Biomechanics

Question 1

Body components of biomechanics

Answer 1

1.) Bones
act as lever arms
2.) Muscles
pull on the bones (contract) to create motion or can
relax to move bones
3.) Joints
influence the degree of freedom of the movement
4.) Ligaments
passive restraint of joints
5.) Tendons
transfer force from muscle to bone
6.) Nervous system
feedback and control over muscles

Question 2

Degrees of freedom of the spine

Answer 2

• three axises yeild 6 degrees of freedom PLUS ability to translate

Question 3

translation

Answer 3

sliding along the transverse plane in infinite number of directions

Question 4

What makes up a lever system

Answer 4

• Fulcum (joint)
• Applied force (muscle = effort)
• Resistance (weight of limb= load)

Question 5

1st Class Lever

Answer 5

fulcrum is between the effort and the load

• trapezius, head, and neck

Question 6

2nd class lever

Answer 6

fulcrum on the end, load in the middle, effort on the other end

• wheel barrow example
• Gastrocs

Question 7

3rd class lever

Answer 7

fulcrum at one end, effort in the middle, load on other end

• elbow, biceps, load in hand

Question 8

Which levers are faster?

Which are more powerful?

Answer 8

Class 1 and 2 are most powerful

Class 3 is fastest

Question 9

Lever class most common in the body

Answer 9

Class 3

Question 10

Where does the effort get distributed?

Answer 10

• Some to the load
• Some to the joint

Think of elbow example- get compression of the elbow joint

Question 11

Moment arm in biological systems

Answer 11

perpendicular distance from the line of action of the muscle to the axis of rotation (joint)

• longer moment arm = more force (more mechanical advantage)

Question 12

Line of pull

Answer 12

Not what a muscle attaches to but where it attaches that matters

**About how a muscle crosses a joint

Question 13

Concentric contraction

Answer 13

muscle shortens and contracts (decrease in joint angle)

Effort exceeds resistance

Question 14

Isometric contraction

Answer 14

Contraction occurs

No movement of the joint

Question 15

Eccentric contraction

Answer 15

muscle lengthens and there is increase in joint angle

Resistance exceeds effort

Question 16

Tone

Answer 16

Continuous low level contraction at all times (no true off)

Question 17

Discuss the changes in moment arm as the elbow flexes and the ability of the bicep to create torque at elbow

Answer 17

• Strongest at 90 degree angle (all of the effort goes to moment arm, none to compression)
• Weakest when arm is straight ( getting more compression and shorter moment arm)

Question 18

does movement only occur through stimulating contractions?

Answer 18

No- you can relax muscles to fall down on purpose

Question 19

Length-Tension Relationship

Answer 19

• Changes in strength is due to length of a muscle

Question 20

Tension

Answer 20

• two opposing pulling forces that stretch and object

Question 21

Compression

Answer 21

• two opposing forces that push towards each other

squeezing IV disc

Question 22

Shear

Answer 22

two opposing forces not inline with one another causing adjacent segments to move opposite

Question 23

Torsion

Answer 23

-Twisting that causes one section to go clockwise and another section to go counter clockwise

Question 24

Disc prolapse

Answer 24

• occurs during sudden compression coupled with flexion and lateral flexion (may include rotation)

Question 25

Where does the highest frequency of spine injury occur? why?

Answer 25

T12-L1

has highest torsional stiffness (highest stress concentration)

Question 26

Cervical trends of motion

Answer 26

• good rotation almost throughout
• good lateral flexion in the middle
• C5/C6 is the most mobile of all the vertebral column

Question 27

Cervical Coupling

Answer 27

-lateral felxion and rotation work together
- rotation proceeds lateral flexion then both occur
together

Question 28

Thoracic trends of motion

Answer 28

• flexion amount increases the more you go down
• Lateral flexion improves with floating ribs (T11)
• rotation lessens in lower thoracics ( Facet joints in the
  saggital plane)

Question 29

Lumbar trends of motion

Answer 29

• good flexion and extension in the lumbar region

- poor rotation throughout lumbar