NORMAL GAIT Lecture outline What is Gait Phases

NORMAL GAIT

Lecture outline ► What is Gait ► Phases of Gait ► Determinants of gait ► Parameters of Gait or Gait Analysis

Basic terminologies ► ► Basic biomechanics COG BOS LOG Stability and mobility ► Tibial movement on ankle joint ► Tibial translation at Knee ► Eccentric work of muscles ►

COG

Work, Energy and Power Energy optimizations § Abnormal excessive energy and fatigue ► Physical scientist and biologist § Work done…force and distance ► Energy potential and kinetic § Muscle use potential energy in eccentric that is negative work ► Power exchange § Knee flexion concentric power gain § Knee flexion eccentric power absorb § Isometric no power exchange ► Cant measure energy in human as vehicle measure

Gait ► ► ► Walk and gait ? ? Define Gait? ? Walking pattern Complex system The ability to initiate or terminate

Gait Cycle - Definitions: ► Normal Gait = § Series of rhythmical , alternating movements of the trunk & limbs which result in the forward progression of the center of gravity § Series of ‘controlled falls’

Pre requisite There are (4) major criteria essential to walking. ► Equilibrium: The ability to assume an upright posture and maintain balance. ► Locomotion: The ability to initiate and maintain rhythmic stepping ► Musculoskeletal Integrity: Normal bone, joint, and muscle function ► Neurological Control: Must receive and send messages telling the body how and when to move. (visual, vestibular, auditory, sensori-motor input)

Phases of Gait

Step and stride length and stride width

Gait Cycle - Subdivisions: A. Stance phase: 1. Heel contact: ‘Initial contact’ 2. Foot-flat: ‘Loading response’, initial contact of forefoot w. ground 3. Midstance: greater trochanter in alignment w. vertical bisector of foot 4. Heel-off: ‘Terminal stance’ 5. Toe-off: ‘Pre-swing’

Gait Cycle - Subdivisions: B. Swing phase: 1. Acceleration: ‘Initial swing’ 2. Midswing: swinging limb overtakes the limb in stance 3. Deceleration: ‘Terminal swing’

► Time Frame: A. Stance vs. Swing: ►Stance phase = 60% of gait cycle ►Swing phase = 40% B. Single vs. Double support: ►Single support= 40% of gait cycle ►Double support= 20%

► With increasing walking speeds: ►Stance phase: ►Swing phase: ►Double support: decreases increases decreases ► Running: ►By definition: walking without double support ►Ratio stance/swing reverses ►Double support disappears. ‘Double swing’ develops

► The stance period consists of the first five phases: initial contact, loading response, mid-stance and terminal stance.

Stance phase

Swing phase

Kinematic Description of Gait Movement of the joints and segments in space –Pelvis, Hip, Knee, Ankle ► Sagittal Kinematics ► Frontal Kinematics ► Transverse kinematics

Saggital kinematics Initial contact (Heel strike) ► Hip 25 -30 flexion ► Knee 0 -5 ► Ankle 0 (90) ► Muscle work ► Stabilizers

Loading Response Phase (Heel Strike to Foot Flat) KNEE: 0° → 15° flexion ► ANKLE: 0° → 10° plantar flexion ► 1 st rocker : Calcaneus ► ► ► Muscle work Quards ---Eccentric DF…. Eccentric T. Antand Post…. Eccentric Hip extensors

Mid stance (Foot Flat to mid stance) ► ► HIP: 25° → 0° KNEE: 15° → 0° ANKLE: 10 PF→ 5°dorsiflexion 2 nd rocker ankle Muscle work ► Hip extensors ► Soleus and gastro…eccentric ►

Terminal Stance Mid stance to Heel off ► ► ► ► HIP: 0 - 20° Ext. KNEE: 0° ANKLE: 5° → 10°DF At end of terminal stance, Begin 3 rd rocker MTP Muscle work Planter flexors No quards and hamstring

Pre swing (Heel Off to Toe Off) HIP: 20° Ext → 0°F ► KNEE: 0° → 40°F ► ANKLE: 10° dorsi flexion → 20° plantar flexion ► ► ► Muscle work Planter flexors Push off Passive knee flexion

Initial swing Toe Off to early HIP: 15 °F ► KNEE: 60°F ► ANKLE: 10° plantar flexion ► ► Muscle work Hip flexors ► Knee flexors ► DF ►

Mid swing ► HIP: 25 °F ► KNEE: 25°F ► ANKLE: 0° ► Muscle work ► Hip flexors ► Quards

Terminal Swing Mid-swing-deceleration ► HIP: 25 °F ► KNEE: 0°-5 ► ANKLE: 0° ► Muscle ► Hip extensors ► Hamstring

Muscle Function 1. Trunk ► Counterbalance trunk flexion movement ► Coordinate rotating trunk opposite from pelvis 2. Abdominals ► rotates trunk in opposite direction of pelvis

Muscle Function 3. Hip Flexors (iliopsoas, TFL, sartorius, rectus femoris, and adductors) ► brief activity at beginning of swing to initiate hip flexion ► silence at mid-swing ► eccentric control of hip extension at terminal stance 4. Gluteus Maximus ► activity begins at TSW, rises during IC ► function with hamstrings to decelerate forward trunk

Muscle Function 5. Hip Adductors ► stabilize the limb at heel strike ► stabilize the limb during external rotation 6. Hip Abductors ► stabilize pelvis in the frontal plane ► control contra lateral pelvic drop 7. Quadriceps ► active from TSW through MST ► extend knee to place foot just prior to IC ► absorb shock and provide knee stability

Muscle Function 8. Hamstrings ► active from end of swing phase through loading response ► preventing hip flexion at beginning of stance ► assist with knee flexion during swing 9. Tensor Fascia Latae ► active at terminal swing with gluteus to stabilize ITB ► active at end of stance and beginning of swing to ► assist hip flexion

Muscle Function 10. Pre-tibial muscles (Tib. Ant. , EDL, EHL) ► – active from initial contact through loading ► response to decelerate ankle plantar flexion ► – active from pre-swing through swing to clear toes ► from floor 11. Gastroc/soleus ► active just after midstance through terminal stance to decelerate forward progression of the tibia ► stabilizes knee at terminal stance (pulls femur posteriorly to extend knee)

Frontal kinematics Hip & Pelvis ► Pelvic Obliquity Near midstance, the CM is high. The swing side of the pelvis drops Down during swing to lower the CM. ► Hip AB-Adduction Hip adducts in early stance about 5°, abducts in late stance about 5°, and returns to neutral in swing.

Frontal Kinematics Subtalar ► In early stance, eversion(pronation) unlocks the midtarsaljoint, allowing shock absorption. ► In late stance, inversion (supination) locks the midtarsaljoint, allowing a rigid forefoot lever for heel off.

Transverse axis Hip, trunk & lower limb ► Pelvic Rotation The swing leg side of the pelvis rotates 10° ► Trunk Rotation Lower trunk (below T 7/T 8 ) rotates with the pelvis. Upper Trunk rotates opposite to this (180°) ► Femoral/Tibial Internal rotation until foot flat, then externally rotates until toe off, then internally rotates through swing.

Gait Initial HC ‘Heel transient’ Foot-Flat HC Mid-stance

Gait Initial HC ‘Heel-off transient’ HC Toe-off

Gait analysis 1. Temporal / Spatial 2. Kinematics • Qualitative Gait analysis • Observational gait analysis OGA • Biomechanical evaluation • GHORT 3. Kinetics 4. Dynamic Electromyography

Temporal and Distance Factors ► ► ► Velocity– 1. 46 m/second (3. 26 miles/hour) Step length – 76. 3 cm (30. 05 inches) Cadence – 1. 9 steps /second Stride length – Walking speed – men-110 steps/minute , women-115 steps/minute

Gait Parameters Males Females Step Length (cm) 79 66 Stride Length (cm) 158 132 Cadence (steps/min) 117 (60 -132) 117 (60 132 Velocity (m/sec) 1. 54 1. 31 Walking Base (cm) 8. 1 7. 1 Foot angle 7 6

GAIT Muscle strength ► Planter ► Quards flexors 5 3 plus ► Hip extensors 3 plus ► Hip flexors 2 plus

Kinetics ► GRF ► COP ► Muscle Torque

Kinetics ► Ground Reaction Forces The equal-and-opposite force the floor exerts on the body during stance Best measured with a force plate Forces are typically resolved into: Vertical Compression (z) Anterior-Posterior Shear (y) Medial-Lateral Shear (x)

Gait Analysis – Forces: ► Forces which have the most significant Influence are due to: (1) gravity (2) muscular contraction (3) inertia (4) floor reaction

Gait Analysis – Forces: The force that the foot exerts on the floor due to gravity & inertia is opposed by the ground reaction force ► Ground reaction force (RF) may be resolved into horizontal (HF) & vertical (VF) components. ► Understanding joint position & RF leads to understanding of muscle activity during gait ►

Kinetics center of pressure ► Represents the centroid of foot forces on the floor ► This is an idealization, because pressures are distributed all over ► When measured by a force plate, it is more correctly called the point of application of the GRF

Force Platform The reaction force produced by the ground is called the Ground Reaction Force (GRF), which is basically the reaction to the force the body exerts on the ground. April 30, 2007 Gait Analysis: Techniques and Recognition of Abnormal Gait

Electromyography 0. 051 mm, insulated, hooked wires 25 Gauge Needle April 30, 2007 Gait Analysis: Techniques and Recognition of Abnormal Gait

Control Mechanisms of Gait Spinal cord Pattern generation 2. Reflex action 3. Execute other rhythmic movements concurrently Brainstem and cerebellum 1. Improve coordination of activation patterns 2. Weight support 3. Active propulsion 1.

Control Mechanisms of Gait Basal ganglion 1. Dynamic stability 2. Initiates movement 3. Terminates movements Cortex 1. Adoptable motor control system to meet goals in different types of environments

Essential Requirements for Successful Locomotion Progression ► Coordinated and rhythmic pattern of muscle activation in legs and trunk ► Requires the ability to initiate and terminate locomotion ► Guide locomotion towards end points that are no t necessarily visible Stability ► Appropriate posture for locomotion ► Dynamic stability Adaptation ► Adaptations to avoid obstacles, navigate uneven terrain, and change speed and direction as needed