Biomechanics
The use of math and physical principles to study and understand movement
Kinematics
The study of movement without regard to the forces that cause that movement
i.e. How far, how much, how fast
Kinetics
The study of forces causing a movement i.e. muscle forces, gravity
Movement is in ____ and about _____
a plane of motion and about an axis of motion
Which movements take place about the anteroposterior axis
abduction/adduction
Which movements take place about the mediolateral axis?
Flexion extension
Which movements take place about the longitudinal axis
Rotation
Supination
Pronation
Which axis of rotation corresponds with the frontal plane of motion
Anteroposterior
Which axis of rotation corresponds with the sagittal plane of motion
Mediolateral
Which axis of rotation corresponds with the transverse plane of motion
longitudinal
Newtons 3 laws?
- motion stays in motion unless an unbalanced, external force is applied to it
- F = ma
- For every action there is an reaction of equal magnitude and opposite in direction
Arthrokinematics
movement between joint surfaces
Osteokinematics
movement between bones
Kinematic chain
linkage of rigid bodies
Why is closed chain greater risk of injury
- because of degrees of freedom
- Closed chain removes degrees of freedom making it harder to change positions
A force is any..
push or pull
How much an object deforms is relative to..
how much stress or force is put on it
Stress =
force
Strain =
length
What changes a stress straiin curve
different material properties
What occurs in the plastic zone of the stress strain relationship
You get disproportionate change in length for given change in force - greater change in length for given force
What does the slope of the stress strain curve represent
stiffness
In the envelope of function what are the 3 zones and the x and y axis
x - frequency y - load Zones: 1. Homeostasis (ADLs) 2. Supraphysiological overload 3. Structural failure
Overstepping you maximum capacity to adapt will result in…
- pain during your effort
- pain after
- morning stiffness
IN the body, do different tissue types have different stress strain responses
yes - 3 different reactions to same strain
what are some reasons the same tissue type undergoing the same stress may tear in different situations
- Temperature
- Fatigue
- Direction of force
- Previous injury or microtears
- Warm-up
- Age
How does emphysema relate to the stress strain relationship
emphysema - lung tissue no functioning as it should. for a given force the lungs of healthy patients stretch more than those of patients with emphysema. Greater energy expenditure to get the same stretch
When does isometric contractions occur
when force is generated by the muscle but is equivalent to external resistance
Force = resistance or equal moments
The relationship between ____ and ____ will dictate the resultant linear/angular motion of a segment
internal forces/moments and external forces/moments
are all muscles always acting throughout the whole movment
no may contract eccentrically, concentrically or not at all
What are external forces
forces acting outside the body
What is a moment
the angular equivalent of force - any push or pull that makes a rotational force
equation for moment
M = f x d
What is the moment arm
the perpendicular distance from the line of action of the force application to the axis of rotation
Moments cause ____ rotation due to ____ force production when one end of a linkage is fixed
angular
linear
What are the two types of linear forces (that we are concerned of in this class)
Shear force
Compression force
Shear force occurs ___ to segment
perpendicular
Compression forces occurs ____ to segment
parallel
What is newtons second law of angular motion - include equation
An object of inertia will angularly accelerate proportional to the Moment applied to it, and inversely to its inertia
Sum(F x d) = I x a
Inertia is ..
the angular component of mass
Biomechanically, the magnitude of the moment is mainly dependent upon the…
joint angle
The joint angle changes two things
effect on moment arm
effect on force generation (actin myosin overlap)
1st class level
Muscle force and resistance force act on opposite sides of the axis
What is an example of a first class lever
occipital condyles in head
2nd class lever
Resistance force is between the muscle force and the axis
What is an example of a 2nd class lever
metatarsal joint
3rd class lever
Muscle force is between the axis of rotation and the resistance force
example of 3rd class lever
elbow
Most anatomical levers are ___
3rd class levers
What is mechanical advantage
the ratio of the muscle moment arm to the resistance moment arm
What is the equation for Mechanical advantage
MA = moment arm muscle/moment arm resistance