Elon Musk is convinced that humans will travel to Mars within seven years.
I don’t doubt that he and his company SpaceX will solve the technological issues to get there.
But, no one is talking about how we humans will manage zero gravity and the transition back to Earth.
Scott Kelly knows a thing or two about this.
Kelly spent 340 days in space on the International Space Station. Three months after returning to earth, his body still hurt from the load due to gravity.
Your bones get stronger by reacting to the load or force placed on them. Sheldon Wenbaum, MD discovered a few years ago small fluid filled tubes inside the bone.1)Fritton, S. P., & Weinbaum, S. (2009). Fluid and Solute Transport in Bone: Flow-Induced Mechanotransduction. Annual Review of Fluid Mechanics, 41, 347–374. http://doi.org/10.1146/annurev.fluid.010908.165136 As you load and unload your leg, for example, the fluid moves in the tubes activating small receptors. A lot like the tiny cells in your ear that help regulate your balance. The receptors then tell the bone cells what to do – make new bone or remove bone.
This entire system though craps out in space. No gravity, no load. In the absence of a signal to create new bone, astronauts lose bone at about 20% over 90 days.
In other words, stress (load) keeps your bones strong.
But, too much stress, your bones break. Maybe it’s just little break or what’s called a “stress fracture”. Or it could be a big break where the bone is shattered.
It seems that bone needs not too much, not too little but just right.
Oh, wait, Isn’t that the three bears and porridge story?
My mind sometimes…
But, anyway, that’s the right idea.
Turns out your entire body needs physical stress: heart, lungs, tendons, ligaments, cartilage, disc. Everything.
But what do you do?
I divide the world into three environments: Sub-Gravity, Gravity, and Super-Gravity.
For example, let’s use walking. Sub-Gravity is walking in chest deep water. Gravity is walking around during the day and Super-Gravity is walking around carrying an extra load.
To work and play in Gravity, you need to train in Super-Gravity. Exercising / training in Gravity isn’t quite enough.
Turns out swimming is of little use which makes sense if you think about how much load due to gravity is involved in swimming. Almost none.2)Guadalupe-Grau, A., Fuentes, T., Guerra, B., & Calbet, J. A. (2009). Exercise and bone mass in adults. Sports Med, 39(6), 439-468.
Walking helps some but not a lot. Remember, walking is a Gravity load.
Running helps more than swimming or walking but the winner is resistance training (Super-Gravity). The variation in loads, angles, speeds involved with strength training gives the bone tubes a lot of stimulation.
Until Musk solves how we will train in Super-Gravity while floating around in Zero-Gravity, missions to Mars are a long way off.
That’s all I have for for now.
Thanks for reading.
References [ + ]
|1.||↑||Fritton, S. P., & Weinbaum, S. (2009). Fluid and Solute Transport in Bone: Flow-Induced Mechanotransduction. Annual Review of Fluid Mechanics, 41, 347–374. http://doi.org/10.1146/annurev.fluid.010908.165136|
|2.||↑||Guadalupe-Grau, A., Fuentes, T., Guerra, B., & Calbet, J. A. (2009). Exercise and bone mass in adults. Sports Med, 39(6), 439-468.|