Flashcards in Module 6 (Ch. 14 and 16) Deck (118):
It is the coordination of ______, not muscles, that creates the movement patterns of the body.
What is the Henneman size principle?
Hierarchy of motor unit recruitment.
When a muscle needs a weak contraction, a smaller motor unit is recruited. When muscle needs a stronger contraction, a larger motor unit is recruited in addition to the smaller unit.
Generally, smaller motor units are innervated by [smaller/larger] motor neurons and contain [red/white] muscle fibers
Smaller motor neurons
Red slow-twitch fibers
Generally, larger motor units are innervated by [smaller/larger] motor neurons and contain [red/white] muscle fibers
Larger motor neurons
White fast-twitch fibers
Implication of recruiting a smaller motor unit first?
Smaller units generally contain red slow-twitch muscle fibers which are adapted toward creating joint stabilization. Therefore, they stabilize a joint before larger motor units are recruited.
What determines the degree of a partial contraction?
Number of motor units recruited
Number of muscle fibers in those motor units
Size of a muscle fiber (how many cross-bridges are made)
Orientation of the pull of the cross-bridges relative to the line of pull of the muscle.
What is intrinsic strength of a muscle?
Strength that muscle generates within itself - sliding filament mechanism (active tension) and elastic recoil property of tissues (passive tension).
What is extrinsic strength of a muscle?
Factors outside of the muscle: leverage of muscle on attachments, angle of pull relative to joint
What is the muscle fiber arrangement of longitudinal muscles?
Fibers run along the length of the muscle (most from attachment to attachment).
The force of the contraction of the fibers in longitudinal muscles is in what direction?
Same as the length of the muscle
What are the most common types of longitudinal muscles?
Triangular (fan shaped)
What is a sphincter muscle?
Circular muscle (e.g., orbicularis oculi) that could be classified as longitudinal
What is a spiral muscle?
Muscle with a twist (e.g., latissimus dorsi) that could be classified as longitudinal
What is the muscle fiber arrangement of pennate muscles?
Arranged in a feather-like manner (central fibrous tendon runs length of muscle with fibers arranged obliquely to central tendon
Is the force of contraction of the fibers in pennate muscles in the same direction as the length of the muscle?
What are the 3 types of pennate muscles?
What is a unipennate muscle?
Central tendon and fibers oriented diagonally off one side of the tendon (e.g., vastus lateralis)
What is a bipennate muscle?
Central tendon and fibers oriented diagonally off both sides of the tendon (e.g., rectus femoris)
What is a multipennate muscle?
More than 1 central tendon with fibers oriented diagonally either to one and/or both sides (combos of uni and bipennates) - e.g., deltoid
What is the difference in length between longitudinal and pennate muscle fibers?
Longitudinal = long
Pennate = short
What is the difference in amount of muscle fibers between longitudinal and pennate muscle fibers?
Longitudinal = less
Pennate = more
What is the difference in amount or sarcomeres/cross-bridges between longitudinal and pennate muscle fibers?
Same number in muscles of the same overall size
Based on fiber orientation, why are longitudinal muscles more suited to create large ranges of motion?
Longitudinal muscles can shorten more than pennate because the fibers are longer
What percentage of its resting length can a muscle fiber shorten?
Why do pennate muscles exhibit greater strength over a shorter range of motion than longitudinal muscles?
Pennate muscles have the same number of sarcomeres generating strength but that is concentrated over a shorter range of motion
A longitudinal muscle is generally better suited for a ______ range of motion contraction but with _____ force.
A pennate muscle is generally better suited for a ______ range of motion contraction but with _____ force.
What are the 2 types of force a muscle can generate?
Active and passive
What is tension in relation to muscle?
pulling force a muscle generates (active or passive)
How is active tension generated?
By sliding filament mechanism (contraction) - muscle expends energy to generate a contraction
What causes passive tension?
Muscle's natural elasticity creates a pulling force that would pull the muscle's attachments toward the center of the muscle.
Why is there a backswing in sports like tennis, golf, and baseball?
It first stretches the muscle that will be performing the stroke and adds the passive elastic recoil force to the active contraction force of the muscle --> more powerful pulling force by muscle
What is active insufficiency?
When a muscle cannot generate sufficient strength actively via sliding filament mechanism (weak due to decreased cross-bridges)
What are the 2 types of active insufficiency?
shortened and lengthened
What is shortened active insufficiency?
Muscle is shorter than its resting length and weak because of decrease in cross-bridges (many are overlapping)
Ex: wrist fully flexed can't make a tight fist (shortened wrist flexors)
What is lengthened active insufficiency?
Muscle is longer than its resting length and weak because of decrease in cross-bridges (actin filaments pulled too far from center and myosin heads can't reach)
Ex: wrist fully extended can't make a tight fist (lengthened wrist flexors)
What is the length-tension relationship?
Relationship between the length of a muscle and the active tension it can generate is related to the length of the sarcomeres and the tension that they can generate.
How much passive tension is there when a muscle is shortened? When it is lengthened beyond resting length?
Shortened = nonexistent
Lengthened past resting = increases
Overall tension [increases/decreases] from a shortened length to resting length? From what?
increases from active tension
Overall tension [increases/decreases] past resting length? From what?
Increases from passive tension
What can happen if you frequently work a muscle from an over-lengthened state?
Tearing/injury to muscle tissue
The length-tension relationship is technically for a [concentrically/eccentrically/isometrically] contracting muscle
What curve expresses tension force better for when a muscle is moving?
Force-velocity relationship curve
What is the force-velocity relationship (concentric contractions)?
The tension force of a muscle is greatest when a muscle is contracting slowly. As contraction velocity increases, tension force decreases.
What explains the concentric contraction force-velocity relationship?
As speed of muscle contraction increases, there is less time for cross-bridges to form.
What is different about the eccentric contraction force-velocity relationship compared to concentric?
Less dependent on velocity of contraction and stays fairly constant/high; much of this results from addition of passive tension as myofascial tissue resists stretching.
What does the force-velocity curve mean to strengthening muscles?
More strengthening occurs if us through eccentrics or slow concentric contractions
What is the pennation angle?
Angle of the muscle fiber relative to the central tendon of the muscle
The greater the pennation angle, the more fibers can be fit in the same mass and the greater relative strength over a shorter range of motion.
However, some of the intrinsic strength of the muscle fibers is lost. Why?
They are not pulling along the length of the muscle
A smaller pennation angle will contribute [less/more] of its force to pulling the attachments toward the center than a greater pennation angle.
What is leverage?
Extrinsic strength factor; the mechanical advantage that a force can have when moving an object.
When we study the motion of the body, it is useful to realize that any movement that occurs will always be a sum total of...
internal and external forces
What is a lever?
Rigid bar that can move
What is the axis of motion?
Point at which the lever moves
What is the lever arm?
Distance from the axis of motion to the point of application of force on the lever
The longer the lever arm, the [less/more] effort it takes to move the lever
What is mechanical advantage?
Advantage of being able to move heavy objects with less effort (using leverage)
What is the disadvantage of mechanical advantage?
A longer lever arm makes it easier to move an object, but the lever arm must be moved a greater distance to move the object a short distance, which doesn't save effort in the end
Why is a doorknob farthest away from the hinges?
Increases the lever arm (leverage; mechanical advantage)
To give a muscle mechanical advantage, do you want the attachments closer or farther from the joint?
Bone/muscle/joint = axis/lever/force?
Bone = lever
Muscle = force
Joint = axis of motion
Although a muscle farther from the axis of motion can generate more force, what is the consequence?
Must move twice as far and therefore difficult to generate speed
Muscles with good leverage can generate [less/more] extrinsic strength
Muscles with poor leverage can generate [less/more] speed
What is optimal angle of pull?
The optimal angle of pull that a muscle has on the bone to which it attaches (usually perpendicular to the long axis of the bone)
The greater the obliquity of the muscle's attachment, the [less/more] of the muscle contraction contributes to the motion at the joint
What is the advantage of an increased obliquity of a muscle's pull?
Greater portion of the force of the muscle's contraction goes into stabilizing the joint.
Why does increased obliquity of a muscle's pull increase joint stabilization?
Portion of the contraction goes toward pulling the bone in toward the joint - adds compression force
What is the definition of a musculoskeletal lever arm?
The measurement of the line that begins at the center of the joint and meets the line of pull of the muscle at a perpendicular angle.
Does extrinsic strength of the muscle's contraction change throughout joint position?
Yes - lever arms change throughout movement.
What is a first-class lever?
Force causes motion and force of resistance to motion are on opposite sides of the axis of motion
What is a second-class lever?
Force that causes motion and force of resistance to motion are on the same side of the axis.
Force that causes motion is farther from the axis than the resistance force
Which of the 3 lever classes has greater leverage for strength of pulling force?
What is a third-class lever?
Force that causes motion and force of resistance to motion are on the same side of the axis.
Force that causes motion is closer to the axis than the resistance force
Which of the 3 lever classes has lesser leverage for strength of pulling force?
Is extensor musculature at the back of the head a 1st, 2nd, or 3rd class lever?
Is plantar flexor musculature of the lower extremity a 1st, 2nd, or 3rd class lever?
Is the brachialis a 1st, 2nd, or 3rd class lever?
What is the advantage of the brachialis?
It has a short lever arm which decreases leverage for strength, but a small amount of contraction will move the forearm through a large range of motion.
It also gains speed despite loss of strength.
What is a mechanical disadvantage?
When the muscle is working against a force with greater leverage.
Which class of lever leads to mechanical disadvantage?
3rd-class because resistance is farther from the joint than the muscular attachment.
May also occur with 1st class if resistance is further than muscle attachment.
Generating a contraction when the muscle is at mechanical disadvantage increases the risk of
Why do clients' "backs go out" when bending over?
Back extensor musculature eccentrically contracts to slow down the descent and then has to concentrically contract to lift the weight of the upper body, which is heavy.
Which is better: stoop or squat bend (with vertical spine)? Why?
Squat, because back stays straight and more vertical. Extensors don't have to counter as much force (decreases lever arm and requires less forceful contraction). Also spinal joints are extended and in more stable closed-packed position.
What is active range of motion?
Joint motion created by mover muscles
What is passive range of motion?
Joint motion created by force other than the mover muscles
Which is greater: active or passive ROM?
What is joint play?
Nonaxial gliding motion (passive); small amount of motion permissible at end of PROM.
What is beyond joint play?
What is ballistic motion?
Joint motion begun actively by client and then completed passively by momentum
Describes most motions of body because it is efficient (allows muscles to relax at certain point)
What is end-feel?
Quality of motion at end of joint's PROM
What are the 6 major qualities of end-feel?
Soft tissue stretch
Soft tissue approximation
What is soft tissue stretch end-feel?
Stretch of soft tissue of joint limits the motion. Indicates healthy joint, usually.
What is soft end-feel?
When soft tissue limiting motion is muscle
What is firm end-feel?
When soft tissue limiting motion is ligament
What is soft tissue approximation end-feel?
Motion ends because compression of superficial soft tissues between 2 body parts moving at joint (ex: elbow flexion)
What is a muscle-bound client?
Clients that have built up muscle mass and joints have soft tissue approximation end-feels
What is bone-to-bone end-feel?
Joint motion ends with 2 bones of joint meeting each other (ex: elbow extension)
Bone-to-bone in a joint that should not feel that way indicates...
pathologic degenerative changes
What is muscle spasm end-feel?
Motion ends due to muscle spasm; feels abrupt and sudden.
What is springy-block end-feel
End range is blocked and joint springs back due to presence of loose body of tissue that becomes jammed between the 2 bones
What is a joint mouse?
Bone fragment that causes springy-block end-feel
What is empty end-feel?
No mechanical obstruction to joint motion but client stops motion due to pain or fear of pain
What is joint mobilization?
Joint play; low-velocity, long-lever arm stretching of the joint.
What is an adjustment?
Joint play; high-velocity, short-lever arm manipulation
Why does a pop sound after an adjustment?
Joints are distracted from each other causing an increase in space within joint capsule and lower pressure in the joint; gases that are dissolved within synovial fluid come out of solution and become gaseous.
What is resisted motion?
Resistance force stops contraction from creating motion at a joint (creates isometric contraction) - by self or therapist
What is a strain?
Muscle injured and torn
What is tendinitis?
What is a sprain?
Ligament/joint capsule injured and torn
What is the difference between diagnosis and assessment?
Diagnosis - assigning of a name or label to a group of signs and/or symptoms by qualified health care professional
Assessment - systematic method of gathering information to make informed decisions about treatment
When active ROM is performed, which are stressed: mover muscles or ligament/joint capsule complex?
Contraction (muscle stress) --> pain
Joint is moved (ligament stress) --> pain
When passive ROM is performed, which are stressed: mover muscles or ligament/joint capsule complex?
Ligament/joint capsule complex (muscles are relaxed so won't elicit pain)
When resisted motion is performed, which are stressed: mover muscles or ligament/joint capsule complex?
Mover muscles (ligament/joint capsule not stressed because joint isn't moving)
When can passive ROM indicate a muscle injury?
When stretch causes pain in antagonist musculature (use active ROM test on that muscle to confirm)
What is the order of assessment procedures?
1. Active ROM
2. Passive ROM
3. Resisted motion
What is the most common problem causing restricted range of motion in clients?
Tight muscles (typically antagonists)