Belted squats for developing abs

[CJ Gotcher]

So we agree up to that final point. However, I'm confident the abs contract tighter with the belt. I'm aware of the studies and the EMG data, & I think the studies are totally fucked. Go watch some videos in the form check subforum. Shitty valsalvas & sloppy torsos everywhere. And these, presumably, are peeps who've read the book & squat quite a bit. I'm confident their EMG data would reflect that found in the studies.

Now go watch some vids of legit strong dudes in the comp log. Huge valsalvas, rigid torsos, efficient movement.

No way an ex phys grad student is going to get a bunch of inexperienced subjects to properly use a belt.

Regarding your idea that the postural muscles can contract maximally via 'volition' independent of load just seems wrong. If what you're saying is true, wouldn't we see equal EMG activity in trunk muscles in squats, deads, planks, chinups, etc? I'd bet whichever of my nuts you'd prefer that we'd see a range of EMG activity.

Also: I'm not saying "compression" is responsible for the increased contraction. I don't know enough about muscle spindles in the trunk musculature to even guess the mechanism of increased contraction...but, the belt shifts the whole "wall" in, p increases, pressing out, and **some sensory shit involving a gradient along the belt happens ?** & makes the abs contract much harder.

John- all fair statements. I agree with you on the importance of valsalva and getting as high an IAP as possible. I agree that a belt will help with that (by capping the outward expansion like the valsalva caps the top). I'm not committed to the idea that the abs don't contract harder- I just don't feel it, and that may just be a matter of experience (and my lack thereof).

I don't think the studies are all that helpful yet- a quick study review check finds most of them are on industry (cargo lifting), and the study results on weightlifters doing EMG are conflicting at best. Jordan picked a good one that I hadn't seen before, but they're not doing real lifting, which is odd. One study with D1 players doing 12RM deadlifts with and without a belt shows the belt increasing RA activity and decreasing EO activity (small for both, but 'significant'). Another one Shows no increase in GM or SE EMG for 90% 1RM squats. This one shows a decrease in RA/EO/SE when using a belt for 90% 1RM squat singles. And this one, by the same guy, shows no change when using a belt in 8RM squats. Mcgill tested bros lifting 'industrial loads' of 70-90 KG and found SE EMG was not affected by wearing a belt.

It shouldn't surprise us, but regardless of what the EMG read, they all reported increased IAP, and the ones that collected it reported faster bar velocities and an increased subjective perception of stability, regardless of whether the abs were contracting harder or not.

[spacediver]

No way an ex phys grad student is going to get a bunch of inexperienced subjects to properly use a belt.

That, right there, sums up the problem with so many of these studies. You need deep, first hand experience intelligently interacting with heavy iron to avoid these sorts of methodological pitfalls.

[John Hanley]

Hanley, I think you know a lot of physics, but damn you for calling me out. Rip, this is gonna be long. I'm sorry.

I think there are two questions. (1) Why does a belt allow a lifter to lift more weight? (2) Does training with a belt increase the strength of the trunk musculature faster than training without one?

I don't know the answers, and won't attempt to answer (2); however, perhaps I can constructively add to the discussion by first discussing the zeroth question: How does the belt work? I don't understand the mechanism behind the "it gives you something to push against" argument, even though that explanation may be true. The "hoop stress" approach makes more sense to me.

The executive summary for the "hoop stress" explanation, as I understand it: The tensile stress in the trunk musculature (and the belt, if worn) produces the abdominal pressure which opposes an anterior movement of the spine. An anterior movement of the spine tries to increase the surface area of the abdominal cavity by increasing the radius, R, of the roughly-cylindrical cavity. Contraction of the trunk musculature tries to keep the surface area, and thus R, fixed.

I'll use the following simplifications. The anterior spine is supported by pressure inside two cavities which are separated by a diaphragm. The abdominal cavity is filled with an incompressible fluid, while the thoracic cavity is partially filled with gas. I'll ignore leaks from these cavities (by assuming we clamp down on sphincters (anal, urethral, and upper esophageal), and the pressure transferred out through the blood is opposed by material surrounding the blood vessels). Furthermore, I'll model the abdominal cavity as a cylinder of radius R and height h, treating the diaphragm as a flat surface, not domed.

Using those simplifications, I'll focus on the abdominal cavity. First, an aside. For incompressible fluids, one change change the surface area but can not change the volume. For example, one can squeeze a water-filled balloon and change its shape, but not its volume (volume can change with a gas-filled balloon). The shape with smallest surface area per volume is a sphere. Water droplets try to form spheres because Nature likes to minimize energy, in this case minimize the surface energy produced by the surface tension at the water-air boundary. The minimum energy corresponds to the minimum surface area.

Similar to the water droplet's surface tension, if we consider the trunk musculature a membrane, contraction of the muscles produces a tensile membrane stress. This stress produces an inward force similar to the hoop stress produced by the belt. The inward force acts to minimize the surface area, and for our cylinder that means reducing R at the expense of increasing h (whose increase will be opposed by the diaphragm). At maximum contractile strength, the cavity will assume a shape with some minimized surface area (although not the minimal surface area). This will also produce a maximized pressure, since pressure is inversely related to radius.

Within the cavity we have incompressible fluid which transfers the surface-tension force of the trunk musculature to the anterior lumbar spine. Let's now assume the forces on all sides of the lumbar spine are balanced. If some external force acts to push the lumbar spine toward the abdomen (that force per unit area is greater than the abdominal pressure), that movement of the spine will change the shape of the abdominal cavity. Opposing that attempt to change the shape, and thus the surface area, is the surface-tension force of the trunk musculature. Movement of the spine tries to increase R, while the contraction of the trunk muscles try to keep R fixed.

In order to hold R fixed, the muscles must contract harder. If the muscles can not produce enough force per unit area, the hoop stress of the belt provides additional inward force. Both oppose an increase of the radius. The belt opposes an increase in its circumference (thus an increase in radius), while the contracted musculature - each fiber opposing an increase in length - oppose an increase to the surface area (also an increase in radius).

This post hasn't been succinct. I'm very sorry, I tried to hastily cut as much as possible. One last point for Hanley (or any other math nerds). John, you got me thinking why does increasing R matter? If you're interested, what I found was with the cavity modeled as a cylinder, an increase in surface area means a positive increase in R (as long as 2R > h). For a tall, narrow cylinder, an increase in surface area is accomplished by a decrease in R. Write down the area of the cylinder and take differentials of both sides. For fixed volume you should find:
dA = 2π dR (2R - h). As long as the term in the parenthesis is positive, positive dR means positive dA.

Well, holy shit I think I really get it. Okay, so what we're doing is minimizing surface area to volume ratio of the abdominal "fluid ball" to maximize P? I need to dick around (get command) of the math regarding "R"...but it's makes perfect, simple sense.

[Savs]

Well, holy shit I think I really get it. Okay, so what we're doing is minimizing surface area to volume ratio of the abdominal "fluid ball" to maximize P? I need to dick around (get command) of the math regarding "R"...but it's makes perfect, simple sense.

Yes, but I prefer to think of the forces rather than the pressure. The forces are the load on the spine and those produced by the trunk musculature. I'll reword the explanation.

• An enclosed volume does not need to decrease in order for the pressure to increase. For example, there is high pressure at the bottom of the ocean. The volume of the abdominal cavity probably does decrease a little because it contains some gas; however, the pressure of the whole is not governed by the ideal gas law.

• The abdominal-cavity shape is constrained by bone structure. In the absence of constraints, the muscles would contract into a spherical shell. For the constrained case, the membrane stress also acts to minimize surface area. It forms a curved surface but doesn't fully realize a spherical shape.

• The curvature of, and stress in, the membrane produces a force perpendicular to the membrane's surface. This force opposes any attempt to increase the surface area of the membrane. The force produces IAP. The IAP balances the force per unit area of the membrane.

• Unlike a rubber sheet, the membrane force produced by the trunk musculature can be increased or decreased without changing the shape (and thus the surface area) of the cavity. Increased motor recruitment increases the force (and thus the IAP), and vice versa.

• The force produced by the belt is only produced in opposition to a force trying to stretch the belt (increase its circumference). It does not produce a force on its own.

Putting those points together may allow an understanding of how the forces (and thus IAP) oppose movement of the spine. Obviously, if the spine were unattached to the cavity wall, it could move through the viscous "fluid" no matter how much the IAP is increased. Since it is attached, a load on the spine attempts to deform the cavity. That attempted deformation - an attempt to change the shape - is opposed by the rigidity of the walls - their opposition to an increase in surface area.

Yes, as the load increases, IAP must increase. The IAP is produced by the trunk musculature directly and by the belt which acts in reaction to the load trying to increase the belt's circumference.

I don't know if this is the best or even correct explanation. Perhaps it omits other important factors.

[Viola]

Yes, but I prefer to think of the forces rather than the pressure. The forces are the load on the spine and those produced by the trunk musculature. I'll reword the explanation.

• An enclosed volume does not need to decrease in order for the pressure to increase. For example, there is high pressure at the bottom of the ocean. The volume of the abdominal cavity probably does decrease a little because it contains some gas; however, the pressure of the whole is not governed by the ideal gas law.

• The abdominal-cavity shape is constrained by bone structure. In the absence of constraints, the muscles would contract into a spherical shell. For the constrained case, the membrane stress also acts to minimize surface area. It forms a curved surface but doesn't fully realize a spherical shape.

• The curvature of, and stress in, the membrane produces a force perpendicular to the membrane's surface. This force opposes any attempt to increase the surface area of the membrane. The force produces IAP. The IAP balances the force per unit area of the membrane.

• Unlike a rubber sheet, the membrane force produced by the trunk musculature can be increased or decreased without changing the shape (and thus the surface area) of the cavity. Increased motor recruitment increases the force (and thus the IAP), and vice versa.

• The force produced by the belt is only produced in opposition to a force trying to stretch the belt (increase its circumference). It does not produce a force on its own.

Putting those points together may allow an understanding of how the forces (and thus IAP) oppose movement of the spine. Obviously, if the spine were unattached to the cavity wall, it could move through the viscous "fluid" no matter how much the IAP is increased. Since it is attached, a load on the spine attempts to deform the cavity. That attempted deformation - an attempt to change the shape - is opposed by the rigidity of the walls - their opposition to an increase in surface area.

Yes, as the load increases, IAP must increase. The IAP is produced by the trunk musculature directly and by the belt which acts in reaction to the load trying to increase the belt's circumference.

I don't know if this is the best or even correct explanation. Perhaps it omits other important factors.

Savs – this is the best explanation I have read so far of what is happening because of the belt. And I didn’t even have to understand exactly how the muscles work. I have one quibble. I think that your explanation works even without claiming there is an increase in IAP. The fact that the belt helps the musculature maintain the abdominal cavity volume and shape as well as maintain the cavity muscle wall tension and/or increase the tension is enough, I think, to explain why the belt works. The belt helps maintain the IAP, which would likely decrease (without a belt) because of the deformation of the cavity due to the heavy load. I believe you explained everything within the laws of physics except how the IAP increases due to the belt. If you have an explanation of this, then I’d like to see it, because it would contribute to the belt’s effect. But, as I said, I don’t think it is necessary. I think the belt works in that it helps maintain the IAP where it would normally have decreased.

[djsilvera]

Savs, I appreciate the model and explanation. It seems that rather than 'facilitating a stronger abdominal contraction,' what the belt actually might be doing is allowing us to use abdominal muscles to increase IAP, through an artificial contraction against the belt. In other words, through the use of the belt, we're using more muscles than would normally be available to us to stabilize the torso.

[Jordan Feigenbaum]

Savs, I appreciate the model and explanation. It seems that rather than 'facilitating a stronger abdominal contraction,' what the belt actually might be doing is allowing us to use abdominal muscles to increase IAP, through an artificial contraction against the belt. In other words, through the use of the belt, we're using more muscles than would normally be available to us to stabilize the torso.

I think that is only one of the mechanisms, actually. Increased intramuscular pressure has a potential of increased motor unit recruitment and having a proprioceptive "thing" to contract against had been shown in other models to increase MU recruitment in addition to the increased IAP and trunk stiffness increase from the belt. All in all I think it's multi-factorial as to how the belt likely increases overall muscle activation and force production.

[Savs]

Viola, djsilvera: The only thing I can say with certainty at the moment is I need to think about this some more. So, I'm going to take more time and think about it!

[mrflibble]

This one shows a decrease in RA/EO/SE when using a belt for 90% 1RM squat singles.

So I dug up the full text for this study. Some of the highlights:

* A massive six (6!) subjects.

* Max squats ranged from 1.5 - 2.38 body weight. No mention of their actual bodyweight. Could be anywhere from early-ish novice to intermediate.

* Tested: no weightbelt, tapered belt, 4" belt

* "A balloon catheter was inserted approximately 10 cm into each subject's rectum in order to measure IAP" - I imagine this might be somewhat distracting. Would it interfere with my ability to use a belt to achieve a stronger abdominal contraction and therefore help explain their results? Perhaps, I really don't know, and don't plan on finding out. The authors didn't either.

* No discussion of bar placement or specific squat form. Squat depth was measured in segments. Second last was 90 degrees. Last was the wonderfully precise "minimum knee/thigh angle"

* Authors note the belted squats showed a greater emphasis on hip extension than knee extension vs squats with no belt. So it seems they're not even comparing the same lift belt vs no belt.

* 5 of the 6 lifters normally wore "some type of weight-belt" - authors failed to specify which type.

* No mention of valsalva. No mention of any instruction provided to subjects on how to use a belt correctly, and no evidence that any of them already had any experience in doing so.

So in other words, pretty much all the study shows is that if you get a small group of ok lifters with (maybe) no experience in using a belt correctly, don't teach them how to use a belt correctly, they won't be able to use a belt correctly.

[CJ Gotcher]

So I dug up the full text for this study. Some of the highlights:

* A massive six (6!) subjects.

* Max squats ranged from 1.5 - 2.38 body weight. No mention of their actual bodyweight. Could be anywhere from early-ish novice to intermediate.

* Tested: no weightbelt, tapered belt, 4" belt

* "A balloon catheter was inserted approximately 10 cm into each subject's rectum in order to measure IAP" - I imagine this might be somewhat distracting. Would it interfere with my ability to use a belt to achieve a stronger abdominal contraction and therefore help explain their results? Perhaps, I really don't know, and don't plan on finding out. The authors didn't either.

* No discussion of bar placement or specific squat form. Squat depth was measured in segments. Second last was 90 degrees. Last was the wonderfully precise "minimum knee/thigh angle"

* Authors note the belted squats showed a greater emphasis on hip extension than knee extension vs squats with no belt. So it seems they're not even comparing the same lift belt vs no belt.

* 5 of the 6 lifters normally wore "some type of weight-belt" - authors failed to specify which type.

* No mention of valsalva. No mention of any instruction provided to subjects on how to use a belt correctly, and no evidence that any of them already had any experience in doing so.

So in other words, pretty much all the study shows is that if you get a small group of ok lifters with (maybe) no experience in using a belt correctly, don't teach them how to use a belt correctly, they won't be able to use a belt correctly.

You made my case for me, Mr. Flibble: "I don't think the studies are all that helpful yet:" I was pointing out that the research is shoddy and a cursory reading appears to be conflicting. The only study in that group with superior lifters and a decent methodology was the one with D1 football players... and they were doing a 12RM DL, which can confound EMG results as the brain 'hunts' for non-fatigued fibers to do the job as the set wears on. The studies I could find off-hand are low-quality or not necessarily relevant to weightlifters... and that's my point. The best approaches we've got are mechanical analysis and experience, not the research (yet).

Savs did a great job of covering the mechanical analysis, and I'm going to have to sit down with a physics and anatomy book to break it down and see if I really 'get' it. Some great lifters and coaches are convinced that their abs contract harder. I don't feel it, and I don't know what the mechanism would be.

Jordan might be right about intramuscular pressure improving recruitment- I'm going to look into that one more. I'm not so sure about having 'something to press against.' If you breathe in deeply and valsalva, pause, then contract your abs hard, the abs recess in away from the belt slightly (as they flatten, slightly reducing volume in the abdominal cavity). I don't know what it is the abs are 'pulling against' besides the IAP pushing the belly outwards, and I can generate a huge contraction doing a forced isometric contraction (plank or standing). Like I said, I'm not committed to anything yet- I just don't understand the mechanism, and I suspect that even if the abs do contract harder with a belt, Jordan is spot-on: the 'final answer' is probably multifactorial.