Biomechanics of Locomotion

Excess Supination

• Stress on the outer side of the foot

• results to ship splints, calluses, bunions

• foot rising above the ground as you walk

Excess Pronation

• Foot rolls toward the inside because the weight is more on the inside of the foot

• Normal foot arch should roll inward by only 15% or less (brief contact with the ground)

• The foot becomes flatter

• If flat footed, they are much likely to suffer from this.

Stride or Gait Cycle

• begins when the heel of one foot strikes the ground and continues up until the the heel of that same foot strikes the ground again

60%

• How much of a gait cycle is part of the stance phase?

40%

• How much of a gait cycle is part of the swing phase?

Stance Phase

• The foot of the corresponding limb is on the ground.

Swing Phase

• The foot of the corresponding limb is no longer the ground.

• It is swinging through to move the body forward

Initial Contact

• Start of loading response

• Beginning of stance period

• 1st part of the initial double-leg support

• Reference foot touches the ground

QAG - Quadriceps Femoris, Anterior Tibial Muscles, Gluteus Maximus

• Muscles used in initial contact.

End Terminal Stance

• C/L limb when reference limb is in initial contact

Loading Response

• reference foot is flat on the ground, receiving your weight forward

• weight is rapidly transferred onto the reference leg

• slight knee flexion to lessen impact

• weight acceptance

• 1st period of double limb support

QGG - Quadriceps femoris, gluteus medius, gastrocnemius

• Muscles used in loading response

Preswing

• C/L limb when reference limb is in loading response

Midstance

• carries all the body weight

• beginning of single limb support

• stability is a major concern

• body weight is balanced over stance leg

QP - Quadriceps femoris, plantar flexors

• Muscles used in midstance

midswing

• C/L limb when reference limb is in midstance

Terminal Stance

• Other limb advances over forefoot and trunk moves ahead of reference limb

• Reference limb now trailing in exrension

• Heel begins to lift off preparing for final push off

SG - Soleus, Gastrocnemius

• Muscles used in Terminal Stance

Terminal Swing

• C/L limb when reference limb is in Terminal Stance

Pre-swing

• Metatarsal heads contact floor, coinciding with the opposite foot making initial contact

• ends with toes-off

• end of stance phase

• toes are pushing off the ground

• 2nd period of double limb support

FH FD - Flexor hallucis longus, flexor digitorum longus

• Muscles used in Pre-swing

Initial Swing

• reference foot is lifted

• rapid knee flexion and ankle dorsiflexion

• shorten limb and meet demand to accelerate

• part of lim advancement, for foot clearance and limb advancement

IR - Iliopsoas, Rectus Femoris

• Muscles used in Initial Swing

Initial Contact-Loading

• C/L limb when reference limb is in Pre-swing

Early midstance

• C/L limb when reference limb is in Initial Swing

Mid-swing

• now under and anterior to HAT

• positioned directly opposite to contralateral limb

• small foot clearance

• limb advancement

ID - Iliopsoas, Dorsiflexors

• Muscles used in Mid Swing

Late Midstance

• C/L limb when reference limb is in Mid Swing

Terminal swing

• tibia perpendicular to floor

• full limb advancement forward as limb decelerates for initial contact

• gait cycle will repeat when foot touches the ground

• prepares for another stance phase

QH - Quadriceps femoris, hamstrings

• Muscles used in Terminal Swing

Terminal Stance

• C/L limb when reference limb is in Terminal Swing

Step Length

• Distance between successive heel strikes of two different feet

Step width

• Horizontal distance between heel centers of two separate feet

• 2-4 inches typically

Stride Length

• Distance between two successive heel strikes of the same foot

Velocity

• distance covered over a given amount of time

80 m/min

• average walking speed

Cadence

• Number of steps completed per unit of time (steps per minute)

50-120-130 steps/min

• average cadence of a typical adult

100-120 steps/min

• average cadence of men

105-125 steps/min

• average cadence of women

Stride Time

• amount of time to complete one stride or gait cycle

Step Time

• Amount of time to complete one step

Stance time

• amount of time to complete one stance

Sinusoidal (Symmetric) Curve

• As the body walks, the COG/COM follows a smooth curve or wave

Single limb support

• when is the COG at its highest?

Double limb support

• when is the COG at its lowest?

Pelvic Rotation

• Forward and backward rotation of the pelvis

• Happens to decrease displacement of COG

• Propels farther the limb

• longer step without lowering COG too much

• 8 degrees (4 forward and backward)

Pelvic drop

• seen in the stance leg in mid-stance

• minimize movement of the body’s COG

• 5 degrees

Lateral Pelvic Displacement

• Towards the stance phase when our pelvis shifts onto the stance leg; to bring weight to your base of support

Knee-Ankle-Foot Mechanism

• Knees will flex to decrease the height of the COG and to smoothen pathway of the COG (sinusoidal curve)

• Knee flexion and ankle dorsiflexion are for shock absorption (in stance phase) and for foot clearance (in swing phase)

• 5 deg to 15 deg

Trunk

• Leans 2-3 cm

• Rotates a few degrees

Right Arm

• swings back about 24 degrees

Left Arm

• swings forward about 6 degrees

Pelvis

• Rotates 4-8 degrees

Running

• increased velocity

• greater balance, muscle strength, and joint ROM

• swing distance is longer than stance phase

• reduced BOS

• No double limb support

Initial Contact

• Part of Running Gait

• Varies (heel, midfoot, forefoot landing)

• Depends on style and speed

• Quicker ground contact

• Higher impact force

Midstance

• Part of Running Gait

• Rapid weight shift

• Brief single-support

• Faster and dynamic transition

Propulsion

• Part of Running Gait

• Powerful and explosive push-off

• Flight phase (both feet are off the ground)

• Greater forward force

Swing Phase

• Part of Running Gait

• Forceful forward swing

• Higher knee lift

• Quicker and more forceful next step

Antalgic Gait

• walking secondary to pain that causes a limp

• Stance phase is shortened relative to swing phase

• Relates to a disorder of the lower back or lower extremity

• lifts and lowers their foot with their ankle fixed in one position

• Crutches are used

• Contralateral limb bears more weight to compensate

Ataxic Gait

• wide-based gait, difficulty standing with feet together

• cerebellar disease

• clumsy, staggering movements

• swagger back and forth and from side to side, titubation

• acute alcoholic intoxication

Titubation

• incordination, swaying of the body, poor balance

Scissoring Gait

• knees and the thighs are pressed or crossed together while walking

• spastic, paraparetic gait in which muscle tone in adductors is marked

  • High muscle tone in adductors

  • Internal hip rotation happens, upper limb cannot separate

• Hypertonia and flexion in legs

Trendelenburg’s Gait

• Excessive pelvic drop

• abnormal gait resulting from a defective hip abductor mechanism

• Gluteus medius and Gluteus Minimus

• Weakness causes drooping in C/L side

• Lateral tilt of the trunk, COG shifts on the stance limb, reducing the drop

• Slanted alignment of Pelvis and Hip

Steppage Gait

• Inability to lift foot while walking due to weakness of muscles that causes dorsiflexion

• raising the thigh up in an exaggerated manner

• difficulty in clearing the does during swing phase

• externally rotating the leg or feet

Parkinsonian Gait

• distinctive, rigid, less steady walk from changes in posture, slowness of movement, and a shortened stride

• lean unnaturally forward in a stooped position

• Shoulders down, hips and knees bent. Upper extremity is in flexion, fingers are usually extended

• Feet dragging on the ground, resulting in shuffling steps

• Involuntary inclination to accelerate

• Reduced arm swing