Stance Phase
instant the foot strikes the ground
which phase am I a part of?
heel strike
initial contact- causes forward acceleration of body to decrease, readies lower body to accept support of upper body
Minimum PE, Maximum KE
I am spent (used up not exhausted lol)
PE that was obtained during mid-stance is spent as body falls forward from its maximum height
LPTA
prevents pelvic rise on stance side
prevents pelvic drop on swing side
keeps COM on trajectory needed to reach max. height at mid-stance
minimizes vertical fluctuations in COG
minimizes energy expenditure
When is KE the greatest?
Initial contact
What two factors make humans efficient bipeds?
smooth exchange between PE and KE
minimal fluctuations in COG
I start with heel off and end with forefoot rocker action, what am I?
Terminal stance
heel off- lifting heel of reference limb off of ground (contralateral limb touches ground for the first time)
forefoot rocker action- reference limb rolls forward around the metatarsal phalangeal joints and body mass is going to move ahead of the leg
I'm the final stage of the swing phase when the reference limb is out in front of the body and the leg is being actively extended. I'm preparing for heel strike!
Terminal swing
limb begins to accelerate in negative directionTransverse pelvic rotation
pelvis rotates forward on swing side
pelvis rotates backward on stance side
increases effective stride length
minimizes fluctuations in COM
I am 60% of a stride and I never leave contact with the ground
stance phase
When is COG at its highest and lowest?
highest at mid-stance
lowest at initial contact
I begin at heel rocker action and end at flat foot, what am I?
Loading response
lower limb responds to loading of upper body mass
lower limb rolls forward over the heel (HRA)
brings foot into full contact with ground (flat foot)
body mass of upper body continues to accelerate in negative direction
Trailing foot of swing limb has lifted off ground and body is falling forward from maximum height
Initial swing
reference thigh is being accelerated forward, spending PE
Valgus Angle of Knee
places knees and feet in midline of body (directly beneath COM)
minimizes lateral shift in COG
conserves movement and energy
when the lower limb rolls forward over the ankle and body mass passes directly over the planted foot
ankle rocker action
What percentage of energy do we spend compared to that of other bipeds?
75% less energy
I'm when PE is at it's highest because COM it at it's highest point on reference limb side.
Mid-stance
Reference leg is being actively extended during which phase?
terminal swing
Stance side knee flexed from _____ to ______
why?
foot flat to mid-stance
controls vertical excursion of COM
prevents over-rise of swing side (vaulting) conserves energy
reference limb rolls forward around the metatarsal phalangeal joints and the body moves ahead of the leg
What are the 5 factors that humans limit horizontal and vertical fluctuations while walking?
1. Lateral Pelvic Tilting Action
2. Transverse pelvic rotation
3. valgus angle of knee
4. stance side knee flexed from foot flat to mid-stance
5. pull of gluteus maximus on trunk (assisted by long hamstrings)
I'm getting into the position to be swung forward and I end with toe off, what am I?
Pre-swing
contralateral limb prepares to be loaded
toe-off- 1st pedal digit (hallux) of reference limb lifted off the ground, weight transfer to contralateral leg complete
fully transfer mass of body onto other limb
This is when lower-limb passes underneath the body as reference limb is swung forward
Tibia reaches vertical position
Mid-swing
note:
heel has not yet struck the ground
leg not yet actively extending
Pull of Gluteus Maximus (w/ long hamstrings) on trunk does what?
prevents flexion of trunk on pelvis- conserves energy
keeps you from falling forward
I'm the mainly passive phase of walking gait
swing phase
The three primary functions of the lower limb
1. locomotion
2. bear weight of upper body
3. provide stability