Countermeasures

Crews run on a harness-tethered treadmill and pedal a cycle ergometer for hours each week to keep the heart and muscles conditioned against the deconditioning of weightlessness.

Spinning a spacecraft or a short-radius centrifuge to create an outward force that mimics gravity. A long-studied but not yet operational countermeasure that could address many effects of weightlessness at once.

Tunable LED lighting that shifts colour and intensity through the day to reinforce the body clock, helping crews sleep and stay alert despite sixteen orbital sunrises a day.

Carefully planned diet and supplementation — adequate energy, protein, vitamin D, and controlled sodium — works together with exercise to protect bone and muscle and to support overall crew health.

A device that applies suction to the lower body, pulling fluids back toward the legs as gravity would. It is studied as a countermeasure to the headward fluid shift and the eye changes of SANS.

The biomedical sensors, health checks, and ground-linked telemedicine that watch over crew health in flight. On missions to Mars, where help is minutes-to-hours away by radio, crews will need to be far more medically autonomous.

Medications used to protect crew health — bone-preserving drugs studied against spaceflight osteopenia, and medicines that manage space motion sickness, sleep, and other conditions in flight.

The measures that sustain crew mental health — private family conferences, care packages, meaningful scheduling and rest, and ground-based behavioural health teams — increasingly important the farther a crew travels from Earth.

Protecting crews from space radiation with mass — hydrogen-rich materials, water, or regolith — and with mission design, such as storm shelters for solar particle events and limits on time beyond the magnetosphere.

Weightlifting in orbit. Devices such as the ISS's Advanced Resistive Exercise Device let crews load their bones and muscles against a resistance in place of gravity — the single most important countermeasure against bone and muscle loss.