Most of us agree that stretching is an important part of training for any sport. However, it’s difficult to know which form of stretching is most effective. PNF stretching has become increasingly popular in gyms and sports clubs, but what is it?
Research has repeatedly shown that proprioceptive neuromuscular facilitation (PNF) stretching techniques provide the most gains in range of motion (ROM) in the shortest amount of time. This is probably on the reasons it’s been increasingly used after workouts. In this blog, adapted from Essentials of Strength Training and Conditioning, 4th Edition, we’re going to the look at the basics of PNF stretching.
What is PNF stretching?
PNF stretching is an advanced form of flexibility training that involves contraction and stretching of muscles. Although the technique was first used in clinical rehabilitation, it’s quickly made it’s way into mainstream gyms because of its perceived effectiveness.
The technique was originally developed as part of the neuromuscular rehabilitation programme. It was designed to relax muscles and increase tone or activity. This is one of the reasons it’s now made it’s way into athletics as a method of increasing flexibility.
PNF stretching techniques are usually performed with a partner and involved both passive movements and active (concentric and isometric) muscle actions.
Although there are thoughts that PNF stretching is superior to others stretching methods, evidence hasn’t been consistently shown. It’s also worth noting that PNF stretching is often seen as impractical as a lot of stretches require a partner and expertise. Back in January 2018, we wrote a blog post discussing the differences between some of the different stretching methods called Static stretching vs. dynamic stretching: Which is the best?
PNF stretching techniques
During PNF stretches, three muscle actions are used to facilitate the passive stretch. Both isometric and concentric muscle actions of the antagonist (the muscle being stretched) are used before a passive stretch to achieve autogenic inhibition. The isometric muscle action is known as a hold and concentric action as contract. A concentric muscle action of the agonist, called agonist contraction, is used during a passive stretch of the antagonist to achieve reciprocal inhibition. Each of these techniques also involves passive, static stretches that are referred to as relax. There are three types of technique for PNF stretches:
- Hold-relax with antagonist contraction
PNF techniques are completed in three phases. With each of the three techniques, detailed below, the first phase incorporates a passive pre-stretch of 10 seconds. The muscle actions used in the second and third phases differ for the three techniques. The second and third phases give each technique its name. Stretches to improve hamstring flexibility have been included below.
The hold-relax technique begins with a passive pre-stretch. This is held at a point of mild discomfort for about 10 seconds. The partner then applies a hip flexion force and instructs the athlete to “Hold and don’t let me move the leg”. The athlete then holds and resists the movement so that isometric muscle action occurs. This is held for around 6 seconds. (figure 14.4). The athlete then relaxes and a passive stretch is performed and held for 30 seconds (figure 14.5). The final stretch should be of greater magnitude due to autogenic inhibition (e.g. activation of the hamstrings).
The contract-relax technique also begins with a passive pre-stretch of the hamstrings. This is again held at the point of mild discomfort for 10 seconds (figure 14.6).The athlete then extends the hip against resistance from the partner. This is so that a concentric muscle action through the full ROM occurs (figure 14.7).
The athlete then relaxes. Following this a passive hip flexion stretch is applied and held for 30 seconds. The increased ROM is facilitated due to autogenic inhibition (e.g. activation of the hamstrings).
Alternatively, the athlete can also attempt to extend the hip and the partner doesn’t allow movement. However, as this is essentially the same as the hold-relax technique, the contract-relax method described here is preferred.
Hold-Relax With Agonist Contraction
The hold-relax with agonist contraction technique is identical to hold-relax in the first two phases. However, the third phase is where the technique differs. During the third phase, a concentric action of the agonist is used in addition to the passive stretch. This is to add the stretch force (figure 14.11). Following the isometric hold, the athlete flexes the hip, thereby moving further into the new ROM. With this technique, the final stretch should be greater, primarily due to reciprocal inhibition (e.g. activation of the hip flexors). Secondly, it also helps with autogenic inhibition (e.g. activation of the hamstrings).
The hold-relax with agonist contraction is the most effective PNF stretching technique due to facilitation via both reciprocal and autogenic inhibition.
Warming up can provide benefits that are known to enhance performance. A warm-up should be geared towards the particular sport or activity an athlete is training for. It should also use an appropriated structure, ensuring that the athlete is completely prepared for the sport or activity. Effective warm-up planning can ensure that the activities prepare for the upcoming session but don’t induce undue fatigue. Additionally, the warm up should be planned so that the activities contribute both to workout goals but also development in the medium and long term. To learn more about planning warm-ups, check out blog post from March 2017, Warm-up advice from Aurélien Broussal-Derval.
Optimal flexibility for performance varies from sport to sport. It’s closely related to the types of movements and actions an athlete is required to perform. The concept of mobility may be more appropriate than flexibility as it focuses on active movement through the required ROM. For athletes that need to increase flexibility then static and PNF stretching techniques will allow for an effective increase in ROM. These techniques should be a key part of an extended training programme. Strength and conditioning professionals should consider each athlete’s unique combination of joint structure, age, sex and sport requirements when recommending stretching protocols.
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