Chapter 16 Flashcards
People don’t really think too much about gait, but why can an abnormal gait be dangerous?
Known to increase loading at the knee and ankle, predisposing people to developing osteoarthritis. It is also associated with injuries at the knee ankle and spine.
What factors influence gait?
Age, barefoot versus shod, heal height, flexibility, strength, injury, floor type, terrain, distance, speed.
What sequence should be taken during a hierarchal analysis of gait. Describe what you are measuring at each phase.
1 - Temporal Analysis: determining relative time between stance and swing phase
2 - Point mass Analysis: body COM is measured during weight acceptance, mid stance and late stance, measuring both vertical and horizontal ground reaction forces.
3 - Rigid Body Analysis: Analyzing joint angles and rigid body mechanics during gait.
begin at the most basic - temporal analysis - and continue down the chain if you need more information
Define one gait cycle.
The time between two contacts of the same foot.
Describe the components of a gait cycle.
One gait cycle can be divided into two general phases - the stance phase (60%) and the swing phase (40%).
Within the stance phase, there are two periods of double limb support (10%).
The stance phase - the most important - is further divided into 3 distinct phases:
From heal strike to flat foot: Weight acceptance phase
From foot flat to heal-off: Mid-stance phase
From heal-off to toe-off: push-off phase
How does the expected gait cycle differ between walking and running?
In running the stance phase is 40% while the swing phase is 60% of the gait cycle.
What is a major limitation to restoring walking velocity after injury?
Stride length
What is the average walking speed of an adult?
1.4 m/s
How do stride length and stride frequency evolve throughout the lifespan?
Stride length:
- increases from childhood to adulthood
- remains constant for 50-60 years of the lifespan
- decreases with increasing age
- is lowered with illness or injury
Stride frequency:
- relatively constant with increasing age
- increases with injury or illness to compensate for decreases in stride length
Describe the expected vertical GRF during the three components of the stance phase during gait.
Weight Acceptance: The GRF will be around 120% of total body weight (COM) as the body is accelerating toward the ground - kind of like landing from a jump.
Thus GRF>Fg
Mid Stance: As the weight is accepted, the knee will bend slightly and the COM will lower, which will decrease the GRF to around 80% of BW
Thus GRF<Fg
Push Off: Another peak in GRF will occur during push-off phase as the COM is accelerating away from the ground. This will be about 120% BW, similar to the weight acceptance phase.
Thus, GRF>Fg.
How would the vertical GRF’s change when walking down hill versus uphill?
When walking uphill the GRF during the Weight acceptance phase will be smaller and the GRF during the push off phase will be larger.
The opposite is true for walking downhill.
What pattern of anterior-posterior GRF are we expected to see during the 3 components of the stance phase?
Weight acceptance: Larger breaking impulse - negative GRF
Mid Stance: relatively stable at 0
Push-off phase: Larger propulsion impulse - positive GRF
positive GRF pushes you forward and a negative GRF pushes you backwards
How can stride length be increased, using the principles of COM and GRF?
1 - Increase vertical GRF at push-off (similar to increasing projectile flight time)
2 - Decrease posterior GRF at weight acceptance (breaking impulse)
3 - Increase anterior GRF at push-off (propulsion impulse)
What is a foot progression angle?
The angle of turnout of the foot during gait - most people have a slight toe-out progression angle.
How do vertical GRF’s change in response to changing the foot progression angle?
The vertical GRF is the same whether there’s a toe-in toe-out or neutral foot progression angle. However, the GRF during the push-off phase is highest in a neutral stance!!
In the toe-in and toe-out the pushoff GRF is lower and the same between the two.
How can you increase the late-stance GRF impulse?
Walk with feet pointed forward! (Will be less with either toe in or toe out)
How does changing the FPA influence the anterior-posterior GRF’s?
Early stance: Both neutral and toe-out FPA, have higher POSTERIOR GRF when compared with toe-in.
Late Stance: Abducted FPA has the lowest anterior GRF and impulse. Toe-in (adducted) has the highest.
How can you decrease the posterior GRF impulse and increase the anterior GRF impulse during gait?
Adduct the feet when walking! (Toe-in)
How should you walk to increase stride length?
Either with feel forward (increase vertical GRF during push-off) or slightly turned in (increase anterior GRF during pushoff, and reduce posterior GRF during early stance).
Why might someone have a toe-out foot-stance?
Usually has to do with excessive external rotation of the hip - perhaps strong/tight external rotators or weak internal rotators.
What data can you get by interpreting joint power?
Whether the muscle group is working concentrically or eccentrically. This data can be combined with NJM to provide the full story of what is happening during movement.
For example:
- positive power combined with a hip extensor NJM = concentrically hip extension
- Negative power + hip flexor NJM = eccentric hip flexor activation
What are the effects of increasing push-off?
1 - increases stride length
2 - increases concentric plantar flexion
3 - Increases eccentric knee extensor work
4 - decreases concentric hip extensor work
5 - decreases concentric hip flexor work
What is the difference between activating the gastrocnemius versus soleus during push-off?
Gastrocnemius Activation:
Stance:
-increased ankle dorsi flexion
- decreased knee extension
- decreased hip extension
Swing:
- Decreased ankle plantar flexion
- Increased hip and knee flexion
Soleus Activation:
Stance:
- Decreased ankle dorsiflexion
- increased knee extension
Swing:
- increased ankle plantar flexion
- large increase in hip and knee flexion
