Proprioceptive Neuromuscular Facilitation Techniques in Rehabilitation

William E. Prentice, PhD, PT, ATC, FNATA

Proprioceptive neuromuscular facilitation (PNF) is an approach to therapeutic exercise based on the principles of functional human anatomy and neurophysiology.12,78 It uses proprioceptive, cutaneous, and auditory input to produce functional improvement in motor output, and it can be a vital element in the rehabilitation process of many conditions and injuries.⁷⁸ It is a manual therapeutic technique that is widely used by clinicians in multiple aspects of injury rehabilitation.⁸⁹

The therapeutic techniques of PNF were first used in the treatment of patients with paralysis and various neuromuscular disorders in the 1950s.⁸⁴ Originally, PNF techniques were used for strengthening and enhancing neuromuscular control.^{15,28,31,58,79} Since the early 1970s, PNF techniques have also been used extensively as a technique for increasing flexibility and range of motion (ROM).^{10,11,19–21,35,39,41,55,66,82,87}

This discussion should guide the athletic trainer in using the principles and techniques of PNF as a component of a rehabilitation program.

PNF AS A TECHNIQUE FOR IMPROVING STRENGTH AND ENHANCING NEUROMUSCULAR CONTROL

Original Concepts of Facilitation and Inhibition

Most of the principles underlying modern therapeutic exercise techniques can be attributed to the work of Sherrington,⁷⁶ who first defined the concepts of facilitation and inhibition.

According to Sherrington, an impulse traveling down the corticospinal tract or an afferent impulse traveling up from peripheral receptors in the muscle causes an impulse volley that results in the discharge of a limited number of specific motor neurons, as well as the discharge of additional surrounding (anatomically close) motor neurons in the subliminal fringe area. An impulse causing the recruitment and discharge of additional motor neurons within the subliminal fringe is said to be facilitatory. Any stimulus that causes motor neurons to drop out of the discharge zone and away from the subliminal fringe is said to be inhibitory.⁴⁹ Facilitation results in increased excitability, and inhibition results in decreased excitability of motor neurons.⁹⁵ Thus, the function of weak muscles would be aided by facilitation, and muscle spasticity would be decreased by inhibition.²²

Sherrington attributed the impulses transmitted from the peripheral stretch receptors via the afferent system as being the strongest influence on the alpha motor neurons.⁷⁶ Therefore, the athletic trainer should be able to modify the input from the peripheral receptors and, thus, influence the excitability of the alpha motor neurons. The discharge of motor neurons can be facilitated by peripheral stimulation, which causes afferent impulses to make contact with excitatory neurons and results in increased muscle tone or strength of voluntary contraction. Motor neurons can also be inhibited by peripheral stimulation, which causes afferent impulses to make contact with inhibitory neurons, resulting in muscle relaxation and allowing for stretching of the muscle.⁷⁶ PNF should be used to indicate any technique in which input from peripheral receptors is used to facilitate or inhibit.²²

Several different approaches to therapeutic exercise based on the principles of facilitation and inhibition have been proposed. Among these are the Bobath method,^6,7 Brunnstrom method,⁷³ Rood method,⁷¹ and Knott and Voss method,⁴² which they called PNF. Although each of these techniques is important and useful, the PNF approach of Knott and Voss probably makes the most explicit use of proprioceptive stimulation.⁴²

Rationale for Use

As a positive approach to injury rehabilitation, PNF is aimed at what the patient can do physically within the limitations of the injury. It is perhaps best used to mitigate deficiencies in strength, flexibility, and neuromuscular coordination in response to demands that are placed on the neuromuscular system.⁴⁶ The emphasis is on selective reeducation of individual motor elements through development of neuromuscular control, joint stability, and coordinated mobility. Each movement is learned and then reinforced through repetition in an appropriately demanding and intense rehabilitative program.72

The body tends to respond to the demands placed on it. The principles of PNF attempt to provide a maximal response for increasing strength and neuromuscular control.^9,84,85 These principles should be applied with consideration of their appropriateness in achieving a particular goal. It is well accepted that the continued activity during a rehabilitation program is essential for maintaining or improving strength. Therefore, an intense program should offer the greatest potential for recovery.⁶⁵

The PNF approach is holistic, integrating sensory, motor, and psychological aspects of a rehabilitation program. It incorporates reflex activities from the spinal levels and upward, either inhibiting or facilitating them as appropriate.

The brain recognizes only gross joint movement and not individual muscle action. Moreover, the strength of a muscle contraction is directly proportional to the number of activated motor units. Therefore, to increase the strength of a muscle, the maximum number of motor units must be stimulated to strengthen the remaining muscle fibers.^35,42 This “irradiation,” or overflow effect, can occur when the stronger muscle groups help the weaker groups in completing a particular movement. This cooperation leads to the rehabilitation goal of return to optimal function.^5,42 The principles of PNF, as discussed in the next section, should be applied to reach that ultimate goal.

BASIC PRINCIPLES OF PNF

Margret Knott, in her text on PNF,⁴² emphasized the importance of the principles rather than specific techniques in a rehabilitation program. These principles are the basis of PNF that must be superimposed on any specific technique. The principles of PNF are based on sound neurophysiologic and kinesiologic principles and clinical experience.⁷² Application of the following principles can help promote a desired response in the patient being treated.

1. The patient must be taught the PNF patterns regarding the sequential movements from starting position to terminal position. The athletic trainer has to keep instructions brief and simple. It is sometimes helpful for the athletic trainer to passively move the patient through the desired movement pattern to demonstrate precisely what is to be done. The patterns should be used along with the techniques to increase the effects of the treatment.
   
2. When learning the patterns, the patient is often helped by looking at the moving limb. This visual stimulus offers the patient feedback for directional and positional control.
   
3. Verbal cues are used to coordinate voluntary effort with reflex responses. Commands should be firm and simple; those most commonly used with PNF techniques are “push” and “pull,” which ask for an isotonic contraction; “hold,” which asks for an isometric or stabilizing contraction; and “relax.”
   
4. Manual contact with appropriate pressure is essential for influencing direction of motion and facilitating a maximal response because reflex responses are greatly affected by pressure receptors. Manual contact should be firm and confident to give the patient a feeling of security. The manner in which the athletic trainer touches the patient influences his or her confidence as well as the appropriateness of the motor response or relaxation.⁷² A movement response may be facilitated by the hand over the muscle being contracted to facilitate a movement or a stabilizing contraction.
   
5. Proper mechanics and body positioning of the athletic trainer are essential in applying pressure and resistance. The athletic trainer should stand in a position that is in line with the direction of movement in the diagonal movement pattern. The knees should be bent and close to the patient such that the direction of resistance can easily be applied or altered appropriately throughout the range.
   
6. The amount of resistance given should facilitate a maximal response that allows smooth, coordinated motion. The appropriate resistance depends to a large extent on the capabilities of the patient. It may also change at different points throughout the ROM. Maximal resistance may be applied with techniques that use isometric contractions to restrict motion to a specific point; it may also be used in isotonic contractions throughout a full range of movement.
   
7. Rotational movement is a critical component in all of the PNF patterns because maximal contraction is impossible without it.
   
8. Normal timing is the sequence of muscle contraction that occurs in any normal motor activity resulting in coordinated movement.42 The distal movements of the patterns should occur first. The distal movement components should be completed no later than halfway through the PNF pattern. To accomplish this, appropriate verbal commands should be timed with manual commands. Normal timing may be used with maximal resistance or without resistance from the athletic trainer.
   
9. Timing for emphasis is used primarily with isotonic contractions. This principle superimposes maximal resistance, at specific points in the range, upon the patterns of facilitation, allowing overflow or irradiation to the weaker components of a movement pattern. The stronger components are emphasized to facilitate the weaker components of a movement pattern.
   
10. Specific joints may be facilitated by using traction or approximation. Traction spreads apart the joint articulations, and approximation presses them together. Both techniques stimulate the joint proprioceptors. Traction increases the muscular response, promotes movement, assists isotonic contractions, and is used with most flexion antigravity movements. Traction must be maintained throughout the pattern. Approximation increases the muscular response, promotes stability, assists isometric contractions, and is used most with extension (gravity-assisted) movements. Approximation may be quick or gradual and repeated during a pattern.
    
11. Giving a quick stretch to the muscle before muscle contraction facilitates a muscle to respond with greater force through the mechanisms of the stretch reflex. It is most effective if all the components of a movement are stretched simultaneously. However, this quick stretch can be contraindicated in many orthopedic conditions because the extensibility limits of a damaged musculotendinous unit or joint structure might be exceeded, exacerbating the injury.

BASIC STRENGTHENING TECHNIQUES

Each of the principles described in the previous section should be applied to the specific techniques of PNF. These techniques may be used in a rehabilitation program to strengthen or facilitate a particular agonistic muscle group.^34,53,54 The choice of a specific technique depends on the deficits of a particular patient.⁶⁸ Specific techniques or combinations of techniques should be selected on the basis of the patient’s problem.⁴

Slow reversal involves an isotonic contraction of the agonist followed immediately by an isotonic contraction of the antagonist. The initial contraction of the agonist muscle group facilitates the succeeding contraction of the antagonist muscles. The slow-reversal technique can be used for developing active ROM of the agonists and normal reciprocal timing between the antagonists and agonists, which is critical for normal coordinated motion.67 The patient should be commanded to push against maximal resistance by using the antagonist and then to pull by using the agonist. The initial agonistic push facilitates the succeeding antagonist contraction.

Slow-Reversal-Hold

Slow-reversal-hold is an isotonic contraction of the agonist followed immediately by an isometric contraction, with a hold command given at the end of each active movement. The direction of the pattern is reversed by using the same sequence of contraction with no relaxation before shifting to the antagonistic pattern. This technique can be especially useful in developing strength at a specific point in the ROM.

Rhythmic Stabilization

Rhythmic stabilization uses an isometric contraction of the agonist, followed by an isometric contraction of the antagonist to produce cocontraction and stability of the 2 opposing muscle groups. The command given is always “hold,” and movement is resisted in each direction. Rhythmic stabilization results in an increase in the holding power to a point where the position cannot be broken. Holding should emphasize cocontraction of agonists and antagonists.

Treating Specific Problems With PNF Techniques

PNF strengthening techniques can be useful in a variety of different conditions. To some extent, the choice of the most effective technique for a given situation is dictated by the state of the existing condition and the capabilities and limitations of the individual patient.87 There are some advantages to using PNF techniques in general.

Relative to strengthening, the PNF techniques are not encumbered by the design constraints of commercial exercise machines, although some of the newer exercise machines have been designed to accommodate triplanar motion and, thus, will allow for PNF patterned motion.¹² With the PNF patterns, movement can occur in 3 planes simultaneously, thus more closely resembling a functional movement pattern. The amount of resistance applied by the athletic trainer can be easily adjusted and altered at different points through the ROM to meet patient capabilities.⁴⁵ The athletic trainer can choose to concentrate on strengthening through the entire ROM or through a very specific range. Combinations of several strengthening techniques can be used concurrently within the same PNF pattern.⁶³

Rhythmic initiation is useful in the early stages of rehabilitation when the patient is having difficulty moving actively through a pain-free arc. Passive movement can allow the patient to maintain a full range while using an active contraction to move through the available pain-free range. Slow reversal should be used to help improve muscular endurance. Slow-reversal-hold is used to correct existing weakness at specific points in the ROM through isometric strengthening. Rhythmic stabilization is used to achieve stability and neuromuscular control about a joint.^13,24 This technique requires cocontraction of opposing muscle groups and is useful in creating a balance in the existing force couples. Some clinicians have indicated that a disadvantage of the PNF stretching techniques is that a partner is required for stretching.⁵⁰ However, it has been demonstrated that self-PNF stretching without a partner is effective for improving ROM.⁹⁰

PNF PATTERNS

The PNF patterns are concerned with gross movement as opposed to specific muscle actions. The techniques identified previously can be superimposed on any of the PNF patterns. The techniques of PNF are composed of both rotational and diagonal exercise patterns that are similar to the motions required in most sports and normal daily activities.

The exercise patterns have 3 component movements: flexion–extension, abduction– adduction, and internal–external rotation. Human movement is patterned and rarely involves straight motion because all muscles are spiral in nature and lie in diagonal directions.

The PNF patterns described by Knott and Voss⁴² involve distinct diagonal and rotational movements of the upper and lower extremity, upper and lower trunk, and neck. The exercise pattern is initiated with the muscle groups in the lengthened or stretched position. The muscle group is then contracted, moving the body part through the ROM to a shortened position.

The upper and lower extremities all have 2 separate patterns of diagonal movement for each part of the body, which are referred to as the diagonal 1 (D1) and diagonal 2 (D2) patterns. These diagonal patterns are subdivided into D1 moving into flexion, D1 moving into extension, D2 moving into flexion, and D2 moving into extension. Figures 14-1 and 14-10 illustrate the PNF patterns for the upper and lower extremities, respectively. The patterns are named according to the proximal pivots at either the shoulder or the hip (eg, the glenohumeral joint or femoroacetabular joint).

Tables 14-1 and 14-2 describe specific movements in the D1 and D2 patterns for the upper extremities. Figures 14-2 through 14-9 show starting and terminal positions for each of the diagonal patterns in the upper extremity.

Tables 14-3 and 14-4 describe specific movements in the D1 and D2 patterns for the lower extremities. Figures 14-11 through 14-18 show the starting and terminal positions for each of the diagonal patterns in the lower extremity.

Table 14-5 describes the rotational movement of the upper trunk moving into extension (also called chopping) and moving into flexion (also called lifting). Figures 14-19 and 14-20 show the starting and terminal positions of the upper extremity chopping pattern moving into flexion to the right. Figures 14-21 and 14-22 show the starting and terminal positions for the upper extremity lifting pattern moving into extension to the right.

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Maintaining Cardiorespiratory Fitness During Rehabilitation Restoring Range of Motion and Improving Flexibility Regaining Muscular Strength, Endurance, and Power Rehabilitation of Elbow Injuries Rehabilitation of Injuries to the Spine Rehabilitation of Ankle and Foot Injuries

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