Musculoskeletal Forces Flashcards
what are external forces?
forces acting outside the body
what are internal forces?
forces derived from inside the body
What are the type of Internal forces?
Active forces
Passive forces
what are active forces?
forces produce by activated muscles
what are passive forces?
generated by passive tension in deformed tissue
Why do we produce internal forces?
predominantly via muscle contraction in order to control external movement tasks
What is the result of internal and external forces?
loading of body tissue
What are the external forces that act on the musculoskeletal system?
Gravity
Wind
Friction
What are examples of internal forces?
muscle
ligament
tendon
cartilage
what are examples of external forces?
gravitational forces
ground reaction forces
What is point of force application?
where the forces are applied
What is angle of force application?
the direction in which the force is applied
What is angle of muscle insertion?
The orientation of the muscle insertion relative to the long axis of the bone
What does the angle of muscle insertion dictate?
Dictates the angle at which the muscle applies force to move the segment
What is the moment or lever arm?
The perpendicular distance between the axis of rotation and the application of force
What does D and D1 represent?
D: internal muscle force moment arm
D1: external force moment arm
What are internal joint moments?
the product of the internal force and moment arm
ex: bicep produces flexion moment in elbow
what are external joint moments?
the product of the external forces and the external moment arm
ex: rotating elbow clockwise to extend elbow
What causes force production?
Activation of muscles by the nervous system
What are the types of muscle activation?
Isometric
concentric
eccentric
What is an isometric activation?
no movement of segment arm is in balance
What is an concentric activation?
force of muscle is able to exceed the external force on the arm
what is an eccentric activation?
external force overpowers the internal force; resists being pulled apart
What is the muscle actions at a joint?
The potential for the muscle to cause a moment in a particular rotation direction and plane
What are the planes of movement?
Frontal
Horizontal
Sagittal
What movements happen in frontal plane?
abduction
adduction
What movements happen in horizontal plane?
external rotation
internal rotation
What movements happen in the sagittal plane?
flexion
extension
What is an agonist muscle?
muscles most directed related to the initiation and execution of a movement
What is an antagonist muscle?
muscles hat have the opposite action as the agonist
During Knee flexion which muscle is the agonist?
Hamstrings
During knee flexion, which muscle is the antagonist?
Quadriceps
what is muscle synergy?
muscle groups that work together to execute a moment in a smooth and coordinated manner
ex: sit to stand uses extensor muscle group synergy
What is muscle force couples?
two muscles producing force in opposite directions resulting in a moment in the same direction
ex: the pelvis tilting
What are the types of lever systems?
1st class
2nd class
3rd class
Lever systems should be _____
Static Rotary Equilibrium (in balance)
What is the first class lever system?
External Force and Internal force are on opposite sides, have same magnitudes and same external and internal moment arms are the same distance
What is the 2nd class lever system?
Internal force has higher moment arm than external moment arm; external force is closer to axis of rotation and has less mechanical advantage; force needs to be higher to keep system in balance
What is the 3rd class lever system?
Internal force is closer to axis of rotation than the external force; internal force has to be doubled of external force; external forcer has larger moment arm; force need to be doubled the size of external force to keep system in balance
What is Statics?
Study of forces actin on a body at rest or moving with a constant velocity
What does static analysis provide?
A simple method for analyzing musculoskeletal problems and used to inform clinical physical therapy decision-making
What are the three laws on Newton?
Law of inertia
Law of acceleration
Law of reaction
What is the law of inertia?
an object at rest or traveling at a constant velocity remains at rest (or at constant velocity) unless acted upon by an external force
What is mass?
quantity of matter in an object
What is mass moment of inertia?
the amount and how mass is distributed in an object
what can inertia be thought of?
An object’s stubbornness to move
What is inertia proportional to?
an object’s mass
what is the law of acceleration?
If unbalance forces are acting on an object, a proportional acceleration in the direction of the greatest force is produced
What is law of reaction?
for every acton (force), there ia a reaction (opposing force) of equal magnitude but in the opposite direction; ground reaction forces
what is static equilibrium?
the sum of the internal and external forces and moments acting on the body are equal to 0
What is static Rotary Equilibrium?
the internal and external moments are equal and opposite
