Biomechanics of Gait and Posture

Question 1

Biomechanics

What is Human Gait?

Gait and Posture

Answer 1

The translatory progression of the human body as a whole, produced by coordinated, rotatory movements of the body segments.

Question 2

Biomechanics

How does reactive postural control differ from anticipatory postural control?

Gait and Posture

Answer 2

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.

Question 3

Biomechanics

Why is a person likely to resprain an ankle after the initial injury?

Gait and Posture

Answer 3

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.

Question 4

Biomechanics

Describe the postural Ankle Strategy.

Gait and Posture

Answer 4

During small perturbations, the trunk stays in neutral and the following muscles contract:
Posterior displacement: TA, quadriceps, abdominals
Anterior displacement: gastroc, hamstrings, paraspinals

Question 5

Biomechanics

Describe the postural Hip Strategy.

Gait and Posture

Answer 5

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.

Question 6

Biomechanics

Discuss consequences of the following major postural deviation:
Flexed Knee Posture

Gait and Posture

Answer 6

• External flexion moment at knee and hip
• Increased quad force required leading to joint compression and increased soleus activity
• Requires more energy

Question 7

Biomechanics

Discuss consequences of the following major postural deviation:
Genu Recurvatum

Gait and Posture

Answer 7

• External extensor moment
• Lengthening of cruciate and posterior ligaments of knee
• Anterior knee compression

Question 8

Biomechanics

Discuss consequences of the following major postural deviation:
Anterior Pelvic Tilt

Gait and Posture

Answer 8

• Increased lumbar lordosis
• Icreased external extension moment
• Degeneration at facets and narrowing of foramen

Question 9

Biomechanics

Discuss consequences of the following major postural deviation:
Forward Head Posture and Excessive Thoracic Kyphosis

Gait and Posture

Answer 9

• Increased lower cervical lordosis
• Increased upper cervical extension
• Degeneration at facets and narrowing of foramen
• Decreased subacromial space

Question 10

Biomechanics

What is a Gait Cycle?

Gait and Posture

Answer 10

The interval of two consecutive initial contacts of the same foot.

Question 11

Biomechanics

What is Stride Length?

Gait and Posture

Answer 11

The distance covered by one gait cycle
(144cm or 56in)

Question 12

Biomechanics

What is Stride Duration?

Gait and Posture

Answer 12

Amount of time spent to complete one gait cycle.
(1.07s)

Question 13

Biomechanics

What is Step Length?

Gait and Posture

Answer 13

Linear distance between two successive stepping point of opposite extremities.
(72cm or 28in)

Question 14

Biomechanics

What is Step Width?

Gait and Posture

Answer 14

The measure of linear distance between paralel lines intersecting the mid-points of the heel on each foot
(8-10cm or 3.5in)

Question 15

Biomechanics

What is Cadence?

Gait and Posture

Answer 15

Cadence is the number of steps per minute.
(108-118 steps/min)

Question 16

Biomechanics

What is the Degree of Toe-out?

Gait and Posture

Answer 16

It is the angle of foot placement at loading respnse
(7°)

Question 17

Biomechanics

What is toe clearance?

Gait and Posture

Answer 17

The distance between hallux and floor in swing phase.
(1.28-1.9 cm)

Question 18

Biomechanics

What is gait speed?

Gait and Posture

Answer 18

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)

Question 19

Biomechanics

What can gait speed predict?

Gait and Posture

Answer 19

Question 20

Biomechanics

At what speed does walking usually turn into running ?

Gait and Posture

Answer 20

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)

Question 21

Biomechanics

What is base of support?

Gait and Posture

Answer 21

The area that bounds the outermost regions of contact between a body and the support surface

Question 22

Biomechanics

What is the Center of Pressure? (CoP)

Gait and Posture

Answer 22

The point at which most of the body weight is acting on the foot.

Question 23

Biomechanics

What are ways to increase stabilty?

Gait and Posture

Answer 23

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

Question 24

Biomechanics

What are the phases of a gait cycle?

Gait and Posture

Answer 24

Stance phase - 60% | Swing phase - 40%

Question 25

# Biomechanics What are the five periods of stance phase? ## Footnote Gait and Posture

Answer 25

1) Initial Contact (Heel Strike) 2) Loading Response (Foot Flat) 3) Midstance 4) Terminal Stance (Heel-off) 5) Pre-Swing (Toe-off)

Question 26

# Biomechanics What are the three periods of swing phase? ## Footnote Gait and Posture

Answer 26

1) Initial Swing 2) Mid-swing 3) Terminal Swing

Question 27

# Biomechanics Define the first period of gait. **Initial Contact** ## Footnote Gait and Posture

Answer 27

The first period is defined as the instant the foot contacts the ground

Question 28

# Biomechanics Define the second period of gait: **Loading Response** ## Footnote Gait and Posture

Answer 28

The second period of gait begins with foot contact and will end with opposite limb toe-off

Question 29

# Biomechanics Define the third period of gait: **Mid-stance** ## Footnote Gait and Posture

Answer 29

The third period of gait begins with opposite limb toe off and ends with ipsilateral heel rise

Question 30

# Biomechanics Define the fourth period of gait: **Terminal Stance** ## Footnote Gait and Posture

Answer 30

The fourth period of gait begins with ipsilateral heel rise and ends with opposite limb foot contact

Question 31

# Biomechanics Define the fifth period of gait: **Pre-swing** ## Footnote Gait and Posture

Answer 31

The fifth period of gait begins with opposite limb foot contact and ends with ipsilateral toe off

Question 32

# Biomechanics Define the sixth period of gait: **Initial Swing** ## Footnote Gait and Posture

Answer 32

The sixth period of gait begins with ipsilateral toe off and ends when the medial malleoli are aligned

Question 33

# Biomechanics Define the seventh period of gait: **Mid-swing** ## Footnote Gait and Posture

Answer 33

The seventh phase of gait begins with the medial malleoli aligned and ends when the ipsilateral tibia is perpendicular to the ground.

Question 34

# Biomechanics Define the eighth period of gait: **Terminal Swing** ## Footnote Gait and Posture

Answer 34

The eighth and final phase of gait begins with the tibia perpendicular to the floor and ends when the ipsilateral foot strikes the floor.

Question 35

# Biomechanics Explain the difference between external and internal moments in gait. ## Footnote Gait and Posture

Answer 35

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.

Question 36

# Biomechanics For each period give the GRF, external moment direction, and muscle activity at each major lower body joint: **Initial Contact** ## Footnote Gait and Posture

Answer 36

**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

Question 37

# Biomechanics For each period give the GRF, external moment direction, and muscle activity at each major lower body joint: **Loading Response** ## Footnote Gait and Posture

Answer 37

**HIP:** GRF: anterior EM: flexion Muscle: Hip Extensors **KNEE JOINT:** GRF: posterior EM: flexion muscle: Quads **ANKLE JOINT:** GRF: posterior EM: PF Muscle: dorsiflexors

Question 38

# Biomechanics For each period give the GRF, external moment direction, and muscle activity at each major lower body joint: **Midstance** ## Footnote Gait and Posture

Answer 38

**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

Question 39

# Biomechanics For each period give the GRF, external moment direction, and muscle activity at each major lower body joint: **Terminal Stance** ## Footnote Gait and Posture

Answer 39

**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

Question 40

# Biomechanics For each period give the GRF, external moment direction, and muscle activity at each major lower body joint: **Pre-swing** ## Footnote Gait and Posture

Answer 40

**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

Question 41

# Biomechanics For the following rockers give the period of gait, GRF involved, and active or passive structures involved: **1st Ankle Rocker - Heel** ## Footnote Gait and Posture

Answer 41

**Period:** IC- LR **GRF:** posterior PF **Structures:** pretibials control PF

Question 42

# Biomechanics For the following rockers give the period of gait, GRF involved, and active or passive structures involved: **2nd Ankle Rocker - Ankle** ## Footnote Gait and Posture

Answer 42

**Period:** LR- TS **GRF:** anterior DF **Structures:** PF’s eccentrically control DF

Question 43

# Biomechanics For the following rockers give the period of gait, GRF involved, and active or passive structures involved: 3rd Ankle Rocker - Forefoot & Toe ## Footnote Gait and Posture

Answer 43

**Period:** TS-PreSw **GRF:** anterior DF **Structures:** PF stretch-shortening cycle

Question 44

# Biomechanics Compare gait differences between a young child and an older adult. ## Footnote Gait and Posture

Answer 44

**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