Educational Resources Lets Talk Science Challenge participants

Doctor pointing to a knee x-ray

Doctor pointing to a knee x-ray (kckate16, iStockphoto)

STEM in Context

Why a Trip to Outer Space Could Be Bad for Your Bones

Subin Rajendran

Summary

Astronauts can experience bone loss in space. To understand why, you need to know a bit about how bones are formed and maintained in your body.

Have you ever seen space travel in the movies? For many people, space travel is a cool and exciting possibility. And it may not be too far off. NASA’s Orion spacecraft may send humans beyond Earth’s orbit. Humans have not gone beyond Earth’s orbit since 1972!

But don’t sign up for a trip to Mars yet! First, you might want to find out how travelling to space can affect your body. Even on short trips close to Earth, astronauts have suffered bone loss!

Did you know?

The term “space” is actually short for “outer space.” You already live in space!

On Earth, you experience the force of gravity. It is what keeps you from floating off into Earth’s atmosphere. Have you ever seen pictures or videos of astronauts floating around in their spacecrafts? This is called weightlessness. Astronauts float because the force of gravity is not very strong in space. This small amount of gravity is called microgravity. This is what damages astronauts’ bones. 

Why does this happen? To understand, let’s look at how bones are formed and maintained in your body.

What are bones made of?

Bones are a type of connective tissue that helps hold the parts of your body together. Bones are made up of bone tissue. Your bone tissue is very similar to your hair. One difference is that bone tissue also has minerals like calcium. Minerals give your bone tissue strength.

Parts of a bone
Parts of a bone including blood vessels, bone marrow, compact bone and spongy bone © 2019 Let’s Talk Science based on an image by Pbroks13 [CC BY 3.0] via Wikimedia Commons).

As you grow, your bones are constantly being broken down and rebuilt. This process is called remodelling. There are two main types of cells that are important for bone structure and maintenance. They have fancy names and do opposite things.

  1. Osteoblasts (os-tee-oh-blasts) build bones using the same kinds of cells that build fat, muscle, and cartilage. 

    1. Osteoclasts (os-tee-oh-clasts) break up bones. They use the same cells as the immune system. These cells help osteoclasts dissolve the minerals on the outside the bone tissue. This releases calcium into the body in a process called resorption.

Osteoblasts and osteoclasts need to be in balance for your bones to stay healthy.

Bone building and bone loss
Osteoblasts build build bones. During this step, calcium is absorbed. Osteoclasts break down bone. During this step, calcium is released back into the body (© 2019 Let’s Talk Science based on an image by Shandristhe azylean [CC BY-SA 3.0] via Wikimedia Commons).

What happens to bones in space?

Problems with remodelling can lead to bone diseases like osteoporosis. Remember how your bones are always being broken and built? People with osteoporosis have more bone loss than bone building. This causes the bones to weaken, which can make break easily. 

Astronauts experience spaceflight osteopenia when they are in space. This condition can cause astronauts to lose bone mass in their legs, hips, and spines. Once the astronauts return to Earth, it can take three or four years for those bones to recover!

Strong and weak bones
The rectangle on the left shows what healthy spongy bone looks like and the rectangle on the right circle shows what weakened spongy bone looks like (Source: cropped image by Partynia [CC BY-SA 4.0] via Wikimedia Commons).

Scientists have learned that spending time in microgravity decreases bone building. This results in bone loss similar to osteoporosis. Remember, astronauts experience microgravity when they are in space. In microgravity, there is not as much stress on astronauts’ bones. That is mostly because they do not have to walk around. By having less stress on their bones, astronauts’ bones can become weaker. 

Scientists know that exercise is important for your bones. Exercise helps keep a healthy balance of bone building and bone loss. The best exercise for your bones on Earth is called load-bearing exercise. Walking, running, and playing sports like basketball are examples. Microgravity makes it hard to exercise in space. Astronauts must strap themselves down to treadmills in order to walk or run! 

CSA Presents: The Hadfield Shake - Exercise on the ISS (2013) by the Canadian Space Agency (2:41 min.).

Did you know?

Astronauts must exercise for at least 2 hours every day while they’re in space!

Chris Hadfield CT scan of left leg
Chris Hadfield undergoes a quantitative CT scan to obtain detailed images of the bones in his ankle, shortly after his return to Earth in 2013 (Source: Canadian Space Agency).

How are scientists studying bone loss in space?

Scientific are doing bone loss research on the International Space Station (ISS). Their goal is to learn more about bone loss in space and on Earth. For example, NASA has a program called Early Detection of Osteoporosis in Space. The scientists in this program  study what the best ways to prevent bone loss are. This project might help scientists find new ways to prevent bone disease. 

Space travel can be risky. But scientists are trying to reduce some of the risks - like the risk of bone loss! And who knows? They might even find a cure for osteoporosis along the way!

Starting Points

Connecting and Relating
  • Would you be interested in going on an long term space mission, knowing it could hurt your bones? Why or why not? 
  • Have you ever broken a bone? If so, how did it impact your life?
  • Do you have any family members who have had osteoporosis? Were they men or women?
  •  
Connecting and Relating
  • Would you be interested in going on an long term space mission, knowing it could hurt your bones? Why or why not? 
  • Have you ever broken a bone? If so, how did it impact your life?
  • Do you have any family members who have had osteoporosis? Were they men or women?
  •  
Relating Science and Technology to Society and the Environment
  • How is space research changing as the world prepares to send astronauts further into space?
  • How can research into bone loss on the International Space Station help people here on Earth?
  •  
Relating Science and Technology to Society and the Environment
  • How is space research changing as the world prepares to send astronauts further into space?
  • How can research into bone loss on the International Space Station help people here on Earth?
  •  
Exploring Concepts
  • How are your bones affected by living in microgravity? 
  • What cells are responsible for regulating bone structure and maintenance in the human body? What does each type of cell do? 
  • What things can help slow down bone loss during a space mission? 
  • Do you think it would be easier or harder to recover from a broken bone in space? Explain.
  •  
Exploring Concepts
  • How are your bones affected by living in microgravity? 
  • What cells are responsible for regulating bone structure and maintenance in the human body? What does each type of cell do? 
  • What things can help slow down bone loss during a space mission? 
  • Do you think it would be easier or harder to recover from a broken bone in space? Explain.
  •  
Media Literacy
  • What movies have you watched that include a human mission in space?  Do these movies show any of the health issues due to microgravity? Provide specific examples from the films.
  • Have you heard any news reports on health studies done with astronauts who have had extended missions to space? What was interesting about the report or the findings?
  •  
Media Literacy
  • What movies have you watched that include a human mission in space?  Do these movies show any of the health issues due to microgravity? Provide specific examples from the films.
  • Have you heard any news reports on health studies done with astronauts who have had extended missions to space? What was interesting about the report or the findings?
  •  
Teaching Suggestions:

  • This article and video can be used for Health & Human Body, Nature of Science and  Space teaching and learning related to astronauts and the impacts of space travel on human body systems. Concepts introduced include gravity, weightlessness, microgravity, connective tissue, bone tissue, calcium, remodeling, osteoclasts, osteoblasts, immune system, resorption, osteoporosis and International Space Station. 
  • After reading this article, teachers could have students complete a Concept Definition Map learning strategy to reinforce the concept of healthy bones. Ready-to-use Concept Definition Map reproducibles are available in [Google doc] or [PDF] formats.
  • Teachers could also have students watch a video of astronauts exercising in space to help keep their bones healthy and strong. A few videos of former Canadian astronaut, Robert Thirsk exercising on the International Space Station are available on this Canadian Space Agency webpage
  • As a hands on component, students could compare healthy and unhealthy bone structure to to types of chocolate bars. For example, a Cadbury Crunchie is like a healthy spongy bone, whereas a Nestle AERO bar has large holes in it like a bone weakened by osteoporosis. 
  • Alternately, students could conduct a simple inquiry is which they examine what happens to a chicken bone in vinegar over time. Vinegar will dissolve the calcium from the bone, making it soft and flexible, demonstrating the role of calcium in maintaining a strong bone structure. 
  • To go further in exploring the effects of the space environment on human body systems, teachers could have the class participate in the Living Space Action Project at: https://letstalkscience.ca/livingspace
Teaching Suggestions:

  • This article and video can be used for Health & Human Body, Nature of Science and  Space teaching and learning related to astronauts and the impacts of space travel on human body systems. Concepts introduced include gravity, weightlessness, microgravity, connective tissue, bone tissue, calcium, remodeling, osteoclasts, osteoblasts, immune system, resorption, osteoporosis and International Space Station. 
  • After reading this article, teachers could have students complete a Concept Definition Map learning strategy to reinforce the concept of healthy bones. Ready-to-use Concept Definition Map reproducibles are available in [Google doc] or [PDF] formats.
  • Teachers could also have students watch a video of astronauts exercising in space to help keep their bones healthy and strong. A few videos of former Canadian astronaut, Robert Thirsk exercising on the International Space Station are available on this Canadian Space Agency webpage
  • As a hands on component, students could compare healthy and unhealthy bone structure to to types of chocolate bars. For example, a Cadbury Crunchie is like a healthy spongy bone, whereas a Nestle AERO bar has large holes in it like a bone weakened by osteoporosis. 
  • Alternately, students could conduct a simple inquiry is which they examine what happens to a chicken bone in vinegar over time. Vinegar will dissolve the calcium from the bone, making it soft and flexible, demonstrating the role of calcium in maintaining a strong bone structure. 
  • To go further in exploring the effects of the space environment on human body systems, teachers could have the class participate in the Living Space Action Project at: https://letstalkscience.ca/livingspace

Learn more

What is Osteoporosis and What Causes It? (2019)

A detailed explanation from the National Osteoporosis Foundation with the aid of video and pictures.

Space Bones, including Space Bones Podcast (2001)

Science@NASA explains some of the explanations scientists have for why astronauts' bones are at risk, including many further links.

Physical Activity in Space (2019)

Article from the Canadian Space Agency shows three different exercises astronauts do on the International Space Station to keep healthy, plus general discussion of space health issues.

References

Canadian Space Agency. (n.d.). What happens to bones in space?

International Osteoporosis Foundation. (2016, February 18). The link between space flight and osteoporosis.

Kirsten, J. (2018). Types of bone cells.

NIH Osteoporosis and Related Bone Diseases National Resource Center. (2018). What is bone?