My thoughts and perspectives on health, science, and logic… Keep an open mind!

Posts tagged ‘structure’

I Wanna Be FLEXIBLE!!! (Part 1)

Well friends, it’s time for another update.  Based on some recent observations (and a good bit of input from some friends and family), I feel it’s appropriate to discuss a topic that seems to be on everyone’s mind — FLEXIBILITY!  (Warning, this’ll be a little longer than my last entry)

It seems you can’t go half a day without hearing someone in your social network or at the workplace talking about how “tight” something feels.  If you were to ask a random room of 200 people from all over this country which ones feel they need to be more flexible, almost every hand would shoot up.  It’s seen as a universally good thing to be flexible.  This is common knowledge.  Right?

Hmm… not so fast.  First off, what IS flexibility anyway, and how can we affect it?  Some people would define flexibility as the ability to move throughout a certain Range of Motion (ROM) at various joints.  Others describe it more as a sensation of “looseness” or softness in the muscles that often like to tighten up.  At the end of the day, we have probably all known those people who seem to be able to contort themselves into all sorts of wacky positions without trouble.  We also know other people who are at the other end of that spectrum (and maybe you’re one of them!).

Isn't it just so unfair?  We all know those people who can do ridiculous things with their body.

Isn’t it just so unfair? We all know those people who can do ridiculous things with their bodies. — (Wikipedia image)

So I’d say it’s all kinds of things, depending on the person and the goals.  A person’s overall capabilities in terms of flexibility/motion will depend on two main factors: 1) Structural limitations and 2) Neuromuscular capabilities.  Sadly, there’s no way I can cover all of the intricacies of the topic in a single blog post.  For this post, I’ll describe a little bit about joint structure: 



This might sound silly, but first we have to define a joint.  A joint is any place where two bones come together/interact.  Note that I didn’t say they have to MOVE!  This is important.  Some joints are completely fused, while others have a little or a lot of motion allowed.  A super detailed description of all of the variations is beyond the scope of this post, but be aware that there are differences.  I’ll probably go into more detail in a future segment that I post as a permanent link.

There are a few fancy words that anatomists and biomechanists use to describe the structure and function of the joints in question.  Specifically, a synovial joint is surrounded by a joint capsule that contains synovial fluid for lubrication and nutrient flow.  The term diarthrodial is often used interchangeably with “synovial” and describes a joint that is “freely moving.”  These are the joints that we most often think about as contributing to the movements that we try to accomplish throughout the day.  Synarthrodial joints, on the other hand, are fused and allow essentially no motion (such as the sutures fusing the separate bones of your skull).  Amphiarthrodial joints allow some movement (think of the intervertebral joints in your spine, etc.).


A breakdown of the six basic categories of synovial joints

For the purposes of this discussion, I’ll focus on synovial /diarthrodial joints.  There are six (6) generally accepted subtypes within this joint category that most of us in the exercise industry are used to.  Note that I have taken the images in this section from the “Synovial Joints” section at  It’s still a little simplified, but it can give you a decent idea of the structure and function beyond what I’m writing about here, and I think the diagrams get the point across nicely.

Anyway, let’s take a look at a “typical synovial joint” as well as the passive structures in the knee joint to get a sense of what’s going on here…

A generic synovial joint (note an enclosed capsule and articular cartilage on the surfaces between bones)

A generic synovial joint (note an enclosed capsule and articular cartilage on the surfaces between bones)

A more realistic diagram of an actual synovial joint -- the knee

A diagram of an actual synovial joint — the knee

So you’ll see that there are a number of structures in a joint that we need to be aware of.  Any one of these can have profound impacts on the ability (or inability) for that joint to move properly.  Let’s take each of these pieces one at a time:

1) The articular cartilage is an extremely smooth covering on the ends of the bones.  It pads and protects the bones from wear.  It also allows for the joints to move smoothly by allowing the ends of bones (articular surfaces) to glide almost effortlessly over one another.  This stuff is REALLY slick!  Note that irritation of this tissue from abnormal stresses can result in problems like osteoarthritis and cause inflammation that limits your range of motion.  That said, proper motion is actually HEALTHY for the joint tissues (including the cartilage).  Cartilage can adapt to stresses and become thicker/stronger where it is loaded IF you do so properly.

2) The tendons are fibrous bands of tissue that connect muscles to bones, allowing them to put force through the bones.  As will be discussed in a later entry, all movement ultimately depends on our muscles’ ability to deliver force to our bones in a sufficient and reliable fashion.  As is the case with muscles, bones, and other joint structures, tendons can adapt to stresses to become stronger.  More on this later.

3) The synovial cavity is the cavity within the joint that contains the lubricating synovial fluid.  This fluid reduces friction in the joint and allows for a sort of nutrient circulation throughout the joint.  The joint tissues can actually begin to atrophy and die without proper flow of these fluids.  Think of the fibrous tissue of the synovial cavity as kind of spongy.  In order for the tissues within the joint to receive proper nutrients and flush out toxic byproducts and waste, we have to “squeeze out” the sponge and then release it again.  We do this through loading and unloading the joint periodically through normal movement.

4) The ligaments are completely passive structures that attach bones to each other and keep the joints moving along a relatively predetermined path.  Too much stiffness in these guys (from scarring/fibrosis, adhesions, etc.) can cause limitations in motion.  Conversely, too much looseness/laxity in ligaments can result in joint instability and a predisposition for abnormal wear and/or dislocations.  When we do a significant amount of stretching, we can (potentially) affect the length of these tissues.  When we stretch out a ligament, it doesn’t readily return to its old length.  That’s something we have to keep in mind when we do really intense stretches, as I’ll discuss later.

5) The bursae (plural of bursa) are small fluid sacs that reduce friction by keeping bones from rubbing against each other and/or prevent soft tissues (tendons, etc.) from dragging over bones and wearing out.  Soft tissue specialists sometimes focus on massaging and manipulating these tissues to allow for greater mobility in a joint.  In extreme cases where they are doing more harm than good, they may be surgically removed.  I’m not currently an expert on the function of these structures, so I’ll save discussion on them for another time.

6) Finally, note the bones themselves!  People often forget about what is the most important passive structure for determining motion.  How are the bones actually shaped???  I’ve seen blatant ignorance of this in a number of places over the years.  But let me say it here and now — YOU CANNOT VIOLATE YOUR STRUCTURE WITHOUT CONSEQUENCES!!!  Some of the worst offenders are martial arts schools and ballet/dance academies where a great deal of emphasis is put on range of motion without a proper understanding of how to manipulate it.  Whatever shapes your bones and joints have will directly dictate what movements you’re capable of accomplishing.  If your pelvis and femur look nothing like Sally’s, you’re not going to be able to do the same movements that she can do.  Period.  You can check out this picture for an illustration of my point:


Note the different shapes we see in people’s femurs. It isn’t hard to imagine that different shapes allow for different degrees of mobility. I’ll explore the hip in more detail in a future post — (Image from Wikipedia)

Now that doesn’t mean it’s all bad if your structure doesn’t allow for a great deal of movement.  Sure, it’s a cool party trick to be able to drop into a split at a moment’s notice, but you make up for that with something that might be much more useful: STABILITY!

You see, your body liberates movement at the expense of stability.  If you let something move around a lot more, then you can’t anchor it in place as well and keep the bones as secure.  Think of the shoulder and how mobile it is.  Now think about how often that thing gets dislocated compared to other joints!

Likewise, if a joint is held in place with more passive structures (bony articulations, ligaments, tighter joint capsule, etc.), then there won’t be as much opportunity for movement.  Dislocations at the hip don’t happen nearly as often as at the shoulder, but you also can’t move it as freely.  In most cases, at least.

What was all that?!?

What was all that?!?

So I apologize if that was a wall of text, but I needed to cover that basic information in order to move forward.  There are a variety of structural variables we have to consider before looking at how we can really move.  Our structure DETERMINES our function.  Once we’ve discovered what our opportunities for movement are, we can then look at our ability to CONTROL that movement.  For that, we’ll have to look at the neuromuscular system and develop more of an understanding of how we tend to become “flexible.”   That’s coming up in PART 2

Thanks for reading!