To Squat or to Bend? Is Bending Dangerous for my Back?

The debate concerning whether or not to bend using spinal flexion is a long and hotly contested one. My personal opinion on this has changed several times over the course of my career working with patients which is a good thing, it means that new evidence is coming to light all the time that changes the complexion of the conversation and that's how science should work! This blog addresses the current evidence surrounding the issue and what the best course of action should for back pain sufferers.

Neutral Spine

The idea behind using a neutral spine or to favour a squat motion when lifting, stems from several different sources. The main idea is that it reduces the load borne by the posterior elements of the spine (the bits at the back) such as the facet joints that in theory, by their nature are a bit too weak to cope with high loads over time without damaging. A second aspect in support of keeping 'neutral' stems from the work done by McGill and colleagues regarding repetitive loading and spinal disc injury. Simply put, the amount of times our discs can cope with repeated bending without damage is limited and so the idea goes, if you can limit the amount of back bending you limit potential disc damage. McGill & Callaghan as far back in as 2001, showed that disc injury is more likely from low load repetitive flexion than heavy lifting, so little and often & Wade et al 2015 have shown an increase in likelihood of disc injury compared to end plate injury at lower loading rates, so just from repeated bending. A further aspect to strengthen this argument is the apparent link stemming from a bunch of papers between a thing called 'ligamentous creep' and spinal flexion. Basically there are physical changes that occur within the spinal ligaments under repetitive or constant flexion load that potentially cause instability in the lower back – which maybe causes injury?

A further point of support to this idea is the relationship between an increase in compressive loading, anterior shear force and back injury. It's pretty much established that bending forward causes an increase in shear forces, or sliding forces, between the vertebrae which of course increase if you're lifting heavy objects, but recently some researchers have also suggested that these forces when combined with compression at least, can link to a greater increase or the risk of injury even with no extra load, so simply by bending rather than squatting.

There are other reasons you can find to back up the idea of squatting when lifting, or at least not bending over all the time. But they all pretty much amount to the same idea, that repeated bending and not keeping a 'neutral' spine can lead to spinal injury.

So what is there to argue about here?

Well first off, there's the relationship between this focus on not bending and a previous blog post I wrote on the topic of fear avoidance. Briefly this is a common process whereby the body protects itself when exposed to a perceived threat, and this can be pretty much anything, I've seen patients suffer with this from tying a shoe, brushing their teeth or deadlifting 200kg and everything in between! Where this links to bending and squatting, is the psychological fear that comes with pain and the association of specific movements with triggering a pain episode. So for example, if you suffered back pain from bending it's possible that you could become fear avoidant when bending over – known in the trade as flexion intolerance. There is an argument here that to suggest patients who have suffered back pain and are avoiding bending out of fear, to simply further avoid bending may be detrimental to their recovery. Especially when given the really quite low percentages of actual spinal injury when looking at overall back pain statistics, some studies have suggested as low as 10% of all back pain is directly a cause of disc injury for example. It might be a better course of action to just teach them to become conditioned to all forms of movement rather than fearful of one.

From a more mechanical point of view, there have been some solid and extensive studies that have provided less than convincing results regarding the clear link between full flexion/bending and spinal disc damage. Veres In 2010, tested the failure rates of discs in different positions including neutral and flexion by basically pressurising them till they failed. The results of which showed several interesting things, including that flexion may actually reduce posterior disc herniations, like the ones that press on nerves! In theory due to the fact that the disc fibres at the back stretch when pressurised in a flexed position which gives them strength against pressure going backwards. So potentially safer than a neutral spine?! They study also showed that internal disc damage is worse in a neutral spine too and with rapid load versus gradual…so the opposite of the MgGill studies back in 2001.

Kingma et al in 2010 also showed some really interesting stuff looking at the same areas. By comparing people squatting vs bending when lifting boxes. Not only did they show that there is actually less sliding force present when lifting something normally, than when trying to keep a neutral spine, but that it might even be pointless to try! As part of their study they measured the actual degree of flexion present in the back between all types of lifting technique with the stats reading only slightly different between bending vs neutral spine squats! This means that your back will still bend even when you try not to!

Although I appreciate these studies are full of jargon the long and short of it is that the situation is clearly more complicated than its simply better to squat than to bend!

So What does this all Mean?

Well… it's pretty clear that there's no hard and fast rule with this stuff. As the papers above showed day to day activities will always involve some back bending so it's probably not a great idea to keep trying to avoid it, especially when you currently have, or have had back pain. Having said that it's probably true that with higher forces and heavier weight come greater demand on the spinal segments so it may be more efficient and back sparing to reduce bend when there are high forces present. One of the most important points in all this though maybe more abstract, and that is that the link between disc damage and back pain is generally pretty poor. With the amount of flexion we do day to day being basically unavoidable, there's a pretty good chance that most of us already have some level of damage present but aren't suffering as a result and disc damage has even been shown to heal of its own accord.. Which is good news of course!