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HUMAN GAITPrepared by:MUHAMMAD IBRAHIM KHANBS.PT(Pak), MS.PT(Pak), NCC(AKUH)

INTRODUCTION TO HUMAN GAIT

Human gait may be define as the translatory progression of the human body as a whole, produced by coordinated, rotatory movements of the body segments is known as gait or human locomotionTASKSWinter proposed the following five tasks for walking:Maintenance of support of HATMaintenance of the upright posture and balance of the bodyControl of the foot trajectory to achieve safe ground clearance and gentle heel or toe landing.Generation of the mechanical energy to maintain the present forward velocity or to increase forward velocityAbsorption of the mechanical energy for shock absorption and stability or to decrease the forward velocity of the bodyGAIT INTIATIONGait initiation may be defined as a stereotyped activity that includes the series or sequence of events that occur from the initiation of movement to the beginning of gait cycle.Gait initiation begins in erect standing posture with activation of the tabilais anterior and vastus lateralis muscles, in conjunction with an inhibition of the gastrocs muscles, bilateral concentric contraction of the tabilais anterior muscles results in a sagittal torque that inclines the body anteriorly from ankles.The CoP is described as shifting either posteriorly and laterally toward the swing foot or posteriorly and medially toward the supporting limb.Abduction of the swing hip occurs almost simultaneously with contractions of the tabilais anterior and vastus lateralis muscle which propels the body toward the support limb GAIT INTIATIONSupport limb hip and knee flex a few degrees 3-10 degree, and the CoP moves anteriorly and medially toward the support limb which allows the swing limb so it can leave the groundThe Gait initiation activity ends when either the stepping or swing extremity lifts off the ground or when heel strike the ground.Total duration of the initiation phase is about 0.64 seconds.KINEMATICSPhases of the Gait cycleGait cycle which is also called as stride is the time interval or sequence of motions which occurs between two consecutive initial contacts of the same foot i.e. from heel strike of the right extremity to heel strike again of the right extremityDistance covered one gait cycle is called the stride length

PHASES OF GAIT CYCLEDuring gait cycle each extremity passes through two major phasesStance phase----60%Swing phase-----40%There are two periods of double support in which one extremity is in initial contact and the other one leaves the groundAt normal walking speed each period of double support occupies 11% of the gait cycle which a total duration of 22% of the gait cycle, normally 20% is usedThe body is supported on a single limb for a duration which makes 80% of the gait cycle.

DIVISONS OF PHASESTwo most common terminologies for the divisions of phases into events of the gait cycle areTraditional (T)Rancho Los Amigos (RLA)In both conventions the gait cycle is divided into percentiles that will be used to clarify events and phases

EVENTS IN STANCE PHASES Heel contact or heel strike (T) refers to the instant at which the heel of the leading extremity strikes the ground. Initial contact (T and RLA) refers to the instant the foot of the leading extremity strikes the ground. In normal gait, the heel is the point of contact. In abnormal gait, it is possible for the whole foot or the toes, rather than the heel, to make initial contact with the ground. The term initial contact will be used in referring to this eventFoot flat (T) in normal gait occurs after initial contactat approximately 7% of the gait cycle . It is the first instant during stance when the foot is flat on the ground.Midstance (T) is the point at which the body weight is directly over the supporting lower extremity. usually about 30% of the gait cycle.Heel-off (T) is the point at which the heel of the reference extremity leaves the ground , usually about 40% of the gait cycle.Toe-off (T and RLA) is the instant at which the toe of the foot leaves the ground , usually about 60% of the gait cycle.EVENTS IN SWING PHASESAcceleration, or early swing phase (T), begins once the toe leaves the ground and continues until midswing, or the point at which the swinging extremity is directly under the body .Initial swing (RLA) begins when the toe leaves the ground and continues until maximum knee flexion occurs.Midswing (T) occurs approximately when the extremity passes directly beneath the body, or from the end of acceleration to the beginning of deceleration. Midswing (RLA) encompasses the period from maximum knee flexion until the tibia is in a vertical position.Deceleration (T), or late swing phase, occurs after midswing when limb is decelerating in preparation for heel strike. Terminal swing (RLA) includes the period from the point at which the tibia is in the vertical position to a point just before initial contact.SWING PHASE

GAIT TERMINOLOGIESTime and distances are two basic parameters of motion.Temporal variablesDistance variablesTEMPORAL VARIABLESStance timeSingle limb support timeDouble support timeSwing timeStride timeStep timeCadencespeed DISTANCE VARIABLESStride lengthStep lengthStep widthDegree of toe out

stance timeAmount of time spent during stance phase of Gait cycle of one extremity.

Single support timeAmount of time that spent during the period when only one extremity is on the supporting surface is a gait cycle

Double support timeAmount of the time spent with both feet on the ground during one gait cycleThe time of double support may be increased in elder patients and in those having balance disordersThe time of double support decreases when speed of walking increases

Stride durationAmount of time spent in completion of one stride or Gait cycleOne stride duration for a normal stride is 1 second.Changes occur in stride length during normal, slow, fast walking.

Stride lengthGait cycle is also called strideThe linear distance between heel strike of one extremity and when the same extremity heel strike again ( time spent in a gait cycle of one extremity)A stride include two steps, right and left but stride length is not always equal to length of two steps as there may be unequal stepsStride length greatly varies among individual because it is effected by leg length, sex, age.Stride length decreases with increase in age

Step lengthLinear distance between two successive points of the opposite extremities.Comparison of the right and left steps provides an indication of gait symmetry, the more equal are the step length more symmetrical will be the gait

Step durationThe amount of time spent in completion of a single step.Its measurements is expressed as sec/stepWhen there is weakness or pain in an extremity step duration may be decreased on the effected side while increased on the unaffected side

cadenceThe number of steps taken by a person per unit timeCadence=number of steps/sec or minShorter step length will result in increase cadence at a given velocityWhen a person is walking with cadence between 80 and 120 steps/min, then cadence and stride length have a linear relationshipIf cadence increases the double support time decreases and vice versaNormal cadence , man=110 steps/minNormal cadence, woman=116 steps/minWalking velocityIs the rate of linear forward motion of the body in a specific directionIt can be measured as, cm/sec, meter/min or miles/hourIf the direction is not specified than term walking velocity is called walking speed

Walking velocity or speed=distance walked/ timeDistance(cm, m, miles, km)Time(sec, min, hour)Step widthStep width, or width of the walking baseIt is measured by the linear distance between the mid point of the heel of one foot and the same point of the other foot.Step width increases if there is increased demand for side to side stability.Normal is 5-10cm

Degree of toe outIt is the angle of foot placement(FP) and may be found by measuring the angle formed by each foot line of progression and a line which intersect the center of heel and second toe.Normal angle = 7 degreeAngle of toe-out decreases as the speed of walking increasesPower generation and absorptionMuscle work concentrically and work positively, produces energy which is used for gait.Muscles work eccentrically and do negative work and absorb energyPath of Center of GravityCenter of Gravity (CG):midway between the hipsFew cm in front of S2Least energy consumption if CG travels in straight line

CGPath of Center of GravityA. Vertical displacement:Rhythmic up & down movementHighest point: midstanceLowest point: double supportAverage displacement: 5cmPath: extremely smooth sinusoidal curve

Path of Center of GravityB. Lateral displacement:Rhythmic side-to-side movementLateral limit: midstanceAverage displacement: 5cmPath: extremely smooth sinusoidal curve

Determinants of Gait Saunder determinantsSix optimizations used to minimize excursion of CG in vertical & horizontal planesReduce significantly energy consumption of ambulationClassic papers: Sanders, Inman (1953)Determinants of Gait :

(1) Pelvic rotation:Forward rotation of the pelvis in the horizontal plane approx. 8o on the swing-phase sideReduces the angle of hip flexion & extensionEnables a slightly longer step-length w/o further lowering of CGDeterminants of Gait :

(2) Pelvic tilt:5o dip of the swinging side (i.e. hip adduction)In standing, this dip is a positive Trendelenberg signReduces the height of the apex of the curve of CGDeterminants of Gait :

(3) Knee flexion in stance phase:Approx. 20o dipShortens the leg in the middle of stance phaseReduces the height of the apex of the curve of CGDeterminants of Gait :

(4) Ankle mechanism:Lengthens the leg at heel contactSmoothens the curve of CGReduces the lowering of CGDeterminants of Gait :

(5) Foot mechanism:Lengthens the leg at toe-off as ankle moves from dorsiflexion to plantarflexionSmoothens the curve of CGReduces the lowering of CGJOINT MOTIONS

The approx. ROM needed in normal gait and the time of occurrence of the maximum flexion/extension for each major joint may be determined by examining the joint angels These angles varies with age, gender, and walking speed.Approx. values may be calculatedAnatomical position for Hip, Knee, Ankle are considered as 0 degree, while the flexion for the hip, knee, and dorsiflexion of the ankle is considered as positive values and extension and planter flexion are given negative values

SAGGITAL PLANEHIP JOINTHip achieve maximum flexion(approx. +20 degree) at initial contact at 0% of the gait cycle and its most extended position (approx. -20 degrees) at about 50% of the gait cycle, between heel-off and toe-offDuring swing phase (mid-swing) hip joint reaches its maximum flexion (approx. +30 degrees) which is maintained during deaccelartionKNEE JOINTThe knee is straight (0 degree) at initial contact and nearly straight just before heel-off at 40% of the gait cycle.During foot-flat 10% of the gait cycle the knee reaches it maximum flexion of (approx. +15 degree)During swing phase(acceleration) the knee reaches upto 60 degree flexion at 70% of gait cycle

ANKEL JOINTThe ankle reaches maximum dorsi flexion of ( approx. +7 degree) at heel-off at 40% of the gait cycle and reaches maximum planter flexion( approx. -25 degrees) at toe-off 60% of the gait cycle

JOINT MOTIONS STANCE PHASESagittal Plane

JOINT MOTIONS SWING PHASESagittal Plane

GRAPHICAL PRESENTATION

NORMAL WALKINGFor normal walking:Hip: ROM approx. 20-30 degree of flexion and extensionKnee: ROM, 0 degree to 60 degree of flexionAnkle: ROM, 25 degree planter flexion to 7 degree dorsi flexion*** If ROM of the above joint are not sufficient than considerable deviation will occure from the normal gaitFRONTAL PLANE JOINT ANGLESDuring the first 20% of the stance of the gait cycle, pelvis or the contralateral side drops about 5 degree which results in hip adduction of the supporting limb.The hip abducts smoothly to 5 degree of abduction, peaking about toe-off, then returns to neutral at initial contactKnee remains more or less in neutral position except for a brief abduction peaking at about 7 degrees in mid swing and then returns to neutral positionAnkle everts from 5 degrees of inversion to 5 degree of eversion in early stance and inverts during push-off

TRANSVERSE ANGLESHip externally rotates until approx. midswing and then internal rotates to near neutral before initial contact.The knee joint remains relatively neutral through out most of the gait cycle but external rotates in late stance until about foot flat.The ankle has three rapid reversals of rotation from about 40% of the gait cycle until initial contact and reaches a point of maximum external rotation at about foot flat.TRANSVERSE PLANE

STAIR GAITStair climbing is an important mode of locomotion having many similarities to that of level groundd locomotion, the difference between the two modes are extremely important for the patient populationThe muscle strength and ROM required for locomotion on level ground does,t ensure that the patient will be able to climb stairs.The trunk ROM during level ground is similar to trunk ROM during descent but differed from the stair gait during ascending in all planes, trunk flexion during ascending gait is atleaset double to that of trunk flexion in descending and level ground gait..STAIR GAITGait on stair is similar to level ground walking in that stair gait involves both swing and stance phases, and to carry HAT.The net internal movements of the hip, knee, ankle during stair ascending and descending when compared to level ground walking, the internal knee extensor movement in both ascending and descending was approx. three times larger that that of level ground.Ankle moments are approx. the samePower generation mainly occur during ascending and power generation absorption occur during descending

RUNNING GAITLocomotion mode which is similar to walking, but there are certain differences.A person able to walk on level ground may not able to run, running requires greater balance, muscle strength, and ROM as walking.Body needs greater balance as running is characterized by reduced base due to lake of double support and the presence of floating periods in which both extremities are out of contact with the ground. Presence of floating periods increases will increase the speed of the running.Greater muscle work required to raise the HAT higher than normal walking and to support HAT. Joints and muscles should be able to absorb more energy to accept and control weight of HAT.RUNNING GAITKnee is flexed about 20 degree when foot strike the ground which also increases forces on the PF joint.Typical base of the support is considerably less than normal walk i.e.: 2-4inchesBoth the feet falls in the same line of progression so the center of mass of the body must be placed over single supported foot.To compensate for the reduced base of support the functional varus angle increases. Which is the angle between bisection of the lower leg and floor, it increases 5 degree during running