Astronaut Shubhanshu Shukla Set To Return: How Human Body Is Impacted In Microgravity

NDTV

11-07-2025

As India prepares to receive its first astronaut, who is returning from the International Space Station, the spotlight turns to the health of Group Captain Shubhanshu Shukla, a decorated officer of the Indian Air Force.
His nearly three-week-long mission aboard the International Space Station (ISS) marks a significant milestone in India's space journey. But what exactly happens to the human body in space, and how does microgravity affect our physiology and psychology?
To understand the science behind space travel, NDTV spoke with Dr. W. Selvamurthy, President of Amity University and a renowned medical physiologist. With decades of experience studying human adaptation in extreme environments, from submarines to the icy heights of Siachen and now to space, Dr Selvamurthy offers a unique perspective on what Group Captain Shukla will experience in orbit.
The Microgravity Challenge
The ISS orbits Earth at an altitude of approximately 400 kilometres, where the gravitational pull is significantly reduced. This creates a microgravity environment - one of the most defining and challenging aspects of space travel.
"In microgravity, the gravitational force that influences our physiological systems is absent," explains Dr Selvamurthy. "The first system to be affected is the cardiovascular system. On Earth, gravity helps regulate blood flow. In space, without that force, blood rushes toward the head, leading to fluid redistribution and pressure changes in the brain," he said.
This shift can cause facial puffiness, nasal congestion, and even changes to vision. The heart, which no longer has to work against gravity, may weaken over time. However, Dr Selvamurthy reassures that during a short-duration mission, these effects are minimal and reversible.
Balance and Orientation
The vestibular system is also impacted by microgravity. This system in our body is responsible for balance and spatial orientation.
"Our sense of equilibrium is maintained by the semicircular canals in the inner ear," says Dr Selvamurthy, adding that "These rely on gravity to function properly. In space, astronauts often experience disorientation, dizziness, and motion sickness."
The cerebellum, which coordinates movement and balance, also changes. Astronauts must adapt quickly to floating in a weightless environment, where even simple tasks like eating or sleeping require new techniques.
Disrupted Biological Rhythms
On Earth, our bodies are synchronised with the 24-hour day-night cycle. But on the ISS, astronauts witness 16 sunrises and sunsets every 24 hours. This rapid cycling of light and dark can disrupt the circadian rhythm - the internal clock that regulates sleep, hormone production, and metabolism.
"Sleep is deeply tied to solar cues," notes Dr. Selvamurthy. "In space, the absence of a consistent light-dark cycle affects neurotransmitters in the brain, leading to sleep disturbances and fatigue," he added.
To counter this, astronauts follow a strict schedule and use artificial lighting to simulate Earth-like conditions. Over time, their bodies adjust to social cues rather than solar ones.
Muscles, Bones, and the Body's Framework
One of the most well-documented effects of space travel is muscle atrophy and loss of bone density.
"On Earth, gravity provides resistance that keeps our muscles and bones strong," says Dr. Selvamurthy, adding that "In space, without that resistance, weight-bearing muscles weaken, and bones lose minerals."
However, these changes typically occur during long-duration missions. "In a short-duration mission, the impact on muscle and bone health is negligible," he adds. "There may be minor deconditioning, but it is not clinically significant."
Astronauts engage in daily exercise routines using resistance bands and specialised equipment to maintain physical fitness.
The Psychological Frontier
Beyond the physical, space travel also poses psychological challenges, too.
Astronauts live in confined quarters, isolated from family and familiar surroundings. "Monotony, sensory deprivation, and the fear of the unknown can lead to stress," says Dr. Selvamurthy.
"Living in a small space with a few people for an extended period can be mentally taxing," he said.
To prepare astronauts for these conditions, psychological training is as important as physical conditioning. Group Captain Shukla has undergone rigorous training to build resilience and adaptability.
Yoga: India's Space Medicine
One of the unique aspects of India's astronaut training program is the integration of yoga.
"Yoga is our Brahmastra," says Dr. Selvamurthy. "It is prophylactic, promotive, and curative. It prevents illness, enhances performance, and aids recovery," he added.
Scientific studies conducted by Dr. Selvamurthy and his team have shown that yoga improves immunity, cognitive function, and emotional stability. "Practices like pranayama and meditation help regulate breathing, reduce stress, and maintain focus," he explains. "They are especially valuable in the closed, high-stress environment of space."
Group Captain Shukla has been trained in yoga as part of his pre-mission preparation. According to Dr. Selvamurthy, this will not only help him stay healthy but also enhance his operational efficiency.
A Confident Return
As India watches with pride, Dr. Selvamurthy offers a reassuring message: "Group Captain Shukla has been carefully selected and thoroughly trained. His physiological constitution, mental strength, and preparation make him well-suited for this mission. I am confident he will return healthy and successful."
This mission is not just a technological achievement-it is a testament to India's growing capabilities in space science, human physiology, and holistic health. With science and tradition working hand in hand, India's journey to the stars is just beginning.