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To flex or not to flex?

I am tall, the kind of tall that turns people’s heads, the kind of tall that has every second person stop and ask me if I play basketball, I feel ashamed when I tell people I do not! Why am I telling you this?

Because I am sick of being told to not bend my back. Reflecting on my time as a student on clinical placement one of the most consistent criticisms was ALWAYS “your body mechanics were not correct” what is correct? And where did this idea come from?

I will tell you one thing; it is hard work not flexing your spine at my height working in public hospitals built in the 1940’s! And this is not just my experience as a student, there are posters for safe lifting in just about every workplace in the country, but is this idea of avoiding spinal flexion to protect your back actually supported by the literature?

It would seem not. There is no evidence to suggest that if you work in an occupation that requires greater spinal flexion you are at any increased risk of developing back pain when compared to an occupation that does not require the same flexion. A systematic review conducted by Swain et al. (2019) concluded “Despite the availability of many reviews, there is no consensus regarding causality of physical exposure to LBP”.

We have all seen a variation of the above image in our workplaces over the years, when van Dieën et al. (1999) set out to investigate which of these two lifting techniques were better at preventing low back pain, they concluded “The biomechanical literature does not provide support for advocating the squat technique as a means of preventing low back pain.”

What if we go into workplaces and try teaching “correct lifting technique”? same outcome! Absolutely no change in low back injury incidence (Sowah et al. 2018; Hartvigsen et al. 2005). I feel vindicated in my ability to lift and lift well with a flexed spine, anyone else who lifts with a flexed spine at work should not feel at increased risk of injury!

It intrigues me the narrative surrounding spinal flexion when you only must flick on the television during ANY sporting event to see that advantages of being strong in a flexed position, take for example cycling, rowing, wresting, field sports, throwing sports and even strong man events! ALL demonstrating how powerful we can be in a flexed position.

Even when cued to lift with a “straight” back can we? No is the answer, when we look at biomechanical studies from Vigotsky et al. (2015); Sayers et al. (2020); McGill et al. (2009) and Aasa et al. (2019) we see consistently in those trying to avoid spinal flexion we simply cannot. And we do not need to with Mawston et al. (2021) recently concluding that “A flexed-back posture is associated with increased strength and efficiency of the back muscles compared to a lordotic posture.”

So, if spinal flexion is not predictive of back pain, it is mechanically more efficient during lifting and we cannot avoid it anyway why are we so fearful of it? Let us start placing a little more faith in our backs! They certainly deserve it for being the strong, adaptable, robust, and resilient structures they are.

If you would like to see what your back can do when given permission to move, we at The Biomechanics are happy to help!


Aasa U, Bengtsson V, Berglund L, Öhberg F. Variability of lumbar spinal alignment among power-and weightlifters during the deadlift and barbell back squat. Sports Biomech 13: 1-17, 2019.

Hartvigsen, J, Lauritzen, S, Lings, S, & Lauritzen, T. (2005). Intensive education combined with low tech ergonomic intervention does not prevent low back pain in nurses. Occupational and Environmental Medicine (London, England), 62(1), 13–17.

Mawston, Grant, Holder, Laura, O’Sullivan, Peter, & Boocock, Mark. (2021). Flexed lumbar spine postures are associated with greater strength and efficiency than lordotic postures during a maximal lift in pain-free individuals. Gait & Posture, 86, 245–250.

McGill SM, McDermott A, Fenwick CM. Comparison of different strongman events: trunk muscle activation and lumbar spine motion, load, and stiffness. J Strength Cond Res 23: 1148-1161, 2009.

Sayers MG, Bachem C, Schütz P, Taylor WR, List R, Lorenzetti S, Nasab SH. The effect of elevating the heels on spinal kinematics and kinetics during the back squat in trained and novice weight trainers. J Sports Sci 38: 1000-1008, 2020.

Sowah, Daniel, Boyko, Robert, Antle, David, Miller, Linda, Zakhary, Michael, & Straube, Sebastian. (2018). Occupational interventions for the prevention of back pain: Overview of systematic reviews. Journal of Safety Research, 66, 39–59.

Swain, Christopher T.V, Pan, Fumin, Owen, Patrick J, Schmidt, Hendrik, & Belavy, Daniel L. (2020). No consensus on causality of spine postures or physical exposure and low back pain: A systematic review of systematic reviews. Journal of Biomechanics, 102, 109312–109312.

van Dieën, Jaap H, Hoozemans, Marco J.M, & Toussaint, Huub M. (1999). Stoop or squat: a review of biomechanical studies on lifting technique. Clinical Biomechanics, 14(10), 685–696.

Vigotsky AD, Harper EN, Ryan DR, Contreras B. Effects of load on good morning kinematics and EMG activity. PeerJ 3: e708, 2015.

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