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HUMAN GAIT. Prepared by: MUHAMMAD IBRAHIM KHAN BS.PT(Pak), MS.PT(Pak), NCC(AKUH). INTRODUCTION TO HUMAN GAIT.
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HUMAN GAIT Prepared by: MUHAMMAD IBRAHIM KHAN BS.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 locomotion
TASKS Winter proposed the following five tasks for walking: Maintenance of support of HAT Maintenance of the upright posture and balance of the body Control 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 velocity Absorption of the mechanical energy for shock absorption and stability or to decrease the forward velocity of the body
GAIT INTIATION Gait 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 INTIATION Support 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 ground The 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 cycle Gait 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 extremity Distance covered one gait cycle is called the stride length
PHASES OF GAIT CYCLE During gait cycle each extremity passes through two major phases Stance 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 ground At 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 used The body is supported on a single limb for a duration which makes 80% of the gait cycle.
DIVISONS OF PHASES Two most common terminologies for the divisions of phases into events of the gait cycle are Traditional (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 event
Foot 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 PHASES Acceleration, 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.
GAIT TERMINOLOGIES Time and distances are two basic parameters of motion. Temporal variables Distance variables
TEMPORAL VARIABLES Stance time Single limb support time Double support time Swing time Stride time Step time Cadence speed
DISTANCE VARIABLES Stride length Step length Step width Degree of toe out
stance time Amount of time spent during stance phase of Gait cycle of one extremity.
Single support time Amount of time that spent during the period when only one extremity is on the supporting surface is a gait cycle
Double support time Amount of the time spent with both feet on the ground during one gait cycle The time of double support may be increased in elder patients and in those having balance disorders The time of double support decreases when speed of walking increases
Stride duration Amount of time spent in completion of one stride or Gait cycle One stride duration for a normal stride is 1 second. Changes occur in stride length during normal, slow, fast walking.
Stride length Gait cycle is also called stride The 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 steps Stride length greatly varies among individual because it is effected by leg length, sex, age. Stride length decreases with increase in age
Step length Linear 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 duration The amount of time spent in completion of a single step. Its measurements is expressed as sec/step When there is weakness or pain in an extremity step duration may be decreased on the effected side while increased on the unaffected side
cadence The number of steps taken by a person per unit time Cadence=number of steps/sec or min Shorter step length will result in increase cadence at a given velocity When a person is walking with cadence between 80 and 120 steps/min, then cadence and stride length have a linear relationship If cadence increases the double support time decreases and vice versa Normal cadence , man=110 steps/min Normal cadence, woman=116 steps/min
Walking velocity Is the rate of linear forward motion of the body in a specific direction It can be measured as, cm/sec, meter/min or miles/hour If the direction is not specified than term walking velocity is called “walking speed” Walking velocity or speed=distance walked/ time Distance(cm, m, miles, km) Time(sec, min, hour)
Step width • Step width, or width of the walking base • It 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 out It 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 degree Angle of toe-out decreases as the speed of walking increases
Power generation and absorption Muscle work concentrically and work positively, produces energy which is used for gait. Muscles work eccentrically and do negative work and absorb energy
Path of Center of Gravity • Center of Gravity (CG): • midway between the hips • Few cm in front of S2 • Least energy consumption if CG travels in straight line
Path of Center of Gravity A. Vertical displacement: • Rhythmic up & down movement • Highest point: midstance • Lowest point: double support • Average displacement: 5cm • Path: extremely smooth sinusoidal curve
Path of Center of Gravity B. Lateral displacement: • Rhythmic side-to-side movement • Lateral limit: midstance • Average displacement: 5cm • Path: extremely smooth sinusoidal curve
Determinants of Gait Saunderdeterminants Six optimizations used to minimize excursion of CG in vertical & horizontal planes Reduce significantly energy consumption of ambulation Classic 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 side • Reduces the angle of hip flexion & extension • Enables a slightly longer step-length w/o further lowering of CG
Determinants of Gait : • (2) Pelvic tilt: • 5o dip of the swinging side (i.e. hip adduction) • In standing, this dip is a positive Trendelenberg sign • Reduces the height of the apex of the curve of CG
Determinants of Gait : • (3) Knee flexion in stance phase: • Approx. 20o dip • Shortens the leg in the middle of stance phase • Reduces the height of the apex of the curve of CG
Determinants of Gait : • (4) Ankle mechanism: • Lengthens the leg at heel contact • Smoothens the curve of CG • Reduces the lowering of CG
Determinants of Gait : • (5) Foot mechanism: • Lengthens the leg at toe-off as ankle moves from dorsiflexion to plantarflexion • Smoothens the curve of CG • Reduces the lowering of CG
JOINT 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 calculated Anatomical 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 JOINT Hip 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-off During swing phase (mid-swing) hip joint reaches its maximum flexion (approx. +30 degrees) which is maintained during deaccelartion
KNEE JOINT The 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 JOINT The 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
