PNF Stretching

PNF stretching (or proprioceptive muscular facilitation) is one of the most effective forms of flexibility training for increasing range of motion (1,2).

PNF techniques can be both passive (no associated muscular contraction) or active (voluntary muscle contraction). While there are several variations of PNF stretching, they all have one thing in common - they facilitate muscular inhibition. It is believed that this is why PNF is superior to other forms of flexibility training (1,2,3,4).

Both isometric and concentric muscle actions completed immediately before the passive stretch help to achieve autogenic inhibition - a reflex relaxation that occurs in the same muscle where the golgi tendon organ is stimulated. Often the isometric contraction is referred to as 'hold' and the concentric muscle contraction is referred to as 'contract'.

A similar technique involves concentrically contracting the opposing muscle group to that being stretched in order to achieve reciprocal inhibition - a reflex muscular relaxation that occurs in the muscle that is opposite the muscle where the golgi tendon organ is stimulated.

Using these techniques of 'contracting', 'holding' and passive stretching (often referred to as 'relax') results in three PNF stretching techniques. Each technique, although slightly different, involves starting with a passive stretch held for about 10 seconds.

For clarity and to compare each technique, think of a hamstring stretch in the supine (on back, face up) position for each example. The athlete places one leg extended, flat on the floor and the other extended in the air as close to right angles to the body as possible.

Hold-Relax

• A partner moves the athlete,s extended leg to a point of mild discomfort. This passive stretch is held for 10 seconds.
• On instruction, the athlete isometrically contracts the hamstrings by pushing their extended leg against their partner's hand. The partner should apply just enough force so that the leg remains static. This is the 'hold' phase and lasts for 6 seconds.
• The athlete is then instructed to 'relax' and the partner completes a second passive stretch held for 30 seconds. The athlete's extended leg should move further than before (greater hip flexion) due to autogenic inhibition activated in the hamstrings.

Contract-Relax

• A partner moves the athlete's extended leg to a point of mild discomfort. This passive stretch is held for 10 seconds.
• On instruction, the athlete concentrically contracts the hamstrings by pushing their extended leg against their partner's hand. The partner should apply enough force so that there is resistance while allowing the athlete to push their leg to the floor (i.e. through the full range of motion). This is the 'contract' phase.
• The athlete is then instructed to 'relax' and the partner completes a second passive stretch held for 30 seconds. The athlete's extended leg should move further than before (greater hip flexion) due to autogenic inhibition activated in the hamstrings.

Hold-Relax with Opposing Muscle Contraction

• A partner moves the athlete's extended leg to a point of mild discomfort. This passive stretch is held for 10 seconds.
• On instruction, the athlete isometrically contracts the hamstrings by pushing their extended leg against their partner's hand. The partner should apply just enough force so that the leg remains static. This is the 'hold' phase and lasts for 6 seconds. This initiates autogenic inhibition.
• The partner completes a second passive stretch held for 30 seconds, however the athlete is instructed to flex the hip (i.e. pull the leg in the same direction as it is being pushed). This initiates reciprocal inhibition allowing the final stretch to be greater.

Here are some other general guidelines when completing PNF stretching:

1. Leave 48 hours between PNF stretching routines.
2. Perform only one exercise per muscle group in a session.
3. For each muscle group complete 2-5 sets of the chosen exercise.
4. Each set should consist of one stretch held for up to 30 seconds after the contracting phase.
5. PNF stretching is not recommended for anyone under the age of 18.
6. If PNF stretching is to be performed as a separate exercise session, a thorough warm up consisting of 5-10 minutes of light aerobic exercise and some dynamic stretches must precede it.
7. Avoid PNF immediately before, or on the morning of competition.