Neurological Considerations for Movement Flashcards
Peripheral Nervous System
Sensory Neurons (Dorsal Side)
- Receive information
Motor Neurons (Ventral)
- Send information
Motor Unit
Nerve cell and all muscle fiber innervated
All of none principal
All fiber types (I,IIa,IIb)
Motor Pool
Groups of motor neurons that innervate a particular muscle
Tongue and hand have greater pools for precision
Tetanus
Action potential sequenced together – tetanus (constant tension)
Muscle Fiber Types
Type 1 - SO
Type 2a - FOG
Type 2b - FG
Type 1 - SO
Slow contraction times (>70 ms)
Generate little tension
Highly fatigue resistant
Maintain posture
Endurance athlete
Type IIa – FOG
Fast contraction times (30-50 ms)
More fatigue resistant than type IIB
Type IIb – FG
Rapid contraction times (30-40 ms)
Innervated by alpha motor neurons
Large neuron to fiber ratios
Power athlete
Recruitment
Tension generated by size and number of moto units recruited
Order of activation for isometric tasks
T1 -> TIIa -> TIIb
May change on task performed may activate Type 2 or synchronous with Type 1 (Ballistic)
Asynchronous activation
Activation is temporally spaced but summed with preceding motor unit activity
Want to turn on muscle but can’t have all areas of the muscle active at the same time; different areas are used. Specific to low loads and endurance events
Synchronous activation
Large and small motor units activated together
- Ballistic movements, adaptations from weight training
- Routine participation may cause change in recruitment order
Neurologically very difficult to get synchronous activation on a 1 rep max.
Frequency Coding (Firing Rate)
High frequency can induce high tension production
Also called rate coding
During isometric tasks - Small vs Large Muscles
Small muscles (ex: hand)
- All units activated when at 30-50% maximum voluntary contraction to increase force, increase firing rate
- Less motor pools
Large muscles (ex: quadriceps)
- Still recruiting motor units at 100% maximum voluntary contraction to increase force
- More fibers per motor unit make it harder to recruit all at motor units in the same motor pool.
Implications of Muscle Testing
Hard to know if someone got more efficent at test or better at recruiting
Reflexes
Involuntary response to stimuli
Quick reflex response to muscle fibers
Monosynapatic Reflex Arc
When sensory neuron is stimulated, it facilitates the stimulation of a spinal cord neuron
Types of Reflexes
- Myotactic Reflex (Stretch Reflex): Causes contracion of a muscle being stretched (Knee Jerk Reflex)
- Flexor Reflex: Initiated by painful stimulus; Causes quick withdrawal/ flexion of the limb
- Cutaneous Reflex: Causes relaxation of muscle with heart or massage
- Propriospinal reflexes: Reflexes processed on both sides and at different levels of the spinal cord; 4 Types: Crossed Extensor Reflex, Tonic Neck Reflex, Supraspinal Reflex, Labyrinthine Righting Reflex
Crossed Extensor Reflex
Causes extension of flexed limb when contralateral limb rapidly flexes
Tonic Neck Reflex
Causes flexion or extension of the limbs when head flexes or extends respectively
Supraspinal Reflexes
Aka Deep Tendon Reflexes
- Reflexes brought into the spinal cord but processes by brain
- Ex: Patella Reflex
Labyrinthine righting reflex
Causes body to return head to neutral positions when the body is tilted or spun
Proprioceptors
Main sensory receptors for muscle
Sense change in joint position, muscle length, or muscle tension
Can be damaged during injury (May or may not fully recover)
Muscle Spindle
- Monitors muscle length
- Intrafusal fibers (Fibers inside the muscle spindle (in line with muscle fibers; senses then sends signal out and receives one back on what to do; safety mechanism))
Types of Intrafusal Fibers
- Nucleat Bag Fibers
- Nuclear Chain Fibers
Nuclear Bag Fibers
Intrafusal fibers with a **large clustering of nuclei in the center **
Type Ia afferent neurons exit from middle portion of the fiber (primary afferent)
- Respond to stretch by initiating stretch reflex, velocity dependent (must be quick; done quickly results in contraction); Protective; Contraction
Nuclear Chain Fiber
Intrafusal fiber with nuclei arranged in rows
Both Type Ia & II sensory neurons exit from this fiber (primary and secondary afferent)
Type 1a: Respond to stretch by initiating stretch reflex; Quick stretch; quick then done; Protective; Contraction
- Ex: Stretch Reflex
Type 2: Feedback does not diminish with time (not velocity dependent), can cause **relaxation in muscle being stretched; Does NOT diminish with time; NOT Velocity dependent **
- Slow and sustained
- Ex: Therapeutic Stretching (Chronic change in length through stretch)
What influences muscle spindle activation?
Gamma motor neuron: Innervates contractile ends of muscle spindle
Gamma bias: Readjustment of muscle spindle length by contracting ends of intrafusal fiber
Gamma Loop: Reflex arc that works with stretch reflex
- Includes afferent, gamma, and alpha pathways
This can change the threshold needed (the length change) for this type of reflexive behavior
Stretch Reflex (Autogenic Facilitation)
Facilitates muscle contraction (via muscle spindle) of a muscle being stretched
During this activation the antagonists relax allowing agonists to produce joint motion (Reciprocal inhibition)
Plyometrics
Autogenic facilitation = 25-30% of force output
Elastic Energy = 70-75% of force output
**Big driver here!!!!! **
Golgi Tendon Organ
Monitors Muscle Tension (Active Tension)
Extrafusal fibers
- Fibers outside of muscle spindle
Inverse stretch reflex
- Initiated by high tension in muscle
- Inhibits contraction of muscle via GTO
- Causes relaxation of a vigorously contracting muscle (Protective)
During treatment with a patient must train the muscles to inhibit the reaction from GTO that is trying to relax the muscle after a surgery or injury
Force - Muscle
Countermovement, quick, use elastic energy = more maximal effort
Trying to get 1a afferent response
Accuracy
Perform movement slower, don’t use elastic energy, don’t use stretch reflex = precise movement
Joint Sensory Receptors
Sensors monitor Joints
Respond to pain, “Swelling”
Ruffini ending
- Sensory receptor in joint capsule that response to change in joint position
Pacinian corpuscle
- Sensory receptor in skin stimulated by pressure
Reason we don’t like swelling
- Edema effects ability to move and sensation
- Very small amounts have large effects
Proprioception - Definition
Joint position sense or threshold to detect motion
Involves supraspinal processing of input from peripheral receptors
Joint Position Sense and Mechanoreceptors
Less Active receptors effects joint position with increase in errors
Effect of Resistance Training on Neurological (Input/Output People who don’t normally workout)
Neural adaptations during the first 4 weeks of training
Strength increases significantly due to neural adaptation significantly increasing
Teach how to use muscles and limit GTO
- Hypertrophy occurs much later past 4-6 weeks
Neuroloigcal Implications to Strength Training
- Significant gains within 4 weeks of training (Due to neuro)
- Neural adaptations to training (Reduction in inhibition - GTO; Increased neural facilitation and synchronization
- Bilateral deficit (Loss of both force and neural output through bilateral training; Train one limb at a time leads to greater force output but doesn’t transfer to specificity)
- Overall decision to train asymmetrically or bilaterally should follow the specificity principle (Ex: Football - Bilateral; Tennis - Unilateral)
- Cross Education - train opposite limb to get less fatigue on untrained limb; Upper body better than lower body
- Patterns of limb movements (Flexors/Extensors)
- Warm up (5-10 min; increases motor unit activity)
- Opposing muscle groups in sequence (Neural Benefits)
- Immobilization (Decreases motor unit activity)
- Inflammation (Decreases muscle acitivation and muscle strength)
- Plyometric exercises (Uses “autogenic facilitation” (25-30% of force output) and elastic energy (70-75% of force output) )
Neurological Implications to Stretching
Static (slow sustained stretch) vs ballistic stretching
Static:
- Minimize muscle spindle activation – Type 1a afferents
- Stimulation of Type 2 afferents of muscle spindle – relaxation
- Extreme stretch – GTO (inverse stretch reflex); Not as much data supporting this
Warm + Stretching
- Improve plasticity of tissues
Does stretching reduce an injury?
Unknown
Time to Stretching
Largest effect >60s
Very inflexible: 6-10 minutes??
Put weight on knee for long period of time
What is PNF?
Contract – Relax (PNF – proprioceptive neuromuscular facilitation)
Used to stimulate relaxation
“Tricks” muscle spindles (Type 1a)
Pushing and talk back through ROM or keep him at end ROM then bring back relax and push further
Agonist
Muscle responsible for a specific motion
Prime vs assistant
- Elbow flexion (Biceps-prime, brachialis-assitant)
Muscles can have additional roles
- Shoulder flexion (Anterior deltoid-prime, biceps-assitant)
Anatagonist
Oppose action of the agonist
Elbow flexion
Biceps – agonist
Triceps – Antagonist
Reciprical inhibition
Allows for movement of one muscle group to move (Ex: Quads) by inhibition of hamstrings
When does simultaneous contraction of agonist and antagonist occur?
Cerebral Palsy (Wasteful metabolically)
E-stim
Synergy
Cooperative role of two or more muscles to procuce the same action
Helping Synergists
muscles with a common action in one place, opposing action in other planes
Ulnar flexion (wrist)
- Flexor carpi ulnaris/Extensor carpi unlaris
- If one is damaged leads to favor it the direction of good muscle
Lateral flexion (trunk)
- Obliques
True
Requires a multi-articular muscle and a muscle that opposes this action at one or more joints (but not all joints)
One muscle stabilizes, one acts
Making a fist
Wrist flexors/extensors
Hamstrings: knee flexion without hip extension
Requires hip flexors
How do we know muscles are Active?
Logic or Palpation
EMG
Ultrasound
Logic or palpation - Active Muscles
Insertions of muscle
Joints crossed
Movement (planes/axes)
Electromyography (EMG) - Active Muscles
- Neural
- Measures voltage differences between two sites (Idea of recruitment when performing an activity)
- Summation of all motor units activation
- Electrodes on/in muscle to determine motor unit activity (How much impulses are going to muscle)
- Fast twitch will be much higher than slow twitch
- How many muscle fibers we have firing
- Tells us the sequence of muscle activity
- Amount of tension??? (None! **Only tension under isometric positions. **)
Ultrasound - Active Muscles
Emerging method! Can measure cross sectional area change
