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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.
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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.
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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!
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Eye-Opening, New Insights & Information on Disc Pressure Measurements from Carl DeRosa’s Workshop at the 2010 Spine Symposium
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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.
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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.
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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)
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“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”.
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” 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).”
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“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”.
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“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”.
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” 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”.
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The Big Question(s)?
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As with every great learning experience I’ve had – It’s seems the more I learn, the more questions I have.
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What questions, if any, do you have now that you’ve read Carl DeRosa’s statements?
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Should this information above in any way change our current exercise selection and opinions on any specific exercises?
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Did you have any Ah-Ha moments from today’s post?
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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?”
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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”
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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.
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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
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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.
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Michael Boyle says:
October 11, 2010 at 3:37 pm
Nick- based on the info, what would you do different?
There has been great controversy over the past several years about the position of the spine (specifically the low back) as it relates to optimal performance and long term health. Is the Lordotic spine healthy? It seems to function quite nicely for a great many athletes. What about the Kyphotic spine? This back position seems to produce the greatest amount of symptoms and problems. But what about the concept of “neutral” spine, how do we define it, what is it? Is it braced, drawn in, tail tucked, flat back bowed, arched or what? How do we attain it? Why are we so worried about it? What happens if I don’t have it? How do I get it? Where do I find it? Who invented it? Let’s look at some definitions.
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Another way to look at this concept is the tilt of the pelvis. In lordosis, the pelvis is rotated forward or anteriorly. In kyphosis, the pelvis is rotated posteriorly. In neutral, the pelvis is aligned. Examining this concept as a performance practitioner rather than a researcher, athletic trainer or physical therapist has led me to some conclusions. First of all, is the pelvic position and the corresponding lumbar spine position resulting in some type of symptom manifesting itself in terms of pain, discomfort, tightness or inhibition of performance? If so, then I will prescribe some corrective exercises, stretching, foam rolling or therapy in order to address the inhibited performance due to pain, discomfort and tightness. I will also refer this person to an athletic trainer for further evaluation. If there is no pain, discomfort, tightness or inhibited performance, then why fix it if it ain’t broke? Most sprinter, hurdler, jumper, power, speed athletes will have a lordotic lower spine. If they are asymptomatic and pass the intrinsic muscle tests for the pelvic floor and lower core region strength, stability and flexibility — then train. The kyphotic person may need some remedial work, regardless of symptom level if you plan on loading the spine with squats, cleans, deadlifts or other types or resistance exercises that place load through the upper core. According to Dr. Stuart McGill, one of North Americas leading experts on the spine and its ability to withstand load a flat lumbar spine will tend to exhibit symptoms or problems much more often under load stress than a lordotic spine. Extension work for the kyphotic spine will be prescribed in order to enhance the thoracic spine area’s ability to withstand load.
My concern is the ruckus over the “neutral” spine concept and its application to performance training. After listening to many experts argue over the efficacy of this concept (it reminds me of the back side of the “drawing in” controversy), reading about this in the various publications concerned with performance and health exercise information as well as coaching thousands of athletes performing literally millions of repetitions over the past 25+ years I have come to the conclude the following observations. In a nutshell, the “neutral” spine is a manufactured and artificial position for the lumbar region. The term I feel much more comfortable with is the “natural” spine position. Here is a practical application of the difference. Have the client/athlete reach overhead until they feel skinny. At this point, have them take a big, deep breath and lock it in as if you were going to punch them in the stomach. While maintaining this core-lumbar position, drop the arms, exhale while maintaining a braced core and drop into a basic athletic position. This is a natural spine position that is ready to absorb and produce force throughout the core region. In order to convince the skeptic, have the client/athlete produce a lordotic lumbar spine while in basic athletic position and then press down on their shoulders much in the manner of a resistance squat load. Repeat this drill with a kyphotic lumbar spine and ask the client/athlete, “which is better to absorb and produce force?”. Then, if the client/athlete or colleague is still not convinced, ask them to assume the “neutral” spine position and repeat the drill a final time. The asymptomatic, “neutral” spine is a manufactured position that is unable to be replicated during the duress of performance. It also goes against the concept of maintaining pillar core integrity in order to transmit the power generated from the legs into the shoulders, arms, hands or implement with very little flexion, extension or rotation in the lumbar spine, until the mobility of the hips and thoracic region have been exhausted.
Dr. McGill explained this concept to me at a seminar in a one on one conversation in which I had asked him why I was being instructed at a performance center to teach the tail tucked position in training performance individuals. His first response was “I would have no idea”. When he laughed and said he would expound upon his point, I knew he was teasing me and asked him to please continue. He asked me if I would humor him in a little experiment. I said “sure”. He then instructed me to assume an athletic position, “tuck my tail” and then react to his instruction for the next 30 or so seconds. At this time he commanded me to “jump, do a squat thrust, shuffle right, shuffle left, do a quarter turn right, do a quarter turn left, squat, buzz my feet, lunge right, lunge left and get back into position”. At this point, he asked me what had happened to my lumbar postural position. I responded that I had no idea. He stated that was his point — artificial/manufactured core positions are not practical to teach for performance athletes that are asymptomatic. In rehab settings in which specific symptoms or deficiencies are being addressed then artificial spine positions are certainly a part of the rehabilitation protocol. The natural lumbar spine position with core integrity prepared to withstand force in multiple planes as well as transmit force in a variety of angles while still maintaining the ability to respire (without holding your breath) is a huge piece of performance that allow us as coaches and trainers to unlock the power of the legs and hips and express that power in our sports. This “natural” spine position combined with hip mobility, the skill of disassociation of the hip — shoulder complex and internal coordination resulting in huge force summation creates the physical performances we all long to enhance with our expertise.
Thoracic spine flexibility exercises: how two rowers used thoracic spine flexibility exercises to relieve pain and continue competing
These two case studies show how rowers can keep their thoracic spine flexible
Most of us know how demanding the sport of rowing can be. Crawling out of bed at 4am for a sleepy two-hour row on a cold winter morning and then backing up in the afternoon for an ergo or a hard session in the gym. Then try and fit everything else in to a normal day, get some 40 winks and do it all again the next day. When you put that much hard work in and make that many sacrifices, injury is devastating. Especially when it could be avoided by doing some simple flexibility work.
A question of technique
Rowing consists of repeating the same cycle of body movements with a large output of force. It is for this reason that rowers suffer mostly from overuse injuries. Thoracic-spine injuries or injuries relating to the thoracic spine in rowers are no different. When dealing with overuse injuries, many aspects of the athlete must be considered and addressed. In rowing, like all sports that involve continually performing the same sequence of movements, technique plays a vital role in preventing injury.
However, perfect technique in sport is something we all strive for but very few actually achieve. Poor technique will cause athletes to become tight in certain areas. If a rower is weak or has poor muscle endurance, then he/she will not be able to row with good technique. A rower must have good core stability and strength around his/her scapulas to hold the correct body position in the boat. Technique and strength are areas where the athlete should continue to try and improve, but excellence in these areas is a long process. In the meantime, rowers are still training hard to improve performance and consequently parts of their body will become tight or stiff. The thoracic spine is one such area.
Sitting too long!
The thoracic spine is the second most commonly injured area in rowers after the lumbar spine. It is considered to be the least mobile area of the vertebral column. This is due to the length of the transverse processes, the costovertebral joints, the decrease in disc height when compared to the lumbar spine and the rib cage. Movements that occur in the thoracic spine are mostly rotation and flexion/extension. Rowers inherently become limited into extension. This is because of the amount of time that rowers are in a seated position and the tendency for rowers to fall into thoracic spine flexion, especially when fatigued. With extension stiffness often comes an associated limitation of movement into rotation. It is essential that rowers do regular flexibility exercises to maintain their thoracic extension and rotation. Otherwise, they place themselves at risk of rib stress fractures, facet and costovertebral joint irritation, which can often refer pain to the chest wall or muscle trigger points in the erector spinae, rhomboids, levator scapulae or upper trapezius. Stiffness in the thoracic spine can also cause an extra load to be placed on other structures such as the lumbar spine and shoulders.
Case Study 1: the rower with right-sided upper-chest pain
Barbara is 50 years old and just loves to row. She rows five mornings a week for up to 90 minutes a time, as well doing a gym programme a couple of times a week that she designed herself. On top of that, she works full-time and looks after her family. Barbara presented to physiotherapy two months before she was due to compete at a major event with a three-week history of right-sided upper-chest pain when rowing, that was getting worse. She has twice had rib stress fractures anterolaterally on the left side and reports always feeling some pain around that area when she rows. Barbara was understandably concerned that she might have stress fractures on the right side. The area on the right where she was feeling pain was not the typical area for stress fractures and she was not tender on palpation through that area. Examination revealed marked tenderness through the right costovertebral joints from T3-7 and limited thoracic extension and rotation to the right.
The diagnosis was made a lot easier when mobilising the costovertebral joints reproduced the right-sided chest pain. Barbara breathed a sigh of relief when I explained to her that I didn’t think she had stress fractures on the right. In fact, she was suffering from a referral of pain from her costo-vertebral joints that related to her limitation of movement in the thoracic spine.
Treatment
Management from here was relatively simple. Barbara rested for two days while we got in and loosened up the area with trigger points to the overlying muscle and joint mobilisations to the costovertebral and facet joints. Barbara felt a significant decrease in pain the next time she rowed. She was convinced that she needed to get flexible in her thoracic spine, and keep it that way, if she was to continue to enjoy rowing.
We started her on regular stretches to improve her extension and rotation and self-trigger pointing over a tennis ball to decrease the muscle tension over the joints. Her new friend became the thoracic wedge, which is designed to increase extension range of movement. The wedge is a hard piece of moulded rubber that you place on the ground with a groove cut away for your spine to sit in. You lie on the ground with the wedge sitting between your shoulder blades and arch over it. The same can be done with two tennis balls taped together. It is a good idea to do this before stretching.
Barbara coincidently started to feel less pain in her ribs on the left side. We progressed her treatment to include mobilising all of the stiff areas in her thoracic spine and some remedial massage therapy to help speed up the process. Within three weeks, Barbara was not feeling pain anywhere in her thoracic spine or ribs when she rowed. This was for the first time in years. She was obviously determined to keep it that way. Her new training programme includes flexibility exercises for her thoracic spine, regular massage therapy and a new gym programme (from an experienced strength and conditioning specialist) that concentrates on her upper-back strength, scapula stability and core stability.
Case Study 2: the rower with right anterior shoulder pain
A week later, I was paid a visit by another extremely fit-looking middle-aged lady. ‘I have been recommended by a good friend of mine whom you’ve just treated,’ she said. Kathy was long-time friend and training partner of Barbara. She also worked full-time and squeezed into her busy week a similar training schedule. Kathy complained of right anterior shoulder pain that had been present for a couple of months when she rowed. It had also started to hurt when she performed any exercises that involved elevating her arm. Her left side was not painful at present, but it had been a problem from time to time.
On assessment, Kathy showed all the positive signs of subacromial impingement. Kathy’s posture was poor. She was rounded through her thoracic spine and her humeral head position was well forward. Impingement tests were positive and her posterior rotator cuff was very tight. I postulated that the impingement related mostly to the posture of her shoulder, which was poor because of her stiff thoracic spine and tight posterior rotator cuff musculature. This was an example of stiffness in the thoracic spine causing excessive load to be placed on other structures We immediately began addressing these two areas. Trigger points through infraspinatus and teres minor were performed in physiotherapy and at home. This can be done quite easily at home with the use of a tennis ball.
Treatment: How to do it
Place the tennis ball behind your shoulder blade and a wall. You can then just rest on any points that are tender. Remember not to roll over these points; maintain the pressure on them until the pain starts to ease, and then go to another point. Kathy had to stretch these muscles after the trigger points. This can be done by taking your arm across your body at shoulder height with a bent elbow and using your other hand to pull your elbow across. If you can’t feel the stretch, try and hold your shoulder blade back as you pull your elbow across. We began to loosen her thoracic spine through joint mobilisations in physio, stretching and the trusty two tennis balls taped together. Kathy’s shoulder posture became noticeably different, and after two weeks of working on those two areas, she was rowing without any shoulder pain. Kathy was convinced that she needed to start addressing these areas with some regular flexibility exercises. Ironically, she had suffered from rib stress fractures in the past and had some ongoing pain in this area. Just like Barbara, Kathy’s rib symptoms also disappeared with the increase in thoracic spine flexibility. Kathy then went to the same strength and conditioning specialist to work on the same areas as Barbara, as well as specific exercises to strengthen through her posterior rotator cuff.
We now had two very happy ladies one week away from competing. Both were rowing without pain for the first time in years. Rowers, take note. Keep that thoracic spine flexible. Don’t let all that hard training be ruined by an injury that could have been prevented.
Sean Fyfe