The Science of Stretching

There is a lot out there about how to stretch, when to stretch, and what to stretch; I am not going to answer any of that, but instead inform you on types of stretching, and how they work on the body. The different types of stretching are self-myofacial release (SMR), ballistic stretching, static stretching, and proprioceptive neuromuscular facilitation (PNF). Some of those sound very scientific, but there is not much to them.

To start we will go over a key parts that react to stretching.

Golgi tendon organs (GTO): is a receptor located around the area where muscle attaches to the bone. The job of the GTO is to determine how tense, or relaxed a muscle is by sending information to the spinal cord, which will either let the muscle continue to work, or send an order to have muscle relax. You may have experienced this before when you are walking and your leg ‘gives out’ momentarily, this is a miss fire of the GTO.

Muscle Spindles: are located in the muscle, embeded in the muscle fibers. The job of the muscle spindle is to determine the length, and rate that the muscle is contracting, or extending. When the muscle spindle finds an agonist muscle group to be overly elongated, or extending to fast it will send a signal to the antagonist muscle group to contract.  Muscle spindles prevent our muscles from over-stretching which would lead to injury.


Types of Stretching:

SMR: also called foam rolling, is something most people dread, but at the same time love! It can cause some pain, to the tight muscles, and once you are done you feel fantastic. Using a foam roller, or a ball (depending on how hard you want the pressure) roll onto the tight muscle. Roll it around until you find the spot that hurts the most, and then sit there for 30 seconds. The reason you stay on this one spot is because it the tightest spot, this will make the muscle really tense, and activate the GTO. You may start really tense, but during the 30 seconds try and relax into it. Doing SMR before stretching can actually help you perform deeper stretches.



Ballistic Stretching: is a dynamic stretching. This involves taking the joints through extreme range of motions rather quickly. By quickly contracting a agonist muscle group to the joints full range of motion will help stretch out the antagonist muscle group, and cause a myotatic reflex. A myotatic reflex (strong reflex) is when a muscle group is quickly stretched, activating the muscle spindle, and sending a signal to the spinal cord, then tells the stretched muscles to quickly contract, and the antagonist muscle group to relax. This type of stretching is good for anyone who needs to quick movements, but anyone doing this type of stretching should know there is a chance that you may exceed the range of motion, and pull a muscle.



Static stretching: is the type of stretching most people are use to doing. This where you stretch a muscle slowly into position as far as you can go, or close to it. The end position is then held for 15-30 seconds, since you slowly go into position the muscle spindles are not activated; a strong reflex does not occur. Holding the stretch for 6 seconds or more will help activate the GTO and a create an inverse myotatic reflex. An inverse myotatic reflex is when the muscle being stretched is sent a signal to relax, and the antagonist muscle it told to activate. If a stretch is held long enough, and deep enough myoclonus may occur, a twitching or spasm of the muscle group, indicating the endpoint of the stretch. Due to the slow nature, of getting into position, injury is pretty unlikely to occur.


PNF: the buddy system of stretching. In this type of stretching you may need the help of another person, or something that can help you hold a stretch, like a piece of rope. There are two ways of doing PNF stretching: contract-relax (CR), and contract-relax-agonist-contract (CRAC). During CR the partner helps slowly stretch the muscles (the antagonist) to its maximal length, to help bypass the muscle spindles, and held there for at least 6 seconds. Then the person being stretched activates the antagonist muscles, well the partner resists for around 6 seconds. This will activate the GTO and cause an inverse myotatic reflex. After the 6 seconds the partner returns relaxed limb to a greater stretch. CRAC uses the first two steps of CR, but then is followed by contracting the agonist muscles of the muscle that is being stretched. This is a great way to stretch, and can really help with flexibility. Make sure the partner can tell when the muscle is at its maximal length, or be sure to communicate when.

SMR: is used to help relax tight muscles, and to help you getting a deeper stretch. Ballistic stretching is a good way to become more flexible, but runs the risk of pulling a muscle if they are not warmed up a bit first. Static stretching is a great way to stretch when you are by yourself. And PNF both CR, and CRAC is a great way to improve flexibility, as long as you have a partner, or an aid to help you.

Steven Moore About Steven Moore

Passionate Personal Fitness Trainer, and NASM Corrective Exercise Specialist at Blitz Conditioning. Prone to spurts of random nonsense. [Read my full bio]

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