Astronauts undergo rigorous academic and equipment training for each space mission. Once they've launched on a mission, their training helps them to complete demanding tests, including space walks. However, spending time in a zero-gravity environment takes its toll on astronauts' bodies. Astronauts may lose between 1 to 2 percent bone mass for every month they are in space, according to NASA, CNN reports. Specialized exercise equipment on board the spacecraft, space shuttle or space station allows astronauts to maintain their conditioning and strength in a zero-gravity environment.
Stationary bicycles are common in a gym and for home use. During a space mission, astronauts use a specialized stationary bicycle, called a cycle ergometer, that is engineered to work in a zero-gravity environment. The cycle ergometer has clip pedals; astronauts may also opt to use waist straps, back supports and hand holds to keep themselves stable while they use the machine, the Canadian Space Agency website explains. The cycle ergometer also has a vibration isolation system to prevent the astronauts' workouts in the cramped quarters of a spacecraft from disturbing any scientific experiments in progress. Like a stationary bicycle, a cycle ergometer provides cardiovascular exercise for astronauts during space missions.
Astronauts also obtain cardiovascular training during space missions by running on a specialized treadmill adapted to anchor the astronaut in place during a workout. The treadmill is fitted with spring-loaded cords attached to each side of the machine. The cords attach to a harness secured around the astronaut's body with a waistband and shoulder straps. More tension cords attach to the astronaut's thighs and lower legs to provide resistance during the workout, the European Space Agency website explains. The resistance cords are adjustable so that they provide between 66 and 100 percent of the astronaut's body weight, which determines how strenuous the workout is for the astronaut.
aRED — advanced Resistive Exercise Device
Strength training presents a special challenge during space missions. To compensate for zero-gravity, NASA developed what it calls the advanced Resistive Exercise Device, or aRED. The large device looks like it belongs in the "Transformers" movie franchise, NASA astronaut Clay Anderson told CNN.
It works on a similar principle as commercial strength-training machines that use resistance bands instead of weights, but aRED substitutes vacuum canisters for weights or resistance bands. Also, aRED includes matched flywheels that spin in opposing directions to duplicate the force of gravity that normally affects resistance training. With aRED, astronauts can perform both upper-body and lower-body exercises, including dead lifts, bicep curls and bench presses to compensate for the lack of work their muscle receive in space, the Canadian Space Agency states.