The use of proprioceptive neuromuscular facilitation in physiotherapy ...

Narrative Review

The use of proprioceptive neuromuscular facilitation in physiotherapy practice Sarah Westwater-Wood1, Nicola Adams2, Roger Kerry1 1

Division of Physiotherapy Education, University of Nottingham, UK, 2School of Health, Community and Education Studies, Northumbria University, Newcastle-upon-Tyne, UK Aims: The aim of this paper is to critically review the evidence base for the use of proprioceptive neuromuscular facilitation (PNF) in physiotherapy practice. Given the evolving understanding of underlying physiological concepts and research developments in the more than 50 years since Herman Kabat originated the concept, there is a need to review the current evidence base. Method: Empirical studies investigating the effectiveness of PNF for increasing range of movement and functional rehabilitation for clinical and non-clinical populations along with patterns and irradiation concepts were reviewed. Results: Although it was difficult to draw definitive conclusions due to the lack of cognate studies and varying methodological quality of papers, a number of studies did demonstrate encouraging results for the use of PNF, particularly with regard to increasing range of movement. Conclusions: Further research is needed to explore individual components of PNF therapeutic approaches and their wider application in key clinical populations such as stroke with standardized outcome measures appropriate to clinical practice. Secondly there is need for the development of new paradigms to fully consider the underlying physiological concepts explaining the effectiveness of PNF.

Keywords: Proprioceptive neuromuscular facilitation, Evidence, Review

Introduction Perceptions of the physiotherapy profession suggest that its practice is often based on treatment techniques that have limited scientific support and are based upon anecdotal evidence.1 It has been proposed that within physiotherapy the science behind therapeutic techniques has not been as strong as the beliefs of therapists in the effectiveness of them. However, since the 1990s, there has been a movement towards promoting evidence-based practice (EBP) within health care and health education.2–4 There is a supposition that through EBP, the most effective treatments can be adopted with justification from current research.5 There can be conflicting views between evidence-based research and results established through clinical practice. In order to integrate these differences a link must be formed between evidence-based research and clinical practice through both empirical research into the treatments currently being adopted in clinical practice3 and reviews such as this. Proprioceptive neuromuscular facilitation (PNF) is a treatment which is widely used by physiotherapists and forms part of the undergraduate Correspondence to: Sarah Westwater-Wood, Division of Physiotherapy Education, University of Nottingham, Hucknall Road, Nottingham, NG5 1PB, UK. Email: [email protected]

ß W. S. Maney & Son Ltd 2010 DOI 10.1179/174328810X12647087218677

curriculum. However, despite the popularity of this approach in clinical practice, the scientific basis is under-researched and the evidence from largely heterogeneous studies is often equivocal. Long before the nature of sensory feedback and biomechanical alignment to motor output was recognized, Dr Herman Kabat proposed PNF as an approach to rehabilitation (Kabat-Kaiser Institute, California, late 1940s). Proprioceptive neuromuscular facilitation has been defined as ‘methods of promoting or hastening the response of the neuromuscular mechanism through stimulation of the proprioceptors’.6 The proposed theoretical principles of the approach are of the body’s neuromuscular components being adaptable or plastic; that plastic changes may be positive (as in sports specific training), or negative (as with contracture or muscle imbalance), and that functional movement occurs in patterns which are spiral in nature.7 These are often largely accepted despite limited supporting scientific evidence. Proprioceptive neuromuscular facilitation techniques are used to target all aspects of muscle training, e.g. sustained isometric activity to mobilize muscle groups thus improving range of movement and/or reduce pain, functional patterns and handling techniques to facilitate both co-ordination and

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stability in muscle groups.8–13 Thus PNF does appear to be a relevant approach to physiotherapists’ core rehabilitation techniques. A growing but equivocal body of evidence has emerged regarding the application of PNF. The purpose of this paper is to critically appraise pertinent available evidence on PNF and to discuss the implications for physiotherapy practice.

Search strategy We conducted an electronic search using Ovid Medline 1966–2009, AMED (Allied and Complementary Medicine) 1985–2009, Embase 1980– 2009 and Cochrane Library 1971–2009. A manual search of the reference sections of relevant articles was also conducted. The search terms included specific and non-specific proprioceptive neuromuscular facilitation words (individually and combined as neuromuscular facilitation and proprioceptive neuromuscular facilitation) along with clinician, perspective and views. The evidence was organized into four different sections – effect of PNF on range of movement (ROM), effect in rehabilitation, implication of PNF patterns and clinicians’ perspectives on PNF. Both neurological and non-neurological cohorts were included.

PNF effect on range of movement There are 11 studies8,11,13–21 investigating PNF techniques which address ROM. These are the specific PNF techniques of contract-relax (CR) and agonist contract-relax (ACR). Different variables and outcome measures, for example, ROM and electromyographic (EMG) measurements have been used prohibiting direct comparisons across studies. In an early study, Sady et al.21 used an experimental design to compare the immediate effects of three stretching techniques (static (SS), ballistic, PNF and control) on ROM in n543 college males. A factorial and post hoc analysis indicated only the PNF group significantly increased flexibility (P( 0.05). The authors concluded individuals could gain rapid increases in flexibility when integrated into training or rehabilitation programmes. However, in the positions for ROM measurement, fixation points which contribute to limiting the movement measured to the joint of interest are not described. In addition the authors themselves discuss the increased variability of baseline measurement reliability (baseline ICC shoulder/trunk/hamstrings 0.85/0.94/ 0.83) respectively as compared with post-intervention measurement (shoulder/trunk/hamstrings 0.94/0.95/ 0.91). This may represent an internal learning effect in the assessors’ skill in assessing these measurements. In a subsequent non-randomized study, Osternig et al.8 compared three stretch techniques, one general stretching technique (stretch relax, SR), and two PNF techniques (CR and ACR), in n530 subjects who

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were divided into three groups. These included two competitive groups (high intensity and endurance sports) and a non-competitive physically active group which acted as a control group (16 male, 14 female; 18–36 years, mean age 24.6 year). Statistical analysis found ACR produced significantly greater ROM than SR and CR (P(0.05). These stretch techniques were also compared in a two groups study design (age 45–55 years and 65–75 years) divided by previous training or untrained groupings (n526 normal males).11 Each stretch technique was found to increase ROM in all groups. However, as with Osternig et al.,8 greater ROM in knee-extension was obtained for the ACR group (P(0.05) than SS and CR in the trained and untrained groups (with the exception of the 65–75 untrained subset). More recent studies concur with these findings. For example, a randomized controlled study of n597 senior athletes (males n566, females n531; mean age 65 years)19 found statistically significant increases in hamstring ROM were attained with men and those aged under 65 years. In this study, three groups were compared, a control group, SS and CRPNF. No statistically significant difference between SS and CRPNF groups was found.19 Conversely, in a larger scale RCT of n5100 subjects (age range 27–57 years)22 the findings support active stretches (neuromobilization and PNF) over passive stretching methods (P(0.05).22 Furthermore, in an assessor blinded RCT of n520 subjects, Godges et al.13 found significant increases in glenohumeral rotation and overhead reach ROM with PNF as an adjunct to soft tissue mobilization alone (ROM P(0.0005; overhead reach P50.009). Overall the findings are equivocal due to the variety of methodologies, populations and measures implemented. However, the studies do provide preliminary evidence of the effectiveness of PNF techniques in increasing ROM over passive stretches. Further investigation of the specific PNF ROM techniques is required. This should include subjects’ perspectives on application of the techniques.18 Isometric and relaxation lengthening techniques are based upon a purported theory of neural excitability depression.15,18 EMG recordings record motor neuron pool activity in muscle. Inhibition is noted as a reduction in H-reflex amplitude. Therefore, it has previously been proposed that EMG is an appropriate outcome measure for this aspect of PNF techniques.15 One such study15 investigated EMG following isometric plantar-flexion contraction (CR) at 65–75% of maximal voluntary contraction in prone. Results indicated that H-reflex amplitudes were depressed following voluntary contraction (CR) (n516, P,0.0001). The brevity of the depression is notable: partial recovery (17–24%) by 1 second and 70% by 5 seconds. The authors cite Schieppati and Crenna23 and Enoka et al.24 as others


who have recorded depression of H-reflex activity. Such findings have previously been interpreted as indicating support for the proposition that PNF isometric techniques influence background neural excitability as a mechanism to facilitate increased range of movement. However, in a study of n524 normal subjects aged 50–75 years18 comparing SS, CR and ACR for knee extension and measuring EMG activity in both biceps femoris and gastrocnemius, the authors found both significantly increased ROM (P,0.05) and EMG activity (P(0.05 biceps femoris and gastrocnemius) for ACR compared with CR and SS. This is contrary to the previous trend in EMG findings. The interpretation of studies using EMG in terms of the effect of PNF on neural systems is currently being questioned.25,26 The reliability of comparing EMG findings where difference in muscle length is an objective has been identified as a potentially confounding variable and concerns have been raised. As Magnusson et al.27 contend, if PNF has been effective, the ROM at which baseline EMG is taken and thus the tension exerted upon the muscle, differs from that of the post-intervention ROM. Their study suggests the torque changes are explained more by passive properties than neuron unit activity. Previous historical interpretation of the inhibitory effect of PNF on neuronal mechanisms (Golgi tendon organ and reciprocal innervations) no longer fully accounts for the variety of EMG findings. More recent development in our understanding of the nervous systems complexity, the role of sensory input and the parallel roles of central and peripheral regulation should be considered to inform new principles and theories of PNF. Other PNF ROM technique variables include contraction duration and intensity. For example, Schmitt et al.16 carried out two randomly assigned experiments investigating the duration and intensity of isometric contractions during stretching. The findings suggested that there was no significant difference between durations of contraction. However, significantly greater improvements were found when the voluntary isometric contraction increased progressively over the treatment period. Contrary to these findings, Rowlands et al.17 compared the effect of two contraction durations of 5 seconds (n511) and 10 seconds (n513) with a non-intervention control (n513) and found that hip flexion was significantly increased in PNF treatment groups (5 and 10 seconds hold) (P(0.01) and between the two treatment groups with 10 seconds duration resulting in statistically significant increased ROM (P,0.01). The principles in terms of dependence upon facilitator applied PNF have been investigated.28 In a two group RCT, a self-administered-PNF (Group I)


(n512), therapist applied PNF technique (Group II) (n514) and a non-intervention control (n514) targeting hamstring flexibility were compared. It was found that although there was a significant improvement between the control and the experimental groups (P(0.01), there was no significant difference between the PNF treatment groups. This study stands alone in considering the influence of the facilitator as a component for the effectiveness of PNF application. The lack of significant difference between the facilitator and self applied groups’ effectiveness supports consideration of integrating PNF principles into any independent home exercise programme. Osternig et al.14 urged caution in applying stretching techniques due to the risk of muscle soreness and strain. Other authors have reported that although the most significant improvements come with ACR, subjects themselves report ACR as the most uncomfortable of the techniques.18 Despite the widespread use of PNF techniques, debate exists regarding the underlying physiological mechanisms responsible for the increased range of motion that results when using PNF stretching techniques. Although most researchers recognize the necessary link between the nervous system and the muscular system some bias the vasoelastic components as more primary than the neural26 whilst others consider the tolerance of pain or stretch sensation as a factor.25 It is likely that there is interplay between both aspects. From the current evidence it is difficult to qualify or quantify the contribution from both the neural and viscoelastic mechanisms that create the adaptations resulting from PNF training. There is certainly scope for a more specific review into the underpinning physiological premise with a purpose of suggesting a more balanced integrative paradigm. In summary existing literature supports increase in ROM as a benefit of PNF.8,11,14–18 CR and ACR were the most commonly used techniques in the studies reviewed.

Functional rehabilitation There is evolving interest in PNF as a technique to improve functional ability. In a small scale experimental interventional study of n511 subjects recruited from an assisted-living population, Klien et al.29 examined the impact of PNF on physical function. A beneficial effect of PNF training was found for flexibility (ROM shoulder flexion P50.016, ankle dorsiflexion P50.09) and isometric strength (hip extension P50.031, ankle flexion P5 0.000 and extension P50.031). Measures of physical function (sit-to-stand P50.042) also improved. Wang30 compared the immediate and cumulative effects of PNF on the pelvic region in patients with hemiplegia (n520). Outcome measures included gait parameters, (gait speed in metres per second and cadence as steps


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per minute). Subjects with hemiplegia of less than 6 months demonstrated immediate improvements in the outcome measures, with these improvements increasing after 12 sessions. Subjects with hemiplegia of more than 12 months demonstrated no improvements after a single treatment; however, they did demonstrate improvement after 12 sessions. In a larger interventional study of n5131 hemiplegic patients, Dickstein et al.31 compared three exercise therapy approaches. These were conventional exercises and functional activities, PNF techniques and the Bobath approaches. Numerous outcome measures were used, focusing on functional independence, muscle tone, isolated motor control and ambulatory status. No significant differences in outcomes were demonstrated after 6 weeks, with the exception of an improvement in the pattern of muscle tone in the PNF treatment group. Kraft et al.32 carried out an RCT of n518 chronic stroke subjects randomly allocated to either a treatment group (EMG stimulation, bias/balance treatment and PNF) or a no treatment control group. The FuglMeyer post-stroke motor recovery test, grip strength and the Jebsen-Taylor hand function test were used to assess the effects of treatment on the paretic upper limb. Improvements were seen with the PNF group compared to the control. Whilst there are more studies focusing upon a hemiplegic population, only one study was identified using PNF for chronic musculoskeletal pain. In an RCT of n586 chronic low back pain patients, the authors33 found both rhythmical stabilization (RST) and combined isotonic exercises (COI) to be statistically significant (P(0.05) in improving trunk muscle endurance (static and performance in both flexion and extension movement), lumber mobility (flexicurve measurement technique) and physical activity (Oswestry Low Back Pain Disability Questionnaire) compared to the control group. Greater improvements were noted in the COI group compared with the RST group in dynamic and static endurance, though greater improvements in lumbar mobility were noted for the RST group. Pain as measured by the Borg Back Pain Intensity Scale (BBPIS), was not significantly different between the three groups although all were improved. The training period of 4 weeks may be considered shorter than recommended for strength and endurance training;34 however, improvements were maintained at both 4 and 8 week follow-up. Further studies are needed to demonstrate long-term gains. The findings from these studies29–33 provide preliminary support for the effectiveness of PNF techniques in improving functional ability with elderly, neuropathological and CLBP patients groups. However, further studies with justification of sample size, standardized outcome measures and

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robust methodologies are required to provide definitive results.

Implication of PNF patterns A fundamental component of PNF is that movement is performed in spiral patterns. In a small scale study of n57 normal subjects, Shimura et al.10 investigated the effects on upper limb muscles (Triceps (T) Brachioradialis (B) and Deltoids (D)) when comparing a PNF treatment position with a neutral position (N). Initiation of active movement and motor cortex activity during a voluntary grasp task were measured with EMG latency and motor evoked potential (MEP). The purported underlying theory for PNF positions suggests they lead to stronger sensory excitation at the cortical level hence preparedness in number and threshold level of motoneurons. Thus one would expect a reduction in EMG latency with larger MEP amplitude in the PNF position. The study results demonstrated this effect with both larger MEP amplitudes (P(0.05) and faster EMG responses (P(0.01) in the PNF position compared to the neutral one. Although a small sample, the results are in keeping with widely accepted neural mechanisms involving the influence of feedback (sensory) position changes on feed forward (motor) threshold activity. Other investigations have considered the irradiation/cross training effects of PNF patterns compared to straight movements.9 Using a double-blind design Arai et al.9 randomly applied six different exercises (PNF pattern and traditional sagital) at three different knee angles to the unaffected limb of six subjects who had unilateral lower limb immobilization in Plaster of Paris. Outcomes were maximal torque (MT) and EMG (unexercised quadriceps) along with the concurrent maximal response torque (IE) (unexercised rectus femoris). All applied exercises had an effect; however, the PNF patterns were found to have a significant cross-education effect (percentage MT unexercised leg P(0.05). Both the mean percentage of IE and MT were above 23% in the PNF movement, while a mean above 13% was not found in any of the other exercises. The above small scale studies provide preliminary findings to support the effectiveness of PNF in terms of MEP and MT.

Physiotherapists’ perspectives Having reviewed the PNF research evidence base, translation in practice should be considered in terms of clinicians’ practice and perspectives with regard to PNF. An extensive literature search found only two citations exploring therapists’ use and views of PNF in clinical practice.35,36 In a small-scale survey conducted in a large regional hospital in the UK, the use of PNF by n5100 physiotherapists and their attitudes and opinions regarding its use and effectiveness in a large regional hospital were explored.36 Sixty-one per cent


of respondents deemed PNF to be appropriate in current clinical practice with respondents agreeing that PNF is a useful range of techniques where appropriate and can be ‘used on a variety of diagnoses across the whole remit of physiotherapy’. The most frequently used techniques reported by the respondents addressed range of movement. In comparison, Claesson et al.35 reported that only 47% of physiotherapists felt there was a place for PNF in the future of physiotherapy in Sweden. This survey used a postal questionnaire with the aim of investigating views on the current usefulness of PNF and future relevance in a population of Swedish physiotherapists. The surveyed population included seven physiotherapy educational establishments and n5200 practising physiotherapists. In considering whether PNF techniques are appropriate in current UK clinical practice, the authors36 summarize their findings confirming that respondents agree that PNF is relevant to current clinical practice and that its implementation is in line with current PNF literature. Further research in this area is warranted to consider whether these findings are representative of larger populations, both regional and international. Patient perspectives and barriers to implementation may also be considered.

Conclusions It is important to emphasize that whilst the majority of the research base into PNF focuses upon its effect on ROM, nevertheless there is a growing body of research investigating PNF not only in functional rehabilitation, neurological30–32 and strengthening,9 but also across a wide range of populations, from student-athletes12 and trans-femoral amputees,1 to trained and untrained older adults11 and the neurologically impaired.30–32 Research has also focused on underlying physiological mechanisms of spiral patterns10 and irradiation/cross training.9 Immediate and long-term effects of PNF have also been considered.13,32 Overall whilst debate continues regarding the underlining physiological mechanisms involved in PNF8,26 current research demonstrates trends towards the effectiveness of PNF as an approach to rehabilitation in a variety of patient and sports populations, for a number of PNF techniques. However, more methodologically rigorous, contemporary studies are required to provide definitive evidence of clinical effectiveness. Further research into the clinical application and physiological premise of PNF techniques is indicated to inform future practice. Research should consider two distinct stems, one being a full and thorough consideration of current physiology/pathophysiology of underlying processes explaining the effectiveness of PNF (in more than ROM techniques). Existing work8–10,25,26 stimulates thought


around the development of new paradigms regarding underlying physiological concepts. Secondly, further research is required into a wider clinical application of PNF and in particular the full range of techniques. There is also a need to investigate clinical practice and attitudes of physiotherapists towards PNF techniques to investigate how the evidence base is being integrated into practice. Finally, a wider variety of patient groups and educational delivery of this approach should be explored. Future studies should be of higher methodological quality using standardized outcome measures. References 1 Yigiter K, Sener G, Erbahceci F. A comparison of traditional prosthetic training versus proprioceptive neuromuscular facilitation resistive gait training with transfemoral amputees. Prosthet Orthot Int. 2002; 26: 213–17. 2 Higgs J, Titchen A. Research and knowledge. Physiotherapy. 1998; 84(2): 72–80. 3 Turner P. Evidence-based practice and physiotherapy in the 1990s. Physiother Theory Pract 2001; 17: 107–21. 4 CSP. Rules of professional conduct. 2nd ed. London: Chartered Society of Physiotherapy; 2007. 5 Barnard S, Wiles R. Evidence-based physiotherapy: physiotherapists’ attitudes and experiences in the Wessex area. Physiotherapy. 2001; 87(3): 115–24. 6* Voss D, Ionta M, Myers B. Proprioceptive neuromuscular facilitation. 3rd ed. Philadelphia: Harper & Row; 1985. 7 Pitt-Brooke J. Rehabilitation of movement, theoretical basis of clinical practise. London: W.B. Saunders; 1998. 8 Osternig R, Robertson R, Troxel R, Hansen P. Differential responses to proprioceptive neuromuscular facilitation (PNF) stretch techniques. Med Sci Sports Exerc. 1990; 22(1): 106–11. 9* Arai M, Shimizu H, Shimizu ME, Tanaka Y, Yanagisawa K. Effects of the use of cross-education to the affected side through various resistive exercises of the sound side and settings of the length of the affected muscles. Hiroshima J Med Sci. 2001; 50(3): 65–73. 10* Shimura K, Kasai T. Effects of proprioceptive neuromuscular facilitation on the initiation of voluntary movement and motor evoked potentials in upper limb muscles. Hum Mov Sci. 2002; 21(1): 101–13. 11* Ferber R, Gravelle D, Osternig L. Effect of PNF stretch techniques on trained and untrained older adults. J Aging Phys Activ. 2002; 10: 132–42. 12 Funk DC, Swank AM, Mikla BM, Fagan TA, Farr BK. Impact of prior exercise on hamstring flexibility: a comparison of PNF and static stretching. J Strength Cond Res. 2003; 17(3): 489–92. 13 Godges J, Mattson-Bell M, Thorpe D, Shah D. The immediate effects of soft tissue mobilization with proprioceptive neuromuscular facilitation on glenohumeral external rotation and overhead reach. Phys Ther. 2003; 33: 713–18. 14 Osternig L, Robertson, R, Troxel, R, Hansen, P. Muscle activation during proprioceptive neuromuscular facilitation (PNF) stretching techniques. Am J Phys Med. 1987; 66: 298–307. 15 Moore M, Kukulka C. Depression of hoffmann reflexes following voluntary contraction and implications for proprioceptive neuromuscular facilitation therapy. Phys Ther. 1991; 71(4): 321–29. 16 Schmitt G, Pelham T, Holt L. A comparison of selected protocols during proprioceptive neuromuscular facilitation stretching. Clin Kinesiol. 1999; 53: 16–21. 17* Rowlands AV, Marginson V, Lee J. Chronic flexibility gains: effect of isometric contraction duration during PNF stretching techniques. Res Q Exerc Sport. 2003; 74(1): 47–51. 18 Ferber R, Gravelle D, Osternig L. Effect of PNF stretch techniques on knee flexor muscle EMG activity in older adults. J Electronmyogr Kinesiol. 2002; 12(5): 391–97. 19 Feland J, Myrer J, Merrill R. Acute changes in hamstring flexibility: PNF versus static stretch in senior athletes. Phys Ther Sport. 2001; 2: 186–93. 20 Decicco P, Fisher M. The effects of proprioceptive neuromuscular facilitation stretching on shoulder range of motion in overhead athletes. J Sports Med Phys Fitness. 2005; 45(2): 183–87.


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components and a therapist-applied PNF-technique on hamstring flexibility. Physiotherapy 2004; 90: 151–57. Klien D, Stone W, Phillips W, Gangi J, Hartman S. PNF training and physical function in assisted-living older adults. J Aging Phys Activ. 2002; 10: 476–88. Wang R. Effect of proprioceptive neuromuscular facilitation on the gait of patients with hemiplegia of long and short duration. Phys Ther. 1994; 74(12): 1108–15. Dickstein R, Hocherman S, Pillar T, Shaham R. Stroke rehabilitation: three exercise therapy approaches. Phys Ther 1986; 66(8): 1233–38. Kraft G, Fitts S, Hammond M. Techniques to improve function of the arm and hand in chronic hemiplegia. Arch Phys Med Rehabil. 1992; 72: 220–27. Kofotolis N, Kellis E. Effects of two 4-week proprioceptive neuromuscular facilitation programs on muscle endurance, flexibility and functional performance in women with chronic low back pain. Phys Ther. 2006; 86(7): 1001–12. American College of Sports Medicine. ACSM’s guidelines for exercise testing and prescription. 8th ed. Philadelphia: Wolters Kluwer/Lippincott Williams & Wilkins; 2009. Claesson B, Siosteen A, Nordholm L. PNF in physiotherapy today and tomorrow – a survey of Swedish physiotherapists. Nordisk Fysioterapi. 1999; 3(1): 3–12. PNF in clinical practise: a survey of clinicians’ views. Proceedings of the Chartered Society of Physiotherapy Annual Congress. Birmingham; 2006. London: The Chartered Society of Physiotherapy.