Principles of Movement Flashcards
Where does most human movement analysis occur?
A lab setting with high levels of variable control
Any movement in the sagittal plane occurs around which axis?
Frontal axis
Any movement in the transverse plane occurs around which axis?
Vertical / Longitudinal axis
Any movement in the frontal plane occurs around which axis?
Sagittal axis
What is Centre of Mass (COM)?
The average position of mass of an object
What is Centre of Gravity (COG)?
The point in an abject where gravity appears to be acting
What is the difference between COM and COG in relation to clinical movement analysis?
They are interchangable, the only way they would change significantly is if you went really high up a mountain
In the standard anatomical position, where is the COM?
Roughly the area of S2, near the bellybutton
What is the line of gravity?
A vertical line from the centre of gravity to the ground or surface the object or person is on
What affect does bending sideways have on both the COM and line of gravity?
The COM stays the same whereas the line of gravity moves sideways
What happens when the line of gravity leaves the base of support?
We become unstable
What are the three types of forces?
Gravitational (Weight)
Applied (Contact)
Inertial (Motion)
Force is a vector quantity, what does this mean?
It has both magnitude and direction
What unit is used to measure force?
Newtons (N)
On a diagram, how is force represented?
As a proportional arrow demonstrating both magnitude and direction
What is meant by the term load?
The force exerted on a surface or body
What is Newton’s First Law?
A body remains in the same state of motion unless acted on by an unbalanced force
According to Newton’s First Law what must happen to a body in order to for it to move?
An unbalanced force must act on it as a balanced force would cause it to remain in motion
What is ground reaction force (GRF)?
The force exerted by the ground on a body in contact with it
Rearrange Newton’s Second Law to find Acceleration, explain how this is relevant in relation to moving weight:
Acceleration = Force / Mass (a=F/m),
Meaning a heavier object will require more force to cause the same acceleration as an object of a smaller mass
What is Newton’s Second Law?
Force = Mass x Acceleration (F=ma)
According to Newton’s First Law, if a body is at rest and the forces acting on it are balanced, what will happen?
The body will remain at rest
Which of Newton’s Laws is being applied here?
“If A exerts a force on B, then B will exert an equal yet opposite force on A”
Newton’s Third Law,
Every action has an equal and opposite reaction
According to Newton’s First Law, if a body is moving and the forces acting on it are balanced, what will happen?
It will keep moving at a constant speed in a straight line
What is Newton’s Third Law?
For every action there is an equal and opposite reaction
What is a lever?
A body segment which rotates around a fulcrum (joint axis)
What produces rotation of a body segment around an axis?
An unbalanced force (most likely generated by internal muscle contraction)
What unit is used to measure a moment?
Newton Meters (NM)
What is moment?
The turning effect which a force has around a fulcrum dependent upon the size of the force and the distance of moment arm
Calculate the moment for this example:
A force of 40N is applied at 50cm from the axis of rotation:
Moment = Force x Distance Moment = 40 N x 0.5 M Moment = 20NM
What is the equation for moment?
Moment = Force x Distance
What is meant by the moment arm?
The perpendicular distance between the application of force and the fulcrum of movement
If a weightlifter is squatting 100ks, what is this force in Newtons?
1000 N
What is meant by resultant force?
The sum of forces acting in multiple directions causing a final effect
What is a collinear force system?
When lines of action of all the forces of a system are operating on the same line
or >–>
Tension is most likely caused by what type of force system?
Collinear when each side is being pulled away on the same line
What is a co-planar force system?
When the lines of action of a set of forces lie in a single plane
A sled push is an example of which force system?
Collinear
The trapezius muscle is an example of which force system?
Concurrent
The erector spinae and iliopsoas work together as a pelvic control anteriorly and posteriorly, what force system is this?
Co-planar
What is a concurrent force system?
Where all forces act on the same point
A scrum is an example of which force system?
Collinear
A seesaw is an example of which force system?
Co-planar
A tug of war is an example of which force system?
Collinear
What is a first order / class lever?
Where the fulcrum is located between the resistance and effort
What is a second order / class lever?
Where the resistance is located between the fulcrum and effort
What is a third order / class lever?
Where the effort is located between the fulcrum and resistance
What lever order is demonstrated through the hip abductors levelling the pelvis during gait?
Give the Fulcrum, Resistance and Effort:
1st Class, fulcrum in middle
Fulcrum = hip joint line
Resistance = weight on other side of body
Effort = TFL / Glut Med / Glut Min pulling down
What lever order is demonstrated through the calf muscle when taking a step?
Give the Fulcrum, Resistance and Effort:
2nd Class, resistance in middle
Fulcrum = Metatarsals
Resistance = Weight of the body slightly behind metatarsals
Effort = Gastrocnemius
How can you remember the order of lever classes?
1, 2, 3
F, R, E
What are most lever orders in the body?
3rd Class
What lever order is demonstrated through the arm lifting a weight (curl)?
Give the Fulcrum, Resistance and Effort:
3rd Class, effort in middle
Fulcrum = Elbow joint
Resistance = The weight in the hand
Effort = Biceps
What mechanical advantage is gained from a longer lever arm?
A larger moment can be generated for a given force
What is the resistance arm?
The distance between load and fulcrum
What is the effort arm?
The distance between effort and fulcrum
What does it mean to have a mechanical advantage of 1?
There will be no advantage (or disadvantage)
What does it mean to have a mechanical advantage of >1?
There is a force advantage and larger objects can be moved with less effort
