There are a number of different types of stretching exercises that can be done to improve flexibility. Here we explain static stretching, dynamic stretching, PNF, and ballistic stretching. It is important to know when a particular type of stretching exercise is most appropriate.
What is static stretching?
Static, or isometric stretching is a type of stretching where the muscle is stretched until your feel a gentle ‘pull’, or stretch on the muscle. The stretch is then held for a period of time, usually upwards of 10 seconds before relaxing the muscle.
- Stretches should always be pain-free. If you feel pain then your muscle will naturally want to tighten to protect itself.
- Static stretching is often used to develop flexibility, particularly after a muscle strain injury.
- In strong healthy muscles however, PNF type techniques may be better for developing flexibility.
This type of stretching is very much in fashion these days, particularly in sport for warming up. it involves stretching your muscles whilst moving, either by leg swings, or by performing sports-specific drills.
- It works ‘with’ sensors in the muscle called muscle spindles.
- Muscle spindles are sensors within the muscle which sense the speed a muscle is being stretched.
A muscle can be flexible with sufficient length. However, if it is suddenly asked to move at speed then sensors called muscle spindles may kick in to prevent it overstretching. This is how stretch related muscle strains can occur.
PNF stands for Proprioceptive Neuromuscular Facilitation and can take on several forms including hold-relax; contract-relax; and rhythmic initiation.
- PNF started to become popular in the 1960s and has since become a common treatment for many physiotherapists and other sports injury professionals.
- PNF can be either completely passive (meaning the therapist moves the limb through its ranges of motion) or active assisted, in which the athlete plays a role in the treatment.
- In this case, it requires an isometric contraction before the stretch.
So for example, to a use hold-relax PNF technique on the hamstrings, the athlete would lay on the back and raise the straight leg up off the bed (contracting the hip flexors Rectus Femoris and Iliopsoas) to the starting position. From here, the therapist or partner provides resistance as the athlete isometrically contracts the hamstrings (as if trying to push the foot back down to the floor) for a minimum of 6 seconds. Following this, the athlete contracts the hip flexors again to raise the leg higher and further stretch the hamstrings.
This works on the theories of reciprocal inhibition (or innervation) and post-isometric relaxation. Reciprocal inhibition is based on a reflex loop, controlled by the muscle spindles. When an agonist muscle contracts (for example the quads, causing knee extension), the antagonist’s muscle is inhibited, causing it to relax (in this example the hamstrings), allowing the full movement of the antagonist muscle (knee extension). Post-isometric relaxation is thought to be controlled by the Golgi tendon organs, sensors within the muscle which are sensitive to muscle tension. When a muscle is contracted isometrically for a period of time, this results in an inhibition of the muscle, resulting in relaxation.
PNF can also be used for treatments other than stretching, for example, muscle strengthening in a rehabilitation setting. PNF in this sense involves spiral-diagonal movements, as are used in most daily and sporting activities. Very few activities use only one plane of movement, there is usually a combination of two or all three planes (flexion/extension; adduction/abduction; and rotation). For this reason, PNF incorporates these spiral-diagonal movements to help train the body in the way in which it is most often used.
This is related to sliding filament theory of muscle contraction.
Ballistic type stretching exercises
This type of stretching is where you stretch the muscle as far as it is comfortable to do so. Then, at the the end range of movement you bounce or force the joint that little bit further.
- This is generally frowned on these days, because the act of forcing a muscle beyond its comfortable range can damage it.
- However, Martial artists and Ballet dancers (extreme joint range of movement is required) often include it in their stretching routines.
- It may also be used in rehabilitation to increase joint range of movement. But be careful!
An example of ballistic stretching is reaching over to touch your toes and bouncing to increase the range. This type of stretching is rarely recommended due to the injury possibilities and no beneficial effect over other, safer, forms of stretching such as PNF and dynamic stretches.
Muscle Energy Techniques
Muscle Energy techniques (or MET’s) are types of stretching exercises similar to PNF, and developed around the same time, in the world of Osteopathy. Like PNF, MET’s use an isometric contraction of the agonist prior to stretching. The difference is in the force of the isometric contraction, which in MET’s are a lot lower. A MET stretch is performed in the following way, using the hamstrings as an example:
The therapist moves the hip into flexion, with the athlete on their back, until they encounter the point of resistance – where the movement stiffens, due to tightness in the hamstrings. They hold this position for 15-20 seconds. They then ease off slightly from the stretch and ask the athlete to try to push the leg back down to the couch, which causes an isometric contraction of the hamstrings. In MET’s, this contraction should be a maximum of 20% of the athlete’s total strength. This contraction is held for around 10 seconds, before the therapist asks them to relax and pushes the limb further, increasing the stretch, until resistance is felt once more. The process is usually repeated 3-5 times for each muscle.
Neural stretching refers to stretching the structures of the nervous system. This is necessary for injuries where there is excess neural tension, for example muscle related sciatic pain.
- Examples also are commonly found in the neck, shoulder, or pelvis area.
- Neural stretches are adaptations of neural tension tests, such as the slump test and the upper limb tension test.
- The limb is taken to the point of stretch and held for a maximum of 10 seconds, although initially, this may be as little as 3-4 seconds to avoid causing damage to the nerves.
- Types of stretching like this should only be performed under the supervision of a qualified therapist.