How bones function.

What they need to stay strong.

What YOU can do to support them.     

by Dr. Sylvia Lim, MPP, Ph.D. Dr. Sylvia Lim teaches alignment and movement in Durham, NC. With training in cultural anthropology, public health, biomechanics, and dance, she is uniquely positioned to see the cultural influences on our health and on our bodies.

Bone health

is a common concern for many, especially as we age. But contrary to popular belief, degenerative bone loss diseases such as osteopenia and osteoporosis, are not systemic, whole-body conditions that are an inevitable part of aging. Rather, your bones remodel in response to the way you carry and use your body. The fact that aging Western populations have high rates of bone loss in certain skeletal sites reflects the ways that we, as a largely sedentary culture, have used our bodies throughout our lives. In this article, we will talk about the various factors that affect bone growth and about positive impact your bone health, and we will give you specific tips and workouts on the rebounder.

Understanding bone remodeling

Bone remodeling is the process by which bone is broken down and built up, with very little change in outside shape. It is the process by which you have supple, healthy, hydrated, and vascularized bone (bone that is able to get nutrients from the local blood vessels). This is bone that is strong, responsive, and supportive of your weight. You can think of a young, green twig, versus a dry, brittle one that snaps easily.

The cells within you responsible for bone remodeling are osteoblasts (the bone building cells) and osteoclasts (bone chewing cells). The osteoblasts and osteoclasts always have to be in an appropriate balance for healthy bone. At a later stage in their lives, osteoblasts turn into osteocytes. Osteocytes themselves no longer build bone, but become the general contractor of the bone-building process.

What tells an osteocyte that bone needs to be built?

A mechanical squish of the cell. In other words, the cell is a mechanical receptor that has to sense compression, pull, or a gentle vibration that physically changes the shape of the cell and moves the fluids within it, much like the way a squeezing sponge will change the shape of the sponge and displaces the water within. That squish is the osteocytesís signal to get crews on the scene for bone building. 

In terms of how your ancestors evolved, the bones in your spine, pelvis, and legs got the signal to build through frequent jogging. Today, with the the hard impact on concrete, jogging is not so much recommended when you have passed your forties. Rebounding, however, offers you exactly the benefit of the "squish" without straining your joints or your back because rebounders, like the bellicon, absorb 85% of this harsh impact and leave you with easily manageable 15%.  

Bones need frequent squishes

For bone health, your body prefers frequent squishes. Think about the example of the sponge: It's the difference between squeezing the sponge several times letting it relax and fill with water between squishes versus squeezing the sponge once and holding it for a length of time. You will get more water squeezed out of the sponge in the first case, which is analogous to more bone-building signals being sent to your osteocytes. That's why rebounding is more effective at building bone than activities such as swimming or long-distance cycling. In fact, long-distance cyclists frequently have fractures of the pelvis and suffer more bone loss than participants in any other sport. Their training, while intense, does not provide necessary frequency of squishes to give osteocytes their cue.

Hard bouncing is contra productive

For optimal bone building, your body also prefers squishes of the appropriate magnitude. Generally speaking, the greater the force, the better the bone building effect. But if the squish is too hard, your body senses it as an excessive force, at which point bone does the opposite and begins to degenerate. That is why long-distance runners, like their cyclist friends, can also suffer from fractures of the pelvis. The pounding on the hard pavement can be too great a strain, and so again, osteocytes are not cued in a way that signals bone building.

Here it becomes obvious why the new generation of springFREE rebounders, like the bellicon or the JumpSport, are beneficial for building bone density and why the conventional spring loaded, hard bouncing rebounders are less helpful.

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