|Year : 2021 | Volume
| Issue : 1 | Page : 1-6
Efficacy of proprioceptive neuromuscular facilitation on dynamic stability, athletic performance, and range of motion of the lower limb – A narrative review
Jabir Munassar Alsulaie1, Mohammed N Alghamdi2
1 Department of Physical Therapy, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia
2 Department of Physical Therapy, College of Applied Medical Sciences, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia
|Date of Submission||24-Feb-2021|
|Date of Decision||08-Mar-2021|
|Date of Acceptance||27-Mar-2021|
|Date of Web Publication||07-Jun-2021|
Mr. Jabir Munassar Alsulaie
Imam Abdulrahman Bin Faisal University, Najran, Postal Code: 61441, Salwa, Dammam
The proprioceptive neuromuscular facilitation (PNF) techniques such as contract-relax-antagonist-contract and contract-relax have been adopted by many researchers in the sports fields to investigate their effects on athletes and amateurs, either alone or by comparing these techniques with other modalities. The researchers to date have been published considerable controversial amounts of literature about the effectiveness of PNF techniques on the athletes' range of motion (ROM), dynamic stability, and performance. This review article aims to analyze the various effects of PNF stretching techniques and how they could be effective for athletes' ROM, dynamic stability, and performance-based on recent scientific evidence. After critically analyzing the published literature, the PNF techniques can increase the muscle flexibility in athletes as well as might be a reasonable method to enhance medial-lateral dynamic stability. However, its effectiveness on athletic performance is still questionable, and further high-quality studies are required.
Keywords: Athlete, dynamic stability, performance, proprioceptive neuromuscular facilitation, range of motion
|How to cite this article:|
Alsulaie JM, Alghamdi MN. Efficacy of proprioceptive neuromuscular facilitation on dynamic stability, athletic performance, and range of motion of the lower limb – A narrative review. Saudi J Sports Med 2021;21:1-6
|How to cite this URL:|
Alsulaie JM, Alghamdi MN. Efficacy of proprioceptive neuromuscular facilitation on dynamic stability, athletic performance, and range of motion of the lower limb – A narrative review. Saudi J Sports Med [serial online] 2021 [cited 2021 Jul 30];21:1-6. Available from: https://www.sjosm.org/text.asp?2021/21/1/1/317859
| Introduction|| |
The concept of neuromuscular facilitation and inhibition has been defined in the early 1900s, and it developed to be clinical proprioceptive neuromuscular facilitation (PNF) by Kabat in 1947. The PNF techniques aimed to assist clients with spasticity and paresis in their rehabilitation with two different methods; either by facilitating muscles to stretch, allegedly over affecting targeted muscles by inhibitory mechanism, or/and enhancing muscles strength through excitatory mechanism., Based on Kabat's concept, there are different types of PNF stretching, such as contract-relax-antagonist-contract, contract-relax, and hold-relax. These stretching techniques, in particular contract-relax-antagonist-contract and contract-relax, have been adopted by many researchers in the sports fields to investigate their effects on athletes and amateurs either alone or by comparing these techniques with other modalities. They aim to increase athletes' and amateurs' muscle flexibility or other essential parameters that could affect athletes' performance in sports activities. The researchers to date have been published considerable controversial amounts of literature on stretching and its types, especially the PNF stretching techniques and their effect on the range of motion (ROM), dynamic stability, and performance. Wherefore, this review article aims to analyze the various effects of PNF stretching techniques and how they could be effective for athletes' ROM, dynamic stability, and performance based on recent scientific evidence.
| Neurophysiology of Proprioceptive Neuromuscular Facilitation|| |
Theoretically, PNF stretching techniques inhibit certain groups of muscle through proprioceptive stimulation, and until now, there is no agreement about the actual explanation of these techniques. However, the exhibited neurophysiological explanations of PNF stretching techniques involve two acceptable hypotheses that elaborate why PNF stretching achieves a higher ROM than other stretching types. The first hypothesis is autogenic inhibition or inverse myotatic reflex that represents the decrease of stretched muscles excitability, which has been referred to as the arose inhibitory input from the Golgi tendon organ (GTO). It is believed that the targeted muscle which has been assisted to be elongated is affected by reducing efferent drive through autogenic inhibition.,,, The second hypothesis postulates that reducing activation levels of targeted muscle is through active contraction of the opposing muscle over the development of reciprocal inhibition, so the resulting targeted muscle elongation is due to the increased Ia-afferent (sensory) input from the opposing muscle.,, In addition to these two hypotheses, other researchers,, believe that the increased ROM due to stretching, mainly static stretching, is causing changes in viscous properties of a musculotendinous unit as well as if the musculotendinous unit is under stretch, the resistance of elongation is decreased over time (stress relaxation). Based on this perspective, Sharman et al. suggested that these findings can be applied to PNF stretching techniques because they have static stretch as a component. However, Konrad et al., and Mahieu et al., in their randomized control trials (RCTs) used the passive-resistive torque measurement to determine if changes have occurred after PNF stretching or not. They have concluded that PNF stretching could not change the musculotendinous unit properties. Moreover, it has to be mentioned that these two studies have a selection risk of bias. Furthermore, Freitas et al., have conducted a systematic review and meta-analysis and revealed that stretching 6–8 weeks cannot evoke musculotendinous unit properties. In addition, it is essential to consider that they have included randomized and nonrandomized studies in their systematic review.
| Efficacy of Proprioceptive Neuromuscular Facilitation on Range of Motion|| |
The PNF stretching is less frequently used in athletic preactivity routines, and this might be due to the need for partner assistance, pain, or uncomfortable sensation. There is a theory of increased muscle strain injury and the greater cytoskeletal damage as a result of performed muscle contraction at highly stretched muscle., However, there is no potential evidence or data to support these claims. On the other hand, PNF stretching could be used to increase muscle flexibility which is defined as the available ROM in a joint or group of joints. This enhancement of the ROM outcome assists in preventing injuries and muscular imbalance., Several studies over the past century have considered the PNF as the most effective stretching technique among others for active people, amateurs, and athletes, and can significantly increase the ROM.,,,,, In addition, Feland et al., and others, have found that one repetition is adequate to gain an expectant ROM between 3° and 9°. Furthermore, it could attain 20° based on the study of Etnyre and Lee over a 12-week period with one repetition of PNF stretching two times per week. Moreover, the PNF stretching should be conducted regularly once or twice per week at least to maintain ROM improvement.
The PNF stretching has two common techniques to increase the ROM, contract-relax which requires a static stretching phase of the targeted muscles pursued immediately by an intense isometric contraction in a cyclical pattern to enhance the ROM and contract-relax-antagonist-contract that includes a further contraction of the opposing muscles which believed to be more effective on men than women upon this RCT, but this study could be prone to gender bias and should be recognized that the males were 49 comparing to 25 females. Nonetheless, even with all these studies that have revealed the increase in the ROM,,,,,, it is not yet possible to proclaim that PNF is the most effective technique among other stretching techniques or not due to the quality of these studies. Based on the GRADE system to classify the level of evidence, Wanderley et al. have conducted a systematic review with meta-analysis. They found that the results of these studies are very low quality of evidence. However, the effectiveness of PNF on ROM is significant and cannot be ignored, but stating it as the most effective stretching technique among others is still debatable. Hence, further studies with high quality are required to negate or endorse this debate.
| Efficacy of Proprioceptive Neuromuscular Facilitation on Dynamic Stability|| |
In many physical activities, flexibility and balance control have revealed that they play important roles and may enhance athletic performance,, and perturbation of any of them could be reduced or prevented with specific exercise programs, since stretching is used as a typical component of an exercise program either in health-care or sports activities. There have been relatively few studies published about the efficacy of PNF stretching on static and dynamic stability. In this study, they have conducted an RCT to assess the effectiveness of contract-relax stretching on static stability and have concluded that contract-relax stretching impaired balance control. However, Ghram et al., have investigated the effectiveness of contract-relax-antagonist-contract and contract-relax on the dynamic stability following the same protocol that has been used in the previously mentioned study for the contract-relax group, which was targeting the quadriceps, hamstrings, anterior tibialis, and calf muscles; after 5 min warm-up and resting 1 min, they performed a maximal isometric contraction of the targeted muscles for 5 s, followed by 5 s of relaxation and 5 s of static stretching. For the contract-relax-antagonist-contract group, the protocol was targeting the same muscles in the contract-relax group and started with 5 min warm-up and resting 1 min then performed a passive stretch to the mild tension point for 5 s, pursued by a 5 s isometric contraction of the targeted muscles, then instructed the participant to contract the opposing muscles group for a further 5 s using an isometric contraction. At the end of the study, they found that the contract-relax-antagonist-contract has a significant improvement in the medial–lateral dynamic stability comparing to the anterior–posterior dynamic stability and the contract relax, which had no significant effects on anterior–posterior and medial–lateral dynamic stability. This result supports an older study by Ryan et al., on postural stability, and they concluded the same outcomes with a differently used contract-relax-antagonist-contract protocol.
Despite these studies,, they did not include the hip abductor and adductor muscles. These muscles play an important and essential role in medial–lateral dynamic stability.,, In contrast, Szafraniec et al. have conducted a non-RCT to investigate the effect of contract-relax stretching targeting hip adductor and abductor muscles on medial–lateral dynamic stability. Their used protocol to both lower limbs was performing three repetitions of passive stretching to the point of discomfort of the targeted muscles followed by 10 s of 50% maximal voluntary isometric contraction, then 5 s relaxation, and further passive movement. As a result of their study, they found that a single dose of contract-relax stretching of the hip abductor and adductor muscles effectively improves medial–lateral dynamic stability.
Moreover, Espí-López et al., in their double-blinded RCT study, have conducted a comparison between manual therapy and contract-relax stretching on hockey players' dynamic stability with the primary outcome that measured by star excursion balance test and differently used contract-relax stretching protocol. Their result demonstrated that both manual therapy and contract-relax stretching significantly improved dynamic stability. However, manual therapy has longer maintained improvement up to 1 month, while the contract-relax stretching was effective for 1 week. Nonetheless, Leblebici et al. showed no statistically significant difference in the dynamic stability performance after performing contract-relax stretching in their RCT. In light of these studies, it is hard to affirm if the PNF stretching effectively improves dynamic stability or which type of PNF stretching is more effective than the other.,,,, And that is because of the lack of the currently published studies that involving this topic and the lack of concealment or blinding in the mentioned studies except Espí-López et al. study which was designed as a double-blinded study. Moreover, due to the variation of the used protocols and outcome measures in the available studies [Table 1], most of these results have been measured pre and immediately post the intervention except Espí-López et al. study which they have reassessed their participants after one month. So, it's still not clear how long the improvement in dynamic stability can be sustained. However, these findings may lead to improve balance control in athletes who are involved in a sports activity that demand high dynamic stability such as football, but further high-quality studies are required.
| Efficacy of Proprioceptive Neuromuscular Facilitation on Performance|| |
Enhancement in physical performance has been a common object and is described by increasing muscular strength, resistance, and flexibility.,, Increasing muscular flexibility has been shown to have an impact on muscular performance. Numerous researchers have argued about the PNF stretching efficacy on athletic performance and carried out their studies with different outcome measures to evaluate athletic performance changes. The majority of the published studies have used the vertical jump test (VJ) as the main outcome measure,,,,,, while other studies have used different methods such as the 1-repetition maximum test, Wingate test, and other specific outcome measures.,, Two studies have investigated the effectiveness of PNF stretching in the long term. Akbulut and Agopyan, (2015), have conducted a non-RCT to investigate the efficacy of the unassisted contract relax for the long term (8 weeks) on kick speed. Hence, they have divided a football team into two groups: controlled and experimental during the competition season. After 8 weeks and by measuring the kick speed within radar gun, they concluded that unassisted contract relax has improved the kick speed. On the contrary, the other study was a single-blind RCT, which assessed the contract-relax effectiveness on the drop jump test in comparison to static stretch and control groups for 6 weeks. The result has shown that none of the experimental groups have a statistically significant effect. In addition, several studies have investigated the short-term effect of PNF stretching on athletic performance. Some of these studies used the cross-over RCT design and investigated the contract-relax efficacy, and contract-relax-antagonist-contract and others used subject experimental repeated-measures design investigating the contract-relax effect on the athletic performance from another stretching type. All these studies have concluded that PNF has no significant impact on athletic performance. However, most of these studies have lack concealment that can affect the revealed results except Yuktasir et al. which they have blinded their investigators who took the measurements. Although, numerous other studies consider that PNF stretching is causing adverse effects that decrease athletic performance and advising that PNF stretching should be avoided. For instance, Oliveira et al. have conducted a cross-over RCT with repeated measurements to 12 football players aiming to investigate hold-relax stretching, which is an uncommon type of PNF stretching techniques. They have compared the hold relax to other stretching techniques to know their effects on the football players performance and other outcome measures. As a result, they concluded that PNF stretching should be avoided because it had a relation with a higher score of the perceived exertion rate and had a negative effect on the VJ test. Despite the small sample size in the previous study and the use of uncommon PNF technique, few studies have the same result with different techniques and protocols, some of these studies have used cross-over RCT design over nine male voulnteers or repeated measurements design over 15 male participants, to assess the contract-relax technique and others used a nonrandomized cross-sectional over 100 male participants. Furthermore, Behm et al. have indicated in their systematic review that longer PNF stretching (>5 min) has a potential greater effect on the risk of injury based on their limited data. However, all these studies that concluded that PNF stretching is causing a negative impact on athletic performance have lack of concealment and a low to a very low quality of evidence-based on the GRADE system which indicates that we can not rely on these results of the currently available studies. Moreover, it has to be mentioned that Behm et al., (2016), in their systematic review have not assisted the risk of bias of the selected studies. Based on the recent and available studies, definitely studies with higher quality are required due to the conflicting evidence with fluctuating quality. Furthermore, most of these studies have examined the short-term effect only with various used protocols, which will form an uncertain judgment based on weak studies.
| Conclusion|| |
The PNF stretching techniques are undoubtedly an effective method to increase the muscles flexibility in athletes but cannot state it as the most effective method yet, and it might be a reasonable method to increase the medial–lateral dynamic stability, specifically in particular sports activities. However, the effectiveness of PNF on muscular performance is still not clear, and further studies with the higher quality should be conducted on this subject.
Human and animal rights and informed consent
This article does not contain any studies with human or animal subjects performed by any of the authors.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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