For a long time now it has been believed that spinal flexion is dangerous for our spine, possibly the worst kind of movement we can do, and a major cause of most injuries, lumbar disc herniation, and even low back pain. Emphasis is placed on the spine to be kept in neutral at all times whether it is during deadlifting or picking up something from the ground. There is still so much fear about bending forward and letting your lumbar spine flex out of ‘neutral.
Recent evidence shows that certain movements are avoided, not because they are harmful, but rather because they are generalized into a category of believed “dangerous” movements.
The aim of this blog is not to abandon the neutral position of the spine but an attempt to clear the air around the flexion of the spine.
It is believed that we bend forward, our discs bulge posteriorly, and slip out.
If that were the case, everyone would have their discs slipping all day along because we as humans require and use spinal flexion for plenty of activities throughout the day, maybe without realizing, like when we bend forward to reach for things or pick up things from the ground, tie our shoelaces or even get up from a chair. In fact, it would be impossible to perform most activities of daily living without some amount of spinal flexion.
The lumbar spine doesn’t bend the way we think it does
As discussed in a previous blog, our spine is a strong structure with an extensive network of ligaments and muscles supporting it throughout.
We have often seen professionals explain to us using spine models how the mechanism of disc herniation occurs.
A very poor attempt is made to demonstrate that when our spines flex, the space between the vertebrae decreases anteriorly and increases posteriorly causing the disc to pop out i.e. herniate and vice versa, as shown in the diagram below
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What this model fails to take into account is that the vertebrae constituting our spine doesn’t exist in our body in isolation but rather is surrounded by an extensive network of muscles and ligaments that supports the spine throughout, allowing for all kinds of movement and not to forget our intervertebral discs are not like jelly doughnuts (a metaphor used to explain the structure of the intervertebral disc that has now backfired), they don’t squeeze out from one corner by due to compression and are firmly attached and secured to our vertebrae by the endplate which is present at both the top and bottom of the vertebrae, holding it in place.
Our spine doesn’t bend the way the spine model shows.
The evidence shows, as it can be seen in the MRI images from Shiamda et al (2015) below, on bending forward i.e. flexing the spine, the lumbar spine just flattens the normal backward/, lordotic curve and therefore the vertebrae remain parallel to each other rather than having increased space posteriorly causing the disc to herniate.
Even when we slouch while sitting. Our lumbar vertebrae still often are parallel to each other and more so when compared to erect sitting. And then there is everyone all over the internet demonizing sitting upright because it is “bad”.
But then what exactly is the cause of lumbar disc herniation?
154 patients with lumbar disc herniation were asked what they thought elicited their symptoms.
62% could not recall a specific event
26% reported it was during normal tasks or activities like closing the door, making the bed, doing housework, missing a step, twisting.
6% reported it was due to heavy lifting.
2% reported it was due to light lifting (loads under 35lbs).
2% reported it was non-exertional like sneezing, sitting.
1% reports it was due to trauma.
Regardless of numerous claims, heavy lifhting or specifically flexion is not associated with symptoms of disc herniations.
Previous researches have concluded lumbar flexion to be bad, where authors dissect the cervical spine of pigs, remove all musculature and repetitively load the segments of the cervical spine like the c3-c4.
In one of the papers, the authors apply axial compressive loads with pure flexion/extension movements for a maximum of 86000 times in a 24 hour period.
It would be incorrect to conclude from these papers that repetitive lumbar flexion is bad since it isn’t completely significant to live humans that have ligamentous and muscular support, don’t flex or extend their spine about 86000 times in 24 hours, and are also adaptable.
A recent study compared the spines of 18 height-matched non-sporting referents to 18 high-volume cyclists who have cycled 150km/week for at least the past 5 years, that is a significant amount of time spent in sustained flexion. They found that high-volume cyclists had better intervertebral disc tissue quality than otherwise healthy, but non-sporting, people. This was characterized by greater disc height and longer T2- time (i.e. better hydration and glycosaminoglycan content), particularly in the nucleus pulposus.
Furthermore, additional studies have shown that spinal flexion is good for disc nutrition.
The authors of one such study conclude, “sitting posture that entails flexion of the lumbar spine causes more fluid to be expressed from the lumbar disc than do the erect posture. The effect is particularly marked in the nucleus pulposus. The fluid flow in flexed posture is sufficiently large to aid the nutrition of the lumbar disc.”
This study looked at the MRI scans of lumbar discs of 17 elite rowers over one year, during their intense pre-Olympic training program as well as their recovery phase, and compared them to healthy non-rowing control subjects.
They specifically looked at the discs GAG content (glycosaminoglycans) which are components that influence its biomechanical properties. Degenerative painful discs often have less GAG content than healthy pain-free discs and depletion of GAGs may result in structural changes and possibly cause pain.
But rowing (which also requires sustained flexion same as high volume cycling mentioned above) was found to produce significantly higher GAG values, indicating that repetitive spinal flexion can have strong training-induced adaptive remodeling processes for spinal discs.
The author’s point of the study points out, “During post-competition recovery, GAG values were not significantly different anymore, indicating a transient effect of training on cartilage with broader therapeutic implications for back-strengthening exercise and resilience.”
It is quite interesting to see that the benefits of disc nutrition were maintained as long as the participants performed spinal flexion, and were seen to diminish during the period of post-competition recovery, emphasizing the importance of consistency for maintenance of the benefits.
The studies mentioned above collectively highlight the point that bending is not bad for our spine and as a matter of fact can be healthier than erect spine postures.
There is also a strong belief that lifting with a flexed lumbar spine has a causative role in lifting-related LBP, and that lifting-related LBP is due to the combined angular position and load on the lumbar spine. As a result, workplace health and healthcare practitioners commonly advise that increased flexion of the lumbar spine should be avoided when lifting and the risk of LBP can be reduced by lifting in a lumbar-neutral or lordotic position. Lifting with a ‘straight back’ has become an accepted principle of occupational and public health worldwide. Healthcare practitioners advocate the advice to lift with a straight back, and the industry has adopted many practices to reduce lumbar flexion when lifting.
A systematic review with a meta-analysis that aimed to answer two questions:
1. Is lumbar spine flexion during lifting a risk factor for LBP onset/persistence? 2. Is lumbar spine flexion during lifting different in people with and without LBP? The authors wrote, “There is currently no credible longitudinal or cross-sectional evidence to suggest that a more flexed lumbar spine during lifting is a risk factor for LBP onset or persistence, or a differentiator of people with and without LBP.”
Even though this systematic review no study incorporated lifts of over 12kgs. The results seem significant and useful since most of the lifting advice is given to people who do not lift heavy and therefore results in even more avoidance, fear, and increased disability, creating an even higher barrier for physical activity.
In another paper, the authors compared the methods to lift a box with either stoop, squat, or weight lifting technique (WLT).
“When lifting the box from the bottom, compression forces showed no significant differences between any of the lifting techniques. Forward shear forces were higher in the WLT than in stoop and squat lifting. In contrast, lumbar flexion was smaller in the WLT than in any other lifting technique. When lifting the box at the handles, Compression forces showed a somewhat different pattern, with only the WLT resulting in significantly lower compression forces (ranging from 20–26%) than each of the other lifting techniques (stoop or squat).”
The authors conclude, “Overall, there does not seem to be a convincing argument, for healthy subjects, to prefer one lifting technique over another when a large box needs to be lifted at the bottom.”
There are studies showing that it is impossible to maintain a neutral spine during squatting and hinging movements.
This study reports that there is up to 26 degrees of lumbar flexion in the bottom portion of the kettlebell swing.
In-vitro studies show that disc herniation is possible even in a neutral spine. This suggests that neutral alone is not downright protective.
And would anyone adopt a flexed spine posture at all times if they get injured when their spine was in neutral? I highly doubt it. So why are we excessively inclined towards the neutral spine being the ultimate and most righteous position?
This is not to say that technique is not important when lifting high loads. Modifications like bracing the core, trying to keep the spine neutral can increase the efficiency of our movement, allow us to lift heavy as well as maybe optimal for athletic performance, as we see in competitive powerlifters but it doesn’t guarantee prevention of injury, as an injury is the cumulative result of a number of factors which can include form, sleep, nutrition, mental stress, etc.
Here is a picture of elite strength athlete lifting:
Regular activities that require flexion of the spine, be it lifting any object or slouch sitting, shouldn’t be feared. And if bending feels painful currently, it could help to modify the movement temporarily and gradually reintroduce it into your routine or consult a physical therapist.
Even if someone lifts heavy with a flexed spine it’s silly to shame them for it and establish doubts in their mind regarding their posture because there is a possibility that they have adapted to that posture well by regular practice and progression or it is just something that feels more comfortable to them.
In conclusion
Flexing your spine is not dangerous.
No one movement can lead to or cause any form of damage
Fear no movement, not even spinal flexion
Add variability to your movement (which includes all motion of the spine, even flexion)
Do what feels good, movement shouldn’t be complicated and stressful.
For more go to Physio Explored Blogs
Cover Photo by MART PRODUCTION
Disclaimer: In the presence of pain all the structures and context must be clinically assessed, this blog is in no way a substitute to a clinical assessment and all must consult a physiotherapist or a physician in such conditions.
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