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Thread: Great video visualizing why we shouldn't flex our back under load

  1. #11
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    Quote Originally Posted by Maybach View Post
    Alright, so this needs to be quashed right now. This kind of thinking is a god damned epidemic in fitness.

    The spine is a beam designed to resist moment force applied at the shoulders, towards the front of the body. This means it experiences both compression (along the inside of the spine) and tension (along the ridge of the back). Is it possible to place a sufficient moment force on the spine that it fails? Yes, obviously, as with all things. That is what is being demonstrated here.

    The beam of the spine resists compression via the disks, and tension via the musculature of the back. If there was no back musculature (or, as is often found, the back musculature is not being called into contraction), then yes, the spine would flex uncontrollably, the only thing resisting the flexion would be the disks, which would fail if the load was sufficiently heavy.

    However, in a normal situation, where the back musculature is being engaged, even if the spine is pulled out of full extension, the spine is merely in one of many configurations which it is capable of resisting. Will the force on the disks be greater than if it was in total extension? Yes. Is it anything to worry about? No.

    Indeed, we often find that a person is failing to engage the back musculature and "resting" on the interior arc of the vertebral discs to keep the spine from flexing uncontrollably. This is undesirable. But it's easily corrected in pretty much everyone. This is not a reason why if the back goes into flexion at all, with fully engaged back musculature, your disks will explode. If you have compromised disks, will you have to exercise greater caution? Yes. But you are not going to compromise your disks doing deadlifts.

    And moreover, strength training at a reasonable volume hardly constitutes "repetitive flexion": you execute 45, *maybe* 50 reps of the squat, and between 5 and 15 reps of the deadlift. You probably "load your back under flexion" more times getting dressed in the morning than you do lifting weights all *week.*

    The actual reason we don't flex out backs under load is that it makes the lift less efficient. Why this is is discussed in detail in the Blue Book. A deadlift with the back in excessive flexion will fail to break the floor before it becomes flexed to such a degree that it places the vertebral discs under an unsafe stress.

    This reply is an attempt to stem the tide of people "deloading their deadlift" to "work on form" because they notice that 265 caused their vertebrae to deflect half a centimeter when the bar left the floor.
    I'm a Physical therapist and anything by Stuart McGill is treated as essentially royal gospel in my profession. He's spent his life researching, teaching and publishing around this stuff. Yet some anonymous bro on a random lifting forum just shredded his entire argument in 2 minutes. Hilarious.

  2. #12
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    Quote Originally Posted by tom33 View Post
    Sure thing, thanks Rip.

    Yesterday’s 335x2x3 (coming back from back tweak): Proton Drive
    These 2 squats look good. Tell us about your deadlift.

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    Quote Originally Posted by Maybach View Post
    I'm fairly certain it has nothing to do with a *herniated disk* because those very much do not feel like "back tweaks."
    What does a "back tweak" feel like? What does a "herniated disk" feel like?

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    A "back tweak" is local pain in a small part of the low back. A "herniated disc" generally presents some referred pain or neurological symptoms.

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    I mean McGill is partially correct, which is why this is so pervasive. The pressure experienced by the disc will be inversely proportional to the area the vertebrae are in contact with it. Therefore the pressure can get pretty damn high if you contort them wrong, even at relatively modest absolute loads.

    But that situation only happens in really two scenarios. One is of the spine is misaligned in some way, so that vertebrae are being forced close together. Twisting your spine while flexed under load is a good way to make this happen. The other is if the muscles of the back are not engaged at all, and the spine is forced into flexion such that the discs are the only thing resisting further flexion. This can happen if the load is in excess of the muscle's ability to resist it, which usually comes when the load comes by surprise. Anyone who has had either of these happen to them knows that it is no small thing. Injury to a disc is acute, and it *hurts*. It isn't "sore." A paramedic friend who I taught to deadlift talks about two ruptured disks in his vertebrae in life defining terms.

    But neither of these things happens during the deadlift unless you are doing something catastrophically wrong, and neither way can occur without your consent. You will note also that there is a world of difference between allowing the vertebrae to come so close as to almost be touching by failing to control the back, and letting your back round a little because you are not strong enough to hold it in full extension. Pretty much any load lifted with the back somewhat engaged will be safe, because that's why the spine is capable of bending in the first place. McGill understands the spine and injuries, but what he doesn't understand is the deadlift.

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    Very well said, Maybach.

    Quote Originally Posted by Maybach View Post
    McGill understands the spine and injuries, but what he doesn't understand is the deadlift.
    Or, by extension, the entire system, which includes the musculature. This is the issue I have with this video (the model may be extremely "biofidelic" for the vertebrae and disks, but it lacks the muscles, and those are rather active factors in vivo.

    This is the same issue I have with a clip I've seen of a cutesy wooden model for illustrating "why you should lift with your legs, not your back", by showing a horrific estimation of spinal flexion when not sumo deadlifting a box in a mechanically implausible way. It ignores the tension of a major component of the system. (It's also only relevant for people who move by an external hand holding a stick out the back of their pelvis...).

    It reminds me of when "experts" tell us not to Valsalva under load, because it spikes blood pressure, and high BP can blow out a blood vessel in your brain...then use the analogy of an overinflated tire. But the fact is that high pressure differential is what blows out the tire. If atmospheric pressure rose at the same time, then higher pressure inside the tire is not only safe, it's necessary to keep the tire in the right shape. And sure enough, their model in turn ignores the increase in cerebrospinal pressure that the effort is introducing...

    As applies to other discussions around here, models are only useful insofar as they are sufficiently complete.

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    Quote Originally Posted by Mark Rippetoe View Post
    A "back tweak" is local pain in a small part of the low back. A "herniated disc" generally presents some referred pain or neurological symptoms.
    I thought that many or possibly even most herniated discs were actually asymptomatic. And that neurological symptoms such as referred pain down the legs are as often due to causes other than herniated discs, such as piriformis syndrome or sacroiliitis. Are back tweaks and herniated discs necessarily mutually exclusive? Can a herniated disc not trigger local pain in a small part of the low back? Are protective muscle spasms indicative of one condition, the other, both, or neither?

    Like Tom, I tweak my back more often than I would like, maybe 6-8 times over the last 3 years. Iíve tweaked it during squats with warmups at 135 and worksets near 400. Iíve tweaked it during deadlifts at 355 and barbell rows at 245. Iíve tweaked it tossing a frisbee 40 feet. For me, a tweak is always initiated with a popping or shifting sensation though I donít think there is any noise or actual movement. Then my back will go into a protective spasm and tighten up. Intolerant to flexion. Often will have localized pain on the right side in the vicinity of the SI joint or the iliac crest. Sometimes it will present with sciatica (burning pain down the outside of the right calf); other times it wonít. The only difference I can see seems to largely be one of degree. Minor tweaks usually donít present with sciatica and resolve within a few days. Major tweaks are usually followed by a day or two of debilitating spasms and sciatica that might take a couple weeks or more to resolve.

    Quote Originally Posted by Maybach View Post
    I mean McGill is partially correct, which is why this is so pervasive.
    Iím barely familiar with McGill solely due my history of back pain. Iíve never read his work. What, specifically, is McGill wrong about in this 91 second video?

    Quote Originally Posted by Mcgill
    At least one mechanism for posterior disc bulge begins with delaminating the collagen that makes up the annulus through repeated and loaded spine motion
    Is it controversial that disc bulges begin with delamination of the annulus? I might quibble with ďloaded" spine motion since its not clear what he means by "loaded". Clearly the spine does not need to be loaded with a barbell for this delamination to occuróplenty of sedentary people have herniated discs. This is a degenerative process that generally occurs over many years.

    Quote Originally Posted by Mcgill
    when the spine is flexed forward and squeezed the hydraulic pressure within the nucleus is directed posteriorly through the delaminated collagen resulting in a dynamic disc bulge
    This seems plausible to me based on my own experience with a flexion-intolerant posterior herniation.

    Quote Originally Posted by Mcgill
    If you eliminate the flexion and stack the vertebra which in an engineering sense directs the thrust line down through the middle of the disc there is no hydraulic effort or pressure directed on the bulge. The whole disc flattens but it does not create a focal disc bulge.
    Again, this hardly seems controversial.

    Quote Originally Posted by Maybach View Post
    Anyone who has had either of these happen to them knows that it is no small thing. Injury to a disc is acute, and it *hurts*. It isn't "sore." A paramedic friend who I taught to deadlift talks about two ruptured disks in his vertebrae in life defining terms.
    A herniated disc can hurt like hell, or it can not hurt at all. Yes, an acute episode can be traumatic the first time or two. You catastrophize; you wonder if you will ever be able to walk again; and then within a couple weeks youíre back to normal. Until you arenít again. After a few episodes you begin to realize that thereís not anything mechanically wrong with your back. A little jelly squished out of your donut and tickled the nerve root and your brain overreacted, as it tends to do. I tweaked my back six weeks ago. Woke up the next morning and collapsed onto the floor getting out of bed. Took maybe 20 minutes to belly crawl to the bathroom and then another 5 minutes to get stood up enough to use the toilet. Today I deadlifted 440x3 which I think tied a previous PR. I would have pulled it for 5 if I didn't have this damn video playing in my head.

    Quote Originally Posted by Maybach View Post
    But neither of these things happens during the deadlift unless you are doing something catastrophically wrong, and neither way can occur without your consent.
    I assure you it is possible to produce symptoms consistent with a disc herniation without twisting the spine or otherwise doing anything catastrophically wrong with a deadlift or squat. It just happens, sometimes seemingly at random. You donít know whether you have a herniated disc unless or until you get symptoms from it.

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    Quote Originally Posted by Matt Dawson View Post
    I thought that many or possibly even most herniated discs were actually asymptomatic. And that neurological symptoms such as referred pain down the legs are as often due to causes other than herniated discs, such as piriformis syndrome or sacroiliitis. Are back tweaks and herniated discs necessarily mutually exclusive? Can a herniated disc not trigger local pain in a small part of the low back? Are protective muscle spasms indicative of one condition, the other, both, or neither?
    Mine was not a complete list. The back is a complicated place.

    Like Tom, I tweak my back more often than I would like, maybe 6-8 times over the last 3 years. I’ve tweaked it during squats with warmups at 135 and worksets near 400. I’ve tweaked it during deadlifts at 355 and barbell rows at 245. I’ve tweaked it tossing a frisbee 40 feet. For me, a tweak is always initiated with a popping or shifting sensation though I don’t think there is any noise or actual movement. Then my back will go into a protective spasm and tighten up. Intolerant to flexion. Often will have localized pain on the right side in the vicinity of the SI joint or the iliac crest. Sometimes it will present with sciatica (burning pain down the outside of the right calf); other times it won’t. The only difference I can see seems to largely be one of degree. Minor tweaks usually don’t present with sciatica and resolve within a few days. Major tweaks are usually followed by a day or two of debilitating spasms and sciatica that might take a couple weeks or more to resolve.
    I used to tweak my back a couple of times a year, usually doing something like putting on my boots. About 15 years ago I tweaked it doing a set of situps, and I started thinking about mechanisms that might cause these things. I decided to stop wiggling my elderly spine around, grinding osteophytes into discs and each other. I have not had a back tweak since then. Squats, presses, and deadlifts provide more than enough work for the muscles that stabilize the spine, without working it through an unstable ROM.

  9. #19
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    Quote Originally Posted by Matt Dawson View Post
    I’m barely familiar with McGill solely due my history of back pain. I’ve never read his work. What, specifically, is McGill wrong about in this 91 second video?


    Is it controversial that disc bulges begin with delamination of the annulus? I might quibble with “loaded" spine motion since its not clear what he means by "loaded". Clearly the spine does not need to be loaded with a barbell for this delamination to occur—plenty of sedentary people have herniated discs. This is a degenerative process that generally occurs over many years.

    This seems plausible to me based on my own experience with a flexion-intolerant posterior herniation.
    He's demonstrating a spine being flexed past it's mechanical tolerances, and then claiming that this represents "loaded flexion." This is akin to snapping a chicken wing apart at the joint and terming this "loaded elbow extension." The fact of the spine being placed in this position causing injury is the part he's right about. What he's wrong about is that a spine under control of the back musculature ever arrives at this position without something being wrong. Even if your back is in flexion, the erectors are doing work to stabilize it. If it's flexed a great deal, the pressure might be higher than if it were in perfect extension, but it's still not going to exceed the capabilities of the anatomy. If it does, the back musculature is probably not being properly engaged.

    McGill is often derided as the "dead pig" guy, because his anatomical research is based on dead pig spines, which obviously do not have any engaged back musculature. It is a crude jab, but gets to the crux of the issue

    Like I said the first time: if you have already burst a disc, the range of tolerable positions becomes a little smaller, the same way the range of tolerable positions for your leg becomes smaller if you have an injured foot, and you almost certainly did not acquire the injury because of anything that happened near a barbell.

    Quote Originally Posted by Matt Dawson View Post
    I assure you it is possible to produce symptoms consistent with a disc herniation without twisting the spine or otherwise doing anything catastrophically wrong with a deadlift or squat. It just happens, sometimes seemingly at random. You don’t know whether you have a herniated disc unless or until you get symptoms from it.
    Well, to be fair, you have a herniated disc, so by definition every symptom you experience is consistent with disc herniation.

    My point was that it is extremely unlikely that your deadlift actually produced your disc herniation, and from what you say, it doesn't appear that "loaded flexion" has any greater chance of aggravating your symptoms than normal, non barbell related activities, unless you have an especially novel frisbee throwing technique. And even then: your symptoms come from the spasms of the back musculature, not that the deadlift is stretching the mechanical limits of your spine anatomy.

    The reason I'm so adamant about this is because the fear of "loaded flexion" is doing a great deal of damage to most trainee's programming. The deadlift has developed a reputation as an especially "dangerous" or "costly" exercise because it stands a chance of allowing the back to collapse into flexion, and this is imagined to cause damage to the discs. It comes from a mixture of anecdotes about guys who injured themselves in one of the many ways non-gym going humans injure themselves, and then blaming "powerlifting", and the voices of scientific authorities like McGill. Like three guys every month come in because their "squat is stuck" and it turns out they "deloaded" their deadlift to be twenty kilos lighter than their squat because their back rounded on the fifth rep and they had a nightmare that looked exactly like this video.

    And I mean, SS doesn't even *train* the back in flexion: some crazy people DO. The deadlift and the squat require your back to be held in extension. The issue is the fear that if you let your back round a little, the (EXTREMELY safe and ergonomic) deadlift becomes "dangerous."

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    Oh, and of course I had forgotten McGill is the one going around saying his clinic is full of people coming to him after their bodies were ruined by heavy squats and deadlifts. An absolutely criminal quack.

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