What Is the Biomechanics of Gait?

Gait refers to the posture and behavior characteristics of the human body when walking. The human body moves the body along a certain direction through a series of continuous activities of the hips, knees, ankles, and toes. Gait involves factors such as behavior, occupation, education, age, and gender. It is also affected by many diseases. The control of walking is very complicated, including central commands, body balance and coordinated control, involving the coordinated movement of the joints and muscles of the lower limbs, and also related to the posture of the upper limbs and trunk. Imbalances in any link may affect gait, and abnormalities may be compensated or covered up. Normal gait has stability, periodicity and rhythm, directionality, coordination, and individual differences. However, when people have diseases, these gait characteristics will change significantly.

Chinese name: Gait analysis

Foreign name: gait analysis

Introduction to Gait Parameters

Gait analysis is a method to study the walking law. It aims to reveal the key links and influencing factors of gait abnormalities through biomechanics and kinematics, so as to guide rehabilitation assessment and treatment, and help clinical diagnosis and efficacy. Evaluation and mechanism research. In gait analysis, there are some special parameters to describe whether the gait is normal or not. These gait parameters usually include the following categories: gait cycle, kinematic parameters, dynamic parameters, myoelectric activity parameters, and energy metabolism parameters.

Gait parameter

Gait cycle (GC): During walking, the process from one heel to the next heel landing is called a walking cycle, usually expressed in time seconds (s). The gait cycle of an average adult is about 1-1.32 s. Each gait cycle in walking contains a series of typical posture changes. People usually divide this typical posture change into a series of periods, called gait phase / period. A walking cycle can be divided into support phase (stance phase) and swing phase (swing phase), and the subdivision can be divided into 8 time phases. Generally, the percentage of the gait cycle (GC%) of this phase is used as a unit to express , Sometimes also expressed in seconds (s). The gait period and phase are shown in Figure 1.

1stance phase Gait parameters 1. Stance phase

Support phase refers to the time that the lower limbs touch the ground and bear the gravity, which accounts for 60% of the walking cycle. The support phase is most of the time supported by one foot. The key difference between walking and running is the time when walking has bipedal support, which is called bi-supported phase, which is equivalent to the period when the support foot first touches the ground and the load-bearing response period or the weight loss response of the lateral foot and the foot off-ground period. The time of the double support phase is inversely proportional to the walking speed. Walking obstacles are often first manifested by the extension of the double support phase to increase walking stability. The supporting phase is further divided into 5 phases:

(1) Initial contact (IC): refers to the moment when the heel touches the ground, decelerating the forward movement of the lower limbs, and determining the position of the foot into the support phase. Therefore, it is the most common cause of abnormal support phase. About 2% of GC.

(2) Loading response (LR): Refers to the process of shifting the center of gravity from the heel to the full foot after the first touch on the ground, accounting for about 10% of the GC.

(3) Mid stance (MS): refers to the time of the middle phase of the support phase. At this time, the supporting feet are all on the ground, and the contralateral foot is in the swing phase. It is the only phase that supports all gravity with one foot. At normal pace, it is about 19% of GC. The main function is to maintain the stability of the knee joint, control the forward inertial movement of the tibia, and prepare for the forward movement of the lower limbs. The muscles involved in this process are the knee muscles and soleus muscles. This period is shortened when the load-bearing weight of the lower limb is less than the weight or the body is unstable, so as to quickly shift the center of gravity to the other foot and maintain the body balance.

(4) Terminal stance (TS): refers to the time when the lower limbs actively accelerate the kick, starting with the heel lifting and ending with the foot off the ground, accounting for about 19% of the GC.

(5) Pre-swing (PS): When walking slowly, there is no kick off, but only the toes leave the ground, accounting for about 12% of the GC.

Single support phase: usually refers to the process from one side of the lower limbs to the ground and the other toes off the ground, the unit is s, which generally accounts for 40% of a walking cycle. The time taken by the single leg support period of one side during walking is actually exactly equal to the stride phase time of the symmetrical lower limbs, and the shortened one-foot support time indicates that the load bearing capacity of the lower limbs is reduced. For the convenience of gait correction and training, the following main points are proposed:

(1) Heel landing: The tension of the lower limb extensor is increased, which is difficult for patients with foot drop and varus.

(2) Full-foot landing: Starting from 7.6% of the walking cycle, the full-foot is flat on the ground. Patients with foot inversion and foot drop are difficult to complete.

(3) The center of gravity is shifted to the ipsilateral side: Because the unilateral lower limbs support the body weight, patients with hemiplegia, joint pain, and poor balance are often too short.

(4) Heel off the ground: Starting from 41.5% of the walking cycle, it is the initial action of pedaling downward. Hemiplegia patients often do not complete sufficiently.

(5) Increased knee flexion: Since 54.1% of the walking cycle, patients with hemiplegia have lower flexion of the knee joint due to the predominance of lower limb extensors, making it difficult to complete.

(6) Toes off the ground: Starting from 60% of the walking cycle, the center of gravity of the body moves to the front of the ankle joint, the toes are forced to the ground, and the forward propulsive force is generated by the pedaling action of the lower limbs. Patients with hemiplegia suffer from lower limb spasm, foot drop, varus, and inadequate separation of lower limbs, so they cannot complete this movement well, which is one of the important reasons for abnormal gait.

Dual support phase: Biped support is the biggest feature of walking. In a walking cycle, when one side of the lower limbs completed the heel lifting to the toes and stepped down to leave the ground, the other side of the lower limbs simultaneously performed the heel landing and full-foot landing movements, so the simultaneous occurrence of both feet Landing stage. It usually accounts for 20% of a walking cycle. The length of this phase is related to the walking speed. The faster the speed, the shorter the double support phase. When the walk changes from running to running, the double support phase becomes zero. The disappearance of the double support phase is the turning point of walking and running, so it becomes the sole criterion for judging whether a foul occurs during the walking race.

Figure 1 Gait cycle and phase

2swing phase Gait parameter 2, swing phase

The swing phase refers to the time between the foot leaving the ground and stepping forward to landing again, which accounts for 40% of the walking cycle, and is divided into three phases:

(1) Initial swing (IS) refers to the activities of the foot in the early period when it leaves the ground. The main movements include clearing the ground and flexing the hip to drive the knee flexing, accelerating the forward swing of the limb, accounting for about 13% of the GC.

(2) Mid swing (MS) refers to the movement of the foot during the mid-swing phase. Foot clearing is still the main task, accounting for about 12% of the GC.

(3) The terminal swing (TS) refers to the end of the step and the movement of the foot before the landing. The main action is to slow down the forward motion of the lower limbs and prepare for foot landing, accounting for about 13% of the GC.

The swing phase is the phase where there is no contact with the ground during walking. The main points of this phase are:

(1) Lifting the feet, starting from 63.6% of a walking cycle, is the acceleration period when the toes are off the ground and the lower limbs are swinging forward.

(2) The maximum flexion of the knee joint starts from 67.9% of a walking cycle, and the lower limbs just passed just below the body.

(3) Maximum hip flexion begins at 84.6% of the walking cycle. At this stage, the lower limbs have been moved forward, and they begin to slow down until the heels touch the ground.

(4) Follow the ground and complete 100% of the walking cycle.

Gait parameter kinematic parameter

Kinematics is a scientific method to study the time and space changes of limb movements during walking. Kinematic parameters refer to some parameters related to time and distance during walking, including time parameters, distance parameters, and time-space. They are commonly used clinical indicators and can detect some basic changes in patients' walking function.

1 Gait parameters 1, time parameters

Time parameters refer to time events related to walking, including single step time, stride time, stride frequency, pace, percentage of ipsilateral standing phase and step phase, and percentage of walking cycle time in each phase of standing phase.

Single step time: refers to the time required to take one step in the walking cycle, that is, the time from the first lower limb heel landing to the contralateral lower limb heel landing again. Time in seconds. Under normal circumstances, the single-step time of both lower limbs is equal. If the bilateral lower limbs take a single step, the gait is asymmetric.

Stride time: refers to the time required to complete a walking cycle, that is, the time from the heel of one lower limb to the ground again. Time in seconds. For comparison between subjects or themselves, stride time is usually expressed as a percentage.

Velocity: The distance traveled per unit time is called walking speed, expressed in m / s, and can also be expressed as a percentage of height or lower limb length. The average natural pace of a normal person is about 1.2m / s.

Cadence: The number of steps per unit time is called the cadence, which is expressed in steps / min. The average natural cadence of a normal person is about 95 to 125 steps / min.

Percentage of standing phase and stride phase on the same side and percentage of walking cycle time in each phase of standing phase: During natural speed walking, standing phase time accounts for about 60% of the walking cycle, and walking phase accounts for about 40% of the walking cycle. During walking, the standing time and stepping time of both lower limbs are equal, and the symmetry of gait is shown in walking. Under certain pathological conditions, the symmetry of this gait may change. For example, patients with hemiplegia because the affected lower limb cannot bear weight effectively and are afraid of falling. Therefore, they are eager to transfer the weight of the body to the healthy side. Asymmetrical gait. Therefore, the ratio of the standing time of both lower limbs, or the step time, is a sensitive indicator of gait symmetry. In clinical examination, this indicator can be used to judge the symmetry of gait.

2 Gait parameter 2, distance parameter

Gait distance parameters include step length, stride length, step width, and foot angle.

Step length: The vertical straight distance between two points when the left and right heels or toes touch the ground successively when walking is called the step length, expressed in cm. One step forward with the left foot is called the left step, and one step forward with the right foot is called the right step. Step length is significantly related to height. The shorter the body, the shorter the step length, and the normal person's step length is about 50 to 80 cm. The step length of young Chinese men is about 55.0-77.5 cm, and the step length of females is about 50.0-70.0 cm. For men and women of the same height, there was no significant difference in step length, and the step length decreased with age. The concept of one step can also be measured by time, that is, the time taken for a single step. In normal people, the length and time of the left and right lower limbs are basically the same. The inconsistency of left and right step lengths is a sensitive indicator of gait asymmetry. If the left foot takes a step forward and the right foot then follows forward to stay parallel or backward with the left foot instead of crossing the left foot, the right step length is zero or negative. The asymmetry of pathological gait such as hemiplegic gait is shortened on the healthy side and relatively longer on the affected side. This is shown as I in FIG. 2.

Stride length: Also known as stride, refers to the vertical straight distance between two consecutive landings on the same heel and back, which is equivalent to the addition of the left and right step lengths, about 100-160cm. When the subjects walked in a straight line (except walking around in circles), the left and right stride steps were almost equal even when there was a noticeable asymmetric gait. Therefore, it is not valid to determine the symmetry of the gait by measuring the stride length. This is shown as II in FIG. 2.

Stride width: refers to the lateral distance between the left and right feet, usually the midpoint of the heel as the measurement point. Step width is an indicator of gait stability. The narrower the step width, the worse the gait stability. This is shown as III in Figure 2.

Toe out angle: refers to the angle formed between the centerline of the sole of one side (the long axis of the foot, the line connecting the midpoint of the heel to the second toe) and the forward direction, which is called the foot angle. It is usually expressed in °. The normal foot angle is about 6.75 °. This is shown as IV in Figure 2.

Figure 2 Schematic diagram of step length, stride length, step width, and foot angle

- Gait parameter time-space parameter

The time-space parameter is a reflection of the motion of the hip, knee, and ankle joints during walking (angle change or displacement, speed, acceleration, etc.), the position of the body's center of gravity, and the position of the pelvis. Commonly used joint angle parameters, joint angle curves, and angle-angle diagrams of different phases in the gait cycle. The angular changes of the pelvis and the joints of the lower limbs during each phase of the normal walking cycle are summarized in Table 1.

(1) Joint angle parameters include the angle of the hip, knee, and ankle when first landing; the maximum extension of the hip, knee, and ankle in the standing phase, and the maximum extension of the ankle is defined as the toe off the ground The angle of the image of the previous frame at the moment; the angle of the hip, knee, and ankle when the toe is off the ground; the maximum flexion angle of the hip, knee, and ankle in the step phase; sagittal hip, Knee and ankle angle changes.

The angle change of hip, knee and manic joints during walking is mainly reflected in the angle-time relationship curve in the gait cycle. The change of the value of a single angle is not significant. By comparing the angle-time relationship curves of the joints of the study subject in different planes with normal people, or left and right feet, or the angle-time relationship curves of different periods before and after treatment, it can reflect the joints of the study subject. Function situation and treatment effect. The angle-angle curve can vividly show the coordination relationship between the two joints during walking. When the nerve and muscle function is abnormal, the angle-angle curve also appears abnormal, indicating that the coordination of the lower limbs on both sides is poor. The curve of hip, knee and manic joint angles with walking cycle is shown in Figure 3.

Hip motion curve: The hip flexion angle reaches its peak in the middle of the stride phase and remains until the beginning of the standing phase. During the period from the heel to the ground toe off, the hip joint reached its peak, and then the hip joint flexed again.

Knee joint motion curve: During one walking cycle, the knee joint flexes and stretches twice. The heels touch the ground immediately before the end of the stride phase, and the lower limbs stretch into the early phase of the standing phase and then flex slightly, that is, knee flexion. The middle phase of the standing phase stretched again, then the knee joint flexed again, and reached a peak early in the stride phase, at which time the knee flexion angle reached 60 degrees. If the knee flexion angle is limited at this time, it will affect the normal forward movement of the calf.

Ankle joint curve: The most obvious feature of the ankle joint curve is that the plantar flexion of the ankle joint reaches about 20 degrees during the 60% of the walking cycle, that is, when the sole of the foot is off the ground. Favorable plantar flexion guarantees that our body can move forward forcefully during walking, so as to ensure normal walking speed.

Figure 3 Curves of hip, knee and manic joint angles with walking cycle

(2) Pelvis: Pelvic movement can be considered as the movement of the center of gravity. The position of the center of gravity of a normal adult when walking is on the midline of the pelvis. From the bottom, the height of the male is about 55% and the height of the female is about 50%. The up and down movement of the center of gravity during walking is a sinusoidal curve, which appears twice in a walking cycle, with an amplitude of about 4.5cm. The highest point is the middle support, and the lowest point is the heel. During the cycle, the left and right sides appear once each, with an amplitude of about 3 cm. The maximum movement occurs when the left and right feet are in the middle stage of support, and the center of gravity is located in the middle of the left and right sides during the bipedal support stage.

Table 1 Changes in the angles of the pelvis and lower joints during a normal walking cycle

Gait parameter

Kinetics analysis is a research method for the force, reaction intensity, direction and time during walking. Dynamic parameters refer to mechanical parameters related to gait, including ground reaction force, joint torque, human body focus, muscle activity, etc. The analysis of the above parameters can reveal the cause of specific gait formation.

1(Ground reaction force, GRF) Gait parameters 1. Ground reaction force (GRF)

The ground reaction force refers to the force exerted by the soles of the feet on the ground during standing, walking, and running. The ground reaction force is divided into vertical component force, front-to-back component force, and internal and external component force, which can be measured through a force platform. Generally, three-dimensional records can be made in vertical, front-to-back, and left-to-right directions. The front and rear component forces reflect the driving and braking capabilities of the supporting leg, the internal and external component forces reflect the lateral load bearing capacity and stability, and the vertical component force reflects the load bearing and off-ground ability of supporting the lower limb during walking. In clinical application, the characteristics of the force-time curve are mainly observed, that is, the peak value of the valley and the time and amplitude of the valley value. When walking, the foot-to-ground contact force has the largest component in the vertical direction, and an extreme value appears at the turning point of each gait cycle. When the heel touches the ground, it has a maximum value. As the foot gradually flattens, the force area gradually increases. The force is reduced. When the foot is completely flat, the force is minimized. When the heel is off the ground, another maximum occurs when the toe reaches the ground. That is, the vertical force curve has a typical symmetry during the entire gait cycle. Bimodal nature. The normal human foot contact force is small in horizontal and front-back directions, and is basically symmetrical. Studies have shown that there is no significant difference in foot-to-ground contact force of humans of different ages.

2 Gait parameter 2, moment

Physically, moment refers to the force that rotates an object multiplied by the distance to the axis of rotation. The formula moment (M) = force (F) x distance (d). Torque is the force that causes a joint to rotate, so it is also called joint torque, which is mainly the result of muscle action. Torque is the final result of the action of muscles, ligaments, and friction. In normal gait, the joint angle does not reach the end of its range of motion, and the friction is very small. Therefore, when the strength of the active and antagonist muscles is unbalanced, the torque that maintains normal joint motion will change. Joint moments include extension moments, flexion moments, and support moments. The so-called supporting moment is the algebraic sum of the moments of the hip, knee, and ankle joints, and it is the supporting force to ensure that the support legs of the standing phase do not hit soft.

3 Gait parameters 3. Acceleration of body center of gravity

The center of gravity of the human is located at the front edge of the second metatarsal bone, in the center of the two hip joints. This center is the part where the body swings minimally when moving in a straight line. When walking, the center of gravity of the person is constantly changing the position and speed not only in the horizontal direction but also in the vertical direction. The vertical velocity change of the body's center of gravity is closely related to the mechanical status of each joint and its active muscles. For example: when analyzing the joint internal force of one knee joint during walking, it is necessary to analyze the position and acceleration change of the center of gravity of each part of the body above the knee joint. The relevant parameter values are essential basic data when performing the knee force analysis of the lower limbs.

4 Gait parameters 4, lower limb muscle group activity during walking

The motive force of walking mainly comes from the muscles of the lower limbs and the trunk. During a walking cycle, muscle activity has the functions of maintaining balance, absorbing shocks, accelerating, decelerating, and promoting limb movements.

(1) Quadriceps: The quadriceps is a bi-joint muscle that flexes the hip and extends the knee. Two quadriceps contraction activities occurred in the first 20% of the walking cycle, starting from the end of the stride phase to the pre-loading phase of the standing phase, that is, the peak of the load response period. At this time, the quadriceps bone acts as an extensor of the knee joint. The second contraction activity occurred after the heel was off the ground, and the toe contraction reached a peak after the toe was off the ground.

(2) Hamstring muscle: The hamstring muscle is composed of the lateral biceps femoris and the semitendinosus muscle located on the medial side. It also belongs to the trans-biarticular muscle group, which is used to extend the hip and bend the knee. The hamstring contraction shown in the picture above begins at the end of the last phase of the cycle and acts as a knee flexor. The hamstring muscles contract centrifugally, decelerating the forward-swinging calf in order to prepare for heel contact. When the heel touches the ground, the hamstring muscles also serve as hip extension muscles to coordinate the gluteal muscle extension. After the mid-standing period, the bilateral lower limbs move forward and the trunk leans forward. To prevent excessive forward leaning, the hamstring muscles extend the hip extension. effect.

(3) Gastrocnemius: The calf triceps includes the gastrocnemius and soleus muscles. The gastrocnemius muscle and the muscles that cross the knee and ankle joints make the hip joint plantar flexion. When the ankle joint is weighted and fixed, the gastrocnemius contraction can pull the lower end of the femur and the upper end of the tibia backward, and passively straighten the knee joint. During walking, as the ankle plantar flexor, the gastrocnemius muscle contracts strongly to the peak during the heel-to-ground kick-off action, and the peak occurs when the heel is off the ground, followed by an explosive ankle plantar flexion and strong The pedaling action of the body will push the body's center of gravity forward vigorously.

(4) Anterior tibialis muscle group: Anterior tibialis muscle is ankle dorsiflexor. When walking with the heel on the ground, the tibialis anterior muscles undergo eccentric contraction to control the ankle joint plantar flexion and prevent the anterior step from slap on the ground when the foot is flat, and when the toes are off the ground, the tibialis anterior muscles again The contraction controls or reduces the plantar flexion of the ankle joint at this time, ensuring that the toes can leave the ground in the step phase, so that the foot clearing movement can be successfully completed. When the tibialis anterior muscle paralysis occurs, the patient will slap on the ground during the heel-to-ground phase, and the foot will sag because the ankle joint cannot be flexed effectively in the swing phase. To compensate for sagging feet, the patient must lift his leg high to complete the step.

Gait parameter

The gait EMG activity parameters are mainly the electrical activities of the lower limb muscles during walking, and the muscle electrophysiological activity that reveals the relationship between muscle activity and gait is an essential part of clinical gait analysis. Surface electrodes are currently used to record the electrical activity of muscles during walking. The surface EMG signal mainly includes the original surface EMG signal and the processed data. The processed data mainly includes time domain parameters and frequency domain parameters. The time-domain parameters mainly include the average amplitude, EMG integral, etc .; the frequency-domain parameters commonly include the average frequency and the median frequency.

1. The surface EMG signal as the most direct form can show the occurrence and rest of EMG activity. The intensity and amplitude of the original EMG signal can reflect the amplitude or strength of contraction to a certain extent. High, the stronger the surface EMG signal, the stronger the contraction. With the gait, the action potentials of the muscle fibers on the right and left rectus femoris, tibialis anterior, biceps femoris, and gastrocnemius muscles begin and end, and after a period of resting potentials appear, there are electromyographic activities and stillness. Periodic changes, the intensity and amplitude of myoelectric signals of the same name muscle on the right and left are basically symmetrical and alternate.

In addition, in natural gait, people can accurately distinguish the gait cycle based on the characteristic changes of the measured electromyographic signal of the original surface of the muscle, and the ground reaction period of the gait cycle, the rapid ankle joint flexion 0 ~ 15 , the ankle joint Flexion was originally performed by the posterior tibialis muscle, but at this time the contralateral toe kick was pushed to limit the movement of the posterior tibialis muscle, and it was antagonized by the centrifugal contraction of the calf anterior muscle group (anteroposterior tibialis muscle, etc.). During this period, the biceps femoris contracted, causing the knee joint to flex slowly from 0 to 15 ° C. At the same time, the rectus femoris muscles performed centrifugal contraction to gradually shift the center of gravity of the body from the heel to the toes. The myoelectricity of the muscles, biceps femoris, and tibialis anterior muscles is active, and the electromyography of the medial gastrocnemius muscle is in an inactive state. After the heel touches the ground, the next step is full-foot ground, heel off the ground, and toes off the ground. Progressive dorsiflexion was started at 10-20 until the toes were off the ground. The ankle dorsiflexion was mainly adjusted by the back gastrocnemius muscle group by centrifugal or elongated contraction to maintain the stability of the ground foot. Therefore, the electromyography of the medial gastrocnemius muscle is active during the middle, end, and pre-swing stages, and the electromyography of the rectus femoris, biceps femoris, and tibialis anterior muscles is inactive. During the swing phase, the ankle joint enters passive plantar flexion to With rapid back extension, the gastrocnemius muscle group begins to stop myoelectric activity, which is mainly accomplished by centripetal contraction of the tibialis anterior muscle. In the later period of swing (final swing), the rectus femoris and biceps femoris cooperate with the tibialis anterior muscle to complete the swing of the lower limbs. In this period, the rectus femoris and biceps femoris muscles were active. The tibialis anterior electromyography is active during the swing phase, while the medial gastrocnemius muscle is inactive.

In short, when walking, the realization of each action is under the regulation of the nervous system, and the related muscle group coordinated activities can complete the normal gait. In the normal gait of normal young people, the EMG activities of the rectus femoris, tibialis anterior, biceps femoris, and gastrocnemius muscles change periodically and coordinately with the gait cycle. The muscles with the same name on the left and right alternate alternately. During the gait cycle, the rectus femoris, biceps femoris, and tibialis anterior muscles are electromyographically active during the pre-standing phase (ie, the ground reaction phase) and swing phase. The medial gastrocnemius muscle is active during most of the standing phase.

2. The processed data is obtained from the original surface EMG signal through the full-wave rectification, smoothing, and analysis functions in signal processing.

Amplitude: The amplitude change mainly reflects the number of motor unit activations during muscle activity, the type of motor unit participating in the activity, and the degree of synchronization of its discharge frequency, which is related to the central control function under different muscle load intensity conditions.

EMG value: The EMG value is the sum of the area under the curve in a unit time after rectifying and smoothing the measured surface EMG signal. It can reflect the strength of the EMG signal over time, and its value reflects the movement. The number of muscle fibers involved in muscle contraction and the discharge size of each motor unit. This parameter mainly reflects the contraction characteristics of the muscle in unit time. When muscles contract, there is a linear relationship between EMG points and muscle strength. When the power of muscle contraction increases, the number of exercise units participating in work increases and the discharge of each exercise unit increases, so the myoelectric score increases, and vice versa.

Average frequency: The average frequency indicates the frequency of the center of gravity of the overpower spectrum curve. Its level is related to the conduction speed of the action potential of the peripheral motor units, the type of motor units involved in the activity, and the degree of synchronization. In addition, human skeletal muscle fibers mainly have two components, slow muscle fibers (type I fibers) and fast muscle fibers (type II fibers), that is, slow muscle fibers are mainly low-frequency potential activities, and fast muscle fibers mainly show high-frequency discharge. The average frequency was also positively correlated with the proportion of type I fibers in the skeletal muscle, and negatively correlated with the proportion of type II fibers.

Median frequency: The median frequency refers to the median value of the frequency of muscle fiber discharge during skeletal muscle contraction. Under normal circumstances, the median frequency value of skeletal muscle in different parts of the human body varies greatly. The effect of composition ratio of type fiber) and fast muscle fiber (type fiber).

Gait parameterEnergy parameter

Energy parameters include energy metabolism parameters and mechanical energy parameters.

The energy metabolism parameter refers to the energy metabolism during walking. During the gait analysis, the gas analyzer can be used to measure and analyze the change of oxygen content in the gas to calculate the energy consumption during walking. It is used to measure walking efficiency. , But can not pinpoint the specific mechanism of anomalies while walking.

Mechanical energy consumption parameters can use kinetic energy, potential energy and its conversion technology to calculate the energy consumption (capacity and energy consumption) of different parts of the body in a gait cycle. It can identify specific parts and periods of high energy consumption during abnormal walking. Help to study the mechanism of gait abnormality and choose the appropriate treatment.

Energy consumption is traditionally measured with an indirect thermal card meter or a physiological consumption index (PCI). The former (calories) is based on the assumption that all energy release responses in the body depend on oxygen intake and is the most widely adopted standard. The most common method for measuring oxygen uptake during exercise is by measuring the oxygen content in the exhaled breath. PCI is proposed by Macgregor, which is calculated by dividing the difference between steady-state walking and resting heart rate and walking speed. This index provides a measure of gait performance using heartbeats per meter. PCI is recommended as an alternative to Vo2 measurement, because under the condition of sub-maximum exercise, there is a linear relationship between heart rate and oxygen intake. PCI is easy to calculate and is widely used in clinical and research.

Oxygen cost (OC): Refers to the amount of oxygen consumed per unit weight and distance of the human body during exercise, the quotient of oxygen consumption and walking distance during walking (OC = VO2 / meter), the unit is ml / kg.m. The subjects used a portable oxygen analysis method to simultaneously collect the exhaled gas during walking, analyze the oxygen consumption, and divide it by the walking distance. The lower the oxygen price, the more energy-saving the walking exercise is. The sign of natural gait is the most energy-saving way of walking. The gold standard for any walking training effect is to reduce the oxygen price.

Heart rate is also regarded as an index of body energy expenditure, and has become an index for assessing energy expenditure in normal children and children with cerebral palsy. Studies have shown that when traveling in normal gait, heart rate and oxygen consumption have a linear relationship before approaching the maximum heart rate. During sub-extreme exercise, the oxygen intake and the heart rate have a linear relationship, so the total heart rate during exercise and recovery can represent energy expenditure. Any change in the heart rate index will represent the change in oxygen consumption, and therefore also represents the energy consumption. change. Wu Kefen and others used the total heartbeat / total walking distance (THBI) during exercise as a new method for measuring energy efficiency, and found that the new index of THBI can represent the energy efficiency of gait in steady state and non-steady state. It is easy to calculate, the required equipment is easily available, the assembly is comfortable, and it is non-invasive. Repeatable statistics show that THBI is comparable to oxygen price, has high sensitivity, and is superior to PCI, and has a similar curve with oxygen price when changing the load.

Energy utilization (energy utility): The measurement of energy utilization is mainly obtained through heart rate, oxygen consumption, and oxygen loss. Under normal circumstances, a proper walking speed can minimize the energy consumption per unit distance. The kinematics of the walking cycle requires that the movement of the body's center of gravity in both the horizontal and vertical directions is minimized, that is, the exercise with the best energy consumption. When walking, not only the kinetic energy is consumed due to the movement of various segments of the body, but also potential energy is generated due to the pulling of joint ligaments and muscles and the transfer of the center of gravity; about 50% of the potential energy generated during walking can be reused.

Further reading

1 Dr. Jacquelin Perry. Gait Analysis: Normal and Pathological Function. Second edition. SLACK Incorporated, 2010

2 Qian Jingguang, Song Yawei, Ye Qiang, Li Yongqiang, Tang Xiao. Biomechanical principles and gait analysis of walking. Journal of Nanjing Institute of Physical Education (Natural Science), 2006, 5 (4): 1-7

3 Zhu Longkang. A review of studies on lower limb joint dynamics and surface electromyography during walking. Journal of Nanjing Institute of Physical Education (Natural Science Edition), 2014, 13 (2): 4-45

4 Sun Jiali, Wang Guiqing. Gait analysis. Chinese Nursing Medicine, 2010, 19 (5): 427-430

5 Li Jianan, Meng Dianhuai. Clinical Application of Gait Analysis. Chinese Journal of Physical Medicine and Rehabilitation, 2006, 28 (7): 500-503

6 Hu Xueyan, Yun Xiaoping. Application of gait analysis in clinic. Chinese Journal of Rehabilitation Theory and Practice, 2003, 9 (11): 677-679

7 Tang Zhengrong, Compiler, Sun Bingzhao, School. Methods of Gait Analysis. Foreign Medicine, Physical Medicine and Rehabilitation, 1996, 16 (1): 10-12

8 Wu Jian, Li Jianshe. Progress in Biomechanics of Human Gait during Walking. Chinese Journal of Sports Medicine, 2002, 21 (3): 305-307

9Guo ZW, Wang GZ, Ding H, et al. A study of kinematic paramet ers of normal youth in gait analys is. Chinese Journal of Rehabilitation Theory and Practice, 2002, 8 (9) 532-533

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