Bio Mechanics Exam 3

Stance Phase

Begins when foot initially hits the ground, ends when foot leaves ground

Swing Phase

Begins when foot completely leaves the ground and ends when foot contacts ground

Stance Phase Events

Initial Contact, Foot Flat, Midstance, Heel-Off, Toe-Off

Initial Contact

Starts gait cycle

Foot Flat

Foot lowers to ground

Midstance

Body weight advances over foot

Heel-Off

Foot becomes rigid lever

Toe-Off

Last contact w ground

Swing Phase Events

Early, Mid, Late Swing

Early Swing

From toe-off to midswing

Midswing

Lower limb is directly under hip

Late swing

Deceleration, right before initial contact

What percentage of gait does toe-off occur

60%

Double-limb support phases %

20%

Single leg support phase %

80% (40ea)

Running

No double limb support

Stride length

Represents 1 complete gait cycle- avg-144cm

Foot angle

Amount of toe out during gait

Avg- 5-7degrees

>angle can leave to retroversion, insufficiencies

Cadence

Steps per minute

Average walker-110 spm

Average runner-150 spm

<.9 m/s

Cant do household activities

<.6 m/s

Fall risk

Motion in pelvis

Transverse or frontal plane

Pelvic Kinematics of Gait

In stance phase, pelvis rotates up and back, opposite for swing

Hip flexion ROM at inital contact

30 degrees

Hip Extension ROM at heel off

10 degrees

Hip Kinematics of Gait

ER at initial contact, to IR by toe-off, Opposite for swing

Knee Flexion ROM at midswing

60 degrees

Knee Extension at midstance

0 degrees

Ankle Dorsiflexion at midstance

10-15 degrees

Ankle Plantarflexion at toe-off

15-20 degrees

First MTP Extension in Heel off

>55 degrees

Two main PROPULSIVE forces in gait

Hip flexion, Plantarflexion

Hip flexor main activity

Advance swing leg in toe-off, lift swing leg enough to clear foot

Hip Extensor main actions

Control hip flexion in terminal swing, Extend hip at initial contact, prevent forward trunk flexion in push off

Hip Abductors main actions

Control pelvis alignment

Knee extensor main actions

Shock absorption at initial contact, extend knee in midstance, flex hip/control knee flexion in toe-off

Knee Flexor main action

flex knee at initial contact, Flex knee at toe off/initial swing to clear foot

Dorsiflexors main actions

Control plantarflexion at initial contact, clear foot during swing phase

Plantarflexors main actions

Control tibia moving over foot during stance phase, provide propulsion during heel-off

Post Tib main actions

Decelerates and controls pronation during initial contact, supinates foot in midstance to toe off