Muscle Foundations

Front 1

What are the basic rules of muscles? (4)

Back 1

1) Muscles CONTRACT; they do not flex (flexion is a joint action in the sagittal plane)

2) muscles only PULL; they cannot push. they contract equally at both ends

3) action of a muscle will be determined by:
-the ATTACHMENTS and PATH of the muscle
-overall engineering

4) muscles must OPPOSE GRAVITY to produce movement or maintain a position

Front 2

What is a concentric contraction?

Back 2

shortening contraction- in an active contraction, muscle wins out over gravity, shortens through ROM

example:
up phases of plie (both hip and knee extensors)
push off into jump

Front 3

What is an eccentric contraction?

Back 3

lengthening contraction- in active role of contraction, muscle allows gravity to win, lengthens through ROM

example:
down phase of plie (both hip and knee extensors)
push off into jump

Front 4

What is a static contraction?

Back 4

holding contraction- muscles contract to hold or maitain a position, no movement produced

Front 5

What are the muscle properties? (5)

Back 5

1) irritability- (or excitability) repsonds to nervous stimuli
2) conductivity- ability to carry impulses
3) contractility- ability to contract
4) distensibility- ability to be stretched (to a limit)
5) elasticity- ability to return from stretch

Front 6

If the muscle is contracting and allowing gravity to win, what type pf contraction is it?

Back 6

eccentric

Front 7

If muscle is contracting and going away from gravity, what is the type pf contraction?

Back 7

concentric

Front 8

What is a motor unit?

Back 8

contractile mechanism

conists of a motor neuron, motor end plates and the muscle fiber it innervates

Front 9

What is the "All Or None Law?"

Back 9

When a motor nerve (neuron) is activated, all of the muscle fibers connected to that nerve will contract with full force or not at all.
(full motor unit will fire)

Front 10

What is "graduation of muscle contraction," and how is it possible?

Back 10

- the ability to contract a muscle with various intensities of force

-possible through selective activation (recruitment) of motor units

Front 11

What are muscle spindles, and what do they do?

Back 11

- imbedded between extrafusal (power-generating) muscle fibers
- sensory receptors: "inhouse" monitor of muscle activity, reports status to CNS
-tells muscles when it needs more force: helps maintain correct muscle tone
-sensitive to stretch, contraction, velocity of contraction

Front 12

What are the two types of stretch receptors?

Back 12

1) quickly adapting- fire when muscle first stretches; rapidly adapt to new length/position and stop firing

2) slowly adapting or non-adapting- keep firing after muscle stops moving-allows for sense of positioning

Front 13

What is the stretch reflex? What problems can it cause? How can it be blocked?

Back 13

if a muscle is placed on stretch, stretch reflex causes a reflexive contraction of that muscle (protective mechanism)

if stretch is quick, contraction will be stronger/more powerful

can contribute to injury by blocking flexibility

can be blocked with conscious control

Front 14

What are the Golgi Tendon Organs?

Back 14

-imbedded in muscle tendon, monitor overall muscle tissue
-contribute to control of muscle activity through full ROM
-sense deep stretch or powerful contraction that has imminent sever injury to muscle
-inhibit motor neuron in stretch reflex loop and muscle relaxes

-if muscle is fatigued, GTo gets stuck in a loop that causes alternately trigger (trembling)

Front 15

What are the (3) factors of muscle engineering that affect a muscle's function and overall effectiveness?

Back 15

-location and attachment of bone

-angle of attachment

-number of joints crossed

Front 16

What is a shunt?

Back 16

proximal attachment of a muscle is CLOSER to the moving joint than the distal attachment
- "stabilizer muscles"

example: rectus femoris in hip flexion

Front 17

What is a spurt?

Back 17

proximal attachment of muscle is FURTHER from the moving joint than the distal attachment
-"mover muscles"

example: psoas in hip flexion

Front 18

What are the general rules for 2 joint muscles?

Back 18

-the main or most effective action is on the distal joint crossed, with assistance at the proximal (at distal there is better leverage)

-tend to act as stabilizers and resist movement at proximal joint when all possible muscle actions are produced

(it will stabilize one, move the other)

Front 19

Why do we have so many 2 joint muscles?

Back 19

to look long, lean
not be cumbersome

Front 20

What are the 1 joint muscles? (mnemonic)

Back 20

"Adding Glue To Soda Pop Prevents Vast Illness"

-Adductor Group
-Gluteals
-Tensor Fascia Latae
-Soleus
-Popliteus
-Pectineus
-Vasti Group
-Iliacus

Front 21

What is an Agonist and an Antagonist?

Back 21

agonist- working or target muscle group

antagonist- muscle group opposite to the target group

Front 22

What is the Prime Mover?

Back 22

muscle that is most effective for a given action
ex: in attitude- sartorius is prime mover because it produces all three actions

Front 23

What is the Assistor?

Back 23

a muscle that assists with a given action but is not necessarily the prime mover

Front 24

What is the Stabilizer?

Back 24

prevents undesirable movement- fixes a bone so the working muscle can produce the desired action

contracts to stabilize a body segment so that other segments can move more effeciently

Front 25

What is the Synergist?

Back 25

works together with other muscles to produce a desired action
magnifies the effectiveness of movement through a given range of motion

ex: the pectineus may act as a synergist to enhance the effectiveness of the sartorius in hip flexion and outward rotation

Front 26

What is the Neutralizer?

Back 26

contracts to prevent an undesirable action of working muscle
most often occurs when 2 muscles work together that have common actions and antagonistic actions

example:
anterior tibialis- dorsiflexion and supinations
perroneus tertius- dorsiflexion and pronation

(neutralize or cancecl each other out in pronation and supination)

Front 27

What is the role of a muscle spindle? What role does the muscle spindle play in the stretch reflex? How can the stretch reflex be used to the dancers advantage? When can it become a disadvantage?

Back 27

The muscle spindle is a sensory receptor that monitors muscle activity
In the stretch reflex, the muscle spindle senses stretch in the muscle, and relays a message to the CNS, which in turn, sends an impulse for the muscle to contract Advantage: If a muscle is placed on a quick stretch prior to contraction, the resulting contraction will be more powerful (elastic energy)
Disadvantage: stretch reflex can cause injury if engaged when muscle is placed on stretch, such as happens through a large ROM