Flashcards in Module 5 Deck (77):
If the force of the muscle's contraction is greater than the resistance to the muscle's contraction...
the muscle will shorten
What is a concentric contraction?
Where the muscle contracts and shortens
If the force of the antagonist is greater than the force of the muscle...
the muscle will lengthen instead of shorten (eccentric contraction)
What is an eccentric contraction?
When the muscle contracts and lengthens
If the force of the muscle's contraction is exactly equal to the resistance force, then the muscle will...
neither shorten nor lengthen (isometric contraction)
What is the mover?
Muscle that generates the force that moves a body part to create the joint action that is occurring ("the action in question").
If the force of the weight of the forearm is greater than the force of the brachialis contraction, the brachialis is eccentrically contracting. What is the mover and what is the antagonist?
What are resistance exercises?
Exercises that incorporate weights, bands, tubing, etc. to train the muscle to contract with greater force than the resistance
What is an isometric contraction?
When the muscle contracts and stays the same length (force of muscle is same as force of resistance)
Why is aqua therapy important for rehabilitation programs?
Supports the body part being moved and decreases the resistance force to the muscle's contraction; gentle way to begin strengthening exercises
If an arm is held out at 90 degrees and we start to adduct, what keeps us from smacking the arm into the body (from gravity's pull)
Eccentric contraction of the abductor muscles, slowing down the movement
What defines a muscle contraction?
When cross-bridges form and create a pulling force toward the center of the sarcomere (even in eccentric/isometric contractions)
If a Z-line is fixed, how does the sarcomere shorten?
Myosin on fixed side slides instead of actin
What is tension?
A pulling force
A muscle is defined as contracting when it generates a _____ force toward its center
What is tone?
Muscle generating tension
What is gravity?
Force caused by the mutual attraction of all physical matter (mass of objects).
Largest mass is Earth, so gravity pulls us downward
The force that gravity exerts on the mass of an object is defined as the _____ of the object
What is gravity-neutral motion?
One in which gravity neither resists the motion nor aids it (when body part is being moved horizontally)
Ex: scapular retraction is a concentric contraction that is gravity-neutral
What kind of contraction is required if we want to move the arm downward faster than the force of gravity (or against a resistance pulling upward)?
What is a negative contraction?
Another term for eccentric contraction because the contraction opposes the force that is creating the action that is occurring (acts as antagonist)
When do eccentric contractions occur?
Usually when force of eccentric contraction is needed to slow down a movement caused by gravity or some other external force
What direction is the force of an eccentric contraction when slowing down act of gravity?
How does eccentric contractions work in slowing momentum of horizontal motion?
If muscle that initated movement were to relax, momentum would keep the body part moving farther than we might want - use eccentric to slow it down
Can we use eccentric contraction to slow momentum of vertical upward motion?
yes - if body part is moving upward too quickly
Which car pedal relates to concentric contractions? eccentric?
Concentric: gas pedal
Eccentric: brake pedal
Although muscles can shorten, lengthen, or stay the same length, the muscle is always generating a _______ force toward its ______
pulling force toward its center
Concentric contraction _____ movement
Eccentric contraction _____ movement
Isometric contraction ______ movement
A muscle that holds a body part in a static position is said to ______ that body part
fix / stabilize
Muscles that fix a body part in place are called
Fixator or stabilizer muscles
Does a mover shorten or lengthen?
What if a mover is eccentrically contracting?
It is no longer the "mover" because it is no longer shortening or causing the "action in question". It is now an antagonist.
A mover muscle can shorten in what 2 ways
1. Concentrically contract and shorten, generating force to create action in question
2. It is relaxed and shortened, because attachments are brought closer together as the joint action is created by another mover force
What is the prime mover?
Within a functional group of movers, the prime mover is the most powerful at performing the action in question
What is a prime mover group?
Muscles that are equally strong at performing the action in question
What is an assistant mover?
Any mover other than the prime mover (or not member of prime mover group)
A mover is also known as an...
What is a force-couple?
2 or more muscles that have lines of pull in different linear directions, but create the same axial joint motion
(Ex: abs pulling pelvis superior and biceps femoris pulling pelvis inferior results in same posterior tilt of pelvis)
In any downward movement, what is always a mover?
What is an antagonist?
Muscle or other force that can perform the opposite action of the action in question (not necessarily opposite all the actions of the mover)
What 2 ways can an antagonist lengthen?
1. Eccentrically contract and lengthen, generating braking force on action in question
2. Be relaxed and lengthen, allowing action in question to occur
What is the prime antagonist?
Among muscles of antagonist group, muscle with most power at opposing action in question is prime antagonist
What is gravity during any upward movement?
What is productive antagonism?
When antagonist is lengthened, it builds up passive elastic recoil tension force which augments the contraction force - gives antagonist stronger force
IF we feel mover muscle is causing the action in question to occur too rapidly, we can command the mover muscle to not contract as hard. In this instance, antagonists usually...
relax and lengthen
What is co-contraction?
When mover and antagonist muscles contract at the same time
Why is co-contraction unhealthy?
Leads to fatigue and injury
When is co-contraction desirable?
When stabilization of a body part is needed
When the movers are contracting, the antagonists are usually
When the antagonists are contracting, the movers are usually
Whichever muscle does contract during the action in question is called
the muscle that is working
Upward movement - what are the movers and antagonists doing?
Movers: concentrically contracting
Horizontal movement - what are the movers and antagonists doing?
Movers: concentrically contracting
Downward movement - what are the movers and antagonists doing?
Antagonists: eccentrically contracting
(unless we want to speed up the downward motion faster than gravity, then movers contract and antagonists relax)
What is a fixator (stabilizer)?
Muscle (or external force) that stops an unwanted action at the fixed attachment of the muscle that is working
(attachment = whatever body part needs to be fixed)
What is a neutralizer?
Muscle (or external force) that stops an unwanted action at the mobile attachment of the muscle that is working
(attachment = whatever body part that is moving during action in question)
A muscle that is working can either be a ______ or a ______
concentrically contracting mover
eccentrically contracting antagonist
Why do we need fixators and neutralizers?
When a muscle contracts, it wants to perform all of its actions. Fixators and stabilizers stop some of the actions from occurring so the intended action can occur by itself.
Ex: bicep curl - biceps wants to flex at arm and elbow. Stabilizer produces isometric extension force to stop flexion at arm.
Mobility muscles tend to be..
larger, longer, and more superficial
composed mostly white fast-twitch fibers
Mobility muscles are also called
Postural stabilization muscles tend to be...
smaller, deeper, and located close to joints
composed mostly red slow-twitch fibers
Primary job of postural stabilization muscles?
Isometrically contract and hold posture of joints fixed while mobility muscles perform their actions
Postural (core) stabilizers are also called
Do postural stabilization muscles engage before or after the mobility muscles?
Before so the joint can be stabilized before powerful muscle contraction
What is one of the major tenets of Pilates?
Strengthen the "powerhouse" of the body - exercises that isometrically tone the core stabilizers and create efficient coordination of these muscles with mobility muscles
Why is core stabilization important?
Creates stronger and more efficient movements
Important for health of the spine
How does core stabilization create stronger and more efficient movements of our body?
Muscle exerts pulling force on its attachments. For one attachment to move powerfully and efficiently, the other must stay fixed.
Movement of muscle that should be fixed will diminish the strength of the pulling force.
How does core stabilization create a healthier spine?
Diminishes unwanted excessive motions of the spine that lead to overuse and abuse --> OA
How does a neutralizer muscle work?
Create a contraction force that is equal in strength but opposite in direction to the force of the unwanted action of the muscle that is working.
May change length in one plane to stop motion in another plane
What are mutual neutralizers?
Two muscles that are both movers (or both antagonists) of the action in question and neutralize each other's unwanted actions.
Ex: right/left trapezius when both contract cancel unwanted frontal/transverse plane actions --> extension of neck
Ex: TFL/sartorius cancel transverse plane actions --> flex at thigh
What is a support muscle?
One that can hold another part of the body in position while the action in question is occurring (can also be external force)
(ex: left paraspinal muscles contract while performing right-sided bicep curl)
What is a synergist?
Muscle (or force) that works with the muscle that is contracting
Can be any other mover or antagonist as well as any other fixator, neutralizer, or support muscle
Can muscles be both synergists and antagonists?
Yes, depending on the joint action
Ex: biceps brachii and pronator teres both flex forearm at elbow (synergist) but biceps supinates and pronator teres pronates (antagonists)
What is coordination?
Co-ordering of muscles in the body in their various roles to create smooth and efficient movement
Why are the clinical effects of sustained isometric contractions typically more important than effects of concentric and eccentric contractions?
Isometric contractions can close off venous supply for long periods which results in a buildup of toxic waste products and irritate nerves. Sometimes arterial supply can be cut off as well leading to possible ischemia.
What is a second-order fixator?
Fixator that contracts to fix an attachment of a fixator or neutralizer during a joint action