Biomechanics and intro to gait

Question 1

Two components of moment profiles

Answer 1

Muscle moment arm influenced by joint angle and muscle force influenced by length tension relationship (actin-myosin overlap)

Question 2

4 challenges of normal gait

Answer 2

1. Maintaining upright posture
2. Maintaining equilibrium
3. Control of foot trajectory
4. Coordination of multiple limb segments

Question 3

Challenge of normal gate - maintaining upright posture

Answer 3

Gravity tends to produce flexion of the trunk. Muscular work is required to act against gravity.

Question 4

Challenge of normal gate - maintaining equilibrium

Answer 4

Swing phases involve single limb support. Neuromuscular response to instability and adaptation to changing surfaces/external forces.

Question 5

Challenge of normal gate - Toe trajectory

Answer 5

Toe must clear the ground (usually only 1.5”). Requires proprioception, tactile sensation, and dorsiflexion.

Question 6

Challenge of normal gate - multi segment coordination

Answer 6

Multiple segments moving in space and influencing each other. Requires proprioception and kinesthesia, adequate neuromuscular coordination.

Question 7

A normal gait cycle is _% stance phase and _% swing phase

Answer 7

60% stance, 40% swing

Question 8

The 3 main tasks of gait are:

Answer 8

1. Weight acceptance
2. Maintaining stability during SL support
3. Limb advancement

Question 9

For what percentage of a normal gait cycle is someone in 2 limb support?

Answer 9

20% (2x 10% between initial contact and toe off of opposite limbs, or if looking at one limb then during loading response and Pre swing)

Question 10

What is the sequence of periods after the event of initial contact?

Answer 10

Weight acceptance, mid stance, terminal stance, pre-swing, initial swing, mid swing, terminal swing.

Question 11

Stance phase includes which periods?

Answer 11

Loading response, mid stance, terminal stance, pre-swing

Question 12

What are the objectives during weight acceptance?

Answer 12

Shock absorption, stability, maintenance of forward momentum

Question 13

What are the objectives of single limb support?

Answer 13

Maintain stability, progress over the stationary foot

Question 14

Which phase during gait is most commonly affected by pathology?

Answer 14

Swing (in single leg support)

Question 15

Objectives of limb advancement?

Answer 15

1. Foot clears the floor
2. Advance the limb from a trailing position
3. Prep for stance phase

Question 16

Does limb advancement occur purely in the swing phase?

Answer 16

No!

Question 17

Normal step and stride lengths, and normal cadence and walking speed

Answer 17

Step = 0.7m
Stride =1.4m
Cadence = 110 steps/min
Velocity = 1.3m/s

Question 18

How does injury affect step and stride length?

Answer 18

Injury tends to reduce the step length of the opposite limb. This is because the time spent standing in single leg support on the injured limb is reduced, therefore reducing swing time of the opposite limb.

Question 19

How do the gaits of older individuals compare to the gaits of younger?

Answer 19

Older individuals tend to have both a slower walking cadence and shorter step/stride length, resulting in a reduced walking speed. They tend to spend more time in dual limb support and have shorter swing phases.