Basic of Biomechanics of Gait

Question 1

Define Gait

Answer 1

Translatory progression of the body produced by co-ordinated rotary movements of body segments

Question 2

What aspects are covered by gait (What is Gait responsible for) 5

Answer 2

• Prevent lower limb collapse
• Maintain Balance and an Upright Posture for walking
• Control foot trajectory for force Absorption (Absorb the forces of the body) Transmission (transmit forces into the ground e.g when pushing off)
• Generate mechanical energy to maintain and increase froward velocity
• Shock absorption and stability

Question 3

Provide an overview of the musculoskeletal system

Answer 3

It allows for the transmission of bodyweight to the ground while maintaining upright body posture

It facilitates the Generation (by muscles) and the transmission (by bones and joints) of internal forces that in turn, enable us to exert external forces on our physical environment

Question 4

Provide an overview of Stability

Answer 4

• Mechanically an object is said to be stable in respect to its base of support when the line of action of its weight intersects the plane of the base of support
• In general the lower the center of gravity and the larger the area of the base of support, the greater the stability

Question 5

What is the most stable position the human body can be in, give details as to why?

Answer 5

• The recumbent position (lying down)
• Because its the Position where the area of the base of support is at its greatest and the height of the centre of gravity is at its lowest
• requires the least amount of muscular effort as all segments of the body are supported by the surface of the ground

Question 6

Define Load

Answer 6

Any force or combination of forces applied to an object

Loads tend to deform the object which they are acting on

Question 7

List the three types of load

Answer 7

Tension, Compression, Shear

Question 8

Detail the three forms of load

Answer 8

• Tension - pulling load that tends to make an object longer thinner along the line of force
• Compression - is a pushing or pressing load that tends to make an object shorter and thicker along the line of force
• Shear - A shear load is comprised of two equal opposite parallel forces that tend to displace one part of the object with respect to its adjacent part along a parallel to and between the line of force

Question 9

If an object experiences tension on one side and compression on another what type of load is being placed upon it

Answer 9

BENDING

Question 10

An object simultaniousley experiencing tension, compression and and shear is experiencing which type of load

Answer 10

Torsion

Question 11

Define strain

Answer 11

• Deformation of an object that occurs as a response to a load
• Strain denotes deformation of Inter-molecular bonds that comprise a structure
• Those inter-molecular bonds then resist by exerting forces that return the object to its original form

Question 12

What are the two main phases of the gait cycle

Answer 12

Stance phase = consists of 62% of the cycle in normal gait

Swing Phase = consists of 38% of the cycle in normal gait

Question 13

How is a full gait cycle defined

Answer 13

The time during locomotion between contact to contact of the same foot (heel strike to heel strike of the same foot)

Question 14

Detail the five events of the stance phase

Answer 14

• Initial Contact
• Loading response
• Mid stance
• Terminal stance
• Pre Swing

Question 15

Describe Initial Contact event of gait cycle

Answer 15

The moment that the foot contacts the ground (usually heal strike in normal healthy gait) 0% of gait

Question 16

Detail the Loading response event of gait

Answer 16

Weight is transferred onto the limb (flat foot absorbing shock) 10 - 12% of gait cycle

Question 17

Detail the Mid stance event of gait

Answer 17

The body progresses directly over a single limb (Identified by position where joints are all aligned pretty much on top of each other Lateral malleolus in line with lateral femoral condoyle (knee), greater trochanter (Hip) in line with the achromiun (shoulder)

Standing on one leg maintaining stance stability

10 - 30% of Gait Cycle

Question 18

Describe Terminal Stance event of gait

Answer 18

Progression continues moving the body forward of the limb and weight is transferred to the forefoot (on the foot were analyzing) Heel Off

30 - 50% of gait

Question 19

Describe the Pre Swing event of gait

Answer 19

Limb is unloaded quickly as the weight is shifted to the opposite lower extremity

50 - 60% of gait cycle

Toe Off - A single moment in time that signifies the end of the stance and the beginning of swing phase

Question 20

Name the three events of the Swing phase

Answer 20

• Initial Swing
• Mid Swing
• Terminal Swing

Question 21

Describe the initial swing event of the swing phase

Answer 21

• Initial Swing - The leg begins to leave the ground and the Femur begins to advance forward
• Occurs at 60 - 73% of gait

Question 22

Describe the Mid Swing event of the Swing phase

Answer 22

• Mid Swing - The knee begins to extend and the foot clears the ground as the femur continues to advance forward
• Occurs at 73-87% of gait
• Can be Identified when the Tibia is in a Vertical position

Question 23

Describe the Terminal swing event of the swing phase

Answer 23

• Terminal Swing - The knee is fully extended as the lower extremity prepares to contact the ground
• Occurs at 87 - 100% of Gait

Question 24

Describe the single limb support phase of gait

Answer 24

Single limb support phase refers to a period during gait where the body is supported by one limb and one foot is in contact with the ground.

The single support phase takes place during mid stance and terminal stance

This phase lasts for around 40% of the cycle

Question 25

Describe the double support phase of Gait

Answer 25

• Double support relates to the part of the gait when both feet are in contact with the ground.
• Gait begins with Right leg heel strike, this initiate the stance phase of the right leg. The first part of stance phase is a period of double support
• This initial period lasts approx 10% of the cycle
• The cycle then transfers into single support and ends with another phase of double support known as Terminal double support which lasts around 10% of the cycle

Question 26

What is Ground reaction force

Answer 26

• Ground reaction force refers to the force exerted by the ground on the body in contact with it.
• When standing, the ground reaction force is equal in quantity/magnitude but opposite in direction to the body weight (zero forces acting on the body)
• When moving the body must push against something to provide the necessary resultant force to move it in the given direction
• Walking = foot pushes obliquely downward and backward against the ground, a ground reaction force is then produced directed obliquely upward and forward equal in quantity/magnitude but opposite in direction to the leg thrust