One of the main limitations for man during prolonged space flight is the issue of inactivity in zero gravity. While in space, astronauts' muscles start to waste and bones start to get resorbed back into the body. To help to protect against this and stay strong, astronauts have to exercise for around two hours a day. However, there is an animal that has already evolved to combat the problems that come with inactivity, and we may be able to learn from it.
Black bears spend up to six months of the year curled up hibernating. During this period, they neither eat nor excrete anything, and yet when they wake up and stretch their legs in the spring, they don’t have an issue with weak bones. Until now, it hasn’t been completely clear how the bears manage to protect their bones, but a group of researchers from Colorado State University think that they now have it figured out.
Normally, the body balances bone formation with bone resorption, always making sure that there is enough calcium circulating in the blood for the healthy function of organs and the production of energy. Previously, it was thought that the sleepy beasts simply maintained this normal equilibrium during their extended period of rest.
But after waking up 13 female bears during hibernation and taking blood and bone samples, researchers discovered that this isn’t quite right. Don’t worry about the bears, though; they were kept at the center during winter and released back into the wild in spring.
The study found that the animals were able to maintain their skeletal structure and strength by suppressing the resorption of bone, with the levels of a protein known to limit the process, called CART, increasing by a massive 15 times during hibernation. In addition to this, they found that the levels of bone-regenerating osteoblast cells, which normally sit on the surface of bone, and two other enzymes involved in bone formation, plummeted.
The scientists hope that by turning to nature and understanding how it has already solved such problems as bone loss, they can find the answers as to how to protect people floating around in space for months on end. If we ever want to send people to Mars, it won’t be the technology that holds us back; it’ll be the fragility of our bodies.