Chapter 5: Re-establishing Neuromuscular Control
Why is it critical to the rehabilitation process?
•Refocuses the athlete’s awareness of peripheral sensation
•Goal = more coordinated motor strategies
•Required to:
–Protect joints from excessive strain
–Provide prophylactic mechanism to recurrent injury
Primary role of articular structures
–Stabilize and guide body segments
–Provide mechanical restraint to abnormal joint motion
–capsuloligamentous tissue and tenomuscular receptor sensory role
•Detect joint motion and position
•Detect changes in muscle length
•Implicated in regulating muscle stiffness prior to loading
–Dynamic restraint system
•Injury results in damage to microscopic nerves associated with peripheral
mechanoreceptors
–Disrupts sensory feedback
–Alters reflexive joint stabilization and neuromuscular coordination
•Surgical intervention
–Restore mechanical stability
–Re-innervate graft tissue by peripheral receptors
•Rehab: Clinicians must work to re-establish and encourage restoration of functional
stability
Rehabilitation should address feedback systems
–Preparatory (feed-forward)
–Reactive (feed-back)
•Four critical elements
–Joint sensation (position, motion, force)
–Dynamic stability
–Preparatory and reactive muscle characteristics
–Conscious and unconscious functional motor patterns
What is neuromuscular control?
•Proprioception
–Conscious and unconscious awareness of joint position
•Kinesthesia
–Sensation of joint motion or acceleration
–Signal transmission through afferent sensory pathways
•Neuromuscular control
–Efferent motor response to sensory information
–Proprioception and kinesthesia
–Feed-forward neuromuscular control
•Planning movements based on sensory information from past
experiences
•Preparatory muscle activity
–Feed-back neuromuscular control
•Continuously regulates muscle activity through reflexive pathways
•Reactive muscle activity
•Dynamic restraint is achieved through preparatory and reflexive neuromuscular control
Dynamic Restraint
•Muscle stiffness
–Ratio in change of force to change in length
–Stiffer muscles resist stretching = more effective restraint to joint displacement
–Modified by muscle activation
•Articular Mechanoreceptors
–Specialized nerve endings that transduce mechanical tissue deformation into
frequency modulated neural signals
•Increased tissue deformation results in increased afferent firing rate or
rise in quantity of mechanoreceptors activated
–Types
•Pacinian corpuscles
•Meisner corpuscles
•Free nerve endings
–Quick adapting (QA)
•Cease discharging shortly after onset of stimulus
•Provide conscious and unconscious kinesthetic sensation in response to
joint movement/acceleration
–Slow adapting (SA)
•Continue to discharge as long as stimulus is present
•Continuous feedback and proprioceptive information relative to joint
position
–Articular afferents
•May only provide feedback under extreme loads
–Musculotendinous sensory organs
•Continuous feedback during submaximal loading
•Tenomuscular Mechanoreceptors
•Muscle spindles
–Detect length and rate of length changes
–Transmit information via afferent nerves
–Innervated by small motor fibers (gamma efferents)
–Project directly on motoneurons (monosynaptic reflexes)
–Stretch reflex
•Stimulation results in reflex contraction
•Continued stimulation (gamma motor nerves) heighten stretch
sensitivity
•Muscle activity mediation
•Golgi Tendon Organs (GTO)
–Regulate muscle activity and tension
–Located in tendon and tenomuscular junction
–Reflexively inhibit muscle activation when excessive tension may cause
damage
–Opposite of muscle spindle
•Produce reflex inhibition (relaxation) during muscle loading
Neural Pathways of Peripheral Afferents
•Encoded signals are transmitted from peripheral receptors via afferent pathways to CNS
•Ascending pathways to cerebral (somatosensory) cortex provide conscious appreciation
of proprioception and kinesthesia
•Sensory information from periphery is utilized by cerebral cortex for
somatosensory awareness and feed-forward neuromuscular control
•Balance and postural control are processed at brain stem (cerebellum)
•Balance
–Influenced by peripheral afferent mechanism mediating joint proprioception
–Partially dependent on inherent ability to integrate joint position sense, vision
and vestibular apparatus with neuromuscular control
•Reflex Loop
–Spinal Level Synapses
•Link afferent fibers with efferent motor nerves
–Contributes to dynamic stability utilizing feedback process for reactive muscular
activation
•Interneurons
–Connect articular receptors and GTO with large motor nerves innervating
muscles and small gamma motor nerves innervating muscle spindles
–Articular afferents have potent effect on muscle spindles
–Muscle spindles regulate muscle activity through stretch reflex
–Hence, articular afferents have influence on skeletal motor nerves and
tenomuscular receptors via gamma motor nerves
–Articular-tenomuscular link
–Muscle spindle feedback loop is responsible for continuously modifying
muscle activity through stretch reflex
–Through coordination of information, muscle stiffness is modified and
dynamic stability is maintained
Feed-Forward and Feedback Neuromuscular Control (Flow Chart)
•Feed-forward Neuromuscular control
–Pre-activation theory
•Prior sensory feedback (experience) is utilized to pre-program muscle
activation patterns
•Responsible for preparatory muscle action and high velocity movements
•Increased muscle activation = enhanced stiffness properties
•Leads
to improvement in stretch sensitivity and reduces electrochemical
delay
•Improves reactive capabilities (added sensory input and superimposed
stretch reflexes on descending motor command
•Feedback Neuromuscular Control
–Continuously adjusting muscle activity via reflex pathways
•May result in long conduction delays
•Best for postural adjustments and slow movements
–Reflex mediated dynamic stability is related to speed and magnitude of
perturbation
•Both systems enhance dynamic stability
–Repetitive activation of synapses = facilitation
•Memory recall of signal = enhanced function
Re-establishing Neuromuscular Control
•Injuries result in decrements in neuromuscular control
–Injury results in deafferentation of ligament and capsular mechanoreceptors
–Joint inflammation and pain compound sensory deficits
–Congenital/pathological joint laxity have diminished ability to detect joint
motion and position
•Proprioceptive, kinesthetic deficits, and mechanical instability = functional instability
•Objective of Neuromuscular Rehabilitation
–Develop/re-establish afferent and efferent characteristics that enhance dynamic
stability
•Afferent and Efferent Characteristics
–Sensitivity of peripheral receptors
–Facilitation of afferent pathways
–Muscle stiffness
–Onset rate and magnitude of muscle activity
–Agonist/antagonist coactivation
–Reflexive and discriminatory muscle activation
–Elements
•Proprioceptive and kinesthetic sensation
•Dynamic joint stabilization
•Reactive neuromuscular control
•Functional motor patterns
•Rehab of Peripheral Afferent Receptors
–Altered peripheral afferent information may disrupt motor control and functional
stability
–Repetitious athletic activity enhances proprioceptive and kinesthetic acuity =
facilitated afferent pathways
–Enhanced joint motion awareness improves feed-forward and feedback
mechanisms
•Rehab of Muscle Stiffness
–Significant role in preparatory and reactive dynamic restraints
–Exercises that encourage muscle stiffness should be incorporated into
rehabilitation programs
•Eccentric exercises
•Chronic overload results in connective tissue proliferation, desensitizing
GTO’s and increase muscle spindle activity
–Power trained vs. Endurance trained athletes
•Power athlete = Faster muscle pre-activation (EMG)
•Endurance athlete = Increased baseline motor tone
•Rehab of Reflexive Muscle Activation
–Reflex latency times may be dependent on types of training (endurance vs.
power)
–Preparatory and reactive muscle activation might improve dynamic stability and
function if muscle stiffness is enhanced in deficient joints
–Decreasing electromechanical delay between joint loading and protective muscle
activation can increase stability and function
•Rehab of Discriminate Muscle Activation
–Unconscious control of muscle activity is critical in balance and coordination
–Restoration of force couples may initially require conscious activation prior to
unconscious control
–Use of biofeedback can aid in this process
•Help eliminate imbalances and re-establish preparatory and reactive
muscle activity
Activities for Inducing Neuromuscular Adaptations
•Open and closed kinetic chain activities
•Balance training
•Eccentric and high repetition low load exercises
•Reflex facilitation
•Stretch-shortening
•Biofeedback training
•Controlled positions of vulnerability
•Proprioception and Kinesthesia Training
–Restore neurosensory properties
–Enhance sensitivity of uninvolved peripheral afferents
–Joint compression is believed to maximally stimulate articular receptors
•Closed chain exercises through available ROM
–Early repositioning tasks are critical
•Conscious to unconscious joint awareness
–Applying neoprene sleeve or ace wrap stimulates cutaneous receptors –
additional proprioception and kinesthesia
•Dynamic Stabilization Training
–Encourage preparatory agonist/antagonist coactivation
–Restores force couples and balances joint forces
•Results in decreased loads on static structures
–Activities that require anticipatory and reactive adjustments to imposed loads
–Combination of balance and stretch shortening exercises
•Encourages preparatory and reactive muscle activity
–Closed chain exercises induce coactivation and compression
•Reactive Neuromuscular Control Training
–Stimulates reflex pathways
–Object is to impose perturbations that stimulate reflex stabilization
•Can result in decreased response time and develop reactive strategies to
unexpected joint loads
•Perturbations should be unexpected in order to facilitate reflexive activity
•Functional Activities
–Objective is to return athlete to pre-injury activity
–Involves sports specific movement patterns designed to restore functional ability
–Can be utilized to assess readiness for return to play
–Stresses peripheral afferents, muscle coactivation, reflexive activity
–Progress from conscious to unconscious
–Develop functionally specific movement patterns, ultimately decreasing risk of
injury
Lower Extremity Techniques (Display illustrations)
•Techniques should focus on muscle groups that require attention
–Progress from no weight to weight assisted
•Use of closed-chain activities is encouraged
–Replicates environmental demands
–Plays on principles of neuromuscular control
•Joint stabilization exercises
–Balance and partial weight bearing activities
–Progress non-weight bearing to full weight-bearing
–Balance on unstable surfaces can begin once full-weight bearing
•Slide board exercises
–Stimulates coactivation with increasing muscle force and endurance
–Stimulating dynamic stability and stiffness
•Stair climbing (forward and backward)
–Emphasis on eccentric strength
•Biofeedback
–Used to develop agonist/antagonist coactivation
–Encourages voluntary muscle activation
•Stretch-shortening exercises
–Eccentric deceleration and explosive concentric contractions
–Incorporate early in process (modified loads)
–Involves preparatory and reactive muscle activity
–Hopping progression
•Double  Single leg
•Sagittal  Lateral  Rotational hopping
•Surface modification
•Rhythmic stabilization
–React to joint perturbations preparatory and reactive muscle actitivity
–Alterations in loads and displacement
•Unstable surfaces
–Linear and angular perturbations, altering center of gravity
–Facilitate reflexive activity
–Ball toss
•Disrupt concentration, induce unconscious response and reactive adaptation
•Trampoline Hopping
–Hopping and landing (double support, single support, rotation)
–Challenge athlete
•Hopping and catching
•Hopping and landing on varying surfaces
•Functional activities
–Restore normal gait
•Athlete must internalize normal kinematics (swing and stance)
•Utilize retro walking (hamstring activity), pool or unloading devices
•Cross over walking, figure 8’s, cutting, carioca, changes in speed
–Functional activities that simulate demands of sport
Upper Extremity (Display illustrations)
•Work to maintain joint congruency and functional stability
–Requires dynamic restraint via coordinated muscle activation
•Injury to static stabilizers
•Failure of dynamic restraint system
–Could result in repetitive loads, compromising joint integrity and
predisposing athlete to re-injury
•Adapt lower extremity exercise for upper extremity
•Closed and open kinetic chain activities should be incorporated
•Muscle stiffness
–Enhance using elastic resistance (focus on eccentrics)
–High repetitions and low resistance
–Upper extremity ergometers should be incorporated for endurance
•Dynamic stabilization
–Stability platforms
–Push-ups, horizontal abduction, tracing circles on slide board with dominant and
non-dominant arms
–Plyometric exercise
•Reactive Neuromuscular Exercises
–Manual perturbations
–Rhythmic stabilization with gradual progression
–Placing joint in inherently unstable positions
•Functional Training
–Developing motor patterns in overhead position
–Reproduce demands of activity
–Emphasis on technique
–Re-education of functional patterns
–Speed and complexity in movement require rapid integration of sensory
information