Caroline spotted a new research article today that has just been published. The study has been done by a group of scientists in Australia (and that’s not the reason it’s upside-down) who work on a very similar area of research to us, looking at how the breathing muscles work and how they respond to different situations. One of the research team actually spent some time in our lab many years ago, so we know them quite well.
Normally, all of the breathing muscles (the main ones being the diaphragm, the muscles between the ribs and some small muscles in the neck) work together to make air move into the lungs. If breathing becomes more difficult (like when people have lung disease), or if your body needs more oxygen (for example during exercise), the brain “drives” the muscles harder by sending more electrical signals down the nerves to those muscles and making them work harder. What we don’t really know is whether the brain is able to decide to send different messages to the different breathing muscles at different times.
In this study, the researchers measured how much air was moving in and out of the lungs, how much the chest and tummy were moving with each breath, how much “drive” was going to the muscles (by measuring the electrical signals going to them), and how much pressure the diaphragm was making with each breath. The measurements were very similar to the ones you can see in two of our videos, including the mouthpieces and the tubes going up the nose and down into the stomach. They made these measurements with the person standing up, lying flat on a bed, and then hanging upside down!
So, we would probably think it would be much harder to breathe when hanging upside down, because your all of your intestines would be pushing up against your lungs, so breathing would almost be like weightlifting. The researchers did find that the pressure that the diaphragm muscle had to generate for each breath was increased (to push those intestines upwards). You’d imagine then that the brain would have to send much more “drive” to the muscles. But no – the researchers found that exactly the same amount of “drive” was going to the diaphragm, and in fact slightly less to the neck muscles than when the people were standing up, even though the people were moving the same amount of air in and out of their lungs with each breath and the diaphragm was doing more work.
So how does this make sense? Well, we know that the diaphragm muscle is in fact stronger when it’s pushed up further into the chest, so actually being upside down makes the diaphragm more efficient. This is why, for the same electrical “drive”, it was able to create more pressure. We have shown this in previous studies in our lab some years ago, and we actually repeat these experiments each year for a group of students. We do breathing muscle strength tests with relaxed lungs (at the end of a normal breath out), then again with completely full lungs (which makes the diaphragm flatten down), and then again after breathing all the way out (meaning the diaphragm is higher up in the chest and more ‘domed’). We see that the best results come from the ‘breathing out’ position, then the relaxed position, and then the lowest strength values from the ‘deep breath’ position.
What’s also interesting about the results of this new study is that it seems the brain is able to work out how efficient the different breathing muscles are at any given time, and then work out where it needs to send its “drive” to. This suggests to us that there might not just be one area of the brain that sends out all the breathing messages, but that it’s a more complicated process than we thought involving a lot more feedback loops. This might be very relevant to many of our studies, so we will be reading this article closely and the findings may well be really useful to us.
But – really and truly – the best thing about this study is that they tipped people upside down! Science really can be fun (though possibly not for the people being dangled over the end of a bed with tubes up their noses…).