9/3c Biomechanics Part 2

Question 1

what does force cause

Answer 1

motion

Question 2

internal forces

Answer 2

muscle force/contraction - any force within the body

Question 3

external force

Answer 3

produced by forces acting outside of the body

• gravity + the weight of a part of the body
• wind
• friction
• change in movement in response to external forces

Question 4

musculoskeletal forces

Answer 4

humans are constantly producing internal forces (predominantly during muscle activation) in order to control external forces during movement tasks

Question 5

active force

Answer 5

muscle activates

Question 6

passive force

Answer 6

forces are generated by passive tension in stretched tissues

-someone moving your body OR doing a quad stretch

Question 7

point of application

Answer 7

where forces are being applied in relation to the axis of rotation

Question 8

center of mass

Answer 8

location where the gravitational forces are being applied at any limb/element of the body

Question 9

angle of insertion

Answer 9

• orientation of the muscles insertion relative to the long axis of the bone
• when you change the angle of insertion, the total force is broken into x and y components
• at 90 degrees force is optimal

Question 10

muscle moment arm

Answer 10

distance between the force that is acting on the body and its axis of rotation

Question 11

what does muscle force do to a joint?

Answer 11

it creates a torque/moment about the joint allowing for rotation

Question 12

linear force measure

Answer 12

N or lbs

Question 13

angular force measure

Answer 13

Nm or lbft

Question 14

static rotary equilibrium

Answer 14

internal moment = external moment:
(Muscle Force x Muscle Force Distance from joint axis of rotation) = ((mass of limb x gravity) x center of mass distance from the joint axis of rotation)

Question 15

Static linear equilibrium

Answer 15

internal force = external force:

force generated by the muscle = reaction force pushing off of joint that muscle is acting on

Question 16

in which position would a PT have to apply more force to maintain specific rotary equilibrium?

Answer 16

the position where the moment arm is less

Question 17

Is a shorter moment arm advantageous to a patient?

Answer 17

Yes and no - the patient has to exert more force, but it makes it harder for the PT to then break their position

Question 18

Muscle Activation

Answer 18

I - Isometric
C - Concentric
E - Eccentric

Question 19

Isometric activation

Answer 19

muscle produces a force while maintaining a constant length. STATIC

Question 20

Concentric activation

Answer 20

Muscle force overcomes the external force and muscle shortens. M(internal) > M(external)

Question 21

Eccentric activation

Answer 21

Muscle produces a force while lengthening. Negatives at the gym, muscle resists being pulled apart - does NOT actively lengthen. M(internal) < M(external)

Question 22

Can muscles have multiple actions based on the position of segments?***

Answer 22

YES

Question 23

Does internal moment arm change when the joint position changes?***

Answer 23

YES - think about a rod with an axis of rotation closer to you vs farther away from you and you are the muscle force. it will be easier for you to rotate the rod when the axis of rotation is farther away from you

Question 24

Conceptual framework for muscle

Answer 24

when a muscle contracts the free-ist segment moves
a muscle action can be produced if a moment arm/mechanical advantage is present for that plane of motion (same muscle can have multiple actions depending on the moment arm and axis of rotation)

Question 25

agonist muscle

Answer 25

muscle or muscle group most directly related to initiation or execution of a movement
-biceps agonist for elbow flexion

Question 26

antagonist muscle

Answer 26

muscle or muscle group that has the opposite action of the agonist muscle group
-triceps antagonist for elbow flexion

Question 27

muscle synergy

Answer 27

muscles work together in synergy to produce a movement

Question 28

force couples

Answer 28

forces in opposite directions produce a movement in 1 direction
-straight leg raise: force couple between your erector spinae, iliospoas, and sartorius