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Disc hydration – Unloading / Loading during the act of sitting.

posture, disc hydration

Disc hydration fluctuates naturally and diurnally. That is, over the course of the day/night cycle we (as humans) lose up to 20% of the water out of our spinal discs. 1 The intervertebral discs are sensitive to load and because of their visceo-elastic make-up they will deform under load. Most notable changes seem to occur under sustained or static loads. 2 3 4 5 6 Therefore, it is important to offload the spine, especially when one sits for an extended period of time.

Recently, a study published in the Lancet 7 looked at the 188 countries and followed them between 1990-2013 and revealed that the number one reason for disability was back pain. Yes, back pain! Not heart disease. Could we extract from this that it is perhaps the introduction of computers and more time sitting? There could be other factors but there little doubt that the human population is moving less and fixated in front of a computer….just like myself at the moment.

Lumbar Disc Changes Associated with Prolonged Sitting

Take a Break and Off-load

This 8 off-loading strategy is thought to relieve the compressive forces of the spine to allow it to refill slightly….interupting sustained compressive loads, which we know is harmful.

Interestingly, a paper published in the Journal of Human Evolution in 2000 9 looked at knuckle walkers and ‘compared to humans, all ape samples show dramatically less spinal disease, especially when considerng vertebral body involvement’ . The authors concluded that this significant difference was likely due to the gait mechanism. And obviously, they use their upper extremities to off-load their spines during the course of their gait cycle.

Therefore, it looks like if you behave more like an ape and use your upper extremities, your spine will benefit. Teach your patients to minimize compressive loads by integrating off-loading strategies in their day to decrease the creep and compressive responses in the spine…..keeping the discs hydrated to prevent disc height loss.

 

 

  1.  Urban,J.P., McMullin,J.F., 1988. Swelling pressure of the lumbar intervertebral discs: influence of age,spinal level, composition,and degeneration. Spine 13, 179–187.
  2.  Adams, M.A., Hutton,W.C., 1983. The effect of posture ont he fluid content of lumbar intervertebral discs. Spine (Philadelphia1976) 8, 665–671.
  3.  Kazarian, L.E., 1975. Creep characteristics of the human spinal column. Orthop. Clin. N. Am. 6, 3–18.
  4.  Keller,T.S., Spengler,D.M., Hansson,T.H. ,1987. Mechanical behavior of the human lumbar spine. Creep analysis during static compressive loading. J.Orthop.Res. 5, 467–478.
  5.  Koeller,W., Funke,F., Hartmann,F., 1984a. Biomechanical behavior of human intervertebral discs subjected to long lasting axial loading. Biorheology 21, 675–686.
  6.  Markolf, K.L.,1972. Deformation of the thoracolumbar intervertebral joints in response to external loads: a biomechanical study using autopsy material.J.Bone Jt. Surg.Am. 54,511–533.
  7. Lancet. 2015 Aug 22; 386(9995): 743–800. 
  8.  Fryer JC1, Quon JA, Smith FW. Magnetic resonance imaging and stadiometric assessment of the lumbar discs after sitting and chair-care decompression exercise: a pilot study. Spine J. 2010 Apr;10(4):297-305.
  9. Jurmain, R Degenerative joint disease in African great apes: an evolutionary perspective. Journal of Human Evolution (2000) 39, 185–203
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