When we move our bodies here on earth, gravity is constantly pulling on us. This makes our muscles and bones stronger, even when we’re not explicitly exercising. But in space, our muscles and bones quickly become weak and start to deteriorate because there’s little resistance for us to work against. One way astronauts on extended space flights combat this is on a special treadmill. They have to exercise an average of two and a half hours a day, six days a week to keep themselves healthy. But a long-term stay in space could lead to a loss of 1.5% bone mass per month, and it takes years back on earth for your body to get back to normal. In addition to exercising, and taking calcium and vitamin D supplements, astronauts also take a medication called Bisphosphonate once a week to prevent bone loss. In addition to your regular antibiotics and decongestants and antidiarrheals, astronauts may also use drugs that improve their cognition. On the ISS, astronauts have to complete extremely long and difficult tasks, like fixing some crucial component of the space station. To help them stay alert, astronauts aboard the ISS may take a drug called Modafinil. It’s actually not a stimulant in the way that coffee or even cocaine is, it’s a class of non-addictive psycho-stimulants called a eugeroic--a wakefulness enhancer. It’s used here on earth to treat narcolepsy patients, and for patients like astronauts, works to enhance attention, executive function, and learning while they stay awake for long-periods of time. Could One of NASA’s Deep Space Challenges Be Solved in the Ocean? | The Swim This video, "What Drugs Do You Need to Survive in Space?", first appeared on seeker.com.