Joan Vernikos who was a researcher for NASA did multiple studies looking at the effects of space on physiological systems and health. Over time they discovered that the effects of space and aging were very similar. Muscle weakness, bone density loss, poor coordination, poor reaction time were all factors that were impacted by both time in space and 'aging'.
There were many other impacts observed in both aging populations and astronauts. Here is just a sample of a long list:
- decreased plasma volume
- decreased aerobic capacity
- increased arterial stiffness
- decreased brain blood flow/ oxygenation
- decreased muscle mass and strength
- decreased sensitivity to insulin
- decreased collagen -> aching joints
- sleep loss and circadian rhythm alteration
- decreased gut motility
- tender feet when walking/ getting out of bed
- vision problems
- increased inflammation
- decreased wound healing
So were the astronauts aging faster in space?
But when they came back to ground the effects were reversed.
So were they then reversing the aging process??
Was it the inactivity causing the body changes?
To test if it was age was a factor they sent 78 year old astronaut into space half expecting his response would be different to those of the other 5 crew because of his age. What they discovered was that his physiological responses were identical
to those of the other 5 crew on the flight. And his recovery once back on earth was the same
as well! It wasn't a question of age.
Joan did lots of earth based studies using continuous bed-rest as a simulation of the conditions in space. She conducted a series of studies to look at what would prevent the consequences of lying in bed continuously for 4 days. What she concluded was a surprise... even for Joan. Just standing up once an hour during waking hours (16 times a day) turned out to be equally (sometimes more) effective than walking 16 times a day for the same amount of time as the standing only group!? It was the change in position to experience gravity that reset the systems not necessarily the activity.
But why, on earth, do these symptoms appear in an aging population?
There is gravity everywhere on earth. We can't get away from it!
What has been teased out by bed-rest studies is that our positioning against gravity is a key element.
- When we are standing we experience 1 G (force of gravity) through our body. As well as the physical loading through our skeleton sending bone building signals to key weight bearing areas, there is also work required by our body to pump the blood back up from our feet, our muscles are activated to hold us up against gravity, the collagen in our joints are squished and when released (when walking or moving) to suck fluid back into the collagen to keep it healthy. These are just a few of many healthy mechanisms that require gravity in order to be healthy.
- When we sit- only half our body (the torso) is being held upright against gravity. So the experience of gravity is only through that portion of our body (less than 1 G).
- When we lie down we only experience gravity through the thickness of our torso or legs (next to 0 G- similar to the weightlessness of space).
30-60 minutes of sitting leads to measurable changes in the body (e.g. fats and sugar processing). Sitting dampens down the vestibular system (responsible for balance), circulation is slowed, the lining of the blood vessels are weakened by not being stimulated. Oxygen doesn't get delivered as effectively and as deeply throughout the body, brain blood flow is reduced, metabolic system slows. Aaaarrrrggghh!!!!
So one of Joan's big take home messages is to develop good G-habits (gravity-habits).
- stand more (keeping in mind that prolonged static standing is problematic too)
- sit less total time
- interrupt your sitting every 20-30 minutes (just standing up has positive impacts)
- move more against gravity (walk, run, take the stairs, sit-down-then-stand-up as many times as you can in 30 seconds, exercise, gardening, play, anything, even just low level posture adjustments and changes in position. Moving and holding yourself against gravity creates beneficial impacts in your body.
Bed rest and reduced gravity produce and accelerate the changes associated with aging (poor balance, loss of muscle mass, loss of bone density, fatigue etc).
Prolonged sitting and immobility reduce the sense of gravity (even though we are constantly surrounded by gravity).
So although we are surrounded by gravity here on earth, we are depriving ourselves of the benefit.