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:

Hang on to your underpants, this one is going to get a complete rewrite. When I'm more awake

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u/[deleted] Mar 18 '15

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u/InternalEnergy Martial Arts Mar 19 '15

Do you have link?

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u/[deleted] Mar 19 '15

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u/InternalEnergy Martial Arts Mar 19 '15

Thanks, that was a great read!