Biomechanics of Gait and Posture Flashcards
Biomechanics
What is Human Gait?
Gait and Posture
The translatory progression of the human body as a whole, produced by coordinated, rotatory movements of the body segments.
Biomechanics
How does reactive postural control differ from anticipatory postural control?
Gait and Posture
Anticipatory postural control identifies a patterned stimulus to change posture and premptively contact muscles to eliminate or diminish unwanted movement.
Reactive postural control responds to unanticipated proprioceptive input (movement) caused by an external force.
Biomechanics
Why is a person likely to resprain an ankle after the initial injury?
Gait and Posture
Due to injury to mechanoreceptors, propioceptive data going to the brain is absent or delayed. Under normal conditions, these signals would reflexively contract muscles to protect the ankle.
Biomechanics
Describe the postural Ankle Strategy.
Gait and Posture
During small perturbations, the trunk stays in neutral and the following muscles contract:
Posterior displacement: TA, quadriceps, abdominals
Anterior displacement: gastroc, hamstrings, paraspinals
Biomechanics
Describe the postural Hip Strategy.
Gait and Posture
During larger perturbations, the hips shift opposite the direction of the potential fall and the following muscles contract:
Posterior displacement: abdominals, quadriceps, TA
Anterior displacement: paraspinals, hamstrings, gastroc.
Biomechanics
Discuss consequences of the following major postural deviation:
Flexed Knee Posture
Gait and Posture
- External flexion moment at knee and hip
- Increased quad force required leading to joint compression and increased soleus activity
- Requires more energy
Biomechanics
Discuss consequences of the following major postural deviation:
Genu Recurvatum
Gait and Posture
- External extensor moment
- Lengthening of cruciate and posterior ligaments of knee
- Anterior knee compression
Biomechanics
Discuss consequences of the following major postural deviation:
Anterior Pelvic Tilt
Gait and Posture
- Increased lumbar lordosis
- Icreased external extension moment
- Degeneration at facets and narrowing of foramen
Biomechanics
Discuss consequences of the following major postural deviation:
Forward Head Posture and Excessive Thoracic Kyphosis
Gait and Posture
- Increased lower cervical lordosis
- Increased upper cervical extension
- Degeneration at facets and narrowing of foramen
- Decreased subacromial space
Biomechanics
What is a Gait Cycle?
Gait and Posture
The interval of two consecutive initial contacts of the same foot.
Biomechanics
What is Stride Length?
Gait and Posture
The distance covered by one gait cycle
(144cm or 56in)
Biomechanics
What is Stride Duration?
Gait and Posture
Amount of time spent to complete one gait cycle.
(1.07s)
Biomechanics
What is Step Length?
Gait and Posture
Linear distance between two successive stepping point of opposite extremities.
(72cm or 28in)
Biomechanics
What is Step Width?
Gait and Posture
The measure of linear distance between paralel lines intersecting the mid-points of the heel on each foot
(8-10cm or 3.5in)
Biomechanics
What is Cadence?
Gait and Posture
Cadence is the number of steps per minute.
(108-118 steps/min)
Biomechanics
What is the Degree of Toe-out?
Gait and Posture
It is the angle of foot placement at loading respnse
(7°)
Biomechanics
What is toe clearance?
Gait and Posture
The distance between hallux and floor in swing phase.
(1.28-1.9 cm)
Biomechanics
What is gait speed?
Gait and Posture
The distance covered per unit of time - typically meters/second or miles/hour.
(1.3-1.4 meters/second)
(2.7-3.1 miles/hour)
Biomechanics
What can gait speed predict?
Gait and Posture
Biomechanics
At what speed does walking usually turn into running ?
Gait and Posture
The transition from walking to running is regulated by energy expenditure. The preferred transition occurs around the same point as when running becomes more economical than walking.
(4.5-4.8 mph)
Biomechanics
What is base of support?
Gait and Posture
The area that bounds the outermost regions of contact between a body and the support surface
Biomechanics
What is the Center of Pressure? (CoP)
Gait and Posture
The point at which most of the body weight is acting on the foot.
Biomechanics
What are ways to increase stabilty?
Gait and Posture
1) Increasing body mass
2) Increasing friction between the body and the surfaces of contact
3) Increasing the size of the base of support
4) Vertically positioning the center of mass as low as possible
Biomechanics
What are the phases of a gait cycle?
Gait and Posture
Stance phase - 60% | Swing phase - 40%
Biomechanics
What are the five periods of stance phase?
Gait and Posture
1) Initial Contact (Heel Strike)
2) Loading Response (Foot Flat)
3) Midstance
4) Terminal Stance (Heel-off)
5) Pre-Swing (Toe-off)
Biomechanics
What are the three periods of swing phase?
Gait and Posture
1) Initial Swing
2) Mid-swing
3) Terminal Swing
Biomechanics
Define the first period of gait.
Initial Contact
Gait and Posture
The first period is defined as the instant the foot contacts the ground
Biomechanics
Define the second period of gait:
Loading Response
Gait and Posture
The second period of gait begins with foot contact and will end with opposite limb toe-off
Biomechanics
Define the third period of gait:
Mid-stance
Gait and Posture
The third period of gait begins with opposite limb toe off and ends with ipsilateral heel rise
Biomechanics
Define the fourth period of gait:
Terminal Stance
Gait and Posture
The fourth period of gait begins with ipsilateral heel rise and ends with opposite limb foot contact
Biomechanics
Define the fifth period of gait:
Pre-swing
Gait and Posture
The fifth period of gait begins with opposite limb foot contact and ends with ipsilateral toe off
Biomechanics
Define the sixth period of gait:
Initial Swing
Gait and Posture
The sixth period of gait begins with ipsilateral toe off and ends when the medial malleoli are aligned
Biomechanics
Define the seventh period of gait:
Mid-swing
Gait and Posture
The seventh phase of gait begins with the medial malleoli aligned and ends when the ipsilateral tibia is perpendicular to the ground.
Biomechanics
Define the eighth period of gait:
Terminal Swing
Gait and Posture
The eighth and final phase of gait begins with the tibia perpendicular to the floor and ends when the ipsilateral foot strikes the floor.
Biomechanics
Explain the difference between external and internal moments in gait.
Gait and Posture
External moments are created when the line of gravity passes at a distance from the axis of rotation. An internal moment must be muscularly created to counteract this motion.
Biomechanics
For each period give the GRF, external moment direction, and muscle activity at each major lower body joint:
Initial Contact
Gait and Posture
HIP:
GRF: anterior
EM: flexion moment
Muscle: Hip Extensors
KNEE JOINT:
GRF: anterior
EM: Extension
Muscle: Quads
ANKLE JOINT:
GRF: posterior
EM: plantar flexion
Muscle: dorsiflexors
Biomechanics
For each period give the GRF, external moment direction, and muscle activity at each major lower body joint:
Loading Response
Gait and Posture
HIP:
GRF: anterior
EM: flexion
Muscle: Hip Extensors
KNEE JOINT:
GRF: posterior
EM: flexion
muscle: Quads
ANKLE JOINT:
GRF: posterior
EM: PF
Muscle: dorsiflexors
Biomechanics
For each period give the GRF, external moment direction, and muscle activity at each major lower body joint:
Midstance
Gait and Posture
HIP:
GRF: anterior to posterior
EM: flexion to extension
Muscle: Only extensors during flexion moment
KNEE JOINT:
GRF: posterior to anterior
EM: flexion to extension
Muscle: Only quads during flexion moment
ANKLE JOINT:
GRF: anterior
EM: DF
Muscle: Plantar flexors
Biomechanics
For each period give the GRF, external moment direction, and muscle activity at each major lower body joint:
Terminal Stance
Gait and Posture
HIP:
GRF: posterior
EM: Extension
Muscle: none
KNEE JOINT:
GRF: anterior then moves posterior before contralateral initial contact
EM: extension to flexion before contralateral initial contact
Muscle: No muscle activity
ANKLE JOINT:
GRF: anterior
EM: DF
Muscle: plantar flexors
Biomechanics
For each period give the GRF, external moment direction, and muscle activity at each major lower body joint:
Pre-swing
Gait and Posture
HIP:
GRF: posterior
EM: Decreasing extension secondary to knee flexion
Muscle: adductor longus and rectus femoris
KNEE JOINT:
GRF: posterior
EM: flexion
M: Rectus Femoris
ANKLE JOINT:
GRF: anterior
EM: DF
M: Elastic recoil of plantar flexors
Biomechanics
For the following rockers give the period of gait, GRF involved, and active or passive structures involved:
1st Ankle Rocker - Heel
Gait and Posture
Period: IC- LR
GRF: posterior PF
Structures: pretibials control PF
Biomechanics
For the following rockers give the period of gait, GRF involved, and active or passive structures involved:
2nd Ankle Rocker - Ankle
Gait and Posture
Period: LR- TS
GRF: anterior DF
Structures: PF’s eccentrically control DF
Biomechanics
For the following rockers give the period of gait, GRF involved, and active or passive structures involved:
3rd Ankle Rocker - Forefoot & Toe
Gait and Posture
Period: TS-PreSw
GRF: anterior DF
Structures: PF stretch-shortening cycle
Biomechanics
Compare gait differences between a young child and an older adult.
Gait and Posture
Child: short steps, uneven step length, Initial contact with flat foot, decreased stride length and cadence, no reverse pendulum
Older adult: decreased velocity, strides, and step length, wide BoS, may need AD
