Much of our understanding of these has come from scientists who used themselves as their own experimental subjects. Special gas mixtures and careful decompression now allow long-term life underwater, with North Sea oil rig workers spending whole months on the ocean floor. People can survive surprisingly low temperatures, however, with cases where those long given up for dead have revived. And animals such as penguins, polar bears, and fish have anatomical adaptations to the cold. She provides non-technical explanations of how muscle works, how energy production links such metabolites as ATP, glycogen, lactic acid, and creatine phosphate, and how the oxygen supply works.
Life has to be protected from huge temperature variations, airlessness, and radiation.
As well as practical problems it poses for everyday living, weightlessness affects the balance and induces muscle and bone loss.