Chapter 5: Re-establishing Neuromuscular Control

1. Chapter 5: Re-establishing Neuromuscular Control

2. Why is it critical to the rehabilitation process? • Refocuses the athlete’s awareness of peripheral sensation and processes them in more coordinated motor strategies • Required to: • Protect joints from excessive strain • Provide prophylactic mechanism to recurrent injury • Complements traditional components of rehabilitation

3. 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

4. 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 • Clinicians must work to re-establish and encourage restoration of functional stability

5. 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

6. What is neuromuscular control? • Proprioception • Conscious and unconscious appreciation 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

7. Motor control mechanisms • 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

8. 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

9. Physiology of Mechanoreceptors • 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

10. 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

11. 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

12. 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

13. Neural Pathways of Peripheral Afferents • Encoded signals are transmitted from peripheral receptors via afferent pathways to CNS • Ascending pathways to cerebral cortex provide conscious appreciation of proprioception and kinesthesia • Two reflexive pathways couple articular receptors with motor nerves and tenomuscular receptors in spinal column • Monosynaptic reflex pathway links muscle spindles directly to motor nerves

14. 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 • 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

15. Reflex Loop • Spinal Level Synapses • Link afferent fibers with efferent motor nerves • Contributes to dynamic stability utilizing feedback process for reactive muscular activation

16. 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

17. Final Common Input • Articular-tenomuscular link • Muscle spindles integrate peripheral afferent information and transmit a final modified signal to CNS • 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

18. Feed-Forward and Feedback Neuromuscular Control • 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 reduce electrochemical delay • Improves reactive capabilities (added sensory input and superimposed stretch reflexes on descending motor command

20. 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

21. Re-establishing Neuromuscular Control • Injuries result in decrements in neuromuscular control • Pathoetiology • 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 lead to functional instability

22. Objective of Neuromuscular Rehabilitation • Develop/re-establish afferent and efferent characteristics that enhance dynamic stability • Elements • Proprioceptive and kinesthetic sensation • Dynamic joint stabilization • Reactive neuromuscular control • Functional motor patterns

23. 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

24. Activities for Inducing 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

25. Neuromuscular Characteristics • 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

26. 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

27. 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

28. 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

29. Elements for Neuromuscular Control • 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

30. Dynamic Stabilization • 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

31. Reactive Neuromuscular Control • Stimulates reflex pathways • Object is to impose perturbations that stimulate reflex stabilization • Can resultin decreased response time and develop reactive strategies to unexpected joint loads • Perturbations should be unexpected in order to facilitate reflexive activity

32. 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

33. Lower Extremity Techniques • 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

34. 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

35. 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

36. 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

37. Unstable surfaces • Linear and angular perturbations, altering center of gravity • Facilitate reflexive activity • Ball toss • Disrupt concentration, induce unconscious response and reactive adaptation

38. 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

39. Upper Extremity • 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

40. 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

41. Reactive Neuromuscular Exercises • Manual perturbations • Rhythmic stabilization with gradual progression • Placing joint in inherently unstable positions

42. 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