Astronauts Health Effects of Space Travel

Astronauts Health Effects of Space Travel

Space travel looks fascinating however, it affects the health of a person or Astronauts both Mentally and Physically. Let’s look at some of the Major Health problems in Space


Cardiovascular Deconditioning

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Microgravity exposure degrades the cardiovascular system’s general condition (heart and blood vessels) and specifically degrades orthostatic tolerance (the ability of the cardiovascular system to supply the brain with enough blood to maintain consciousness while an individual stands upright).

In simple terms, space flight pushes fluids concentrated in the lower body up into the upper body. This is called “fluid shift”.

Fluid is redistributed and body mass changes during space flight

Fluid shift causes the space traveler’s face to puff out, producing uncomfortable cold-like symptoms, such as a blocked nose and headache.

In addition, to control increased blood flow the heart enlarges. This “flooding” in the upper part of the body (hypervolemia) causes the body to correct this situation by getting rid of some of the “excess” fluid (called negative feedback). The astronauts get far less thirsty than normal, and the kidneys increase urine output. However, the brain corrects the ‘flooding’ assuming the whole body is affected. This counter-correction causes hypovolemia, or in other words, a ‘drought’ due to a lack of fluid volume.

One method of counteracting the effects of microgravity is to apply lower body negative pressure (LBNP), recreating the effects and benefits of exercise on Earth.

During longer space flights the body is able to moderate extreme fluctuations between hyper and hypovolemia, especially if combined with exercise. However, all space travelers return to earth with a condition called “cardiovascular deconditioning”.

Balance Disorders

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Astronauts experience neurosensory (hand-eye-head coordination, posture, balance and gait) disturbances during space flight and upon returning to Earth.

The human body is designed to sense gravity on Earth directly through receptors known as otolith organs, or the utricle and the saccule in the inner ear. The detection of the rotational movement is done by the semicircular canals, both of which are in the inner ear. Gravity sensors in the joints and touch sensors in the skin are also involved. By sensing the relation of the body to other objects, the eyes contribute. In the microgravity environment of space, however, the otolith organs are stimulated differently.

During weightlessness, sensory information sent to the brain no longer corresponds with the body’s decoding procedures on Earth. This signal conflict causes disorientation. While floating, the astronaut’s eyes ‘see’ the roof and floor of the shuttle but there is no other sensory input to connect the concept of “up” and “down”. This is why astronauts can become dizzy and confused. While the brain will adapt to space flight conditions to some degree, once the astronaut returns home, the body responds again to a “new” environment. And the process starts all over again. The astronaut is dizzy and confused on Earth until the brain readjusts itself.

The aim of the body is to reach an Earth-normal state as soon as possible.

The challenges that the astronauts face in space can be solved, and artificial gravity can ease the changes upon return to earth.

Much research into space life science focuses on a deeper understanding of the processes involved in brain perception of the orientation of the body in three-dimensional spaces. Researchers should develop procedures with sufficient information in hand to protect the space crew members from these disruptions, particularly when crews return to Earth after long space travel.

Weakening Of Bones

The skeleton of a human is made up of 206 bones. All of which work together to allow movement and maintain posture within a 1G environment.

On Earth, the average adult skeletal system contains 1,000 grams of calcium and 400 to 500 grams of phosphorus.

Within ten days of experiencing weightlessness, calcium and phosphorus rapidly leaches out of the space traveler’s bones and is excreted in his or her urine and feces. In Space, calcium loss is ten times the rate of an elderly person on Earth suffering from osteoporosis.

One countermeasure proposed to prevent bone density loss is onboard exercise using a treadmill and ergometer.

Space life scientists and researchers researching aging are interested in how exercise affects bones, whether hormones or medications can prevent bone loss or promote bone formation, and whether ‘exercises’ translate into biochemical signals that induce bone formation and resorption.

Determining how the body converts these forces into signals which may show whether and how exercise or medications can prevent osteoporosis in the elderly and in astronauts.


Human muscles adapt readily to new situations. They can be activated when signaled to do so by the brain. However, if muscles remain inactive for a period of time, they begin to waste away or “atrophy”. In context to space flight, muscles can be roughly grouped into ‘anti-gravity’ and ‘other’ muscles. Anti-gravity muscles are composed of slow-twitch muscle fibers designed to support body weight in gravity. The ‘other’ muscle group, therefore, consists of fast-twitch fibers designed to support the body’s soft tissue and organs.

In microgravity, rapid deterioration of anti-gravity muscle and the transformation of slow-twitch muscle fibers into fast-twitch muscle fibers takes place. When astronauts return to earth, muscles that support the body against gravity have experienced excessive muscle mass loss along with loss of muscle strength, making walking extremely difficult.

While exercise in Space might seem the simple answer, it is in fact quite a complex science in itself. On Earth, short-duration exercise builds up muscle bulk and strength. In Space, because of the slow-twitch, fast-twitch composition of muscles, exercise needs to expend less than 30% of the maximum muscle power continuously over a long duration in order to slow down the rate of muscle atrophy.

Sleep Disturbances

Human life on Earth has developed to be in tune with the cycles of daylight and darkness that stem from our planet’s 24-hour rotation. An internal biological “clock” acts as a timekeeper. The ‘biological clock’, or Circadian Timing System (CTS), prepares the body and mind for restful sleep at night and active wakefulness during the day and requires time cues from the environment in order to keep it synchronized with the 24-hour rotation of the Earth.

During the space flight astronauts may have difficulty sleeping. Several factors contribute to these sleep problems, such as the excitement of space flight itself, ambient noises in the spacecraft’s close confines and the absence of normal day/night cycles. Also, the sun rises and sets in low Earth orbit every 90 minutes.

Sleep disruption can lead to jet-lag like symptoms such as fatigue, boredom, irritability, withdrawal, insomnia and depression.

To improve sleep quality, many astronauts take medicine to induce sleep. However, these drugs may have unintended side effects on performance and mental alertness. Researchers have studied melatonin, a naturally occurring hormone produced in the pineal brain gland, in the search for a better sleep aid. Study on Earth suggests melatonin can make sleep easier, an attribute that is particularly important if astronauts are scheduled to sleep at a time of day when their bodies are not producing the hormone.

Most sleep disturbances found to occur near the first and last days of the space mission due to heightened anticipation, noise and excitement.

Depressed Immune Responses

The human immune response system, or the capacity of the body to combat infection, is momentarily depressed by space travel. This decreased proliferation in the immune system of infection-fighting cells replicates the mechanism of aging on Earth. It is not clear, however, whether aging or other factors that normally accompany aging, such as reduced activity, are causing this immune system disorder.

It is difficult to find models of age-related changes in immune function, so microgravity can be a very beneficial model system to use to improve the understanding of changes due to aging.

Recommended Books:

How to Astronaut: An Insider’s Guide to Leaving Planet Earth

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