Stretching

PNF

Proprioceptive Neuromuscular Facilitation (PNF) stretching

PNF refers to a stretching techniques in which a muscle group is passively stretched, then contracts isometrically against resistance while in the stretched position, and then is passively stretched again through the resulting increased range of motion.

There are a number of different versions of PNF stretching but the most frequently used method is when the muscle that is being stretched is isometrically contracted for 6-10 seconds before the muscle is relaxed and stretched at the end range of movement. PNF stretching can be done on your own but it is more often done with the help of a partner.

Two methods of PNF are outlined below, the Contract-Relax Method and the Contract-Relax with Agonist Contraction (CRAC) method.

Contract-Relax Method

The target muscle is stretched passively. The muscle is then isometrically contracted for around 7 – 10 seconds. The muscle is relaxed for 2 – 5 seconds then stretched again passively for 7 – 10 seconds. The action can be repeated up to 6 times. The final stretch should be held for longer.

Contract-Relax with Agonist Contraction (CRAC)

The technique is similar to the CR method but after the isometric contraction an active stretch is applied. For example in a lying hamstring stretch the individual contracts the hip flexor muscle and pulls the leg towards the chest.

Role of the Golgi Tendon Organ (GTO) in PNF Stretching

Knowledge of the GTO is crucial for understanding how PNF stretching works. In this method of training the muscle being stretched is taken to the end range of motion then contracted isometrically before a relaxed static stretch occurs. During the contraction phase, significant amount of tension occurs within the muscle and tendons. The GTO is stimulated, counteracting the stretch reflex caused by muscle spindle activation and causing an inhibitory reflex and therefore relaxation of the muscles being worked on. The relaxation of the stretched muscle and contraction of its antagonistically paired muscle enables the joint to be taken to a greater range of motion, so this leads to improved adaptations in muscle length. It is also thought that another benefit of PNF stretching is that the intrafusal fibres in the stretch receptors are lengthened so in future stretches the muscle can be taken to a further range of motion before the stretch reflex occurs.

The Golgi Tendon Organs (GTO) are receptors that are found in the tendons of the body. They monitor information about the tension or force experienced by a muscle and tendon. When high force could lead to injury in the muscle or tendon, the GTO causes a relaxation of the whole muscle (an inhibitory reflex).

Dynamic Stretching

Dynamic stretching is when the limb or joint is taken through the full range of motion using slow controlled movements.

Examples include; arm circles, leg swings, lunges, heel flicks, knee raises etc. Dynamic stretches are more suitable for a warm-up and are probably better suited for this purpose rather than trying to increase flexibility.

Ballistic stretching is an extension of this method but the movements are much more explosive. This type of stretching is likely to lead to DOMS and should be avoided 24-48 hours prior to competition unless it is included in a warm-up for an activity that involves these types of contractions (e.g. fast bowler in cricket or a javelin thrower).

Static Stretching

Static stretching like all stretching methods is used as a method to improve range of movement and is when the joint/limb is taken to the end range of motion and held for a specific period of time. Static stretches need to be held for over 20 seconds (and under 60 sec.) for there to be any benefit (some exam boards mention holding the stretch for over 6 seconds). The stretched muscle should feel slightly uncomfortable but pain should not be experienced.

Static stretches that are done alone are called Active-static stretches – active because the person doing the stretch works (is active) to move the limb or body into the correct position. Passive-static stretches are when a partner does the work and moves the person/limb into the correct position.

Key guidelines for static stretching:

  • There is no movement once the muscle is stretched
  • It tends to target individual muscles rather than muscle groups
  • Is often active but can be passive
  • Can be performed alone or with a partner
  • Suited to cooling down post activity
  • It is considered to be the easiest method of stretching
  • Considered to be the safest method of stretching
  • Static stretching involves maintaining a muscle at its elastic limit

Disadvantages of static stretching:

  • Not sport specific
  • Lack of movement can potentially lead to increased risk when performing ballistic activities
  • Adaptations are slow to occur
  • If used as part of a warm-up can impair performance. By its static nature it can lead to a loss of core temperature.
  • If performed incorrectly can cause skeletal or muscular injury
  • Only stretches one / few muscles at a time
  • Boring