In CrossFit, we build muscle, and we also build bone. Machines need strong bones. But machines are more than just engines or in the case of our athletes, more than just muscle. In order for machines to pull and push, lift and press, they need structure and support.
We don’t use machines. We build them.
Of course, building bone is far less sexy than building muscle. I’ve yet to hear someone say, “Check out the femurs on that guy!” or “Her tibias are phenomenal.” But building and strengthening bones are very important parts of what we do at The Arsenal.
A recent New York Times article, “Why High Impact Training is Good for Your Bones” states:
“Bones should be jarred, for their own good. Past experiments have definitively established that subjecting bones to abrupt stress prompts them to add mass or at least reduces their loss of mass as people age.
Recently researchers at the University of Bristol gathered male and female adolescents — the body accumulates bone mass rapidly at this time of life — and had them go about their daily routines while they wore activity monitors. The bone density of the volunteers’ hips was also measured.
A week later, the scientists reclaimed the monitors to check each teenager’s exposure to G forces, a measure of impact. Those who experienced impacts of 4.2 G’s or greater — though these were infrequent — had notably sturdier hipbones. Additional work done by the same researchers showed that running a 10-minute mile or jumping up onto and down from a box at least 15 inches high was needed to produce forces that great. The significance of these findings is that people should probably run pretty fast or jump high to generate forces great enough to help build bone.”
Box jumps! Running! CrossFit!
CrossFit involves various functional movements and exercises so we can pound our bones from all sorts of angles.
The bone remodeling process is very interesting and dynamic, and I could geek out on this for another few thousand words. (Don’t worry, I won’t.)
The direction and line of forces through the bone have a significant effect on the bone-building process. If force is transmitted through a line of strong dense bone tissue, it has less of an effect on bone formation than if that same force were transmitted through a line of weaker bone tissue.
And even more interesting, if the normal line of force changes due to a change in a movement pattern and strong bone tissue is no longer transmitting large forces, it will lose its high strength and the minerals will be redistributed over time to support the new line of force. That’s just one reason compensatory movement patterns, either due to injuries or faulty movements, can be so dangerous.
When a normal movement pattern is restored after a long time or a lifetime of faulty movement, bones can potentially break when large forces transmit through weakened bone tissue. This can cause broken or fractured bones, bone spurs or even avulsion fractures–when a piece of bone is broken off by a tendon during muscle contractions.
This is why you need to ease back into the WODs, if you are returning from an injury or new to movement training. Keep from jumping around for the first few weeks of training to allow the bones to experience the pressures of lower-impact movements while the bone structure begins to remodel. Every few weeks increase the height of boxes the speed of runs in small increments. In generally healthy and well-nourished people, 15-24 weeks of progressive training is long enough to remodel and harden bones into well adapted force-transmitting machines.
In short: Train your bones the right way with proper technique and intensity and you can avoid serious potential injuries. Our bones can change shape and density over time to adapt to our changing lives and activities.
So beat your bones!