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I have to take a few deep breaths as I start to write about biomechanics. Biomechanics is a topic that could easily take several semesters of classes and several prerequisite classes to understand completely. It involves concepts from physics and a thorough knowledge of anatomy and physiology. Our purpose here, however, will be to give you a simple description of what biomechanics is and how you can improve your health with a simple concept or two.

'Biomechanics' literally translates as 'life mechanics'. It is applying the laws of physics to living things. We will apply a couple of simple concepts of physics to the human body. The basic concepts that we are going to use are 'base of support' and 'center of gravity'. In fact, these are very similar to the concepts in the section on posture, even though we didn't use those words. Your base of support is whatever part of your body is interacting with the surface that is supporting you. If you're standing, its the area covered by your feet. If you're sitting, it's the area covered by your feet(if they're touching the ground) and your buttocks. If you're lying get the idea. Your center of gravity is dependent on how you have your body aligned or 'configured'. For example, if you are standing, your center of gravity is typically the intersection of two lines: a line that passes through you from front to back through your 'belly button' and a line that passes through you from side to side that divides you in equal front and back segments. Proper biomechanics involves keeping your center of gravity over your base of support.


This is oversimplified, greatly, because to do this topic justice we would want to look at the alignment of your feet, legs, low back etc.; your skeletal alignment; joint mobility; muscular imbalances, strength and flexibility; the state of your nervous system; balance and coordination and more. But we're simply looking at one concept that may help you.

What if you lift something? Everyone has heard that they should 'lift with their legs' or 'bend their knees'. This is correct. But they usually bend their knees and bend their trunk forward at the same time. This moves your center of gravity outside of your base of support, and makes your body work a lot harder than it needs to, and this is when things go wrong. In my years as a physical therapist, I've had more than a few people come to me with severe low back pain that began after bending down to pick up a piece of paper or a Kleenex. It wasn't the weight of the paper, it was the weight of their upper bodies and the strain that it placed on their low back and it's myriad of components that created the pain and the problem. If they had kept their upper bodies straight, over their base of support, more than likely they never would have hurt themselves.

Lifting things adds another component to biomechanics: the object that is being lifted. If you are lifting a twenty pound ball, and you hold it near your center of gravity, it is roughly a twenty pound load on your body. If you hold that object in front of you with your arms extended, the amount of load put on your system multiplies in direct correlation to the distance the object is from your body. Keep objects that you are lifting close to your center of gravity.

When people are walking, especially older people that may be 'hunched over' and weak, they are always looking for something to lean on. This is understandable and OK. What is not OK is when they reach for the object that they want to lean on. This can move their center of gravity outside of their base of support and result in a fall. I believe that following this simple concept can prevent a great number of falls in the elderly every year. Simply walk the extra step to whatever it is you want to lean on. Don't reach.

You might start to figure that biomechanics is similar to 'dynamic posture'. You're right. We've oversimplified it, but it's useful just the same. Just like with our other topics, change slowly and only to the extent that you're comfortable. If you have any questions, call us or another outpatient orthopedic physical therapy clinic. You may have extenuating circumstances that makes our simple lesson inadequate, or worse yet, harmful. It's worth the phone call and maybe a visit or two. Otherwise, good luck from Physical Therapyworks!

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