Neuromuscular Fundamentals

muscles provide ____

protection, dynamic stability, posture and support, produce body heat

muscles make up ___

40-50% body weight

aggregate muscle action

muscles working in a group to achieve a joint motion; 215 pairs

parallel fibers

parallel to length of muscle, greater ROM

pennate fibers

shorter fibers, unipennate, bipennate, multipennate

action

specific movement of joint resulting from contraction of muscle that crosses joint

intrinsic muscles

muscles within or belonging solely to a body part on which they act

extrinsic muscles

muscles that arise or originate outside of body part on which they act

innervation

segment of nervous system responsible for providing stimulus to muscle fibers in specific muscle

Isometric contractions

active tension developed within muscle, joint angle remains static; may prevent motion

Isotonic contractions

muscle developing active tension to cause or control joint movement

concentric

contraction or shortening of muscle, causing motion

eccentric

lengthening of muscle, controlling motion

isokinetics

type of dynamic exercise using concentric and eccentric contractions; constant speed of movement

agonist

primary movers

antagonist

cause opposite action of agonist

stabilizers

surround joint or body part, contract to stabilize area; essential for distal joints

synergists

assist in action of agonist, refine movement

force couples

two or more forces pulling in different directions, causing rotation on an axis

determination of muscle action

lines of pull, dissection, palpation, models, electromyography, electrical stimulation

anatomical lines of pull

direction of force a muscle creates, factors include attachments, planes of motion, muscle relation to joint axes of rotation, muscle length, position of other joints, etc.

epimysium

outer connective tissue covering of muscle

perimysium

bundles of muscle fibers

endomysium

encases muscle fibers individually

sarcomere

functional unit of skeletal muscle

actin

thinner protein that contributes to the contracile properties of muscles

myosin

thicker protein; crossbridges attach to actin during muscle action to assist in contraction process

blood capillaries in sedentary people

3-4 per fiber

blood capillaries in athletes

5-7 per fiber

All or None Principle

regardless of number, individual muscle fibers within a given motor unit will either fire and contract maximally or not at all

motor unit

single motor neuron and muscle fibers it innervates

proprioception

subconscious mechanism by which body regulates posture and movement by responding to stimuli originating in proprioceptors of joints, tendons, muscles, and inner ear

kinesthesis

conscious awareness of position and movement of body in space

Fiber I

SO, slow speed, high fatigue resistance

Fiber IIA

FOG, fast speed, intermediate fatigue resistance

Fiber IIB

FG, very fast, low fatigue resistance

greatest amount of tension can be developed when muscle is stretched between ____

100-130% resting length

contraction velocity

maximal force depends on velocity of contraction and activation state

angle of pull

angle between line of pull of muscle and bone of insertion

rotary component

muscular force that acts perpendicular to long axis of bone

angle < 90 degrees

stabilizing force because pull directs bone toward joint axis

angle > 90 degrees

force is dislocating due to pull directing bone away from joint axis

uniarticular muscles

cross and act on only joint they cross; brachialis

biarticular muscles

cross and act on two different muscles; maintain relatively constant length

concurrent movement

muscles perform same motion at same time

countercurrent movement pattern

muscles perform opposite motion at same time

active insufficiency

reached when muscle becomes shortened to point that it cannot generate or maintain active tension

passive insufficiency

reached when opposing muscle becomes stretched to point where it can no longer lengthen and allow muscle movement