysis is an inspection method to study the walking law, aiming at revealing the key links and influencing factors of gait abnormality through biomechanics and kinematics, thus guiding rehabilitation evaluation and treatment, and also contributing to clinical diagnosis, curative effect evaluation and injury mechanism research [2].
At the same time, gait analysis is also an effective means to objectively record human walking patterns and systematically evaluate walking function, and it is an important part of rehabilitation evaluation. In clinical work, for patients with neurological or musculoskeletal diseases that may affect their walking ability, gait analysis is needed to evaluate whether there is abnormal gait and the nature and degree of abnormal gait, so as to provide the necessary basis for analyzing the causes of abnormal gait, correcting abnormal gait and formulating treatment plans [5].
2 Normal and abnormal gait patterns
2. 1 normal gait The so-called normal gait refers to the gait of a healthy adult walking in the most natural and comfortable posture, which has the following three characteristics [6]: stable body, appropriate step size and minimum energy consumption. Normal gait needs the dynamic integration of central nervous system, peripheral nervous system and skeletal muscle, which is completed through a series of activities of pelvis, hip joint, knee joint, ankle joint and toes, while the trunk is basically kept on the supporting surface between the feet [7]. Normal gait should be flexible movement of hip joint, knee joint and ankle joint, good balance ability of the body and coordinated and smooth movement of head, trunk and limbs [8]. The normal gait is stable because the center of gravity is located in the pelvis to the minimum, plus appropriate joint movement and appropriate strength. If these cannot be guaranteed, it will lead to abnormal gait.
2.2 Gait cycle is called walking cycle, which consists of supporting stage and swinging stage [9]. The supporting stage refers to the period when the foot touches the ground, including five periods: foot touching the ground, foot touching the ground, middle support, heel off the ground and toe off the ground; Swing stage is the period when the feet leave the ground, which consists of three periods: acceleration period, swing middle period and deceleration period. In a normal walking cycle, the supporting stage accounts for 60%, of which about 10% is the double supporting stage and the swinging stage accounts for 40%. These percentages are measured when normal people walk at a comfortable speed, and will change greatly with the change of walking speed. Accelerating walking speed will prolong the time of single support stage and shorten the time of double support stage [10]. When walking, the body's center of gravity moves up and down about 5, and the pelvis rotates back and forth about 8. The maintenance of normal gait should be 30 flexion and 65438 extension of hip joint+00; The knee joint is fully extended and flexed by 60; Ankle flexion 20, dorsiflexion about 15 [1 1].
2.3 Abnormal Pathological Gait Clinical rehabilitation intervention involves many pathological gaits of central nervous system, including abnormal gait (hemiplegic gait) caused by central nervous system injury (stroke) [12]; Gait abnormality caused by diffuse brain injury (cerebral palsy) (such as scissors gait or dance gait caused by cerebral palsy) [13]; Abnormal gait caused by minor brain injury or disease ("duck gait") [14] and abnormal gait caused by basal ganglia disease (such as the forward gait of patients with Parkinson's disease) [15] and so on. Abnormal gait caused by peripheral nerve injury (loss of innervation of specific muscle groups) is also very common in clinic, such as gluteus maximus gait, gluteus medius gait, quadriceps femoris gait, tibialis anterior gait and gastrocnemius and soleus muscle weakness gait [16]. However, the clinical diagnosis of the above pathological gait mainly depends on its primary disease history, clinical manifestations and naked eye detection. Therefore, at present, there is still a lack of quantitative and accurate analysis of gait abnormalities in patients' marching process, and it is difficult to put forward targeted diagnosis and treatment programs in assisting clinical diagnosis and treatment.
3 Classification and methods of gait analysis
Gait analysis is a research method of biomechanics. Based on the concepts and processing methods of mechanics and the existing knowledge of human anatomy and physiology, the walking function of human body is comparatively analyzed [17]. Gait analysis can be divided into qualitative method (visual analysis) and quantitative method (instrumental analysis).
3. 1 qualitative analysis Clinicians usually perform visual gait analysis, that is, medical staff visually observe the walking process of patients, and then draw preliminary analysis conclusions according to their own impressions or the results of item-by-item evaluation of some observation items and their rich clinical experience [18]. Visual inspection can only be qualitative, not quantitative. It is necessary to observe the movement of joints, muscles and pelvis and the coordination of body posture when the patient walks from the side, front and back [19]. This type of gait analysis can't provide quantitative information, and it has many limitations because of the speed and complexity of human walking. If it is the difference or compensation under pathological gait, the situation will be more complicated. Therefore, before, during and after gait training, we can observe the changes of various parts of the patient's body in detail through direct or indirect (video) observation [20], such as whether the head is raised; Whether the neck is centered; Whether the shoulder strap of the affected side is pressed down and whether the scapula is retracted or extended forward; Whether the trunk twitches, twists to the affected side or leans to the healthy side; Whether the affected pelvis bulges, kyphosis, rotates forward or backward; Whether the linear arrangement of hip, knee and ankle is normal; The load and center of gravity deviation of the affected lower limb; The tension of extensor and abductor muscles of lower limbs increases, and the degree of hip flexion, knee flexion and ankle dorsiflexion increases; The amplitude of arm swing; Step length, step width and step speed; Knee joint control ability; Varus and valgus of feet; Symmetry and coordination of the whole action [2 1].
3.2 quantitative analysis quantitative analysis of gait has been gradually applied to clinical and scientific research in China, providing an accurate and effective means for objective evaluation; The basic parameters of gait analysis (pace, pace and step length), phase and period, standing phase moment and lower limb joint angle can be quantitatively analyzed to guide gait training.
3.2. 1 Kinematics analysis Kinematics analysis is a scientific method to study the temporal and spatial changes of limb movement during walking, which mainly includes: determining the overall time and space of walking and determining the direction of limb movement. The spatio-temporal pattern of foot landing is the end point of comprehensive walking. In the time and space continuous process of standing stage and swinging stage, basic variables can be measured to describe gait. These data can be obtained by measuring the distance and time when the foot touches the ground, such as using ink and paper, foot switches and some more complicated technical systems [22].
At present, segmented motion measurement is commonly used, that is, three-dimensional dynamic analysis of a specific joint or motion center. The dynamic change of joint motion angle in all directions during walking and its relationship with walking phase are obtained. Commonly used analysis methods are: ① Synchronous camera analysis. Set 2 ~ 6 cameras around the 4 ~ 8 m walking channel, record the walking images of the subjects at the same time, decompose the movements of the subjects, and observe and analyze them in a synchronous and slow way. ② Three-dimensional digital analysis. 2 ~ 6 detectors (digital detectors or special cameras) continuously acquire the signals of joint markers when the subject walks, and convert them into digital signals by computer to analyze the three-dimensional motion characteristics of the subject [23]. When more than two detectors collect the same mark at the same time, three-dimensional image reconstruction and analysis can be carried out. The output results include: three-dimensional gait reconstructed digitally, three-dimensional angle change of each joint, speed and phase. Joint markers are generally placed at the joint or center of gravity to be observed. ③ Analysis of joint goniometer. Fix the measured joint with a special joint goniometer, record the angle change of joint activity, convert it into digital signals, and reconstruct gait with a computer [24]. The advantages are simple operation, especially convenient upper limb examination; The disadvantage is that it is difficult to accurately record the rotation and tilting activities of the body.