Strength and Power: Proprioceptor Slides

Muscle Proprioceptors

Muscle spindles and Golgi Tendon organs

Propriceptor Characteristics

specialized receptors that provide info about musculoskeletal movement and position, sensitive to changes in length

Functions of Proprioceptrs

1. detect amount, direction and rate of change of body movement 2. Provides info about body and limb position 3. provides kinesthetic info and automatic reflexes

Where are proprioceptors located?

muscles, tendons and joints…. also includes surrounding and protective tissues such as capsules ligaments and other fibrous membranes

Joint Kinesthetic receptors

located in connective tissue capsule in diarthrotic joints and stimulated by changes in position caused by movement at the joints

Neuromuscular spindles

Muscle Spindles

Neurotendinous Receptors

Golgi Tendon Organs

Extrafusal Fibers

Muscle fibers

Intrafusal fibers

Muscle spindles

Afferent

towards the CNS

Efferent

away from CNS toward the muscle

Alpha Motor neuron

innervates the extrafusal fibers(muscle fibers)

Gamma Motor neuron

innervates the intrafusal fibers(Muscle spindle at the polar ends)

Gamma Bias

setting of muscle spindle sensitivity by gamma neurons

Alpha-Gamma co-activation

simultaneous activation of alpha and gamma neurons by the same signal, this process allows the muscle spindle to shorten with muscle to still allow detection

Alpha-Gamma co-activation allows the muscle spindle to what?

send a signal from the primary afferent of spindle to the spinal cord which loops back to the muscle via alpha motor efferent, causing the muscle to contract and the spindle to still allow for detection

Function of Muscle spindles

monitor stretch and then to initiate a contraction of the muscle to reduce the stretch

What does the muscle spindle contain?

specialized fibers called intrafusal fibers located parallel to and within the muscle fibers

Equatorial region of muscle spindles

center area that is sensitive to stretch that will send signal to spinal cord causing the muscle fibers to contract to relieve the stretch

Muscle Spindle: Nuclear bag fiber

Sends signal via primary afferent (anulosprial) when stretched

Muscle Spindle: Nuclear Chain Fiber

sends signal via secondary afferent (flower Spray)

Alpha Efferent Neuron

sends signal from CNS to muscle fiber to cause it to contract

Gamma efferent

Sends signal to polar ends of spindle to cause them to contract which stretches the equitorial region

Afferent to tendon

detects tension on tendons and sends signs to CNS that theres tension on the tendon

Muscle spindle stimulation: External Stretch

stretching the whole muscle, causing the spindle to stretch

Muscle spindle stimulation: Internal stretch

contracting the ends of the spindle via the gamma efferent system

A stimulated muscle spindle will exert an excitatory effect upon:

the muscle which it lies(agonist), to cause a contraction ti alleviate the stretch

A stimulated muscle spindle will exert an facilitatory effect upon:

synergistic muscles, to assist with contraction of the agonist

A stimulated muscle spindle will exert an Inhibitory effect upon:

antagonist muscles to prevent or make it more difficult to contract that muscle

Reciprocal inhibition

relaxation of the antagonist muscle while the agonist contracts…EX: Triceps are relaxed during a bicep curl

Example of external muscle spindle stimulation may involve pre stretching of a muscle…

bouncing barbell off chest in benchpress to elicit the stench reflect to increase force of contraction

Example of internal muscle spindle stimulation involces anticipatory responses and stretching

attempting to lift a weight that is lighter than expected will almost cause it to be thrown

Main Function of Golgi Tendon organs

monitor tension on the tendons to reduce the tension if it is too high

Where are the golgi tendon organs located?

on the musclotendinous junction and in series to the muscle fibers

What is the golgi tendon organs effect on its own muscle?

Inhibitory (autogenic inhibition)

Autogenic inhibition

muscle under high tension is signaled to inhibit itself via Golgi tendon organs

Golgi tendon organs are less sensitive to what compared to muscle spindles?

passive stretch

What are golgi tendon organs highly sensitive to?

stretch imposed by contracting muscle

Golgi tendon organs activity is increasd by?

contracting muscles

High tension on tendons will stimulate what

the golgi tendon organs which then send a signal to cause the muscle to relax

Inhibition reflex of golgi tendon organ

muscles are capable of greater contractile force than their structure can withstand so inhibition reflex of GTO is to protect the muscle and associated structures

Example of the Inhibition Reflex

not being able to hold on to weight during max deadlift

Training effect of Golgi tendon organs

increased ability to override golgi tendon organs which allows for greater forces/tension to be produced but also increases risk of injury

Fast bounce stretching

activates stretch reflex, gentle oscillations (eccentric contracts can decrease muscle stiffness)

Static Stretching

resets muscle spindle activation sensitivity to a new length via the gamma efferents by statically holding the stretched position

PNF Stretching Step 1/3

Hold a position statically to allow resetting of the spindle to a new length

PNF Stretching step 2/3

contracting the muscle to be stretched maximally to activate the GTO to cause the muscle to relax. this is known as autogenic inhibition which also facilitates contraction of antagonistic muscle groups

PNF Stretching step 3/3

Contracting the muscle antagonistic to the muscle to be stretched which will cause a relaxation of the muscle to be stretched which is known as reciprocal inhibition

Mechanisms/Constraints of ROM/Flexibility: Neurogenic Constraints

voluntary and reflex control over the muscle group undergoing stretch

Mechanisms/Constraints of ROM/Flexibility: Myogenic constraints

passive and active resistive properties of whole muscle undergoing stretch, if the condition is active then the neurogenic and myogenic constraints are interactive

Mechanisms/Constraints of ROM/Flexibility: Joint constraints

resistive forces comprising the articular tissues, which involve the physical structures of the articulation of the bones, the joint capsule structure and related ligamentous attachments

Mechanisms/Constraints of ROM/Flexibility: Skin/subcutaneous connective tissue

frictional constraints

Stretch Reflex

myotatic reflex or monosynaptic reflex

Tendon Reflex

inhibition(relaxation) of tension producing muscle by golgi tendon organs

Tonic Labyrinthine Reflex (TLR)

primitive reflex found in babies until about 4 months old where head movement results in symmetrical actions of the upper and lower limbs

Examples of TLR

Flexion of head results in flexion of upper and lower limbs and vise versa

Tonic Neck reflex (TNR)

Primative reflex found in babies from 6-9 months, includes STNR and ATNR

Symmetrical tonic neck reflex (STNR)

provides separation of movement between the upper and lower body

Asymmetrical tonic neck reflex (ATNR)

provides separation of movement between the right and left side of the body

Examples of TNR: Flexion of head results in

flexion of upper limbs and extension of lower limbs

Examples of TNR: Extension of head results in

extension of upper limbs and flexion of lower limbs

Examples of TNR: Rotation of head to one side (SAME SIDE EFFECT)

extension and abduction of upper limb

Examples of TNR: Rotation of head to one side (OPPOSITE SIDE EFFECT)

flexion and adduction of upper limb

What head position would maximize force in an overhead press/bench press?

Extension

What head position would maximize force in an Arm Curl?

flexion

Gamma

to the muscle spindles

Alpha

to the muscle fibers