2Normal gait is defined as (form of bipedal locomotion) or as a method of locomotion involving the use of the two legs, alternately , to provide both support and propulsion at least one foot being in contact with the ground at all times . It is a series of rhythmic alternating motion of arms, legs, and trunk that create forward motionIn order to walk1- each leg able to support body wt without collapse2- maintain static and dynamic balance during single leg stance for maintenance of upright posture.3- sufficient power for limb motion and to advance the trunk.4- the swing leg able to advance to a position where it can take over the supporting role.
3For proper gait5- proper proprioceptive system6- normal vision7- training and experiencesPhases of gait cyclesThe gait cycle begin from heel contact of one foot to the next heel contact of the same foot.During one gait cycle each lower limb has two phases single stance phase and single swing phase
4Stance phaseFrom heel contact tell toes off of the same foot (60% of gait cycle) called wt bearing or supporting phaseIt is subdivided into three intervals1-initial double stance (10% of cycle of stance)2-single leg support (40% of cycle of stance)3-terminal double stance (10% of cycle of stance)
5Five sub-phases of stance phase Initial contact or heel strike 2% of gait cycleLoading response or foot flat 2-10% GCMid-stance body wt over one leg 10-30%GCTerminal stance or heel off 30-50% GCPre-swing or toe off 50-60% GC
6It is subdivided into three sub -phases Swing phaseFrom toe off to just prior to heel strike of the same foot . Called non wt bearing period 40% of GCIt is subdivided into three sub -phases1- initial swing or acceleration from just toe off till maximum knee flexion or the swinging limb is direct under the body 60-73%GC2- midswing from max. knee flex. Till tibia vertical on ground 73-87% GC
73- terminal swing or deceleration from vertical tibia position to just before heel strike % GC Increase of gait velocity will decrease gait cycle time and swing time will increase in relation to stance and double leg support & with running no double leg support and there is a float period
8Gait analysis Consists of kinematic and kinetic analysis The kinematic analysis includes1- distance and time variables2- measurement of joint angles of lower limb and upper limbs3- determinants of gait
91- Distance and time variables 1- step length 70.5cm(64cm female-73cm male)2- stride length3- the width of the base of support 1 to 5 inches4- degree of toe out about 7 degree
10Time variables Step time Stride time Stance time 0.6 sec Swing time 0.4 secSingle limb timeDouble limb timeCadence: number of steps / unit time. average 113/minWalking velocity : distance/min .average 82m/min
112- measurement of joint angles Lower limb (hip, knee and ankle joints angles in sagittal, frontal and transverse planes)Upper limb (shoulder, elbow and wrist joints angles in sagittal, frontal and transverse planes)Head ,trunk, and pelvic displacement during gait cycle in vertical, lateral and progression.
123- determinants of gait6 determinants present adjustments made by the body that help to keep the motion of COG to a minimum.1- first determinant : pelvic rotation in the transverse plane2- 2nd determinant lateral pelvic tilting in the frontal plane3- 3rd knee flexion in stance phase
134th and 5th determinants : knee, ankle and foot interaction 6th one : physiologic valgus of the knee . The width between the hips cm and the normal step width 8 cm so because the base of support is narrow , little lateral motion of the body is necessary to shift the COG from one Lower Limb to another over the base of support (5-10 degree is the valgus angle of the knee )
14Functions1- the determinants minimize the up and down , and side to side motion of COG to reach only 2 inches2- they produce a smooth sinusoidal curve of the COG3- decrease the energy expenditure during normal walking
15Kinetic analysisIt is the analysis of the forces acting on the body during the gaitIt includes internal and external forcesExternal forces : like inertia, gravity, and ground reaction forceInternal forces : by the muscles which assisted by tendon, ligaments, joint capsules and bony component
16External forcesThe force of gravity acts directly down word through COG of the body at which the body weight is represented by a line . The GRF represents the force of the ground on the foot and it is equal in magnitude and opposite in direction to the force of gravity
17From lateral view .it passes via Line of gravityIt is an imaginary vertical line which passes perpendicularly in the body and connects between the COG of the segment above by the COG of the segment belowFrom lateral view .it passes viaVertexMastoid processAtlanto-occipital jointBehind the cervical spineAt the junction of cervico-dorsal vertabraeAnterior to the body of the dorsal spine
18At the junction of dorso-lumbar vertabrae Posterior to the body of the lumbar vertabraeAnterior to 2nd sacral vertabraJust behind or via the axis of the hip jointAnterior to the axis of the knee jointAnterior to the ankle joint at the level of tarsal bones at about 5- cm
20From front view or back view The vertical LOG passes through the body’s COG which bisects the body into equal halves with the body is equally distributed between the two feet.The location of the LOG relative to the axis of motion of body segment will determined the motion direction .
22GRF vectorAre forces that act on the body as a result of interaction with the ground and composed of 3 forces . One vertical and two horizontal forces (mediolateral-anteroposterior)
23The point of application of GRFV is the body center of pressure(COP ) which located in foot in unilateral stance and between the feet in bilateral standing postureThe COP move from psterolateral edge of the heel at heel strike to 2nd and 3rd toes at terminal stance in linear fashion
24The pathway of GRFV During stance phase in saggital plane Initial contact: anterior to hip and knee and post. To ankleLoading response : anterior to hip and post. To knee and ankleMidstance : post. To hip and anterior to knee and ankleTerminal stance :post. To hip and anterior to knee and anklePreswing: post. To hip and knee and anterior to ankle joint
25Internal forcesThey are developed during gait by muscles and the structure which assist the MS by resisting, transmitting and absorbing forces like ligaments, tendons, capsules and bones.The moment created by GRFV is counteracted by muscles activities and other soft tissues
26As a principle to identify muscle action and type of contraction put in your consideration If the GRFV passed anterior to joint the posterior muscles will produce counterforceThe relation between this forces will determined the desired motion