What is Happening in a Stretch and How Should it Feel?

Welcome back to our series on how to start a quality mobility practice. Read the previous article about articulations (step 1).

In this article we talk about stretching and how to safely create and manage the feelings associated with it.

What is a stretch?

The term “stretch” or “stretching” is commonly used in the yoga and fitness world, but what does it really mean? More importantly, what is happening in the body when we perform the pattern of a stretch.

If we look at some of the top definitions online, we find that a stretch is:

: to straighten or extend one's body or a part of one's body to its full length, typically so as to tighten one's muscles or in order to reach something. - Oxford Dictionary

: to extend (one's limbs, one's body, etc.) in a reclining position - Merriam Webster

: to draw out or extend (oneself, a body, limbs, wings, etc.) to the full length or extent (often followed by out) - Dictionary.com

These descriptions are limited to say the least, they simply describe positioning.

Let’s be clear, there are better definitions online, however these are the norm, the ones that millions of people use as their “truth”. Even the Wikipedia description is lacking (and I had to fix it!).

Stretching is a form of physical exercise in which a specific muscle or tendon is deliberately flexed or stretched  extended in order to improve the muscle's felt elasticity and achieve comfortable muscle tone. The result is a feeling of increased muscle control, flexibility, and range of motion - Wikipedia

Not only do these definitions lack the details necessary to perform a stretch safely and effectively, their vague description leaves to much room for error and injury. The stretching process is a lot more complicated than just positioning a limb. We are working with the tissue in a way that needs to be controlled and articulated correctly while under tension.

What is happening with the tissue in a stretch?

It all starts with something called the Stretch Reflex.

The Stretch Reflex

The stretch reflex (also called the myotatic reflex) is the signal or trigger to resist a change in muscle length as it stretches to the available end range. When a muscle is stretched, the muscle spindle is as well. The muscle spindle records change in length along with the speed
of that change and sends the information to the spine. This communication activates the stretch reflex, which works to resist the change in length by causing the stretched muscle to contract. The quicker the muscle length changes, the stronger the contractions will be. This simple function of the muscle spindle helps to maintain muscle tone and protects the body from injury.

There are two aspects that make up the stretch reflex, a static aspect and a dynamic aspect. The static aspect is in use as long as the muscle is being stretched, however the dynamic aspect only activates in moments involving quick increases to the muscle
length. The static and dynamic aspects of the stretch reflex relate to the two kinds of intrafusal (spindle) muscle fibers: nuclear chain fibers, which are responsible for the static aspect; and nuclear bag fibers, which are responsible for the dynamic aspect.

The range of motion determined by the stretch reflex is based on previous experiences and the muscles ability to function at a particular range. If the central nervous system determines that the muscles are not strong enough to control a particular range of motion, it will not allow that range to be achieved. If one wants to increase the range of motion, the stretch reflex needs to be safely overridden in some way.

Example:

Holding a stretch for a prolonged period of time also holds the muscle in a stretched position. The muscle spindle starts adapting to the new length and reduces signaling to the stretch reflex. This begins to activate the lengthening reaction.

Safely overriding the stretch reflex to increase range of motion is known as the lengthening reaction.

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The Lengthening Reaction

The lengthening reaction (also called the inverse myotatic reflex) prevents the muscles from contracting at end range, causing them to relax.

This is the signal to override of the stretch reflex. Contracted muscles produce force where the muscle and tendon are connected. This is where the Golgi tendon organ is found. The Golgi tendon organ records the change in force and the rate of that force change. It then sends this information to the spine. When the force exceeds a certain threshold, it activates the lengthening reaction, preventing the muscles from contracting and causes them to relax. It is easier to stretch or lengthen a muscle when it is not working to contract.
It can typically take 30-90 seconds of holding a passive stretch (pose) for the lengthening reaction to occur.

Spindle vs. Golgi Tendon Organ Responses

• Spindle afferents respond to changes in muscle stretch (contraction)
• Golgi tendon organ afferents respond to changes in muscle force (relaxation)

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Stretching Infographic

How should the stretch feel?

The feeling of a stretch is the most important factor when it comes to effectively communicating with the nervous system. It is also one of the hardest aspects to convey when teaching the process. You may hear people refer to this as your “edge” or your “flexibility”. As explained above, they are referring to the stretch reflex, the point where the tissue automatically contracts to resist.

Less is more when learning to measure the feeling (stretch reflex) in a stretch position. Your body is always listening and the slightest amount of tension will register in the nervous system. Think about how easy it can be to wake someone up from sleeping. This means that minimal tension is needed to create change in the tissue. How much tension? That depends on the current strength and range of an individual and their body.

Use these equations for tension and how it relates to adaptation and injury in the tissue.

Tension ≤ Tissue Capacity = Adaptation

If the tension is less than or equal to the capacity of the tissue, adaptation will occur. The capacity of the tissue is that “edge” of what you feel you can handle, the tension you can safely resist.

Tension > Tissue Capacity = Injury

If the tension is greater than the capacity of the tissue, an injury will occur. The injury could range from a slight muscle strain all the way up to a tear of the tendon or ligament depending on the amount of tension.

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Time Under Tension

Time under tension (TUT) is used in strength training, bodybuilding, stretching and various other movement principles. It is the building block of communication between the mind (nervous system) and body (tissue).

It refers to how long the tissue is under strain during a movement or static position. By putting the tissue under longer periods of strain, you can cause extensive tissue breakdown leading to the principle progressive adaptation. Time under tension can be used to build strength, flexibility or both at the same time (also known as mobility)!

1. Beware of locking-out. Avoid spending long amounts of time in the easiest part of a movement pattern (with the legs locked out during a fold for instance). The easiest part of a movement presents the least amount of stress on your tissue, or even worse, stressing the joint with leverage.
2. Try to maintain a steady tempo. It should feel like you are moving in slow motion. Only using more tension when needed or dependent on the exercise.
3. Focus on the eccentric portion of the movement. This refers to repeating the process or pattern in reverse with a concentration on the movements that require more tension. Slowing down the eccentric portion of a movement pattern causes more tissue damage and hence encourages more growth.
4. Concentrate on form. With the longer movement patterns, fatigue will set in and compensations will occur. Try not to cheat yourself by loosing form or doing partial patterns.
5. Reduce the tension or load. Can’t finish the last few reps, decrease tension (weight/resistance) and continue the movement. Make the entire movement pattern accessible so you don’t need to cheat to get through it.
6. Maintain intensity. Simply completing the movement pattern doesn’t guarantee increases in strength and/or flexibility. The tension and movements need to be challenging enough to cause fatigue towards the end of the pattern.

Where should you feel the stretch?

Now that we understand tension and how it applies to tissue growth, it is important to know where to focus the tension in a pose or movement pattern. This is done by learning your body’s articulations and being familiar with your current end ranges.

Lunge

Let’s use the example of a lunge. While there are many different articulations happening at once to create the position, the focus of tension is in one articulation. The backside hip extension.

This is the area you are stretching, this is where you should feel it.

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Pyramid

Now let’s take a look at Pyramid pose. Among the many articulations happening to make the position, the focus of the stretch is knee extension in the front leg.

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Downward Dog

Lastly, let’s review Downward dog. While there are two connection points on the ground (closed chain), the focus of the position remains in the knee extension of both legs.

Now I know what you may be thinking, it can be legs or shoulders, and that’s correct. However the problem with making downward dog primarily a shoulder stretch lies within the available shoulder flexion and the ability to hold ones weight up at the same time. Either of these factors can make it hard to achieve the shoulder flexion “stretch” and could lead to overloading the tissue capacity ..or an injury. So while it is possible, it should be thought of as a more advanced option.

A pose or movement pattern is made up of many different articulations in the body, all working together to express what the mind intends. As the joint articulations improve in range and strength, more complex patterns and poses can be achieved. Simply put, the better you can individually articulate the joints, the more mobile you will become.

How do you measure and improve flexibility?

In order to increase flexibility, you need to measure it against a starting point. This is the information the stretch reflex provides, it demonstrates the current end range available. Once you know the end range in a stretch position, you can then lightly resist and challenge the tissue.

Tension ≤ Tissue Capacity = Adaptation

As long as you don’t exceed the capacity, the process will build strength in the tissue, creating a new end range overtime.

This is the secret to increasing flexibility.

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We are just scratching the surface when it comes to stretching. The concepts discussed so far have been:

1. Learn the Joints (Articulations)
2. Master the Stretch (Measurement)
3. Now to Stay Limber! (Movement)

In the next article (step 3) we learn the difference between flexibility and mobility. The foundation of what it takes to stay limber and live better.