The wellness community has many opinions regarding the necessity and applicability of stretching. Before delving into whether or not stretching is necessary, good, bad or ugly, let’s first define and reflect on this popular word.
What do you think of when you hear the word "stretch"?... Flexibility? Active? Static? Passive? Lengthening muscles? Health? Injury prevention? Micro tears? Recovery? Relaxing? Strength? De-stressing? Yoga? Gumby?
At Vitality, we consistently hear all of the above (and more) and we would like to attempt to take a look at these perspectives individually from a more scientific approach so that we can leave the inaccurate opinions behind and move forward making good decisions regarding our health and performance goals.
Many people consider stretching a means of creating plasticity, or when muscle length is affected permanently (so long as you keep stretching, right?!?!) Ever heard someone say that they want to create long and lean muscles through stretching?
The fact is that the physiology of muscle fibers is not like rubber bands (or plastics) at all, but more like multiple layers of velcro where the contractibility of the muscle is dependent on the number of "fiborous teeth” (actin and myosin) that are gripping one another. Strength diminishes when too few "teeth" are gripping and when ALL are gripping (see picture below). This is called length tension.
(Contraction_chem114a. Digital image. N.p., n.d. Web. 23 Feb. 2016.)
Another cool fact is that depending on how you stretch the joint(s), different muscles and other soft tissue will be more lengthened than others. A slight change in adjecent joint position (ex. hip position during a knee stretch), rotation (internal or external), or plane (so many options) and BAM... different muscles are reaching the outer limits of their length. In every joint position, different muscles are at different length tensions. Pretty amazing if you think about it. There's far more going on in there than we often give credit.
Getting back to the teeth...when the joint angle is increased and the involved muscle for that position is lenghthened, the last layers of “teeth” are hanging on by a thread. The muscle can no longer be lengthened, its force is diminished, and therefore the force is transmitted to our precious connective tissue, which is also the last line of defense for our joints.
This connective tissue does NOT however have the great qualities of elasticity that our muscles do, and inappropriate forces can permanently change their length and alter the structural roles they each play in stabilizing the joint. And that is how our joints can become injured.
So why stretch and when? What are our intentions? Lets tackle flexibility in this blog.
If you ask Google you will find an array of definitions highlighting that flexibility is the range of motion available at one or more joints. However, what we often don't consider is how we are accomplishing that joint range.
Let's break this word down into its' two roots; flex and ability. Consider this: Do you have the ABILITY to FLEX into that range? And, do you have the ABILITY to control every position of that range? (Seemingly, these words should be included in the definition when used in a beneficial context.)
Anatomically, the word flexion is used to describe a decrease in joint angle. For example, bending the elbow is flexion. Flexion is also loosley used to describe a muscular contraction, but because we experience the sensation of tension we usually have a tendency to focus on the extensors that "tighten" when we move into flexion. Hint, hint....the science of muscular contraction has shown us that in many cases it IS the contractibility of the flexors that is most important in achieving active end ranges. Because you know it's all about the strength, bout the strength, no trauma...
If we really want to understand what's going on (physiologically speaking) with a muscle while a stretch is taking place, we first need to undertand how the joint angle is being achieved. Actively or Passively?
An active stretch is used to define a stretch where the contraction of the shortening tissue is overcoming the tension of the lengthening tissue. An active stretch is a very local and controlled type of stretch that requires strength. Some people interpret that when the whole body's motion forces a joint into a position, because the body is moving, it's active. But that's not really accurate. When we are talking about an active stretch, we are strictly talking about the muscles of the affected joints pulling the joints toward their respective extremes. If the acceleration is created by contractions of muscles at different joints, then the stretch would fall into the passive category (even though your body is contracting to get there!!!)
And a passive stretch is used to describe a stretch in which the joint angle is accomplished by a force other than the shortening tissue's contractibility pulling the joint into its extreme range. A passive stretch can also be called an end of joint range eccentric contraction. Ah, we will leave that for another discussion as well.
When you think about a passive stretch, think forcing or pushing the joint into its extreme, when you think about an active stretch, think about pulling a joint into its available extreme.
A static stretch describes a stretch where the extreme of motion is still, but could either fall into the active or passive categories depending on how the joint got there in the first place. And there are many different versions of static stretching regarding magnitude and time spent in the extreme in addition to how the person got into the joint position.
Let's take a little quiz and test what we have learned. Is the above picture featuring an active, passive or static stretch??
The answer is passive and possible static because we really can't tell if shes holding that position or moving in and out of the pose. The reason...Gravity. In this example, gravity makes her body mass the resistance and her extensors are contracting to achieve and maintain the position. In other words, it is the contractibility of her lengthening muscles that is creating the end range, not her joint flexors.
In Part II, we will take a closer look at some of these complex stretches, determine which joints may be involved, and analyze how local joint positions can affect our overall "stretching" range.
I'm busy working on my blog posts. Watch this space!