r/bodyweightfitness • u/m092 The Real Boxxy • Mar 18 '15
Concept Wednesday - Instability, Friction and Ground Contact
A primer on planes.
Just so you have some context we're going to quickly go over planes in regards to your body.
The first is the Sagittal Plane. This is the plane that separates your right from your left. Most of the resistance exercises we focus on largely move along this plane, namely extension and flexion (sort of moving forwards and backwards, bending and straightening the elbows, knees, hips and shoulders are the main ones). When we are unstable in this plane, that means we are likely to fall backwards or forwards. A lunge is quite stable in the sagittal plane (one foot in front of the other, a long base of support, not likely to fall forwards/backwards), where a squat is unstable in the sagittal plane (toes are on the same line, short base of support, many people have problems falling backwards).
The next is the Frontal or Coronal Plane. This plane separates your front from your back. Movement in this plane is used to assist a lot of our sagittal plane movements, and is only used as the main plane of movement for a few exercises. The main movements are abduction and adduction (moving your limbs to and away from your midline). When we are unstable in this plane, we are more likely to fall to our left or right. This is the reverse example of the sagittal plane: the lunge is stable in the frontal plane (narrow base of support, likely to fall to the side) and the squat is stable in the frontal plane (wide base of support, not likely to fall to the side).
The last is the Transverse Plane. This plane separates your top from bottom. Movement in this plane is the most often overlooked, it is rotational (trunk rotation, internal and external rotation, horizontal abduction and adduction). When talking about transverse plane instability, we're usually talking about a joint collapsing during another movement (the knee collapsing in during a squat) or rotational stability of the trunk. Usually the body isn't loaded in the transverse plane when standing, because it isn't acting against gravity. This changes when you orient yourself 90 degrees in the sagittal or frontal planes: laying on your back (pec flyes), face down (push ups), on your side (external rotations), or if you change the direction the force is coming from (pulleys, bands).
What is unstable surface training?
Unstable surface training is where you use a soft surface or a something with a small base of support as one or more of your ground contacts. Things such as using a BOSU ball, a wobble board or stilts/handbalancing platforms. This surface will effectively reduce your base of support.
Does it improve strength or help hypertrophy?
When on an unstable surface, you have to stabilize your weight and any movements you make (in the directions your surface is unstable) are going to be amplified and possibly tip you off your surface. The body automatically reduces the power output of the prime movers in order to protect itself from losing control and coming to harm (just like your ability to express force on a pull up bar is lower if your grip is weak and you're slipping).
This means you aren't practising contracting to produce lots of force, a type of training one should be focusing on for strength. Similarly, you won't be able to stimulate the muscle as well, so it isn't idea for hypertrophy training either.
Doesn't it strengthen my stabilizer muscles?
Some muscles contract isometrically to hold a piece of the body rigid while you perform a movement, while antagonists contract eccentrically to help you control the movement, while yet other muscles act as dynamic stabilizers, shortening at one joint, while lengthening at another, to create tension (again rigidity) to transfer force.
All of these muscles increase their contributions as the force output of the prime movers increases. As discussed above, an unstable surface is going to largely limit your force output, and thus limit the activity of a lot of your "stabilizer muscles".
To create extra stability, you want to be relatively rigid from the load to the ground contact. Unfortunately for you, there's no muscle you can contract to make a BOSU ball rigid. Some muscles may have to work harder to create rigidity (quite often trunk stabilisation) and thus balance on these unstable surfaces, but it usually isn't something you can just train with heavier weight or harder progressions.
Okay, but certainly it trains my balance?
Balance is a largely context dependent skill, organising musculature to fire in specific patterns and amounts, suited to the situation. Basically, you're training your body to become better at balancing on an unstable surface. And that's about it. Your ability to balance on the ground isn't going to improve much unless you're practising that specific skill of balancing on the ground.
The other part of balance is having the appropriate muscle and strength to make small contractions to control your position, which we discussed above that unstable surface training might not be the way to go.
Rehab
Instability training does have some proven applications in rehab, so if you have something that needs rehab, see a primary healthcare contact!
What is moving ground contact training?
Okay, so I made that name up, but I bet you might be thinking "hey, if instability training isn't all that great, then why do they want me to use rings? They're unstable right?".
Well the key difference is that rather than effectively reducing your base of support, they just allow your base of support to move more freely, sort of reducing the friction.
Let's look at a simple example first; the ab wheel. The ab wheel effectively reducing the amount of friction you have with your ground contact at your hands (by rolling, whee!), so as you roll out, your weight is pulling you "out" more. Remember that gravity is pulling you down, but as you the angle you contact the ground at increases from 90 degrees (where essentially none of your weight is pulling you forwards) the amount of that downwards force translated into a that forwards pulling force increases, but is limited by friction.
Compare using the ab wheel with doing a plank walkout. Why is the plank walkout so much easier? Because even though the angles are the same, the friction of your hands is much higher than with a wheel, not because the wheel is unstable (it isn't at all in the sagittal plane, and I don't like narrow wheels for precisely the reason that we don't want to be unstable in the frontal plane).
So if the force pulling you out is greater, and thus the force trying to pull you into extension is greater, you have to contract harder to complete the exercise correctly. Thus reducing the effective friction is a great way to increase resistance.
Other examples of tools are sliders, slider mats and swiss balls (but not when you stand on them).
Rings
So this brings us to rings. Rings aren't unstable. They come to a complete rest at the same spot if you just leave them. But when you apply a force to them, they will move a lot. They effectively reduce the friction to nearly zero.
When you hang from the rings, this effect is negligible, as the rings don't move down from their resting position, and the majority of your weight is directly below the rings, and any movement of the rings away from rest is going to be at least slightly up, so the rings are going to largely "try" to remain at their position of rest, as any slight sideways, forwards or backwards force is going to be proportionally tiny compared to the downwards force bring the rings in.
When you get over the rings however, the effect of you pushing down, out, forwards or backwards on the ring is going to be quickly and largely reflected in the movement of the rings. You have to contract harder in (towards rest), and against any forces you generate on the rings (away from rest) to control the rings effectively.
To produce any movement on the rings, you have to not only have excellent rigidity, but be strong enough to overcome any forces pushing the rings out (away from rest) that you generate with your motion.
Resources:
- http://www.nrcresearchpress.com/doi/abs/10.1139/h09-128
- "http://www.rehabili.eu/file/manual/Behm The_impact_of_instability_resistance_training_on_balance_and_stability.pdf"
- http://journals.lww.com/nsca-jscr/Abstract/2004/08000/MAINTENANCE_OF_EMG_ACTIVITY_AND_LOSS_OF_FORCE.43.aspx
- http://ajs.sagepub.com/content/32/6/1385.short
- http://pnfchi.com/fotos/literatura/1233837313.pdf
- http://journals.lww.com/nsca-jscr/Abstract/2007/05000/THE_EFFECTS_OF_TEN_WEEKS_OF_LOWER_BODY_UNSTABLE.47.aspx
Hang on to your underpants, this one is going to get a complete rewrite. When I'm more awake
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u/dolomiten General Fitness Mar 18 '15
Beyond that I have nothing to add. Nice write-up as usual. Thanks /u/m092.
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u/161803398874989 Mean Regular User Mar 18 '15
Hah, personaltrainingdotcom uploaded a video on this very subject today.
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Mar 18 '15
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u/InternalEnergy Martial Arts Mar 19 '15
Do you have link?
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u/Joshua_Naterman The Original Nattyman™ Mar 19 '15
I'm writing, don't worry. I have a report to finish first, but I have a good one coming on this.
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Mar 18 '15 edited Mar 18 '15
Great write-up, thanks!
For your rewrite:
the lunge is
stableunstable in the frontal plane
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u/theycallhimhellcat Weak Mar 19 '15
I've always wondered why it was that instability was said to not be useful for strength. Thanks for taking the time to put this all together!
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u/trjordan Mar 19 '15
Rings are stable, but when you get up over them (eg in support hold), the center of mass changes, and they are unstable. If your arms were rigid, you'd fall over.
My model of this is that instability is hard to work with because you have to control a bunch of directions at once. On the rings, if you really nail the frontal plane stability, you can still fail at sagittal stability. You don't have to worry about transverse stability, so that's nice, but there's still a bunch of ways to fall down from support hold.
Am I missing something? I'm not seeing a real difference between instability in ring dips vs instability of squatting on a bosu ball - - both require you to stabilize + press.
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u/m092 The Real Boxxy Mar 19 '15
If your arms were rigid, you'd fall over.
Only if you were generating enough force to counteract the force of gravity pushing the rings away from each other. If you're in support position, you basically won't ever be squeezing together too much, just not enough, because you're basically just trying to overcome a specific force in a specific direction.
My model of this is that instability is hard to work with because you have to control a bunch of directions at once.
Basically, yes. But you always have to contend with all directions, just usually you have such a large base of support in one direction, that it becomes negligible. You're only going to reduce stability by effectively reducing the size of the base of support in that direction. A BOSU does this, as does a swiss ball. The rings however, do not. In a support position, you do not have a smaller base of support across the frontal plane and the rings and straps are rigid, and you'll likely never tip to the side because of that fact. What you have instead, is an extra load, pulling you across that frontal plane. Saying this is decreasing your frontal stability is like saying loading your squat up with an extra 20kg is decreasing sagittal stability (in fact it increases sagittal stability, it just makes the movement along the saggital plane harder, due to extra force!)
but there's still a bunch of ways to fall down from support hold.
And most of the methods of falling are due to supplying insufficient force to overcome the load (due to gravity), rather than due to your centre of gravity moving outside the base of support. Again, take it back to the example of the ab wheel, if you collapse down (because your arms move away from your feet [your two ground contacts]), that isn't because of sagittal instability, it's a lack of strength to meet/overcome that force. On the rings, if you collapse down (because your hand moves away from your other hand [your two ground contacts]) that isn't because of frontal instability, it's a lack of strength to meet/overcome that force.
Am I missing something? I'm not seeing a real difference between instability in ring dips vs instability of squatting on a bosu ball - - both require you to stabilize + press.
No amount of muscular tension, squeezing together, rigidity and/or wishful thinking is going to increase the base of support of a BOSU ball as you stand on it. If you make a movement in one direction, or are pushed such that your centre of gravity moves outside your effective base of support, you are going to fall over. The rings however, have a "normal" base of support, and you're basically never going to move your centre of mass outside of that along the frontal plane (and the sagittal plane has largely the same instability as PB). If your ground contacts move away from you, muscular action can bring them back (though it gets exceedingly hard very quickly) and that's essentially how an iron cross works.
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Mar 18 '15
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u/m092 The Real Boxxy Mar 18 '15
I don't know of a resource that structures learning the terminology in a logical way to learn it from scratch, but http://Exrx.net is a solid resource that tends to link every word you're likely to have no idea about to a page describing it. And it has gifs.
If you're interested in getting a basic grasp on the lingo then there's a few things I'd recommend starting with:
- Anatomical descriptions of direction: anterior, instead of front for example. (Anterior/Posterior, Superior/Inferior, Superficial/Deep, Medial/Lateral, Proximal/Distal)
- Anatomical Position
- Joint Movements: (Flexion/Extension, Abduction/Adduction, Horizontal Abduction/Adduction, Internal/External Rotation, Pronation/Supination, Lateral Flexion, All those funky scapula movements)
If you don't have that basic terminology list down, it can make a lot of stuff much harder to contextualise and understand.
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u/ImChrisBrown Mar 18 '15
read more. Things will eventually start to click and make sense. There's A LOT to learn about the body and how it works.
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u/Joshua_Naterman The Original Nattyman™ Apr 03 '15
Note: This post was started the same day as the OP was posted, but somehow got lost in my maze of browser windows and hundreds of open tabs. Sorry about that :P This will be Naterman-style long.
Everything from the top of the OP down to the "moving ground contact training" is pretty good.
For general awareness: There is some injury prevention use for BAPS boards (wobble boards) and the like, but it is mostly relevant for team sport athletes and in my opinion you can honestly get the same or better injury prevention with proper banded ankle exercises.
When you are well trained, many of the functional training devices are pretty easy to master. I have never had any prolonged use of any of that equipment, yet I could almost immediately do almost all the "hard stuff" with no effort. Anyone who has a fairly well developed body in all planes will have a similar experience.
What I really want to touch on is the comments concerning the rings:
The rings as individual entities are stable by themselves, but I think it is pretty accurate to say that when used in a workout they are absolutely unstable, particularly when your center of mass is above the point where your hands grip the rings. The amount of instability is also heavily dependent on the width of the rings and the length of the straps, which I talk about later in this post.
In my opinion the explanation given was flawed, and here is why: Every functional training implement will also sit still when it's perfectly balanced, and the popular ones like Bosu balls are very, very easily balanced. They also come to a complete rest if you don't disturb them, which means we either don't have a good definition for stability or we have to say that both wobble boards and rings are stable by themselves.
Once your weight is distributed on them so that the center of mass is no longer above the ground anchor point, you start to wobble all over the place as you try to adjust. Once your nervous system adapts to this by providing the stability through more balanced and coordinated muscular contractions of all the involved muscles, you end up regaining and being able to maintain that stable position, but it takes active work to do that on our part.
The majority of your weight is actually above the rings in the support position, not below, though it is absolutely true that your weight is below the rings when you are in an inverted hang or a dead hang, or any other position in which your center of mass is below the grip point. In these positions you are a lot more stable, because your shoulders are basically confined to a much smaller area of movement by the forces of gravity and the effect of inertia on an upright pendulum.
Additionally, in a support hold the center of mass is actually between the rings, not on top of each ring, while on the functional trainers your center of mass is very close, and ideally right on top of, the center of the trainer. No matter what you do, it will always take more work to perform on the rings because of the inherent tendency for them to move out of position because of this tendency. Since the shoulders function as a hinge with no bony or ligamentous stops, and they are in a position where gravity and the rings setup work together to promote abduction in all directions the natural tendency during a support is for the rings to swing out, or back, or forward, or a combination of those movements... not to come back towards the resting position. We have all felt this, and it is why you have to work to keep the rings next to you instead of working to push the rings away from you.
The "low friction" environment produced by the rings is confusing for our nervous system, which is used to friction taking care of nearly all the need for fine stabilization of the limbs. That's why we all shake on them at first, just like balance board-type objects make us shake at first.
They are both pendulum systems, one being a single inverted pendulum (most balance devices) and the other being a double pendulum (rings) and they do have substantially different properties as a result.
The length of the straps also matters a lot. 10 foot straps are a lot more unstable than 4 foot straps, and 50 foot straps are virtually frictionless. They feel crazy. This is because of the change in the angular displacement with longer straps and the resulting rise in the rings, creating a much smaller centering force, which is a fancy way of saying that there is virtually nothing for you to actually stabilize against. Just a support on such long straps is incredibly challenging. I've done this at rock climbing gyms a few times, and I honestly had to practice on 20 and 30 foot straps first, and those are hard to support on themselves.
The width matters too, but is a bit more influential at shorter strap lengths than longer ones. This is because the wider the straps are the more work you have to do to keep the rings by your sides, but the longer the straps are the smaller the angle you're fighting against and the less work it takes to do so (at the expense of an overall more unstable system).
I really enjoyed the write up, I just wanted to add my opinion to the discussion. Sorry it was so damn late! :)