Vol. 15 •Issue 26 • Page 40
The Truth About PNF Techniques
Proprioceptive neuromuscular rehabilitation is more than just stretching and functional movement
Mention proprioceptive neuromuscular facilitation (PNF), and most clinicians think of stretching or functional movement patterns. While it is true that PNF focuses on stretching and functional movement, it is also much more. PNF techniques help develop muscular strength and endurance, joint stability, mobility, neuromuscular control and coordination-all of which are aimed at improving the overall functional ability of patients.
Developed in the 1940s, PNF techniques are the result of work by Kabat, Knott and Voss.1-3 They combined their analysis of functional movement with theories from motor development, motor control, motor learning and neurophysiology.1
To that end, PNF techniques have broad applications in treating people with neurologic and musculoskeletal conditions, most frequently in rehabilitating the knee, shoulder, hip and ankle.4
Stretching is a main component of PNF. In fact, PNF stretching is superior to other stretching techniques.5-7
Neuromuscular inhibition procedures reflexively relax the contractile components of shortened muscles so patients can gain range of movement. Various techniques are used, among them:
Hold-Relax. Familiar to most clinicians, this technique involves lengthening a tight muscle and asking the patient to isometrically contract it for several seconds.
As the patient relaxes, the clinician lengthens the involved muscle further and holds the stretch at the newfound end-range of motion. This technique relies on the firing of the Golgi-tendon organ (GTO) to cause reflexive muscle relaxation. It's easily applied and can be incorporated in home exercise and preventive programs.
But while activating the GTO can increase flexibility, it also may predispose the patient to injury. Specifically, PNF stretching can decrease activity of selected hamstring muscles. A sudden stretch, which might occur during functional activity, may predispose patients to increased risk of musculotendinous injury, if PNF stretching is applied directly before activity.8
Hold-Relax with Agonist Contraction. This technique follows the same procedure as the Hold-Relax technique. However, after the tight muscle is contracted isometrically against the clinician's resistance, the patient concentrically contracts the muscle opposite the tight muscle to actively move the joint through the increased range.1 The clinician then applies a static stretch at the end of this new range of motion and repeats the process several times.
Agonist Contraction. With this stretch, the clinician passively lengthens the tight muscle (the antagonist) to its end-range. The patient then concentrically contracts the muscle opposite the tight muscle (the agonist) to move the joint to a new position in the range of motion.1 The clinician applies mild resistance during this contraction, being careful to allow for movement through the range of motion. This technique uses reciprocal inhibition to encourage the tight muscle to relax and lengthen during agonist muscle contraction.
Of the three techniques, the Hold-Relax is the most frequently used.4 But over the last decade, the Hold-Relax with Agonist Contraction has gained popularity.4 Research indicates that sub-maximal contractions that are progressive in intensity over the course of a rehab program increase flexibility.9 For the best results, clinicians should use PNF stretching early in the rehabilitation program and gradually increase the intensity of the contractions throughout the rehab process.
While clinicians know the difference between the three techniques, they often intermix terminology. For example, many clinicians and authors refer to Hold-Relax stretching as Contract-Relax stretching. Some even incorporate a concentric contraction of the tight muscle against minimal resistance before applying a second stretch.
This procedure, however, is incorrect and doesn't allow for maximum gains in flexibility; any firing of the GTO is negated by the time the person moves the extremity back to the starting point of the concentric contraction.
Along with stretching, PNF strengthens the body through diagonal patterns, often referred to as D1 and D2 patterns. It also applies sensory cues, specifically proprioceptive, cutaneous, visual and auditory feedback, to improve muscular response.1 The diagonal movements associated with PNF involve multiple joints through various planes of motion. These patterns incorporate rotational movements of the extremities, but also require core stability if patients are to successfully complete the motions.
Two pairs of diagonal patterns exist.10 These patterns can be performed in flexion or extension and are often referred to as D1 flexion, D1 extension, D2 flexion or D2 extension techniques for the upper or lower extremity.1 Although patients can perform these patterns with many forms of resistance, the interaction between patient and clinician is key to the early success of PNF strengthening.1
This interaction requires manual resistance throughout the range of motion through carefully positioned hand placement and appropriately choreographed resistance. By placing the hands over the agonist muscles, the clinician applies resistance to the appropriate muscle group, while guiding the patient through the proper range of movement.1
In using manual resistance, the clinician can make minor adjustments as the patient's coordination improves or fatigue occurs during the rehab session. In general, the amount of resistance applied is the maximum amount that allows for smooth, controlled, pain-free movement throughout the range of motion.10 In addition to manual resistance strengthening, PNF diagonal patterns enhance proper sequencing of muscular contraction, from distal to proximal. This promotes neuromuscular control and coordination.1
To enhance coordination, movement and stability, clinicians use numerous techniques during PNF exercises, among them:
Rhythmic stabilization. This technique, which incorporates passive movement of the joint through the desired range of motion, is a teaching tool to re-educate the neuromuscular system to initiate the desired movement. The technique begins with the clinician passively moving the extremity through the desired movement pattern at the desired speed several times. It then progresses to promote active assistive or active movement, with resistance, through the same pattern to help the patient improve coordination and control.
Slow reversal. This technique involves a dynamic concentric contraction of the stronger agonist muscle group. A second dynamic concentric contraction immediately follows, this time involving the weaker antagonist muscle group.1 Rest periods don't occur between contractions. Therefore, this technique promotes the rapid, reciprocal activities the agonist and antagonist muscle groups need for many functional activities.
Slow reversal hold. This technique adds an isometric contraction (hold) at the end-range of each muscle group. It's especially beneficial in enhancing dynamic stability of the larger proximal muscle groups.
Alternating isometrics. This technique encourages stability of postural trunk muscles and stabilizers of the hip and shoulder girdle. With alternating isometrics, the patient "holds" his position, while manual resistance is alternately applied in a single plane from one side of the body to the other. No motion should occur.
Instead, the patient should maintain the starting position of the involved limb. This technique can strengthen the trunk, a single extremity or bilateral extremities, and can be applied with the limbs in the open- or closed-kinetic chain.
Alternating rhythmic stabilization. This technique is simply an extension of alternating isometrics in which the involved muscle groups co-contract. Rhythmic stabilization is most commonly performed in a closed-chain position to further enhance muscular co-contraction and joint stability.1
With this technique, the clinician applies manual isometric resistance in a multidirectional pattern. The clinician may apply simultaneous manual resistance in multiple directions, forcing the multiple muscle groups to contract simultaneously to support and stabilize the extremity. This technique is particularly beneficial in isometrically contracting the proximal joint rotators.1
PNF exercises can be applied to patients of all ages. Klein et al. found that using PNF techniques for older adults improved range of motion, isometric strength and selected physical function tasks.11
Additional studies have shown that PNF stretching is superior to static stretching in improving hamstring flexibility in people 45 to 75 years of age.12
One study compared PNF stretching to static stretching in active seniors. While static stretching and PNF stretching yielded gains in hamstring flexibility, PNF stretching was most beneficial in participants younger than 65.13
Still another study demonstrated the value of PNF stretching vs. static stretching when comparing the techniques in Special Olympic athletes.14
Whether promoting flexibility, developing muscular strength and endurance, improving joint stability or increasing neuromuscular control and coordination, PNF is a valuable part of every rehabilitation program. Proprioceptive neuromuscular facilitation encompasses all aspects of the rehabilitation process-and can help patients with various dysfunctions achieve their goals.
References are availale at advanceweb.com/pt; click on the references tool bar.
James R. Scifers is program director for the athletic training education program at Western Carolina University in Cullowhee, NC. He is a practicing athletic trainer and board-certified specialist in sports physical therapy.