Mission to Mars: The Ultimate Challenge For The Human Body
Updated: Sep 7, 2022
By Denis Boucher, Ph.D.
We don't think about it, but our bodies evolve in gravity. Our muscles allow us to fight against it. Lifting an arm, walking, and bringing a fork to our mouth involves a constant struggle against gravity.
On the other hand, this struggle allows us to maintain our muscle mass. Because each movement to overcome gravity generates a cascade of events (release of chemical messengers) inside our body that helps support and develop our muscle mass. In more scientific terms, it is the primary mechanical stimulation essential to our survival.
As soon as gravity disappears, our body no longer receives any stimulation. Without it, the cascade of events stops. Our muscles no longer receive the message that tells them they must adapt. They lose their building blocks: proteins. In other words, we lose our muscle mass.
To avoid muscle atrophy, astronauts must train in space for two hours daily. Exercise equipment allows putting the muscles under resistance. It stimulates them and reawakens this cascade of events necessary for muscle growth.
When an astronaut trains for only two hours a day, his muscles remain for 22 hours in an environment that provides no stimulation. In these conditions, training only serves to compensate. Inevitably, in space, the muscles lose their capacity. As a result, their volume and efficiency decrease, considerably reducing their fitness level.
The first mission to Mars will significantly challenge the human body. It will take months to get to Mars and back to Earth, plus the time spent on Mars.
The astronauts will spend many months in an environment that favors muscle atrophy. That's why the search for countermeasures to this phenomenon is of paramount importance.
We know that fighting gravity is essential to maintaining muscle mass. We also know that strength training promotes muscle development by providing mechanical stimulation and causing the metabolic stress necessary to trigger the cascade of chemical messengers leading to muscle mass development. This development results in the accumulation of protein in the muscles.
Muscle mass remains stable when the construction of muscle proteins (anabolism) equals their destruction (catabolism).
Muscle mass is lost when the destruction of muscle proteins is more significant than construction. Muscle mass loss occurs in zero gravity or when a person is sedentary.
A gain in muscle mass is present when the building of muscle protein outweighs its breakdown. So, increasing muscle protein buildup is an option. The option is also to reduce muscle protein breakdown while maintaining protein buildup stability. Or the last possibility, increase muscle protein synthesis while reducing its rate of destruction.
The best strategy to stop muscle mass loss would be to recreate gravity in space. But this will not be the case during the first mission to Mars. Thus astronauts will have to exercise a lot, but it will be far from a perfect solution.
So how do we solve this problem? We know what to do on Earth. Move and exercise. In space, exercise serves to compensate, but there are many hours in zero gravity without mechanical stimulation.
You will understand that I do not have the answer to this fascinating problem. But we already know a lot about muscle development. Muscles need mechanical stimulation and metabolic stress (obtained from training and gravity) to remain stable or grow.
The fascinating question I've been asking myself for years is: is it possible in zero gravity to lure the body into believing it is undergoing mechanical stimulation?
In other words, how can we trigger the cascade of events that stimulate muscle development without using gravity or training?
I don't have the answer yet, but you must admit it's an exciting research topic.