KINESIOLOGY: GAIT PART III (EXAM V)

____ _____:

- quadriceps active in the very late stage of swing phase in preparation for heel contact

- act concentrically to extend the knee and support the weight of the body during mid stance

- major burst of activity occurs shortly after heel contact

Knee extensors

____ _____:

- hamstrings are most active from just before to just after heel contact

- before heel contact: decelerate knee extension for foot placement

- initial 10% of stance: active to assist with hip extension and provide stability to the knee through coactivation

- short head of biceps femoris also assists with knee flexion during swing phase

Knee flexors

____ _____:

- 2 periods of activity: heel contact & swing phase

- heel contact: strong eccentric activation to decelerate passive PF

- deviation = foot slap

- from heel contact to foot flat, may also assist with decelerating pronation

- swing phase: produce sufficient DF of the ankle to cleat the toes from the ground

- extreme weakness results in "drop foot" during swing phase

Tibialis anterior

____ ____ compensations:

- increased hip & knee flexion

- hip hiking

- hip Circumduction on swing limb

- vaulting (stance side)

Tibialis anterior

_____ _____ & ______ ____ _____:

- decelerate PF of the ankle at heel contact

- assist with DF of the ankle and extend the toes during swing phase

- minor activity during push off may provide stability to the ankle through coactivation with the ankle PF

Extensor digitorum & extensor hallucis longus

Ankle _____:

- soleus and gastroc are active throughout most of stance phase (except during first 10%)

- from 10% of the gait cycle to heel off, they eccentrically control DF

- major burst of activity occurs near heel off and decreases readily at toe off

- push off: shortening which creates torque that helps with forward propulsion of the body

PF

____ ____:

- active from 5-55% of the gait cycle

- decelerates pronation (5-35%)

- supinates from 35-55% (mid stance toe off)

- acts both the foot & tibia throughout mid and late stance phase of gait

- deviation: excessive pronation

Tibialis posterior

______ muscles:

- brevis & longus active from 10% to just before toe off

- counteract strong inversion of deep posterior muscles

- longus assists to:

1. Hold the first ray rigidly to the ground, firm BOS

2. Foot acts as a rigid lever during terminal stance and pre swing

Fibularis

_____ muscles of the foot:

- typically active from mid stance to toe off

- stabilize the forefoot and raise the medial longitudinal arch (provides rigid lever)

- helps with controlling toe extension between heel off & toe off

Intrinsic

____ _____ ____:

- during ambulation forces are applied under the surface of the foot with every step

- foot forces: applied to the ground by the foot

- applied to the foot by the ground

- equal magnitude but opposite direction

- follows a Cartesian coordinate system (vertical, anterior, posterior, and medial lateral axes)

- peak is at a percentage of body weight

Ground reaction forces

_____ GRF:

- 120% BW

Vertical

_____ _____ GRF:

- 20% BW

Anterior posterior

_____ _____ GRF:

- 5% BW

Medial lateral

Vector summation performed for the vertical & anterior posterior components of the GRF leads to classic ____ representation of the GRF for a single step

Butterfly

____ forces:

- directed perpendicular to the supporting surface

- peak 2x in a given gait cycle

- slightly greater than BW at loading response and terminal stance (slightly less than BW in mid stance)

- GRF greater than BW is needed to decelerate the downward movement of the body during loading response

- relative "unweighting" of the body

- higher GRF at terminal stance serves to reverse the downward movement of the body's COM as the PF are pushing forward

Vertical

____ ____ forces:

- shear forces applied parallel to the supporting surface

- longer steps and faster walking speed increase the magnitude of horizontal GRF (increased friction between foot & ground needed to prevent slipping) —> why we take short narrow steps when walking on icy surfaces

- shear forces result from the COM being posterior or anterior to the foot

- propulsive force of one limb is counter balanced by braking force of opposite limb

- slowing down requires greater braking force and speeding up requires greater propulsive force

Anterior posterior

___ ____ forces at heel contact:

- GRF is in the posterior direction

- sufficient friction required between the foot and the ground to prevent the foot from slipping forward

Anterior posterior

____ ____ forces at terminal stance & pre swing:

- force directed anteriorly

- foot applies a posteriorly directed force to the ground to propel the body forward

- magnitude of the propulsive force depends on walking speed and attempts to accelerate

Anterior posterior

Peak anterior posterior GRF is typically equal to ___% of BW

20%

_____ directed GFR slows forward progression of COM

Posteriorly

_____ directed GRF accelerates COM

Anteriorly

____ ____ forces:

- magnitude is relatively small and more variable across individuals (depends on the relationship between the position of the body's COM and the location of the foot)

- during the rest of the stance, COM is medial to the foot creating a medially directed GRF

Medial lateral

____ ____ forces during initial 5% of gait cycle:

- small, laterally directed ground reaction shear force is produced to stop the small lateral to medial velocity of the foot

Medial lateral

Throughout stance ___ directed forces:

- decelerate the lateral movement of the COM initially

- then accelerate the COM medially toward the contralateral LE

Medially

The path of ___ ___ ____ under the foot throughout stance follows a relatively reproducible pattern

Center of pressure

The location of ___ ___ ____ helps to explain the tendency of the ankle & foot to PF and evert at heel contact

Center of pressure

____ ____:

- center of pressure just lateral to the midpoint of the heel

Heel contact

___ ____:

- lateral midfoot region

Mid stance

___ __ to _____ ____:

- medial foot region

Heel off to toe off

Joint surfaces, ligaments, and tendons are all subjected to large ___, ____ or ____ forces during walking

Tensile, compressive or shear