October 8, 2010
Disc Pressure Measurements – Should it affect exercise selection?

These days, some of the most talked about research in regards to the lumbar spine and low back health is disc pressure measurements. This is where researchers measure the intradiscal pressure (pressure on the spinal discs) in response to compressive load. You’re probably familiar with this chart (below) by Nachemson, where he displays how disc pressure changes (increases and/or decreases) depending on body position.

Probably two of the most well known researchers on Disc pressure measurements are Dr. Alf Nachemson and Dr. Stuart McGill (who happens to be one of the researchers of whom I most respect). In his books, Dr. McGill has also provided some great research comparing the lumbar disc pressure during a multitude of different torso training exercises from crunches to planks to bird-dogs.

.

After reading much of the Disc pressure research (like the above), it only seamed to makes sense to me and plenty of other coaches and therapists that this information can/should be used to influence our exercise selection. In that, in the hopes to reduce injury risk potential, we would choose the torso exercises which placed the least amount of compression on the disc and avoid the exercise which were shown to place the most compression on the disc. This is why you’ve seen a huge movement away from exercises like ab crunches, which have been shown to create high amounts of disc pressure. And, you’ve seen a recent movement toward using mostly isometric exercises like ab planks, in which the lumbar spine doesn’t move and is kept neutral.

.

The problem is, every time you think you’ve got it all figured out, you discover new information that gets you thinking and questioning your approach.That’s precisely what happened to me while recently attending Carl DeRosa’s workshop at the International Spine Symposium. You may feel the same way after reading the information I’ve got for you below!

.
Eye-Opening, New Insights & Information on Disc Pressure Measurements from Carl DeRosa’s Workshop at the 2010 Spine Symposium

.

First off, Carl DeRosa and Jim Porterfield are both extremely nice guys who seem very approachable and enjoy sharing their knowledge. I learned a great deal of valuable information form each of thier presentations. Today, I’m focusing on Carl DeRosa’s lecture – I will address what I learned from Jim Porterfield in a future post.

.

During his lecture, Carl DeRosa (from Porterfield & DeRosa) brought up some amazing points, you may not have previously heard, about using Disc pressure research to influence our exercise selection and/or as an indicator of the risks to the low back involved in using a specific exercise.

.
I recorded much of Carl DeRosa’a lecture – Here’s some key quotes from his lecture in regards to disc pressure measurements and exercise selection:

(Note: I’ve underlined certain aspects of these quotes which have really got me thinking)

.

“There are a small number of clinical cases where you should be concerned with compressive forces on the disc. But, the majority of them – No, not that concerned. Here’s why: because the Annulus Fibrosus is built for compression. The bulk of it and the way that it’s structured – it’s function is really to absorb compression”.

“Now, if you’ve got a spine where you’re concerned that somebody has discogenic problems, discogenic nerve root: where increased compression is problematic. I think you have got to be concerned with with that” . ”On the other hand, if you’ve got a patient who’s got a Stenotic Spine (Spinal Stenosis) and it’s the posterior elements you’re concerned about compression. I think with that patient: You want them in a flexed position lifting all the time. You don’t want to teach them to restore lordosis or anything like that because compressive loads to a degenerative posterior arch is problematic”.

.

” Compression is stability!” – ” What we see when we look at these unstable spines, it’s squeezing it together (through muscle contraction), for a lack of a better term – That’s what the stability is (compression).”

.

“The comment was made about taking Nachemson’s work and translating it into the clinic – When you look at disc pressure in terms of what is the biggest cause of an increase in disc pressure, the hierarchy goes like this: the biggest influence on disc pressure is muscle contraction – that’s number one – because our torso muscles almost all run north south!” . “It’s the contraction of the Psoas attached to the lumber vertebrae that squeezes together. It’s the contraction of the superficial deep erector spinae/multifidus squeeze together – that’s the number one influence to disc pressure”. ”Number two is ligamentous prestress. When you think of our ligaments like the anterior and posterior longitudinal ligaments – they all have a certain prestress (tension) to them already. So there’s some give, but there always pulling the vertebrae down hard”. “And, the last is superincumbent forces. So, it’s weight and body position – those are actually last influences on disc pressure”.

.

“When you look back at disc pressure work and even at the disc pressure work that’s been done recently, what you notice is: it’s the state of muscle contraction that results in the increased disc pressure”. “So for example: when I flex my spine forward (forward bend) when standing, it has a higher disc pressure than when I’m standing tall. It’s not because I’m bending over (flexing forward), it’s because the bending forward position has increased muscle contraction and the standing position doesn’t have muscle contraction”. “If I stand up tall, disc pressure is “X” – But, if I stand tall while holding a 5lbs weight out in front of me (like a front shoulder raise), disc pressure is “X+Y”. “You see, Disc pressure has nothing to do with body position, it has everything to do with the level of muscle contraction”.

.

” The reason sitting has a higher disc pressure than standing is because when you’re standing, you distribute compressive load 80% to the bone-disc-bone interface and 15-20% to the facet joints. When you sit, you shift your weight line forward and you bring about 95-100% compressive load to the bone-disc-bone interface, and there’s an unloading of the facet joints”. That’s why disc pressure is slightly higher in sitting than in standing”.

.
The Big Question(s)?

.
As with every great learning experience I’ve had – It’s seems the more I learn, the more questions I have.
.
What questions, if any, do you have now that you’ve read Carl DeRosa’s statements?
.
Should this information above in any way change our current exercise selection and opinions on any specific exercises?
.
Did you have any Ah-Ha moments from today’s post?

.

ShareThis
previous post: Alli McKee in the 2010 issue of “Off the Couch” by Oxygen Magazine! next post: One Minute Muscle Builders!
5 Responses to “Disc Pressure Measurements – Should it affect exercise selection?”

1.
Tsvetan vassilev says:
October 8, 2010 at 7:59 am

Please be so kind as to read Stuart McGill’s work again.
1. Shear forces and not compression forces do the most damage/quickest/with lowest forces.
2. Compression forces are “dangerous” only with (full) flexion.
3. Repetative motion and full ROM flexion suck.
4. Loading a (full ROM) bent spine is bad.
5. Bending(flexing) a flexion-intolerant(discogenic) patient may produce pain and further injury.
6. Muscle contraction increases compression forces, but that is not such a bad thing.

That’s all from “Low Back Disorders”
2.
Steven Rice Fitness says:
October 8, 2010 at 10:12 am

I don’t see anything here that contradicts my recollection of McGill. Certainly there is a lot of research to be done, and feedback from “real world” application of the science.

In my approach I don’t think about disk compression so much as keeping the spinal muscles and ligaments from being strained. A neutral spine keeps the muscles and ligaments where they are strongest, as well as keeping the disks loaded evenly.
3.
Chi says:
October 8, 2010 at 11:42 am

Hi Nick, thanks for sharing this.

It may be helpful to add to things to this excellent post.

First of all the measurements of Nachemson were on L3, the part that is not representative for the problem area’s L4 and L5. So discussion based on Nachmeson’s works is always a bit controversial.

Second, compression is only a part, but a vital part of the equation, the other one is shear. Although a sit-up will generate 3.300 N of compression, the biggest problem is the combination compression AND shear. Compression in a hazardous angle will add to the problem. Compression is therefor important.

Third, the disc can handle compression very well, but the rest of the structure may not. A plank can lead to backpain (even with a neutral spine), due to the compression from the core muscles. It’s probably not the disc, but all the other structures getting irritated by compression. Compression is important to all structures, not just the disc.

Fourth, not all discs are created equal. The strength (amount of collagen fibres) of the discs is highly dependent on genetics. Since you cannot see this from the outside, you take a risk by having high compressive forces. If someone has a weak disc, you will get into trouble and the question is will you take the risk?

Fifth, compressive forces will lead to flatter disc, so does gravity. After a night sleep, you are almost an inch longer, compressing the vertebrae and that’s the reason why most back pain patients have severe symptoms when they wake up. After they start moving, the hydrostatic pump start to work (compressive forces go down) and there is symptom relieve. It’s the same reason why prolonged sitting leads to pain. It is not just the load shift, but you actually shrink almost a cm due to the gravity (Deurssen LLJJ 2003). In space with no gravity, the disc increases in size and back pain will arise (ESA research). In all cases, even when the disc is not damaged, compressive forces are involved in backpain.

Although I can see why you want to raise these points (it does deepen our understanding), it may not change our exercise selection. To my understanding, compression can be a problem, but not always on the disc.

Chi
4.
Brad Josse says:
October 9, 2010 at 1:55 pm

Hello Nick,

And I want to thank you for sharing this information that would otherwise be inacessible to people in faraway places (New Zealand).

I feel that the primariy issue in training lower backs (or any area) is tissue loading tolerance. This is why Mcgill seems to favour an endurance based approach when initially training the low back. In my own experience, it’s repeated loading and subsequent failure of soft tissue not freak mechanical accidents that seem to account for most low back pain. So, while some exercises are undoubtably safer/more effective than others, I think that the real key is loading parameters/recovery time.

Thank you again.
5.
Michael Boyle says:
October 11, 2010 at 3:37 pm

Nick- based on the info, what would you do different?