Biomechanics Pt. 2 (9/3c) Flashcards
Proximal on Distal / Distal on Proximal
Different ways of moving, but provides same essential movement
If a Pt is struggling with a motion (EX: prox on dist), you could consider the complimentary motion (EX: dist on prox)
Kinetics
describes the effect of forces on the body
Force
a push or pull that can produce, arrest, or modify movement
Force = mass*acceleration
When acceleration is zero, force equals ___
zero
Standard International Unit for Force
Newtons (N) = 1 kg x 1 m·s2
Force is mathematically displayed/defined as a ___
vector
Vector
has magnitude AND direction, often represented by arrows
Magnitude = length
Direction = indicated by arrow head
Internal forces (IF)
forces derived from inside the body
External forces (EF)
produced by forces acting outside the body
Humans produce IFs mostly via ___ ___ to control EFs during movements
muscle activation
Interaction between IFs and EFs result in
Loading of body tissues
Active forces (IF)
forces produced by activated muscles
Passive forces (IF)
forces generated by passive tension in stretched tissues
Examples of external forces
Gravity, wind, friction
Point of application
where forces are being applied
Especially in relation to joint’s axis of rotation
Angle of insertion
orientation of the muscles insertion relative to the long axis of the bone
Dictates the direction of application of force to the bone
Moment arm/Mechanical advantage
distance between the force acting on the body and its axis of rotation
Muscle force is applied to the bone segment at a distance (D) from the axis of rotation of the joint
D1 moment arm > D moment arm
D1 moment arm is (less than/equal to/greater than) D moment arm?
Greater than >
Joint moment
muscle force x moment arm
D= muscle force moment arm
D1= external force of gravity acting on forearms center of mass
Moment
torque
Linear kinematic measures
Force
Newtons (N) OR Pounds (lbs)
Angular kinematic measures
Moment/torque
Newtons x meters (Nm) OR Foot pounds (ft-lbs)
Static Linear Equilibrium
internal force = external force
EX: Internal force= biceps muscle force
External force= weight of forearm
Joint reaction force= reaction force of humerus pushing down
Static Rotary Equilibrium
internal moment = external moment
no rotation occurs around the joint
Internal moment (IM)
muscle force x internal moment arm
External moment (EM)
external force x external moment arm
Muscle action
potential for a muscle to produce osteokinematic rotation around an axis of rotation in a plane of motion
based on anatomical positions and there can be multiple movements based on orientation
When a muscle contracts, the ___ segment moves
Freest
3 Types of Muscle Activation
Isometric
Concentric
Eccentric
Isometric muscle activation
muscle produces force while maintaining constant length
Internal moment = external moment
Concentric muscle activation
muscle produces force while shortening
Internal moment > external moment
Eccentric muscle activation
muscle produces force while lengthening
Internal moment < external moment
Muscles do not actively lengthen
Agonist muscle
muscle or muscle group most directly related to initiation or execution of a movement
EX: biceps = agonist for elbow flexion
Antagonist muscle
muscle or muscle group that has an opposite action of the agonist muscle or group
EX: triceps = antagonist for elbow flexion
Muscle synergy
muscles often work together to produce a particular movement/task
Force couples
forces in opposite directions working together to produce a movement in one, same direction
EX: turning a steering wheel
