Chapter 1 Flashcards Preview

Biomechanics II > Chapter 1 > Flashcards

Flashcards in Chapter 1 Deck (47)
Loading flashcards...
1

Factors to Consider in gait

Gait is efficient (100 calories/mile) when biomechanically sound

Complicated process a) 100 bones, 200 muscles involved

Significant involvement of pelvis and lumbar spine

2

Pronation

Eversion, dorsiflexion

In gait, it usually refers to movement of the calcaneus, which produces motion in the subtalar joint.

This is different than the way we use the term in posture analysis where it refers to a position of the foot.

In gait, it's a dynamic movement. In posture, it's a static position.

Importance in gait
A normal amount of pronation happens during gait.
An excessive amount can lead to problems.

3

Supination

Inversion, plantarflexion

In gait, it also usually refers to movement of the calcaneus, which produces motion in the subtalar joint.

Again, this is different than the way we use the term in posture analysis where it refers to a position of the foot.

In gait, it's a dynamic movement. In posture, it's a static position.

Importance in gait
A normal amount occurs during gait, but if excessive, can also lead to problems.

4

Phases of Gait

stance phase - weight bearing, approximately 60% of gait cycle

swing phase - toe-off to heel strike, approximately 40% of gait cycle

5

stance phase

heel strike

midstance

propulsive period

6

heel strike

(contact period)

Toe-off opposite foot

Knee extended

Foot dorsiflexed

Leg decelerating

Subtalar joint pronating throughout

Note that even though the subtalar joint is pronating (calcaneus rocking laterally), the foot itself is in a supinated position.

27% of stance phase

Major function: transfer weight and shock absorption

Note to remember:
At any given moment during the stance phase, the subtalar joint is doing the opposite of the position of the foot itself (pronation or supination).
o For example, if the foot is in a supinated position (e.g., heel strike), the subtalar joint is pronating.

7

midstance

Weight-bearing period between foot flat and heel lift

Toe-off completed for opposite foot

Foot in full contact with floor

40% of stance phase

Subtalar joint supinating

Note that even though the subtalar joint is supinating (calcaneus rocking medially), the foot itself is moving toward a pronated position.

Major functions:
bearing weight
convert foot from adaptive shock absorber to rigid lever for propulsion

8

Propulsive period

Period between heel lift and toe-off (push-off)

33% of stance phase

Subtalar supination continued and completed

Note once again that even though the subtalar joint continues to supinate (calcaneus rocking medially), the foot itself is in a pronated position.

major functions:
-transfer weight from lateral to medial side of foot, and to ball and toes for even propulsion
-shifting weight of body to other foot

9

Swing phase

toe-off to heel strike, approximately 40% of gait cycle

Acceleration phase

midswing

deceleration

10

Gait Determinants

Efficient gait has minimal vertical oscillations; additional energy is used for these vertical displacements.

Determinants are biomechanical properties which decrease vertical oscillations and allow for more efficient motion.

Normal oscillation pattern
High point: midstance (either foot)
Low point: double weight bearing (toe-off/heel strike)

11

Six classical determinants

Pelvic rotation

Pelvic tilt

Pelvis shift

Knee flexion

Knee-ankle relationship

Hip flexion

12

Pelvic rotation

Rotation of the entire pelvis away from the side of the forward leg

I.e., when the right leg is forward, the pelvis is rotated to the left.

4° to each side

Axis of rotation in the opposite hip

Result is decreased angle between leg and floor, and between hip and leg (i.e., decreased hip flexion)

Vertical displacement decreased by 3/8 "

13

Pelvic tilt

Pelvis dips inferiorly on the swing side (4-6°)

Opposite hip adducts (weight bearing hip)

Gluteus medius is important to prevent excessive adduction of weight bearing hip (Trendelenburg test)

Decreases vertical displacement 1/8"

14

Pelvis shift

Pelvis shifts toward stance side (approximately 1")

Hip adduction on stance side

Smoothes pelvic motion, helps maintain balance

15

Knee flexion

Stance leg knee goes from full extension (heel strike) to 15° flexion; knee re-extends as toe-off approaches

Important shock absorber

Decreases vertical displacement 1/8"

16

Knee-ankle relationship

Similar to knee flexion determinant

Ankle 90° at heel strike, plantar flexion follows, then dorsiflexion as toe-off approaches

As heel raises during toe-off, vertical lift smoothed out by knee flexion

17

Hip flexion

Acceleration stage of swing phase

Moves foot forward with minimal vertical undulation

Would have to raise pelvis without hip flexion

18

Which are the prime movers of gait?

Prime movers
(1) hip flexors/extensors



19

Major muscles of gait

Gluteus maximus and medius

Hamstrings

Gastrocnemius and soleus

Tibialis anterior

Quadriceps

Iliopsoas

TFL

20

Muscle activity during Heel Strike of stance phase

heel strike

(deceleration and
stabilization)
(a) Hamstring activity decreases
(b) Quads - extend knee
(c) Gluteus medius - stabilizes
pelvis, abducts hip
(d) Paraspinal muscles - keep
pelvis from dipping excessively
(e) Tibialis anterior - dorsiflexes
foot, eccentric contraction as foot makes contact

21

muscle activity during acceleration of swing phase

Acceleration

(a) Hip flexors (iliopsoas and quads) flex hip and accelerate forward
(b) Tibialis anterior contracts so toes clear floor

22

Concentric Contraction

the force generated is sufficient to overcome the
resistance, and the muscle shortens as it contracts.

23

Eccentric Contraction

the force generated is insufficient to overcome the resistance and the muscle lengthens as it contracts.

24

Muscle activity during midstance of stance phase

Midstance

(a) Body weight being pulled over
foot by the body's momentum
(b) Gastroc., soleus, and TFL
braking and controlling
(3) Toe-off
(a) Propel body weight forward (i.e.,
upward and toward other foot)
(b) Gastroc and soleus contraction

25

Muscle activity during Propulsion of stance phase

Toe-off

(a) Propel body weight forward (i.e.,
upward and toward other foot)
(b) Gastroc and soleus contraction

26

Which are the stabilizers of gait?

Stabilizers
(1) hip abductors/adductors

27

Which are the decelerators of gait?

Decelerators
(1) hamstrings and gluteus maximus to slow down swing

28

muscle activity during decelleration of swing phase

Deceleration

(a) Contraction of gluteus maximus and hamstrings decelerates and prepares limb for heel strike

29

What are the important aspects of physical examination of gait?

(1) Nervous system integrity
(2) Coordination and integration of movements
(3) Muscle strength and health
(4) Biomechanical integrity and stability of involved joints

30

What are the methods of evaluting gait?

a) Complex and difficult process to assess
b) Begin with general observation and overview
c) Break down into component parts