Kinesiology Exam 2-Biomechanics

Front 1

what is biomechanics?

Back 1

the study of the mechanics as it relates to the FUNCTIONAL and ANATOMICAL analysis of biological systems and especially humans

Front 2

understanding levers: force and torque.
FORCE:

Back 2

that which pushes or pulls through direct mechanical contact or through force of gravity to alter the motion of an object:
-pushes or pulls on an object.
- ability to accelerate an object
-ability to deform an object

Front 3

force is a _____ quantity

Back 3

vector
-magnitude and direction
-also a point of application
-direction of force

ex: all three characteristics must be identified- for a weight lifter to lift a 250 N barbell. the lifter must apply force greater than 250 in an UPWARD direction, through the CENTER OF GRAVITY of the barbell

Front 4

magnitude of Muscular force

Back 4

direct proportion to the NUMBER AND SIZE of fibers contracting in a muscle

-influenced by muscle length
-represented by the length of the force vector

Front 5

point of application

Back 5

point at which force is applied to an object.
this point is always through the center of gravity
-the muscles attachment to a boney lever
- on the mechanical axis of the bone

Front 6

direction of the muscular force vector

Back 6

is the direction of line of pull of the muscle
-described as the angle of attachment
-it's the angle between line of pull and the portion of mechanical axis between the point of application and the joint

Front 7

analyzing the force vector allows you to understand how muscle force:

Back 7

stabilizes the joint
and causes motion of the segments

Front 8

vector components

Back 8

rotary: perpendicular to non rotary
non rotary: always on the mechanical axis. parallel to mechanical axis of bone

0 degrees =all non rotary
(less than)<45> rotary
>45 degrees but <135> non

90 degrees= all rotary (strongest force)
>135 degrees non > rotary

often the angle of pull for a muscle is <45 degrees so more STABILIZATION is produced than joint motion

Front 9

levers 3 components

Back 9

axis of rotation (A): the axis is the point at which the lever moves.
Force (F or effort E): force being applied to it to cause its movement against a Resistance (R) or weight.
(look on page 70)

Front 10

different classes of levers

Back 10

first class: FAR or EAR (the resistance arm and force arm are moving in opposite directions). used to produce balanced movement (agonist is producing force, antagonist is providing resistance) ex: seasaw

secondary class: ARE or ARF (resistance arm and force arm are moving in the same direction). designed to produce movement. large resistance can be moved by a small force. ex: wheel barrel, plantar flexion of the ankle to move the body up onto its toes.

third class:RFA or REA (resistance arm and force arm are moving in the same direction). designed to produce speed and range of motion and range of motion (most common type)

Front 11

how does the patella effect angle of pull and the rotary and non-rotary components?

Back 11

it changes the angle of pull of the muscle providing the force

-this increase in angle of pull increases the rotary component.

ex: if we did not have our patella the line of action would be much more shallow and the rotary component would not be perpendicular. we basically wouldn't be able to walk. the closer the muscle is to the bone the less range of motion you get

Front 12

what is eccentric force?

Back 12

not through the CM (center of mass) or axis of rotation, produces torque. goes through the side

Front 13

what is torque?

Back 13

the turning effect of an eccentric force: also known as moment of force or moment

-equals the product of the : force magnitude and the length of the moment arm

Front 14

torque: Moment arm

Back 14

is the perpendicular distance from the line of force to the axis of rotation.

torque may be modified by changing either: force or moment arm

the moment arm only exists when it is eccentric (different than contraction)

Front 15

example: Door.
for equal torque...

Back 15

a small MA (really close to axis of rotation-door hinge) needs a LARGE force

a medium MA needs a medium force

a large MA needs a small force

Front 16

body weight of a segment can be altered instantaneously so...

Back 16

torque of a segment due to gravitational force can be changed only by changing the length of the moment arm
ex: think of a crunch. when your up the moment arm (between ~ribs to hips) gets smaller

Front 17

force x moment arm=

Back 17

torque

Front 18

look at page

Back 18

74-75! for levers!!!

Front 19

what are the functions of levers?

Back 19

-overcome a resistance larger than the magnitude of the effort applied (using a small force to overcome a large resistance) ex: car jack, wheel barrel

-increase the speed and range of motion through which a resistance can be moved (used to gain range of motion and speed at the expense of force) ex: hitting a golf ball

-Balance force (used to balance a force and a load) ex: seasaw

Front 20

the principle of levers

Back 20

any lever will BALANCE when the product of the force and the force arm equals the product of the resistance and the resistance arm
OR
when the force torque equals the resistance torque
FxFA=RxRA

Front 21

mechanical advantages of levers

Back 21

MA>1=EA >RA= mechanical advantage- multiple force

MA&lt;1>&lt;ra>&lt;1>1, =1
2nd class= EA >RA >1
3rd class=Ma is &lt;1 less than one

EA/RA or R/E (if the EA is bigger than RA then it is an advantage)

Front 22

short levers enhance angular velocity while...


strength needed to maintain angular velocity increases as

Back 22

sacrificing linear speed and range of motion


the lever lengthens

Front 23

what needs to be considered when analyzing rotary motion?

Back 23

torque and levers

Front 24

so what is the best position for the body to be in when we are trying to produce the maximum amount of torque (how do you position yourself when you have to push a heavy piece of furniture)

Back 24

get low and even with the piece of furniture

Front 25

how does the musculo-skeletal system designed with mainly 3rd class levers work to our benefit

Back 25

range of motion. limbs can go fast and far

Front 26

describe the torque, as joint goes from extension to mid flexion to full flexion

Back 26

small big small