Biomechanics Flashcards
Biomechanics
the application of mechanical laws to living structures, specifically to the locomotor system of the body
Application of biomechanics analyses
- improvement in sports skill techniques
- design of sports equipment
- prevention of injuries
- clinical analyst of movement pathogens
- design of prostheses
Qualitative movement analysis
a non-numerical description based of a movement on direct observation
Quantitive movement analysis
a movement is analyzed numerically based on measurements from data collected during movement
Mass
quantity of matter contained in an object (kg)
Force
mass x acceleration (N)
Weight
amount of gravitational force exerted on body
Volume
amount of space that a body occupies
pressure
force distributed over a given area (pressure= force/area)
Compression
pressing or squeezing force directly axially through a body
Tension
pulling or stretching force directly axially through the body
shear
force directed parallel to the surface
mechanical stress
F/A similar to pressure
Lever
a rigid bar that turns about the axis (bone)
force point
exact point where force is applied (contraction of muscle)
resistant point
exact point where resistance acts
fulcrum
axis of motion (joints)
Example of first class levers
- teeter-totter
- seesaw
Example of a first class lever in the human body
Triceps muscles acting on elbow joint
Example of a second class levers
- wheelbarrow
- bottle opener
The third class lever is most common in an our body (T/F)
TRUE
An example of a third class lever in the human body is
the biceps muscle producing flexion at the elbow joint
Third class levers are always ________ levers because….
speed levers because FA is always less than RA
NOTE: F x FA = R x RA
Mechanical advantage formula
MA=FA/RA
When FA of. a lever is long than its RA what type of lever is this?
Force lever
When RA is longer than force are it is called a
Speed lever
If RA is three times as long as FA what is the mechanical advantage
MA=1/3 (when force point is going down 1m, the resistance point will move 3m in same period)
What is the force arm?
It is the perpendicular distance from the fulcrum to the line of action of the force acting on the force point
What is the resistant arm
it is the perpendicular distance from the fulcrum to the line of action of the resistance acting on the resistance point
First class levers can be have mechanical advantage of?
MA= 1
MA= > 1 (FA>MA)
MA= <1 (FA<MA)
2nd class leavers are always _________ and 3rd class levers are always ____________
1) force
2) speed
Describe moment arm
the perpendicular distance between the forces line of action to the axis of rotation
Torque is though as a _______ force
rotary
The formulas for Torque is
Torque = F x D (moment arm)
What is the centre of gravity
it is an imaginary point in the centre of the body where the weight of the body is balanced
What can be defined as the centre of gravity
- the point of intersection between cardinal planes (frontal plane, sagittal plane, traverse plane)
-The point of exact centre where the body can rotate free in all direction
-The point around which the weight is equal on all opposite sides
where is the CG approximately located for the human body
6 cm below the belly button or 5 cm anterior to the second sacral vertebra
What influences CG
- changing body positions or limb positions
- addition of external weight (like a backpack)
Why is it important to determine CG?
- used to describe movement of body through space
- important for stability
- important factor in calculating amount of work done
Reaction board method
used for static position of human body
describe balance and where should CG be located
ability to control equilibrium
CG must remain within the base of support
describe stability
firmness of balance
How to increase stability
- increasing body mass
- increase size of the base of support
- increase friction between body and surface contacted
- horizontally position CG near the edge of the base of support towards the oncoming external force
- vertically position the CG as low as possible
Describe newtons first law
Law of inertia
- a body will maintain in a state of rest or constant velocity unless acted on by an external force that changes its state
Inertia is directly _________ to mass
proportionally
Describe newtons second law
Law of acceleration
F = ma
Describe newtons third law
Law of inertia
- When a body exerts a force on a second body, the second body exerts reaction force of equal magnitude in opposite direction on the first body
What is the equation for momentum
momentum = mass x velocity
The formula for work is
Work (J) = Force x Distance
What is power formula
Power (w) = Force x velocity
In running….
1) there is a period where both feet are off the ground
2) there is no period where both feet are in contact with the ground
In running, the __________ phase is a much smaller portion in the total gait cycle than walking
stance
Powerwalk?
kinetic energy harvester
When EH is on what happens
20% drop in metabolic cost and 28% drop muscle activity
Equation for running speed is
running speed = stride length x stride rate
Length of stride is primarily dependent upon leg ______ and __________ of stride
1) length
2) power
What does leg speed depend on
it depends on muscle contraction and neuromuscular coordination in running
When lifting a heavy box you should
1) get someone to help to minimize the actual weight of the load being handled
2) ensure you have a stable base, so stand facing the object with your feet flat at shoulder width and pointing straight ahead
3) keep the object as close to your body to minimize reaction torque on lower back
4) face in the direction in which you intend to move the object
5) get a good grip so you don’t loose control
A rounded back can cause ________ disc compressive force and ligament strain
L5/S1
The probability of ___________ is increased by repeated full _________ of trunk
1) herniation
2) flexion
How will standing or extending the trunk benefit you before you go to lift a heavy object
it will prepare the disc and the posterior passive tissues to reduce risk of injury
