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Archive for the ‘Anatomy/Structure’ Category

Squats — Front or Back?


“Shut up and SQUAT!!!”

Ronnie Coleman doing his thing, of course

Ronnie Coleman doing his thing, of course

Few exercises in the gym are as loved and as hated as the ever-present squat.  If you’ve spent any length of time in the exercise world, you’ve undoubtedly encountered countless individuals who swear by the practice of grabbing a bunch of weight and dropping their butts to the ground.  Many more engage in the practice sans weight (just think about how many 30-day fitness challenges involve bodyweight squats).  Whatever the flavor, it’s pretty widely accepted that squats are the “go-to” exercise for building the derriere of your dreams.  While I COULD spend this entire post picking apart some of those misconceptions, I’ll save that for another day.  Instead, I’ll assume that you’ve determined that this movement is appropriate for your body and goals and get right to the meat of this write-up.  That is, a comparison between TWO TYPES of squats.

— Allow me to interject before we go any further that I am not a big fan of sticking labels on exercises and saying, “THIS is the way it must be done!”  At the end of the day, such an approach is inappropriate if you’re trying to tailor an exercise to a particular body for a specific goal.  BUT, in the spirit of simplicity, I’ll make some generalizations so I can get some basic points across.  —

Now that that’s cleared up, let’s continue.  The main focus of this post is to look at the difference between the back squat and the front squat in terms of how they might load the different joints and musculature of the body.  While both movements certainly challenge the legs, hips, lower back, etc. to some degree; the exact amount of effort required at each region of the body will change depending on exactly where you put the weight and how your joints move.  To give some understanding of this, we need to understand what joints are going to be moving during a squat-like exercise in the first place.  The list of main players, in no particular order, will be as follows as we descend during a squat:

1.) Ankles — Increasing dorsiflexion (shin moves toward the top of the foot)

2.) Knees — Increasing flexion (knees bending, smaller angle between the calf and back of the thigh)

3.) Hips — Increasing flexion (torso and fronts of the thighs get closer together)

*.) On the way up (coming out of the squat), these movements will necessarily be reversed!

** NOTE ** I’m assuming a bunch of other joints are able to stay still during the motion.  If you can’t keep the rest of the body relatively stable during this exercise, then you shouldn’t be doing it!  I’m also not mentioning motion of the intrinsic joints in the foot, as such a discussion is beyond the scope of this post.  We could spend all day talking about how the foot does or doesn’t move during different activities.

Anyway, all exercises that are traditionally known as a squat will include movement at the 3 joints listed above.  The question is how MUCH movement will occur!  That will depend on a bunch of different factors that I’ll try to hint at here.  Let’s start by looking at a diagram of three different squat scenarios.  On the left is a low-bar back squat (where the bar is kept relatively low on the back, as the name implies).  In the middle is a high-bar back squat (I’ll let you figure out why it’s called that).  And on the right is a front squat:

Much thanks to Lon Kilgore for the illustration.  Note the different body angles between the different squat configurations (Low bar, high bar, and front).

Much thanks to Lon Kilgore for the illustration. Note the different body angles between the different squat configurations (Low bar, high bar, and front).

 

WARNING — SCIENCE AHEAD!!!

 

So — What do you notice?  In each scenario, the hip, knee, and ankle are obviously bending.  But do you notice how the angles are all markedly different?  That’s worth taking a moment to appreciate.  This is due to a little thing called PHYSICS!  Specifically, the center of mass of your body (including the weight you’re lifting) has to stay over your base of support in order for you not to fall over.  Let me say that again:

Your CENTER-OF-MASS must stay over your BASE OF SUPPORT to stay upright!!!

Your center of mass refers to the point about which all of your body mass is distributed.  If you averaged the positions of ALL of the mass you have, that hypothetical average “spot” is where the center of mass would be.  It’s also called the center of gravity.  If this falls outside of your base of support, you can’t stay upright.  In the case of a standing exercise, that base of support is your feet!  So the bar plus your body weight will need to be balanced over your feet for you to remain standing (or “squatting”).  In the pictures above, you can think of that vertical dashed line as passing through the center of mass.  Notice that it’s over the feet in all three cases.  So when you move the bar farther forward or backward, you also have to adjust your body position to compensate and KEEP that line from falling in front of or behind your feet.

If you have to hold your body in a certain position for the lift when the bar is on your back (picture on the left), it should make sense that you’ll have to lean backward more if you decide to put the bar IN FRONT of your body instead (picture on the right).  Think about it — you’ve just put more weight in front, so you have to bring some of the weight back somehow to keep yourself balanced over your feet.  A great way to do that is to sit more upright.  And that’s exactly what we see in the front squat picture.  Notice also that sitting upright means that we have to bend differently at the knees, hips, and ankles if we want to get down into the bottom position.  Look at the angles in the picture closely!  If we have LESS hip flexion, we have to make up for it by having MORE knee flexion and ankle dorsiflexion.  This coordinated movement has to occur for us to get into the bottom position effectively.  Keep that in mind 🙂

So you can see that you’ll have to adjust your body position to accommodate the way you’re holding the weight.  If the weight moves, the body has to move as well.  You do this all the time when you carry things and move around in a typical day.  Most of the time, you probably don’t even notice!

Alright, that’s all well and good.  We’ve established a basic understanding of how the body can move to adjust to different bar positions.  But what does that really mean in terms of what muscles get used?  To explain this, I need to throw another picture at you.  This picture will be similar to the previous one, but it points out another aspect that I haven’t yet talked about:

 

Edited image gratefully borrowed from barbellacademy.com — Note the distances between the hip and knee joints and the dashed vertical line of force.

So here you see three pictures that are similar to the ones in the previous image.  But instead of joint angles, we’re pointing out something different.  See the horizontal lines coming from the knee and hip joints at each squat position?  They help us to visualize how far those joints are from the line of force (that dashed line representing body weight and the bar in this case).  That distance — the blue line for the hip, and the green line for the knee — is known as the moment arm for the joint.  It’s the perpendicular distance between the axis of rotation (the pivot point or joint in this image) and the line of force being applied to it.  If that all sounds kind of wordy, think of it this way:

How does a wrench work?  It is a tool that lets you grab onto a nut or a bolt and turn it.  And we all know that a longer wrench makes it easier than a shorter one.  But why?  The answer is simple — the longer wrench has a longer moment arm.  That’s important, because the amount of torque (rotational or turning force) that you generate at a joint or axis (the bolt you’re trying to turn, in the wrench example) is directly related to how far away the force you’re applying is.  A long wrench gives you a longer lever, which means you can apply force to turn the bolt from farther away.  That imparts a greater torque to the bolt, making it easier for you to turn it!

So taking that logic back to the squat example, what do we see?  When the joints are farther away from the weight, we can see that the weight will generate more torque at those joints.  That means the weight has a greater mechanical advantage to cause those joints to move (hip and knee flexion, in this case).  So if we’re trying to lift the weight, that means that OUR MUSCLES have to generate more force to oppose that weight.  So if the weight on the bar stays the same, then moving a joint farther away from that imaginary dashed line in the picture will make our muscles work harder at those joints!  We can see that the front squat creates the greatest moment arm at the knees in this picture, while the low bar back squat creates the greatest moment arm at the hips.

With that understanding, we can then say the following (assuming we haven’t altered anything else about the lifts):

1) A front squat will tend to require more work at the knees, AND

2) a back squat (particularly with a lower bar) will tend to require more work at the low back/hips

 

END OF SCIENCE-Y STUFF!

 

So there you have it — a somewhat wordy explanation for WHY a back squat is different from a front squat.  Note that this is still EXTREMELY simplified, and there are many other factors that can further affect how these movements challenge your body.  People with different body segment lengths will “fold up” differently, and some people have much more joint range at the hips, knees, and ankles than others.  As such, not everyone will be able to achieve the same depths or positions.  That’s okay!  But if you understand some of the basics behind body mechanics, you’ll be better equipped to understand why that is and what might be the best approach for your workouts.  There are also different artificial tools that can affect a squat — such as lifting shoes, Smith machines, hack squat machines, etc.  So this is just scratching the surface!

Finally, this was just looking at some basic joint mechanics and trying to appreciate how the major body segments are moving in relation to one another.  Want to know how that affects specific muscles in the hips and legs?  Stay tuned for a future entry that will examine some of the muscular anatomy of the area and give a little insight into what’s actually responsible for lifting you (and that bar!) up off of the floor!

Cheers 🙂

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I Wanna Be FLEXIBLE!!! (Part 2) —


So I left off a while back having discussed the MAIN STRUCTURAL COMPONENTS responsible for flexibility (bones, ligaments, etc.) to give some idea of the hard limits that we have to our total joint range.  But as most of us realize, that’s not the whole picture.  After all, it’s not usually our skeleton that’s restricting us in day-to-day activities.

Where do we typically feel “tight” instead?  In our muscles!  And that brings me to the major focus of this blog entry — the NEUROMUSCULAR SYSTEM!!!

You see, the primary job (mechanically speaking) that our muscles have is, simply put, managing joints.  Put another way, they’re primarily responsible for making sure that the bones can actually maintain proper contact with each other, can move (or not move) properly, and that force can be distributed throughout our bodies in an appropriate way.  If our muscles are working well, then we’re having a good time.  If not, then we start to see dysfunction — in the form of pain, arthritis, weakness, poor performance, coordination issues, and all sorts of other not-so-fun stuff.

 

A less-than-optimal neuromuscular system often leads to pain and other issues -- from www.treatingpain.com

A less-than-optimal neuromuscular system often leads to pain and other issues — from http://www.treatingpain.com

 

So to illustrate how some of this works, we have to break down the actual structure of a muscle and the “stuff” it interacts with.  Note that this will be PRETTY basic, but there’s still some science ahead.  So saddle up!

Muscles are, at least in my opinion, some of the coolest things ever devised by nature.  They consist of tons of tightly packed subcellular machinery that allows our bodies to convert the chemical energy of our food and the products of food breakdown into actual mechanical energy (FORCE)!  This is no small feat.  I won’t get into the metabolic pathways and mechanisms that govern this right now, but just know that there’s a lot of stuff that has to happen for your muscles to work!  So let’s talk a little about their structure (feel free to skip this portion if you’re already familiar with basic muscle structure):

 

— BEGINNING OF SCIENCE!!! —

 

***Keep in mind that this post is going to talk about skeletal muscle.  This is the stuff that attaches to our bones and helps us move.  There are two other types of muscle — cardiac (heart muscle) and smooth (which operates in our organs and around blood vessels) — but this isn’t immediately relevant to us.  So I’ll stick to skeletal muscle today.***

 

First off, I want you to look at the structure of a typical muscle.  Notice that it’s a big hunk of tissue that’s attached to a bone by something called a TENDON.  But when we break it down, we see that the whole muscle is actually comprised of a bunch of chunks of  muscle units called “fascicles.”  The word “fasciculus” actually means “bundle” in Latin.  This makes perfect sense, as you can see that each fascicle is really a bundle of individual muscle fibers.  I sometimes like to think of it as a bundle of straws wrapped in a thin sheet of tissue.  And all of those bundles come together to make the whole muscle.  Also– in muscles, a “fiber” is the same thing as a “cell.”  So keep that in mind if you see it anywhere else.  Again, FIBER = CELL.

 

Skeletal_Muscle_Fibers

Muscles have a really cool structure — notice how muscle fibers (cells) are bundled together into fascicles, and then THOSE are bundled together again. It all packs together into what we know as a whole muscle — Taken from http://www.medicalook.com

 

This gives a good basic overview of how our muscles are organized on a larger scale.  Now let’s look a little closer at a single muscle cell (one of the straws) to see how it’s put together:

 

So we see that, even on a smaller scale, things are bundled up in a similar fashion.  Inside a single cell, we see these individual cylinders called "myofibrils" that have their own components within THEM -- from www.24manuals.com

Smaller bundles of “straws” within each of the ones from the previous diagram — from http://www.24manuals.com

 

So we see that, even on a smaller scale, things are bundled up in a similar fashion. Inside a single cell, we see these individual cylinders called “myofibrils” that have their own components within THEM.  It is within these myofibrils that the smallest functional unit of a muscle is found — THE SARCOMERE.  I won’t get too deep into how this little guy works, but suffice it to say, these are where the magic really happens.  Here’s one last picture to help you visualize things on this microscopic level:

 

A diagram of the basic structure of a SARCOMERE -- from www.studyblue.com

A diagram of the basic structure of a SARCOMERE — from http://www.studyblue.com

 

So all you really need to know about sarcomeres is this — tiny little proteins (filaments or myofilaments) inside the sarcomere attach and “crawl” over each other so that each end (the Z-disc or Z-line) is pulled toward the middle.  Now all of these sarcomeres are attached end-to-end (in “series” as it is known).  If we zoom back out a bit, we can imagine how the whole muscle will shorten as each individual subunit shortens.  Here’s a neat way to visualize this:

Imagine you and nine friends are all side-by-side, and you each represent a single sarcomere.  You each have your arms outstretched and are holding hands with the person next to you.  Now imagine that, while doing this, you’re sitting on a REALLY slick surface so you can pull all of the people on either side of you closer to your position.  If you pull your arms in (“contract” like a sarcomere), you get “thinner” and the people on either side of you will slide in towards you.  The overall length of the system (all 10 people) will get a LITTLE BIT shorter.  Now imagine if ALL TEN of you do the same thing.  Every person pulls the people they’re holding hands with closer to them.  As you might imagine, the whole chain will get MUCH shorter, as everyone is pulling their arms in at the same time.  This is what happens within a myofibril, and within a whole muscle on a larger scale.  The whole muscle shortens, because TONS OF INDIVIDUAL SARCOMERES SHORTEN.

I mentioned earlier that muscles generally attach to our bones at what is called a tendon.  While they don’t generate force directly, healthy tendons are absolutely vital for allowing us to transmit that force from our muscles to the bones (or vice-versa) and do all of the things that we ask our bodies to do.  If a tendon fails, then the muscle can’t do its job.  This is important to keep in mind, as these structures are often overlooked when we talk about building strength and power and developing our physiques.  We’ll look at tendons and how they are involved in stretching a little more later.

 

— END OF SCIENCE!!! —

 

So from all of this, we can see that there’s an intricate structure that contributes to the way our muscles do their jobs.  Millions of tiny units work together to create the large-scale movements that we see and use every day.

I needed to go into the structure of muscles a bit so you have a basic understanding of the pieces that make up the whole.  Muscles are an intricate (and WAY COOL) system of components that come together beautifully to allow us to perform all of the actions of daily living that we take for granted.  Without muscles, there is no controlled movement.  So now that you know a little bit more about how muscles are put together, what about the effects of stretching?  How does attempting to move into extreme ranges affect these tissues?  I’ll describe this in the next entry 🙂

 

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: 

 

*** WARNING — BIT OF SCIENCE AHEAD!!! ***

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.).

909_Types_of_Synovial_Joints

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 cnx.org.  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:

FemurAngles

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!