Improving Neuromuscular Control










CHAPTER 14


Improving Neuromuscular Control


OVERVIEW


The entire rehabilitation process is focused on restoring function as quickly and as safely as possible. An important component of function is neuromuscular control. Neuromuscular control involves the detection, perception, and utilization of relevant sensory information in order to perform specific tasks (see Chapter 3). It is now well accepted that a neuromuscular control impairment can change normal movement patterns and increase the risk of musculoskeletal injury. Successful performance of a task requires the intricate coordination of various body parts using the information provided by peripheral receptors located in and around the articular structures. This feedback provides information that assists with proprioception, balance, and kinesthesia (see Chapter 3). In terms of segmental joint control and spinal posture and orientation, each joint in the kinetic chain must have the ability to maintain the optimal alignment, biomechanics, and/or control required for the task being performed. If there is a loss of optimal alignment, biomechanics, and/or control, this is defined as failed load transfer (FLT) at that joint.1 While a single segmental loss of control often correlates with changes in posture orientation, multisegmental loss of control results in an inability to maintain the required spinal posture or orientation required for the task to be performed. The presence of a loss of segmental or multisegmental control involves an assessment of:



img whether there is adequate range of motion;


img whether there is sufficient strength output;


img whether there is the ability for automatic control of the joints in the kinetic chain that exhibit FLT;


img whether pain negatively impacts the performance of the task.


Neuromuscular rehabilitation (NMR) is a method of training used to enhance these unconscious motor responses, by stimulating both the afferent signals and the central mechanisms responsible for dynamic joint control.2 The aims of NMR are to improve the ability of the nervous system to generate a fast and optimal muscle-firing pattern, to increase joint stability, to decrease joint forces, and to relearn movement patterns and skills.2 Electromechanical delay (EMD) is defined as the time interval between the onset of electrical activity of the muscle and the mechanical response of the muscle.3 It corresponds to the time needed for the contractile component in the muscle-tendon complex to initiate stretching of the elastic component series,4 and its duration is related to the mechanical properties of the elastic component series (see Chapter 1).5 The shorter the EMD duration, the faster the muscle force transmission and the better the performance and protective reflex. Significantly longer EMDs in the vastus lateralis, vastus medialis obliquus, and fibularis (peroneous) longus have been reported in patients with anterior cruciate ligament reconstruction,6 patellofemoral pain syndrome,5 and unstable ankles,7 respectively, compared to healthy individuals. In addition, a number of studies have shown a decrease in EMD following neuromuscular reeducation training.8–11


Before developing an NMR program, the faulty movement pattern or absent motor skill must be identified.12 In addition, individuals must have the adequate muscle strength to perform training exercises correctly. If weaknesses are present, training activities must begin at a more baseline level that includes weight training, technique instruction, and performing single plane versus multiplanar movements.12 The three major components of NMR are proprioceptive retraining, balance retraining, and stabilization retraining.


PROPRIOCEPTIVE RETRAINING


Because the afferent input is altered after joint injury, proprioceptive training must focus on the restoration of proprioceptive sensibility to retrain these altered afferent pathways and enhance the sensation of joint movement.13 In designing exercises to improve three-dimensional dynamic upper and lower extremity postural stability, the clinician should consider the following:4



img Postural differences between patients


img Upper and lower extremity loading pathomechanics


img The joint positions for optimal muscle moment arm lengths


img The interplay between global and local proprioceptive mechanisms


img The concept of rehabilitating movements that facilitate the development of synergistic upper and lower extremity muscle function14


Although ROM and progressive resistance exercises (PREs) help reestablish joint proprioception, they are not as effective in restoring function as exercises that involve a technique or task training. Technique or task training involves the performance of specific movements with an emphasis on proper technique, with a progression to weight shifting, and changing directions, and then more advanced techniques, such as performing a cut maneuver, as appropriate.12 According to Voight and Blackburn,13,15 the standard progression for proprioceptive retraining involves:



  1. Static stabilization exercises with closed-chain loading and unloading (weight shifting). This phase initially employs isometric exercises around the involved joint on solid and even surfaces, before progressing to unstable surfaces. The early training involves balance training and joint repositioning exercises and usually is initiated (in the lower extremities) by having the patient place the involved extremity on a 6–8-inch-high stool, so that the amount of weight bearing can be controlled more easily. The proprioceptive awareness of a joint can also be enhanced by using an elastic bandage or orthotic, or through taping.16–21 As full-weight-bearing through the upper or lower extremity is restored, a number of devices, such as a mini trampoline, balance board, Swiss ball, and wobble board, can be introduced to increase the level of difficulty.
  2. Transitional stabilization exercises. The exercises during this phase involve conscious control of motion without impact and replace isometric activity with controlled concentric and eccentric exercises throughout a progressively larger range of functional motion. The physiologic rationale behind the exercises in this phase is to stimulate dynamic postural responses and increase muscle stiffness. Muscle stiffness has a significant role in improving dynamic stabilization around the joint, by resisting and absorbing joint loads.22
  3. Dynamic stabilization exercises. These exercises involve the unconscious control and loading of the joint and introduce both ballistic and impact exercises to the patient.

A delicate balance between stability and mobility is achieved by coordination among muscle strength, endurance, flexibility, and neuromuscular control.23 The neuromuscular mechanism that contributes to joint stability is mediated by the articular mechanoreceptors (see Chapter 3). These receptors provide information about joint position sense and kinesthesia.20,21,24,25 The objective in NMR is to restore proximal stability, muscle control, and flexibility through a balance of proprioceptive retraining and strengthening.


Initially, closed kinetic chain exercises (CKCEs) are performed within the pain-free ranges or positions. Open kinetic chain exercises (OKCEs), including low-level plyometric exercises, may be built upon the base of the closed-chain stabilization to allow normal control of joint mobility (see Chapter 12).


The neuromuscular emphasis during these exercises is on functional positioning during exercise rather than isolating open- and closed-chain activities.23 The activities should eventually involve sudden alterations in joint positioning that necessitate reflex muscular stabilization coupled with an axial load.21,23 Such activities include rhythmic stabilization performed in both a closed- and an open-chain position26 and in the functional position of the joint (see Chapter 12).23 The use of a stable, and then an unstable, base during CKCEs encourages cocontraction of the agonists and antagonists.26


Following treatment of any joint, retraining of the muscles must be carried out to reestablish coordination. Proprioceptive neuromuscular facilitation (PNF) techniques are especially useful in this regard. PNF techniques require motions of the extremities in all three planes.27 PNF techniques that use combinations of spiral and diagonal patterns are designed to enhance coordination and strength.28 The diagonal patterns 1 and 2 (see Chapter 10) are appropriate, with resistance being added if needed.


BALANCE RETRAINING


Neuromuscular control and balance testing are described in Chapter 3. Deficits in the motor components of balance control can be caused by sensorimotor integration impairments, neuromuscular impairments, and deficits due to aging (see Chapter 3). As outlined in Chapter 3, impaired balance can be caused by injury or disease to any structures involved in the stages of information processing: somatosensory input, visual and vestibular input, sensory motor integration, and motor output generation.29 Age-related balance dysfunctions can occur through a loss of sensory elements (degenerative changes in the otoconia of the utricle and saccule; loss of vestibular hair cell receptors), the ability to integrate information and issue motor commands (decreased number of vestibular neurons), and muscle weakness. Diseases common in aging populations can lead to further deterioration in balance function in some patients (Ménière’s disease, benign paroxysmal positional vertigo [BPPV], cerebrovascular disease, vertebrobasilar artery insufficiency, cerebellar dysfunction, and cardiac disease). Falls can be markers of poor health and declining function, and they are often associated with significant morbidity.30 More than 90% of hip fractures occur as a result of falls, with most of these fractures occurring in persons older than 70 years of age.30,31 One-third of community-dwelling elderly persons and 60% of nursing home residents fall each year.32 Risk factors for falls in the elderly include increasing age, medication use, cognitive impairment, and sensory deficits.30,33 Elderly persons who survive a fall experience significant morbidity.34 Hospital stays are almost twice as long in elderly patients who are hospitalized after a fall than in elderly patients who are admitted for another reason.30,35


Balance retraining focuses on the ability to maintain a position through both conscious and subconscious motor control. There are many factors to consider when developing an intervention program for balance impairment. The clinician needs to consider the patient’s impairments across all systems and decide which impairments can be rehabilitated and which require compensation or substitution.


It is also important to determine the cause of the impairment—whether the problem results from musculoskeletal, neuromuscular, sensory, or cognitive (e.g., fear of falling) impairment.36 The key elements of a comprehensive evaluation of individuals with balance problems include the following:37



img A thorough history of falls, including whether the onset of falls are sudden versus gradual; the frequency and direction of the falls; the environmental conditions, activities, presence of dizziness, vertigo, and lightheadedness at time of falls; current and past medications, and the presence of a fear of falling.


img Assessments to identify sensory input and/or sensory processing deficits, abnormal biomechanical and motor alignment, poor muscle strength and/or endurance, and decreased range of motion and/or flexibility. Of particular importance is core strength.36


img Assessment of coordination, and awareness of posture and the position of the body in space.


img Tests and observations to determine the impact of balance control system deficits on functional performance.


img Environmental assessments to determine full-risk hazards in a person’s home.


Studies have shown that proprioception and kinesthesia do improve following rehabilitation.20,38 For example, habituation exercises have proven beneficial for patients with acute unilateral vestibular loss, and adaptation and balance exercises have produced positive outcomes in patients with chronic bilateral vestibular deficits.39 The type of intervention will depend on the deficits found during the clinical examination and typically involves improving one or more of the following categories:37



img Static balance control


img Dynamic balance control


img Anticipatory balance control


img Reactive balance control


img Sensory reorganization


img Vestibular rehabilitation


Because balance training often involves activities that challenge the patient’s limits of stability, it is important that the clinician takes steps to ensure the patient’s safety. This may necessitate the use of a gait belt, performing the exercises near a railing, and closely guarding the patient. Examples of agility and perturbations activities are outlined in Table 14-1. Balance training to promote static balance control during the early phase involves changing the base of support (BOS) of the patient while performing various tasks, first with their eyes open and then with the eyes closed. The lower the center of gravity (COG), the more stable the patient feels. Thus, the prone or supine positions provide the lowest COG and the most support, sitting the next, with standing providing the highest COG and the least support. The usual progression employed in balance retraining involves a narrowing of the BOS while increasing the perturbation and changing the weight-bearing surface from hard to soft or from flat to uneven.











TABLE 14-1


Agility and Perturbation Training Examples





































Activity


Progression


Sidestepping: the patient steps sideways, moving right to left and then left to right, approximately 10–20 ft, repeating two times in each direction for a total of four times.


The width of steps and the speed of steps are progressed every 1–2 sessions. The activity is initiated on a level surface and progressed to sidestepping over low obstacles when the patient is able to sidestep on level surfaces without difficulty.


Braiding activities: the patient combines front and back crossover steps while moving laterally (walking carioca). During each activity, the patient moves right to left and then left to right, approximately 10–20 ft, repeating two times in each direction for a total of four times.


The activity is progressed by increasing the width of steps and the speed of steps every 1–2 sessions.


Front and back crossover steps during forward ambulation: the patient crosses one leg in front of the other, alternating legs with each step, while walking forward approximately 10–20 ft. The patient then walks backward to the start position while crossing one leg behind the other, alternating legs with each step.


Two repetitions are performed, beginning with partial crossover steps and progressing to full crossover steps when the patient’s performance improves. The width of steps and the speed of steps can be progressed every 1–2 sessions.


Shuttle walking: plastic pylon markers are placed at distances of 5, 10, and 15 ft. The patient walks forward to the first marker, then returns to the start by walking backward. The patient then walks forward to the 10-ft marker, then returns to the 5-ft marker walking backward. The patient then walks to the 15-ft marker, returns to the 10-foot marker walking backward, then finishes by walking to the 15-ft marker.


The activity is progressed by increasing the width of steps and the speed of steps every 1–2 sessions.


Multiple changes in direction on command during walking: the clinician directs the patient to either walk forward, backward, sideways, or on a diagonal by cueing the patient randomly with hand signals.


The duration of the exercise bout is approximately 30 seconds.


Double-leg foam balance activity: the patient stands on a soft firm surface with both feet on the ground and the clinician attempts to perturb the patient’s balance in a random fashion.


The duration of the activity is approximately 30 seconds. The difficulty is progressed as the patient improves by progressing to ball catching with the clinician perturbing the patient’s balance while standing on foam and progressing to single-leg support if tolerated.


Tilt board balance training: the patient stands on a tilt board with both feet on the board. The clinician perturbs the tilt board in forward and backward and side-to-side directions for approximately 30 seconds each.


The difficulty of the activity is progressed by adding ball catching during the perturbations and progressing to single limb support perturbations based on patient tolerance.


Rollerboard and platform perturbations: the patient stands with one limb on a stationary platform and the other limb on a rollerboard. The clinician perturbs the rollerboard in multiple directions, at random, and the patient attempts to resist the perturbations. The activity lasts approximately 30 seconds and is then repeated by changing the limbs on the platform and the rollerboard.


If the patient has difficulty doing the activity in full standing, the activity may begin with the patient in a semi-seated position, with the hips resting on the bed. The activity is progressed to the full standing position as tolerated.


Data from Fitzgerald GK, Piva SR, Gil AB, et al. Agility and perturbation training techniques in exercise therapy for reducing pain and improving function in people with knee osteoarthritis: a randomized clinical trial. Phys Ther. 2011;91(4):452–469.




Dec 27, 2016 | Posted by in ORTHOPEDIC | Comments Off on Improving Neuromuscular Control
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