The story so far: At around 3 am IST on March 19, a capsule bearing the astronauts Sunita Williams, Barry Wilmore, Aleksandr Gorbunov, and Nick Hague splashed down off the coast of Florida, US. The four were returning from the International Space Station back to the earth; of them, Ms. Williams and Mr. Wilmore were wrapping up a roughly nine-month stay on the ISS, which they reached in June last year onboard Boeing’s Starliner capsule. Mr. Gorbunov and Mr. Hague were returning after a six-month stay onboard the ISS. NASA — which employs Mr. Hague, Ms. Williams, and Mr. Wilmore — has a regimen in place for the trio to follow now that they are back, to ensure they are in good health and are able to re-adapt to living with gravity after spending months in microgravity.
How does extended spaceflight affect humans?
The ISS is in low-earth orbit and its occupants experience microgravity, i.e. a very small but non-zero gravitational force. This affects the body in many ways, including allowing fluids to flow more easily towards the brain, reducing the tension acting on muscles, and lowering bone density.
These consequences have cascading effects of their own. For example, the lower bone density causes more minerals to be deposited in the kidneys instead, leading to a higher risk of kidney stones.
Thus, astronauts like Ms. Williams and Mr. Wilmore maintain a strict routine of exercises and dieting onboard the ISS, tailored among other things to help increase the blood-cell regeneration rate, work the heart, and engage the brain.
NASA and other space agencies also have crafted specific programmes to make sure astronauts don’t become stressed or anxious by their workload or by the confined space they’re forced to occupy for months at a time.
While more and more people have gone to space with each new decade, the data about the effects of spaceflight on their bodies and minds is insufficient to make proper conclusions with. This is because the number of spacefaring individuals is still much smaller than in a clinical trial; human bodies can differ on a variety of parameters; and different missions have different spaceflight profiles.
Many agencies are currently pursuing programmes to systematically study astronauts’ health, including a standardised set of tests and benchmarks.
How are astronauts monitored in space?
In September 2024, the Office of the Chief Health and Medical Officer at NASA released revised standards that specify the medical tests and checkups astronauts must undergo to stay fit before, during, and after spaceflight. The standards also say how astronauts should be treated once they return to the earth after either short (less than 30 days) or long (more than 30 days) missions. NASA regularly flies long missions: it rotates the crew onboard the ISS once every six months, for example.
The standards also specify what tests and checkups need to be conducted for astronauts flying on private missions. One example of this is the upcoming Axiom Mission 4, which will carry a crew of four on a 16-day mission to the ISS. One of the crew members will be Indian astronaut-designate Shubhanshu Shukla.
According to the standards document, “The operational medical monitoring requirements for pre-flight, in-flight, and post-flight phases are used to establish flight readiness, establish baselines, effectively guide in-flight countermeasures and assessments, and guide rehabilitation of crew members to their baseline health status following spaceflight.”
In long-duration missions, astronauts like Ms. Williams and Mr. Wilore are required to evaluate themselves two weeks, three months, six months, and nine months after launch and submit their reports to the crew medical officer. There will be a private medical conference every day for the first week, then once a week, as well as before and after spacewalks. During spacewalks, their ECG and heart rate will be monitored.
There will also be a hearing assessment once every three months and ocular assessments after one, three, six, and nine months. The body mass will be measured a week after launch, then monthly. The astronaut’s blood and urine will be tested six months after launch and as and when clinically indicated, and they will be screened for deep-vein thrombosis and blood-flow anomalies one and two months after launch as well as 42 days before the return flight.
In addition, the astronauts will be monitored for their strength and conditioning and their exposure to radiation.
How are astronauts rehabilitated post-flight?
Once Mr. Gorbunov, Mr. Hague, Ms. Williams, and Mr. Wilmore splash down on March 19 and are retrieved, they will need to undergo rigorous post-flight rehabilitation. This includes a slew of medical tests and physical rehabilitation procedures.
According to NASA, “Post-flight reconditioning is unique for each astronaut and varies by individual. While most crew members reach their preflight fitness baseline within the first 45 days of returning to earth, it is not uncommon for NASA to extend reconditioning programs to meet an astronaut’s specific needs and the pace of recovery.”
According to a chapter in the 2020 book ‘Principles of Clinical Medicine for Space Flight’, astronauts who have been in space for 20 days were able to regain their pre-flight fitness levels in a week.
On the day they return, crew members will undergo a physical exam, a neurological assessment (which includes checking for headaches, vertigo, nystagmus, and dynamic stability), resting and ambulatory ECG, eye tests, checks of their skin, blood and urine tests, and tests to check for symptoms that appear when standing straight but not reclining (orthostatic tolerance).
They will also have follow-up physical exams three days, one or two weeks, and two months after the descent. There will be follow-up tests on many of these counts as well as tests conducted according to the clinical indications.
Depending on the parameter that needs to be checked, the tests are required to be conducted by the crew surgeon, the deputy crew surgeon or the partner flight surgeon. A mission psychologist may also perform psychological checks at one and 10 days after the return.
What does physical rehabilitation entail?
The medical tests are accompanied by physical treatments to make sure the crew members’ bodies are able to readjust to the earth’s gravity after a long duration spent in microgravity.
Just as their in-flight routines were carefully planned by experts, Ms. Williams and Mr. Wilmore will follow a pre-planned routine on the ground until they have recovered their pre-flight fitness levels. The latter routine includes, among other things, measures to minimise musculoskeletal and spinal-cord injuries and to relieve stiff muscles and nausea.
In 2024, four experts with the Indian Air Force published a paper in the Indian Journal of Aerospace Medicine, where they detailed the post-flight rehabilitation of an astronaut after six months onboard the ISS.
According to this paper, the crew surgeon, the flight surgeon, and a physiotherapist may assess the need for massage therapy for crew members from the day of their return. In the subsequent week, crew members undergo a series of “physical reconditioning” exercises for two hours every day: warm-up exercises on elliptical, rowing and bicycle trainers; tasks to exercise the back and lower limbs; activities to coordinate the limbs and improve their stability and the gait; posture exercises like throwing a ball while walking; and stretching.
In the week after, the exercises expand to include jogging and playing ball-games in water.
Every day, the medical and physiotherapeutic personnel have a private conference where they assess each crew member’s progress and plan activities for the next day.
Published – March 18, 2025 01:26 pm IST
