Re-establishing establishing Neuromuscular

Transcription

1 Re-establishing establishing Neuromuscular Control Why is NMC Critical? What is NMC? Physiology of Mechanoreceptors Elements of NMC Lower-Extremity Techniques Upper-Extremity Techniques Readings Chapter 6 Olmstead et al. (2002). Journal of Athletic Training. 37(4), Riemann & Lephart (2002a), Journal of Athletic Training, 37(1), Riemann & Lephart (2002b), Journal of Athletic Training, 37(1), Why is NM Control critical to the rehab process? Refocuses the patients awareness of peripheral sensation Process signals Processes signals into more coordinated motor strategies Protect joints from excessive strain Provide prophylactic mechanism to recurrent injury Dynamic restraint system Articular structures Stabilize and guide body segments Provide mechanical restraint to abnormal joint motion Capsuloligamentous tissue Detect joint motion and position Tenomuscular receptor Detect changes in muscle length Implicated in regulating muscle stiffness prior to loading

2 Injury results in damage to microscopic nerves associated with peripheral mechanoreceptors 1. Disrupts sensory feedback 2. Alters reflexive joint stabilization and NM coordination Must work to re-establish & encourage restoration of functional stability Rehabilitation should address feedback systems Preparatory (feed-forward) Reactive (feed-back) Four critical elements What is NM control? Conscious and unconscious appreciation of joint position Sensation of joint motion or acceleration Signal transmission through afferent sensory pathways Efferent motor response to sensory information Proprioception and kinesthesia

3 Motor control mechanisms 1. Feed-forward neuromuscular control Planning movements based on sensory information past experiences Preparatory muscle activity 2. Feed-back neuromuscular control Continuously regulates muscle activity through reflexive pathways Reactive muscle activity Dynamic restraint is achieved through preparatory and reflexive neuromuscular control 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 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 & high velocity mvts 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 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 Comerford, M. J., & Mottram, S. L. (2001). Functional stability re-training: principles and strategies for managing mechanical dysfunction. Manual Therapy, 6(1), 3-14.

4 Physiology of Mechanoreceptors The dynamic restraint system is mediated by specialised nerve endings called mechanoreceptors Articular Mechanoreceptors Specialized nerve endings that transduce mechanical tissue deformation into frequency modulated neural signals Increased tissue deformation results in increased afferent firingi rate or rise in quantity of mechanoreceptors activated Provide sensory information concerning internal and external forces acting on the joint 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 Relieved distribution Differ between joints, shoulder v knee Musculotendinous unit sensory organs Continuous feedback during submaximal loading

5 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 in agonist Continued stimulation 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

6 Re-establishing Neuromuscular Control Proprioceptive, kinesthetic deficits and mechanical instability lead to Injuries result in decrements in NM control functional instability Pathoetiology Injury = deafferentation of ligament capsular mechanoreceptors Joint inflammation and pain compound sensory deficits Congenital/pathological joint laxity have diminished ability to detect joint motion and position 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

7 Activities for Inducing NM 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 Key Neuromuscular Characteristics Altered peripheral afferent information Enhanced joint motion awareness Repetitious athletic activity 1 2 Role in preparatory and reactive dynamic restraints Exercises that encourage muscle stiffness = ECC 4 3 Unconscious control of muscle activity critical Restoration of force couples may initially require conscious activation Reflex latency times may be dependent on types of training electromechanical delay = stability function Elements for Neuromuscular Control Proprioception Kinesthesia Training Dynamic Stabilization Reactive Neuromuscular Control Functional Activities 1. Restore neurosensory properties 2. Enhance sensitivity of uninvolved peripheral afferents 3. Joint compression may maximally stimulate articular receptors 4. CKC exercises through available ROM 1. Encourage preparatory agonist/antagonist coactivation 2. Restores force couples and balances joint forces 3. Combination of balance and stretch shortening exercises 4. CKC exercises induce coactivation and compression 1. Stimulates reflex pathways 2. Impose perturbations that stimulate reflex stabilization 3. Can result in decreased response time and develop reactive strategies to unexpected joint loads 4. Perturbations should be unexpected to facilitate reflexive activity 1. Involves sports specific movement patterns designed to restore functional ability 2. Can be utilized to assess readiness for return to play 3. Stresses peripheral afferents, muscle coactivation, reflexive activity 4. Progress from conscious to unconscious 5. Functional specific movement, ultimately risk of injury

8 Peak knee flexion during jump-landing (pre-training v post-training). A LOWER LIMB LANDING ASSESSMENT TOOL FOR ATHLETES AT RISK OF DEVELOPING KNEE INJURY Kerry Mann, Suzi Edwards, Stephen Bird Bachelor of Exercise Science Honours research project Lephart et al. 2005, British Journal of Sports Medicine. 39: Lower Extremity Techniques Balance and partial weight bearing activities Balance on unstable surfaces can begin once full-weight bearing Stimulates coactivation, increasing muscle force and endurance Stimulating dynamic stability and stiffness Emphasis on eccentric strength Lower Extremity Techniques Used to develop agonist/antagonist coactivation Encourages voluntary muscle activation 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 React to joint perturbations preparatory and reactive muscle actiivity Alterations in loads and displacement

9 Lower Extremity Techniques Linear and angular perturbations, altering center of gravity Facilitate reflexive activity Ball toss: disrupt concentration, induce unconscious response and reactive adaptation Hopping and landing (double support, single support, rotation) Challenge athlete Hopping and catching Hopping and landing on varying surfaces 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 Techniques Stability platforms Push-ups, horizontal abduction, tracing circles on slide board with dominant and non-dominant arms Plyometric exercise Manual perturbations Rhythmic stabilization with gradual progression Placing joint in inherently unstable positions 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