Chapter 14. Improving Neuromuscular Control

At the completion of this chapter, the reader will be able to:

1. Define the components of neuromuscular control.

2. Describe ways in which neuromuscular control can be improved through physical therapy.

3. Describe a number of exercises that can be used to improve neuromuscular control.

4. Provide examples to enhance balance retraining.

5. Explain the concepts related to stabilization retraining.

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. Successful performance of a task requires the intricate coordination of various body parts using information provided by peripheral receptors located in and around the articular structures (see Chap. 3). This feedback provides information that assists with proprioception, balance, and neuromuscular control. It is now well accepted that neuromuscular control impairment can change movement patterns and increase the risk of musculoskeletal injury.

Neuromuscular rehabilitation (NMR) is a method of training the enhancement of these unconscious motor responses, by stimulating both the afferent signals and the central mechanisms responsible for dynamic joint control.1 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.1 Before developing a neuromuscular training program, the faulty movement pattern or absent motor skill must be identified.2 In addition, before initiating a neuromuscular training program, individuals must have 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.2 The three major components of NMR are proprioceptive retraining, balance retraining, and stabilization retraining.

Because 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.3 In designing exercises to improve three-dimensional dynamic lower extremity postural stability, the clinician should consider the following: 4

• Postural differences between patients
• Lower extremity loading pathomechanics
• Hip, knee, and ankle joint positions for optimal muscle moment arm lengths
• The interplay between global and local proprioceptive mechanisms
• The concept of rehabilitating movements that facilitate the development of synergistic lower extremity muscle function

Although ROM and progressive resistance exercises (PREs) help reestablish joint proprioception, they are not as effective in restoring function as exercises that involve technique or task training. Technique or task training involves the performance of specific movements with an emphasis on proper technique, with the primary chosen movement being one that results in a large percentage of injuries, such as changing direction, transferring from sit to stand, or more advanced techniques such as performing a cut maneuver.2 According to Voight,3,5 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.6–11 As full-weight-bearing through the extremity is restored, a number of devices, such as a minitrampoline, balance board, Swiss ball, and wobble board, can be introduced. Exercises on these devices are progressed from double-limb support to single-leg support to full support while performing sports-specific skills.

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.12

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.13 The neuromuscular mechanism that contributes to joint stability is mediated by the articular mechanoreceptors (see Chap. 3). These receptors provide information about joint position sense and kinesthesia.10,11,14,15 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 mild plyometric exercises, may be built upon the base of the closed-chain stabilization to allow normal control of joint mobility (see Chap. 12).

The neuromuscular emphasis during these exercises is on functional positioning during exercise rather than isolating open- and closed-chain activities.13 The activities should involve sudden alterations in joint positioning that necessitate reflex muscular stabilization coupled with an axial load.11,13 Such activities include rhythmic stabilization performed in both a closed- and an open-chain position16 and in the functional position of the joint (see Chap. 12).13 The use of a stable, and then an unstable, base during CKCEs encourages co-contraction of the agonists and antagonists.16

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.17 PNF techniques that use combinations of spiral and diagonal patterns are designed to enhance coordination and strength.18 The diagonal patterns 1 and 2 (see Chap. 10) are appropriate, with resistance being added as appropriate.

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. 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.19 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.20 The key elements of a comprehensive evaluation of individuals with balance problems include the following:21

• 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.
• 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.20
• Assessment of coordination, and awareness of posture and the position of the body in space.
• Tests and observations to determine the impact of balance control system deficits on functional performance.
• Environmental assessments to determine full-risk hazards in a person's home.

Studies have shown that proprioception and kinesthesia do improve following rehabilitation.10,11 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.22 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:21

• Static balance control
• Dynamic balance control
• Anticipatory balance control
• Reactive balance control
• Sensory reorganization
• 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 includes 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 involves changing the base of support of the patient while performing various tasks, first with their eyes open and then with the eyes closed. The lower the center of gravity, the more stable the patient feels. Thus, the prone or supine positions provide the lowest center of gravity and the most support, sitting the next, with standing providing the highest center of gravity and the least support. The usual progression employed in balance retraining involves a narrowing of the base of support while increasing the perturbation and changing the weight-bearing surface from hard to soft or from flat to uneven.

• Balance training for adults usually begins in the short sitting position, which allows the feet to provide anterior support. This position can be made more challenging by placing a wobble board or Swiss ball under the patient's buttocks. The patient is then progressed to quadruped, through tall kneeling, and finally to the standing position.
• Balance training for the pediatric population usually begins in the “W” sitting position, then to “Indian-style sitting,” then to quadruped, through tall kneeling, and finally to the standing position.

Once the patient is able to stand, the structured sequence such as the one that follows is recommended.

• Static control of the trunk without extremity movement. These exercises involve closed chain loading/unloading. The patient is positioned in standing, with the feet positioned approximately shoulder-width apart. The purpose of the starting position is to provide a stable base from the proximal segments and trunk onto which challenges can be superimposed. For example:
  • Manual perturbations to a stable trunk. The clinician applies gentle perturbations to the patient's trunk in different directions.
  • Weight shifting while maintaining postural equilibrium. Initially, the patient, with the feet positioned approximately shoulder-width apart, is instructed to alternate transferring weight through one lower extremity then the other. Then the patient is asked to put one foot in front of the other and to transfer the weight from the rear foot to the front foot and back again.
• Dynamic control of trunk without extremity movement. For example, maintaining both feet on the ground while bending at the waist. As indicated, the range of motion is increased from a small range to a larger range.

Once this is mastered, the progression moves to exercises that incorporate static control of the trunk with extremity movement(s) superimposed using the following progression:

• Standing with the feet positioned approximately shoulder-width apart, the patient is asked to flex the hip and knee, so that the foot is approximately 6–8 inches off the floor. The exercise is repeated using the other leg. To add a challenge to the exercise, the patient can be trained with the eyes closed, or the patient can stand on an unstable surface.
• Standing with the feet positioned approximately shoulder-width apart, the patient grasps resistive-tubing with one hand and pulls the tubing toward the body using a smooth, comfortable motion (Fig. 14-1). This produces a forward weight shift that is stabilized with an isometric counterforce consisting of hip extension, knee extension, and ankle plantarflexion.23
• The patient stands sideways to the resistive-tubing. The tubing is pulled by one hand in front of the body and the other hand behind the body to equalize the force and minimize the rotation (Fig. 14-2). This causes a lateral weight shift, which is stabilized with an isometric counterforce consisting of hip abduction, knee cocontraction, and ankle eversion.23
• The patient stands with his/her back to the tubing in the frontal plane (Fig. 14-3). The tubing is pulled to the body from behind, causing a posterior weight shift, which is stabilized by an isometric counterforce consisting of hip flexion, knee flexion, and ankle dorsiflexion.23

The aforementioned single plane exercises are progressed to multiplanar exercises in the following manner:

• PNF movement patterns are initiated using resistive-tubing. Initially the patient stands with both feet shoulder-width apart, and then the exercises are progressed so that the patient is standing on one leg. In addition to using resistive-tubing, medicine balls can be used.
• Ballistic extremity movements while maintaining trunk stability are introduced, first in sitting and then in standing. For example, maintain the sitting position while throwing a medicine ball (Fig. 14-4).

At the earliest opportunity functional tasks must be incorporated. A typical functional activity progression includes:

• Closed-chain activities (squats, lunges) initially, then open-chain activities superimposed on the closed chain by adding extremity motions to the squats and lunges (Fig. 14-5).
• Sit–stand–sit activities focusing on moving the body mass forward over the base of support, extending the lower extremities and raising the body mass over the feet, and then reversing the procedure.
• Stand–to–sit transitions focusing on balance control while pivoting and changing direction.
• Floor to standing raises using progression of side-sit to quadruped to kneeling to half kneeling to standing.
• Gait activities: ambulating forwards, backwards, sideward at varying speeds and base of support widths (narrow to wide). Resisted walking and/or running can also be used.
• As appropriate, multidirectional drills including jumping (two-foot takeoff followed by two-foot landing), hopping (one-foot takeoff followed by landing on the same foot) (Fig. 14-6), and bounding (one-foot takeoff followed by an opposite-foot landing).23

Stability normally involves the interaction of three systems—the neurological or central control system, the passive or inert tissues (e.g., ligaments, capsule), and the contractile (muscular) or active system (see Chap. 3).24

The neutral zone is a term used to define a region of laxity around the neutral resting position of a joint (see Chap. 2).25 The neutral zone refers to the position of a joint in which minimal loading is occurring in the passive structures (all of the noncontractile elements of the joint including the ligaments, fascia, joint capsules, and non-contractile components of muscle), and the contribution of the active system (the muscles and tendons which surround and control joint motion) is most critical.26,27

In both the spine and the extremities, certain muscles work as either mobilizers or stabilizers. The peripheral stabilizers rely on stabilization of the two primary dynamic bases or core structures—the pelvis and the scapula. The pelvis acts as a base for the whole body, especially for the spine and the lower limbs, whereas the scapula acts as a base for its respective upper limb.24 During peripheral joint movement, the peripheral stabilizer muscles normally contract first to stabilize the core structures from which the mobilizers work.24,32 The mobilizers then contract, resulting in a controlled movement pattern. For example, during upper extremity activity, the scapular stabilizers contract first to stabilize the scapula before the other shoulder muscles move the upper extremity into a functional position. However, with injury, a pathologic process, or other abnormality, an abnormal stabilizer recruitment pattern can develop, resulting in a dominance of the mobilizer muscles and eventual weakening of the local stabilizers.24,32

For stabilization retraining to be effective, the clinician must, therefore, ensure that a stable base is present from which the mobilizers can act. Once the stabilizer muscles are functioning efficiently, training of the mobilizer muscles can begin using the following sequence: isometric to concentric, to eccentric, and ecocentric (pseudo-isometric) contractions, and finally to functional movement (see Chap. 12).24

The body has several natural stabilization methods including muscle contraction, muscle spasm, osteophyte formation, scar tissue formation, and adaptive shortening of inert tissue or muscle.24 While the clinician cannot impact some of these natural stabilization methods such as muscle spasm, osteophyte and scar tissue formation, the clinician can use muscle contraction and adaptive shortening to the patient's advantage.

Stabilization retraining involves approximately 6 stages with 12 steps:24,32,33

• Stage 1. This stage typically occurs in the acute phase of healing.

  Step 1: Decrease pain. This can be accomplished through muscle relaxation techniques, patient education on joint resting positions and proper body mechanics, the use of electro physical agents, working in the pain-free range, and the use of medication.34

  Step 2: Allow freedom of movement and proper arthrokinematic movement of the joint. This can be accomplished through joint mobilization (joint capsule), prolonged passive stretch (inert tissue and muscle), muscle energy techniques (muscle), active release techniques (muscle), manipulation (joint), and neurodynamic techniques (nerve), depending on the tissue causing the restriction.24

• Stage 2. This stage is initiated once pain is under control and normal arthrokinematics are restored.

  Step 1: Ensure that the individual muscles will contract when and how they should, starting with an isometric contraction of the isolated muscle (stabilizers first). The initial emphasis is directed toward strengthening any weak stabilizer muscles using the inner range or muscle test position.

  Step 2: Ensure proper muscle recruitment and reeducation so that the muscles contract in the correct order—stabilizers first, then mobilizers. Once the patient can contract the muscle isometrically, concentric movement within the range that the patient has control using the mobilizers can be initiated, but only if the stabilizer muscles function properly.24 Finally, training progresses to the use of eccentric contractions which allow the patient to maintain control of the base while lengthening during functional movements or slowing down a particular motion.24

  Step 3: Ensure muscle imbalance between muscle groups to ensure that the various force couples work together correctly and function to enable control and eliminate incoordination. In general, to correct muscle length, one should exercise lengthened muscles in the inner range to shorten them, and stretch short muscles to lengthen them.24

• Stage 3. This stage should only be initiated when the patient has learned to statically control the core structures.

  Step 1: Correct endurance and strength discrepancies. Exercises for stabilizer muscles may involve high-load, low-repetition training, although the focus should be on lower loads and high repetitions to build up resistance to fatigue.

• Stage 4. This stage is typically initiated at the same time the stage 3, provided the patient has successfully completed stages one and two and can demonstrate control of the core.

  Step 1: Retrain proprioception. Proprioceptive retraining is outlined at the beginning of the chapter.

• Stage 5. This stage involves the integration of five different steps into the program.35

  Step 1: Reeducate stabilizing muscle statically. This is achieved by ensuring proximal stabilization of the core while allowing distal movement through the extremities. Short arc movements are performed initially while the clinician observes for the expected proper sequence of muscle contractions (stabilizers then mobilizers), correct force-couple action, and good muscle cocontraction (static stabilization).

  Step 2: Teach advanced static stabilization exercises. This involves taking the patient into the mechanism of injury position and asking him or her to hold the position statically against resistance.

  Step 3: Teach dynamic stabilization exercises. This involves the use of controlled movement patterns to ensure the development of proper movement patterns (engrams—see Chap. 3) and voluntary control. Exercises during this step involve movement of the core, with the control muscles acting eccentrically while distal joints are moved concentrically through the full range of movement.

  Step 4: Teach advanced dynamic stabilization exercises. Exercises during this step include multidirectional stability training that require control of functional speeds, progressive eccentric exercises at functional speeds, and stressing of functional diagonal patterns used in the activities to which the person plans to return.

  Step 5: Teach functional stabilization. Functional activities are initially broken down into their component parts before performing the whole movement.

• Stage 6

  Step 1: Maintain or restore fitness throughout. Depending on the location of the injury, endurance exercises are prescribed for the upper extremities or lower extremities to improve or maintain cardiovascular fitness (see Chap. 15).

  Step 2: Return to sport or heavy manual labor as appropriate. In order to return to sport or heavy manual labor, there should be:24

  • Complete resolution of acute signs and symptoms
  • Sufficient dynamic, functional range of motion of all joints involved in the activity
  • Adequate strength, endurance, and proprioceptive/kinesthetic sense to perform the expected skills successfully
  • No alteration of the patient's normal mechanics that could predispose him or her to reinjury