In the beginning, there was Earth. And with any mass, there exists gravity. Irrespective of how you believe we organisms came to exist on this planet, there is one common theme that all life is intertwined with : the force of gravity. It is this force that requires careful attention when it comes to our musculoskeletal system- the system that moves us.
This is very apparent when a new born begins to adapt to the new forces. Babies have a hard time holding their own heads up and new born calfs struggle to keep their four limbs in order.
In the development of our spine, only three weeks after gestation, an important structure develops in which the rest of the body grows around. This structure is the notochord which in turn develops into the compressive resistance tissue named the intervertebral discs (IVDs). More sepcifically, the nucleus pulposus. These are the fundamental structures that hold our vertebrae apart from one another and resist the forces of gravity. IVDs are cartilage.
There is something very unique about this structure. It is home to zero blood vessels in its early years. Movement, allows to delivery of crucial materials to and from these amazingly resilient structures. That is, if there is a sustained load on cartilage, it deforms, compresses and loses the most essential nutrient of all—-water.
- ISSLS Prize Winner: Dynamic Loading–Induced Convective Transport Enhances Intervertebral Disc Nutrition, SPINE Volume 40 , Number 15 , pp 1158 – 1164 ↩