Unit 2 Flashcards
Myotatic/Stretch reflex
responds to quick stretch with muscle contraction
Where/what is receptor in stretch reflex
muscle spindle in the muscle belly
tendon reflex
responds to muscle tension with muscle relaxation
where/what is receptor in tendon reflex
golgi tendon organ in tendon
force
pushes or pulls through direct mechanical contact or through force of gravity to alter motion of an object
-pushes or pulls
-ability to accelerate or decelerate
-ability to deform object
vector quanity
has magnitude, direction, and point of application
Muscle force vectors
LOA with force vector arrows
- longer arrow means more force
- arrowhead shows direction of force
- point of application is origin/insertion
Force of a muscle determined by
- generally # of muscle fibers contracting determines total muscle force
- muscle size, shape, and fiber arrangement
what are the two types of fiber arrangements
parallel and pennate
Parallel fiber arrangement
arranged parallel to the length of the muscle, produce most ROM
- brachioradialis, sartorius, rectus abdominus, pectoralis major
Pennate fiber arrangement
fibers arranged obliquely to their tendon, produce the most force
- tibialis posterior, rectus femoris, deltoid
what is maximal force influenced by
- nervous system activation
- muscle length
- muscle velocity
how does nervous system activation influence maximal force
highest with high frequency of firing of motor units
how does muscle length influence maximal force
close to resting generates more force than shortened or lengthened position
how does muscle velocity influence maximal force
as resistance increases, maximal velocity a muscle can contract concentrically decreases
as resistance increases, eccentric velocity increases
Angle of pull
angle between LOA and the bone on which it inserts (angle toward the joint)
moment force (rotary force)
when a muscle pulls straight up from the bone, it has the most movement force (90 degree angle of pull)
-closer to 90 degrees, the more movement force
Stabilizing force (non-rotary force)
smaller angle of pull = higher stabilizing force
destabilizing force (non-rotary force)
greater angle of pull is more destabilizing >90
how does muscle’s AOP change
changes with joint motion, even if muscle force stays the same, movement force and stabilizing force changes as the joint moves
stabilizing muscles
small angle of pull regardless of joint position
- rotator cuff, subclavius, deep lateral rotators of the HJ, popliteus
patella role
changes the angle of pull of muscle providing force
- increases AOP
- increases moment arm
- increases movement force,
- increase effort torque
- decreases stabilizing force
torque
a turning effect produced by a force
- force not through center of mass or axis of rotation produces torque
torque equation
force magnitude X length of the moment arm
Moment arm
perpendicular distance from the line of force to the axis of rotation or center of mass
resistance torque
torque created by weight you are trying to move
effort torque
torque created by your muscles
concentric movement
effort torque > resistance torque
Isometric movement
effort torque = resistance torque
Eccentric movement
effort torque < resistance torque
how can force and moment arm modify resistance torque
force: light or heavier weights
Moment arm: modify technique - change either axis of rotation/cm of where the resistance force is applied
how can force and moment arm modify effort torque
Force: ns activation, muscle length, contraction velocity
Moment arm: change joint angle
rotary force
does not pass through axis of rotation, produces torque
non-rotary force
passes through axis of rotation, no moment arm, doesn’t produce torque
lever
a rigid bar that can rotate around a fixed point when an effort force is applied to overcome a resistance force
what is the fulcrum/axis of rotation in the bodies
joints
what is the effort force in joints
contracting muscles
effort arm
moment arm of the effort force
- perpendicular distance from LOA of a muscle to the joint
Resistance arm
moment arm of the resistance force
- perpendicular distance from the resistance force to the joint
balance of levers
MA = 1, the product of the effort and effort arm equals the product of the resistance and resistance arm
Mechanical advantage
MA >1 easier to move resistance
Mechanical disadvantage
MA < 1 more effort for less resistance but resistance moves further and faster
MA equations
R/E
EA/RA
Agonist muscles
the concentrically or eccentrically contracting muscles during the exercise
- active
Prime movers
muscle that contributes most to the movement
Assisters/synergists
muscles that assist with the movement
Antagonist
muscle that would perform an action opposite the antagonist
- passive when performing a lift or controlled lowering exercise
- opposite side of joint to the agonist
Stabilizer (fixator)
contract isometrically to fixate or stabilize the area to enable another segment to move
Neutralizers
prevent undesired action of one of the agonists
Steps to naming agonist group
- determine which phase of the exercise is the lifting phase
- determine action during this phase
horizontal movement agonist group
muscle group causing (starting) the movement is the agonist
