Lecture 12 - Gait and Posture Flashcards
What is postural sway?
- Normal standing posture can be compared to an inverted pendulum
- Occurs in two dimensions:
a) Anterior-posterior
b) Medial-lateral
What is sway?
Characterized by:
1. Center of pressure (COP)
2. Center of mass (COM)
What is the ideal posture concept?
- Requires least amount of energy
- Minimizes stress on joints
- Minimizes loads in ligaments and muscles
In the sagittal plane, what is the alignment in the spine?
- Kyphosis: In thoracic and sacral region
- Lordosis: In lumbar and cervical region
When does the development of the spinal alignments occur?
Primary curve:
Babies born with kyphotic spine
Secondary curve:
1. Cervical lordosis develops with head control
2. Lumbar lordosis develops with gait
What is Cobb’s angle?
- Describes the angle of different spinal regions
What is the relationship between pelvis and spine?
- Orientation of pelvis is common in clinical evaluation
- Anterior pelvic tilt: Increased lordosis of lumbar spine
- Posterior pelvis tilt: Decreased lordosis of lumbar spine
In the sagittal plane, what is the alignment of the head?
- Typical: Ear aligned with shoulder
- Aging: Ear is forward in relation to the spine
In the frontal plane, what is the spinal alignment?
“Right-left” symmetry
What is postural malalignment?
Exp: Scoliosis
- Contributes to altered joint and muscle mechanics
- Produces impairments that lead to pain
What are muscle imbalances reported in postural malalignments?
- Muscles on one side of the joint are held in a lengthened position and the antagonistic muscles are shortened
- Length changes produce joint impairments including weakness and limited ROM
What is the gait cycle?
Movement pattern beginning and ending with ground contact of the same foot
What is a step?
Movement of a limb from ground contact of that limb to ground contact of the opposite side
What is stride?
Movement of both limbs during 1 gait cycle
What are the two phases of gait?
- Stance (60%)
- Swing (40%)
What are the tasks of stance phase in locomotion?
- Provide adequate support
- Absorb shock of impact between the limb and ground
- Provide adequate forward/backward force for progression
What are the tasks of swing phase in locomotion?
- Safe limb clearance
- Appropriate limb placement for next contact
- Transfer of momentum
What are the ways gait can be characterized?
- Periods
- Tasks
- Phases
Exp: Support periods
What are the kinematics of locomotion?
- Spatial parameters (distance)
- Temporal parameters
- Angular joint displacement
What are the factors affecting kinematic gait characteristics?
- Walking speed
- Age
- Height
- Weight/BMI
- Aerobic conditioning
What are the spatial parameters?
- Stride length
- Step length
- Step width
- Foot angle
What are the temporal parameters?
- Stride time
- Speed
- Cadence
- Stance time
- Swing time
- Swing/stance ratio
- Double support time
- Single support time
What are two ways to walk faster?
- Increase cadence
- Increase step length
What are the effects of speed on the gait cycle?
- Walking speed affects swing and stance times
- Increased speed = decrease cycle length
- As stance decreases, double support decreases and single support increases
What are ways to measure angular displacements of the joints?
- Video/photography
- 3D motion capture
- Markerless motion capture
- Sensor based
What plane is has the largest ROM?
Sagittal plane
Which plane is the easiest to capture?
Sagittal plane
What is the angular displacement of the hip in the sagittal plane?
- Single “wave”
- Starts/ends with flexion
- Less extension than flexion
What is the angular displacement of the knee in the sagittal plane?
- Peak 1: Loading
- Peak 2: Foot clearance
What is the angular displacement of the ankle in the sagittal plane?
- Neutral at foot contact
- Plantarflexion in loading
- Plantarflexion to clear foot
What is the angular displacement of the hip in the frontal plane?
- Affected by the pelvis
- Adducts in stance
- Unloaded hip in swing abducts
- Increased abduction/circumduction during swing related to plantarflexion weakness
What is the angular displacement of the knee in the frontal plane?
Slight motion (2-10 degrees)
What is the angular displacement of the ankle in the frontal plane?
- Initial contact in slight inversion
- Foot “rolls” into neutral/eversion in stance
- Returns to inversion position during swing
What is the angular displacement of the hip in the transverse plane?
- A function of the transverse plane motion of the pelvis and femur
- Forward rotation of the pelvis contributes to lateral rotation of the ipsilateral hip
- Femur rotates medially
How is muscle activation measured?
Using EMG
What are the types of contractions?
- Eccentric: lengthen
- Concentric: shorten
- Isometric: no change
What is the muscle activation of the TA?
- Eccentric contraction prevents foot slap (in stance)
- Isometric contraction aids in toe clearance (in swing)
What is the muscle activation of the tricep surae?
- Concentric contraction towards end of stance phase (generates power for push off and helps with clearance)
What is the muscle activation of the quadriceps?
- Active preceding initial contact through opposite toe off (also late phases of stance)
- Turn on in synchrony with hamstrings to provide stability to the knee joint
- Acting to help the knee extend before initial contact
What is the muscle activation of the hamstrings?
- Slow down the “whip” of the knee before initial contact (during swing)
- Works in harmony with the quadriceps for control of knee
What is the muscle activation of the gluteus maximus?
- Major hip extensor
- Active preceding initial contact of stance
- Prevent collapsing to the ground
How are 3D ground reaction forces collected?
Using force plates
What is the vertical ground reaction force?
- “Double bump” curve shape
- Peaks > 100% body weight correspond to COM acceleration upwards
- Valley during single-limb support
What is the anterior-posterior ground reaction force?
- Negative: deceleration phase
- Positive: acceleration phase
What is the medial lateral ground reaction force?
- Smallest forces
What are the kinetics of gait?
Comprises…
- Forces
- Moments
- Power
- Energy
What is dynamic equilibrium?
- During gait, body segments undergo large linear/angular accelerations
- Newton’s second law is required:
Linear: F = ma
Angular: M = Iα
What are the two ways to analyze kinetic quantities in gait?
- Inverse dynamics: Calculate net joint forces and moments of force from kinematic information
- Forward dynamics: Know force in muscles, joints, etc and predict movement
What is a link segment?
Break body into segments
Exp: foot, thigh
What is Newtons second law?
Unbalanced forces produces an acceleration
What is Newtons third law?
For every force, there is an equal but opposite force
How are net moments analyzed?
- Represent the net moments from all muscles, ligaments and soft tissues
- Net external moments: moments applied to the joint due to external forces
- Net internal moments: moments applied to the joint by muscles and soft tissue
What are the joint moments in the sagittal plane?
Moments can be interpreted based on knowledge of muscle activity and ground reaction forces
In the sagittal plane. what are the joint moments in the hip?
- Initial contact: Gluteus maximus resists flexion, resulting in internal hip extension moment
- Stance: Results in extended hip
- Swing: Hip flexors actively contract to flex hip
In the sagittal plane, what are the joint moments of the knee?
- Initial contact: Brief flexor moment related to hamstring
- Early stance: Large extension moment to control knee flexion
- Flexion moment eventually flexes the knee
In the sagittal plane, what are the joint moments of the ankle?
- Initial contact: Brief dorsiflexion moment to control foot slap
- Late stance: Plantarflexion moment to resist dorsiflexion and plantarflex ankle
What is joint power?
- Joint moment (M) x Angular velocity (ω)
- Rate of work measured in watts
What is the joint power during concentric movements?
Generate power (positive)
What is the joint power during eccentric movements?
Absorbs power (negative)
Where is joint power generate?
By the..
1. Hip (flexors and extensors)
2. Ankle (plantarflexors)
