As I know everyone is bored reading about physical activity and diet, I thought I’d give up and do a blog about space. After all... who didn't want to be an astronaut at some point? Unfortunately for the blog...this isn’t quite the case… but this week we do get to speak to John Noone, a PhD researcher at Dublin City University's School of Health and Human Performance and the National Institute for Cellular Biotechnology, who works in conjunction with the European Space Agency. So...what can space research tell us about our health?
Key Question: How are space and physical inactivity linked?
As you know from a few blog posts, physical inactivity is one of the leading risk factors for many diseases such as cardiovascular disease, obesity and type 2 diabetes. With the advancement of technology, it is likely that sedentary behaviors will continue in the future. The problems with being inactive were talked about in posts #10 (click here) and #11 (here) which include severe changes to our muscles, fat tissue, cardiovascular system, bone mineral density (a marker of bone health) and reduction in our fitness levels (click here, here, here).
What’s the link to space?
During space flight astronauts not only get exposed to radiation but the lack of gravity they experience results in many of the physiological changes experienced with prolonged physical inactivity. Let’s start with our bones. During our lives the bones in our body are broken down by cells called osteoclasts and are reformed by osteoblasts. This is balancing act occurring throughout life. However, when exposed to the effects of microgravity (just like when we are inactive), our bones are not required to support as much weight! Therefore, our osteoclasts breakdown bone more than the osteoblasts can build it, reducing the bone composition (bone mineral density), weakening the bones and putting astronauts at increased risk of bone breaks and fractures (click here).
Lack of gravity also leads to change in the distribution of blood around the body, increasing blood pooling in the head and reducing it in the legs and lower extremities. This shift affects much of the body but particularly the heart, altering its shape and modifying cardiovascular function. If that wasn’t bad enough, pooling of blood in the head can increase the pressure around the brain and the eye, impairing the astronauts’ vision, while also negatively effecting the neurovestibular system leading to poor balance and spatial orientation (pardon the pun!). Finally, the change to fluid distribution and the lower energy expenditure due to microgravity has a bad effect on our muscles. Not only is there a loss in muscle (click here for more information), but there is also change to its composition and reductions in muscular strength, endurance, power and neuromotor function, all of which are critical for health but also an astronauts productivity during a mission. These changes can go unnoticed in an astronaut’s day-to-day performance in space. However, they become very clear on their return to Earth due to the change from microgravity to Earth’s gravity (9.81 m/s2).
Can we counteract these changes?
Currently (click here), astronauts are asked to exercise for up to two hours every day (FOUR times the recommended amount on Earth) whilst in space to try and deter these changes. Commercial and governmental agencies across the globe are also working on alternatives to exercise to help preserve the health of our astronauts for longer. These include optimizing their nutrition, (such as protein supplementation) in an attempt to preserve muscle mass (click here), antioxidant and anti-inflammatory supplementation to help control stress provoked by microgravity (click here) and pharmacological countermeasures such as testosterone or alendronate (click here) to help preserve both muscle and bone throughout space flight. Unfortunately, to date no countermeasure has been successful in counteracting all of the aforementioned changes. As such, scientists are focusing on combination therapies of all of the above in an effort to unlock the antidote to the effects of weightlessness.
The take home message: exposure to microgravity causes rather nasty physiological changes in astronauts. Rather worryingly, many of these happen when we are very inactive. Not only is this a fascinating area of research, but it supports the need to be active in our daily lives!
Don't forgot to sign up for the blog (click here) and follow us on Instagram (click here).