Why astronauts get back pain.
You might think that spending time in space with no gravity would be a nice rest for your back, but you would be wrong. Studies have shown that over half of US astronauts experience back pain during their missions, and that overall they have more than 4 times the risk of getting herniated discs compared to the general population.
It used to be thought that this increase in back pain problems was due to their intervertebral discs swelling after taking in extra water during periods of weightlessness. However, a 2022 study where a group of astronauts were MRI scanned before and after space missions, showed that this wasn’t the case. What the study did clearly show was that their lower backs both became stiffer and lost muscle mass. The decrease in movement in their backs was around 25%, and they lost about 7% of lean tissue in a key lower back muscle called multifidus. This is a deep stabilising muscle that contributes to the natural curve (lordosis) of the lower back. Previous studies have also shown that astronauts' lower backs tend to lose their natural lordosis shape, becoming more flattened.
So what can we learn from this study?
For me, this is a classic illustration of the ‘use it or lose it’ principle. Our backs, and in particular our discs that sit between our vertebrae, rely on constant loading to remain healthy. The study also shows that it doesn’t take much of a loss (7%) of the key muscle (multifidus) to change the shape of the lower back and predispose you to disc herniations.
Importantly, it’s not just astronauts that have problems with weakened multifidus muscles. Studies in the general population have clearly shown an association between decreased size (atrophy) of the multifidus muscles and lower back pain. The good news is that it’s possible to increase the size and strength of your multifidus muscles by following a simple exercise program.
A classic way of training your multifidus muscles and developing more control and stability in your lower back is by performing the ‘bird dog’ exercise. See the short 1 minute video below for a demonstration of how to perform the exercise. Please note, some people may need a gentler version of the ‘bird dog’ to start with, so don’t do it if it is causing any pain.
Back pain, particularly low back pain is one of the main things I treat, so if you are worried about your back and would like an assessment of your back’s mobility and strength, including a tailored exercise program, please book an appointment (25% discount for astronauts).
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