What Happens to Bones When You Stop Moving | Peter Attia AMA 37

What happens to your bones if you truly aren't using them? This is obviously not a subject that is relevant to a lot of people directly, but I think indirectly it's relevant to a lot of people. So this is, you know, space is just the most extreme version of what we would call disuse osteopenia. So as the name suggests, disuse osteopenia occurs when bones are chronically unloaded, leaving to a very unfavorable combination of high bone resorption and low bone formation. So it's the same thing that's happening with the osteopenia from aging. It's just much more accelerated and much more extreme. So again, the most extreme version of this is astronauts. And I don't know much about what they do in space, but I suspect that they go out of their way to figure out ways to load astronauts in space so that, you know, they don't have to deal with this in its highest form. But I think for most people where this is relevant is bed rest. So lots of people have to undergo bed rest for all sorts of reasons, right? Pregnant women often are placed on bed rest if they are experiencing fetal retardation. And I mean that not cognitively, but growth retardation, right? So if in the third trimester the fetus isn't growing at the rate that is expected, not uncommon that the OB will ask the mother to gradually reduce her impact until more and more energy can be reserved for the fetus. You can also see, you know, bed rest being necessary for various types of injuries. Of course, we know today that we don't want to rest people nearly as much as we used to. I mean, there was a day 50 years ago when if somebody hurt their back, they were put on two weeks of strict bed rest. Today we know that that's absolutely the last thing you want to do. So bone loss due to, you know, disuse osteopenia is incremental and it's progressive with time and it occurs more rapidly as you would guess in the trabecular bone than in the cortical bone. So this is the trend we've seen over and over again. And frankly, it can be about 2% per month in microgravity, partial paralysis, which I should have mentioned as well, so paralysis-based injuries or immobilization with injury. And in the most extreme setting with complete paralysis, it can be up to 7% per month. So Peter, for people who are experiencing that type of immobility, is there anything in particular they should be thinking about or they can do to kind of help with the BMD concern? Yeah, the first would be any form of PT that can actively load muscles. So I don't know if there's, I actually don't know how much data exists on this, but that's one of the things that I think is interesting about cyclic BFR. And that's why the minute I was out of surgery, I got permission from my surgeon to put my, you know, katsu cuffs on my arm and just start cycling the BFR. I wanted to put little bits of stress on that bicep just to have it moving. And again, keep in mind, I was very fortunate. I did not have a bicep tendon repaired. If I did, I would not have been allowed to do that. But, you know, I had to keep my arm completely immobilized, but I was still able to get sort of compression on the bicep. And, you know, basically if you, let's say you're bedridden with a certain injury, there are still other muscles in your body that don't pertain to that injury that can still be moved and put under load. And even if you're doing these things isometrically, right? So a person is holding you and you're resisting against them without actually moving in the bed. That's important. Now, there was a super interesting mouse study that we found that used a bisphosphonate to inhibit the osteoclastic bone reabsorption in a mouse model where the mice were given botulotoxin to basically prevent them from moving, I think, one part of their leg. So if you, I think we have this figure here as well. Yeah, it's figure 10. Yeah. So what you're looking at here is in the first bar on the left is just sort of the baseline. And then you have control mice in black. And then in white, you have what happens to the animal that we're just given botulotoxin. So these were the animals that were basically immobilized because botulotoxin, of course, paralyzes their legs. And then the botulotoxin plus the bisphosphonate on the right. And I think there's a pretty profound result, right? You're looking at this in the femoral neck and in the middle of the upper part of the femoral bone below the neck. And you can see that the bisphosphonate plus the immobility really looks no different from the control. And it's a clear contrast to how the untreated animal looks. So, you know, look, these are 16 week old female mice. You know, is this going to be true in humans? I have no idea, but I find this type of research very interesting. And frankly, I hope more people are doing this type of research because I think immobility is a huge problem with everybody. But once you start to deal with an aging population, it becomes more significant. How many times have we talked about that study where, you know, a group of 65 year olds, I believe were immobilized for two weeks and lost, if I'm not mistaken, something of the neighborhood of about four pounds of lean mass in two weeks. And that, you know, we talked about that through the lens of how much you lose lean mass, but think about what that's doing to BMD and think about how long people are immobilized beyond two weeks, especially as they're I'm Peter Attia. This podcast relies exclusively on premium subscribers for support, which allows us to provide all our content without taking a single penny from advertisers. I believe this keeps my content honest, making it a trusted resource for listeners like you. 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