I’m sure most people at some point in their lives have heard their health care practitioner ram home the importance of proper ergonomics, whether it be lifting at work, or just simple posture advice to protect your lower back. But what exactly happens to your lower back when you don’t lift correctly, or slouch in your desk chair? It helps to know a few things about the spine to answer this question. The spine is made up of vertebrae, and between the vertebrae are discs. These discs are very important in the absorption of load and distribution of force applied to the spine; in simpler terms they are shock absorbers. It is when the spine can’t distribute forces placed on it that injury occurs.
The most vulnerable position for your lower back to be in is forward bending with a twist. Unfortunately, this is the position a lot of people still take when lifting objects! In a normal spine, forward bending will cause compression to the disc at the front, and mild projection to the back. Adding in a twist will further compress the disc. This alone can cause injury, let alone adding additional weight when lifting!
When you bend over with just your spine, your center of gravity shifts, and all the force is placed on your lower back, which is already in a compromised position. The lower back is now taking the load of your upper body, which is approximately half your body weight. Then adding on the additional weight of the object you’re lifting and its no wonder the poor low back can’t cope! Imagine a 100kg male, using incorrect lifting techniques to pick up a 10kg create full of tools. Bending forward alone is approximately 50kg to the low back, then that extra 10kg on top equaling a whopping 60kgs of force that the spine needs to distribute! Ouch!
The same applies to a slouched sitting posture. Slouching just 20 degrees will add 30% extra pressure to your low back and that weight is directly related to the body weight above. Once again if you take a 100kg male, with an upper body weight of approximately 50kgs, slouching will add 65kg of force through the base of the spine!
So now that you know the basics of what goes on in the low back during poor ergonomics, what can be done about it? This is the beginning of a series of ergonomics tips to help aid in protecting your low back, watch this space!
- CUErgo. Biomechanics of safe lifting. Cornell University: Professor Alan Hedge; [2015/02/07, cited 2015/02/10]. Avail from: http://ergo.human.cornell.edu/DEA3250Flipbook/DEA3250notes/lifting.html
- Gail M, Jensen MA. Biomechanics of the lumbar intervertebral disk: a review. J Phys Ther [internet]. 1980 [cited 2015 March 10]; 60:765-773. Avail from: http://www.physicaltherapyjournal.com/content/60/6/765.full.pdf
- Anderson CK, Chaffin DB. A biomechanical evaluation of five lifting techniques. App Ergo [internet]. 1986 [cited 2015 March 10]; 17.1: 2-8. Avail from: http://deepblue.lib.umich.edu/bitstream/handle/2027.42/26237/0000317.pdf?sequence=1
- USDA. Safe lifting technique. USA: [updated 2015 March 9; cited 2015 March 10]. Avail from: http://www.aphis.usda.gov/emergency_response/downloads/health/Appendix%203-5-B%20Lifting-Moving%20concerns.pdf
This article is for information purposes only. Please consult your Osteopath or primary healthcare professional for further information.