Harrison et al’s (1999) excellent review of the knowledge of the biomechanics of sitting proved very enlightening; they concluded the optimum seated position in order to minimise muscular effort and pressure on the lumbar discs was leaning slightly back from vertical (about 120 degrees to the horizontal), with approx. 5cm of lumbar arch support, a slight backward tilt in the seat base (which encourages you to lean back against the back support), a gap at the bottom of the seat back (for buttocks and sacrum –bone at the bottom of your spine), and make sure the seat base isn’t too long (leads to pressure at the back of the knees). However, their review also led them to conclude “Oftentimes, the theoretic ideal chair and sitting position are not preferred by subjects’ comfort ratings” i.e. the science and art of sitting often differ!
A more recent study by Makhsous et al (2009) demonstrated that “off-load”sitting reduced load on the muscles in the lower back; this requires that the back portion of the seat you’re sitting on (the bit under your “sitting bones”) is lower down, bringing more pressure onto your thighs, and that there’s an increased lumbar support. They noted in their summary that this “may potentially reduce sitting related lower back pain”. Again, nothing certain here.
O’Sullivan et al (2012) looked at the question of a fixed back support versus a more free-floating support or even sitting on a ball with no back support. They concluded that “overall the evidence suggests that dynamic sitting approaches are not effective as a stand-alone management approach for lower back pain”.
And what about lumbar supports themselves? Jellema et al (2001) concluded that there was limited evidence that these help to avoid or ease lower back pain.
Unfortunately, as far as science is concerned, I’ve asked an overly complex question. Harrison et al’s conclusion (in bold above) pretty much sums things up for me.
Long periods of sitting make my lower back ache, and if done over several days, increase the likelihood that I’ll get an “acute episode”. Perhaps another reason for this is that I’m often doing things I don’t want to do when sitting! Remember, pain isn’t just due to mechanical factors! (Read “Mindfulness for lower back pain” for more on this.)
Below are my own recommendations based on the scientific knowledge and 20+ years of clinical (and personal) experience of lower back pain and sciatica:
- Vary your seated posture – there is no perfect position
- Sit higher up with an “open hip angle” if possible
- Make sure you understand and get to know the seat you’re sitting on
- Stand whenever possible
- Go for little walks
- Listen to your pain (use it or lose it, but don’t abuse it)
If you’d like a practical guide to all of this, watch our video on seated ergonomics. And for any help with lower back pain or sciatica, just email me
Harrison, D.D., Harrison, S.O., Croft, A.C., Harrison, D.E., Troyanovich, S.J., 1999. Sitting biomechanics Part I: Review of the Literature. Journal of Manipulative and Physiological Therapeutics 22, 594–609.
Jellema, P., van Tulder, M.W., van Poppel, M.N.M., Nachemson, A.L., Bouter, L.M., 2001. Lumbar Supports for Prevention and Treatment of Low Back Pain: A Systematic Review Within the Framework of the Cochrane Back Review Group. Spine February 15, 2001 26, 377–386.
Makhsous, M., Lin, F., Bankard, J., Hendrix, R.W., Hepler, M., Press, J., 2009. Biomechanical effects of sitting with adjustable ischial and lumbar support on occupational low back pain: evaluation of sitting load and back muscle activity. BMC Musculoskeletal Disorders 10, 17–17.
O’Sullivan, K., O’Keeffe, M., O’Sullivan, L., O’Sullivan, P., Dankaerts, W., 2012. The effect of dynamic sitting on the prevention and management of low back pain and low back discomfort: a systematic review. Ergonomics 55, 898–908.