Effects of Space / Zero Gravity on the Human Body

Long-term exposure to the microgravity environment of space is associated with increased risk of cardiovascular disease, muscle degeneration, and bone loss. We should be careful not to underestimate the health risks associated with long-term exposure to space. With increasing human exploration in space in the future, scientists should focus on understanding how the human body reacts in a microgravity environment over an extended period of time.

What are the risks of space travel for astronauts?

In the past few decades, space travel has become more accessible and also safer. Nevertheless, there are still health concerns with travelling in space. For instance, astronauts can suffer from muscle atrophy, bone loss and vision problems due to a lack of gravity. Low levels of radiation from the sun and space can also trigger skin cancer and increase chances of cataracts.

How does being in space affect your health

Astronauts have reported having difficulty sleeping and balancing blood pressure as well as experiencing constant headaches. One of the theories is that the reason these problems arise is because there is no gravitational pull. This causes fluids in the body to pool and flow less freely, leading to increases in intracranial pressure as well as distorted sleep patterns.

Long-term health risks of living in space

Living in space has long-term physiological and psychological risks that may not be evident until years later. For instance, a number of health problems that can arise from living in zero gravity, such as muscle atrophy and bone decay. Apart from having to deal with issues like radiation, astronauts also have to put up with psychological stress of being isolated from other people.

Effects of Spaceflight on the Human Body

In space, astronauts on the International Space Station (ISS) are exposed to a completely different environment than that of Earth’s. They are able to ensure most of the human body’s requirements are met as well as other conditions, such as acceptable temperature and pressure. However, there are certain aspects which cannot be dealt with, such as microgravity. This means that they have no weight and therefore, experience some adverse effects on their health. Many astronauts experience nausea, vomiting, dizziness, and headaches in the initial hours of weightlessness. This is because their bodies are adjusting to the lack of gravity. The condition is called space adaptation syndrome (SAS), a type of motion sickness. It is caused as the vestibular system adjusts to weightlessness. SAS symptoms include vertigo, nausea, headaches, vomiting, lethargy, and malaise.

The following are a number of ways the body of the astronauts on the International Space Station are affected:

  • Loss of senses (proprioception)
  • Changes in fluid distribution
  • Musculoskeletal system deterioration

Effects of a Zero Gravity/ Low Gravity on Bone Structure and Strength

NASA has found that a lack of gravity causes significant physical changes in the body, including many related to bone density and strength. The human skeleton is not used to the absence of gravity, and it changes significantly when weightless. The lack of gravity causes astronauts’ bodies to atrophy; bones lose calcium because they are no longer working against resistance or required to maintain posture.

A study published in the journal “Osteoporosis International” found that astronauts lose an average of 1% bone density per month when they are in space. Bone and muscle atrophy is a serious issue for astronauts and is something that needs to be addressed. It not only affects the astronauts but also their ability to function in space. Moreover, some muscles can atrophy very quickly, with some reporting that astronauts can lose up to 20% of their muscle mass in just 5-11 days. Weightlessness and the microgravity environment prevents the spine and other bones from being strengthened as there is no load or resistance. Scientists believe that the best way to fight this is through increased exercise. Hence, the International Space Station is equipped with exercise equipment including two treadmills, an Advanced Resistive Exercise Device (aRED) and a stationary bicycle. Astronauts are instructed to spend at least two hours per day exercising on these equipment.

Effects of a Zero Gravity/ Low Gravity on the Cardiovascular System

A low gravity or zero gravity environment can have a detrimental effect on the human cardiovascular system. It is also reported that astronauts will lose upto 22% of their blood fluid volume, and because the heart will have to work less hard, it will begin to atrophy. This will cause low blood pressure and other related conditions. Interestingly, a microgravity environment can cause blood to pool / collect in the upper body, causing facial edema and other side effects.


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