Welcome back to the Midlife Strong interview series, where we tackle new and innovative lifestyle/health factors for midlife women. I’ve been following the research on inspiratory muscle strength training (IMST) for a while now and got the chance to pick the brain of Daniel Craighead, one of the key researchers in this area.
Daniel H. Craighead is an assistant professor with Integrated Physiology of Aging Laboratory at the University of Colorado Boulder. His research interests include how IMST can lower systolic blood pressure and improve overall endothelial, cerebrovascular, and cognitive function.
I was a little flustered during the interview because my screen was dark. I passed all the health checks and couldn’t figure out what was wrong. So, we continued with the interview and later I realized the light I attached to my laptop was covering the camera!
So please forgive the dark screen. Next time, I’ll get it right. Here are some links from the interview, including options for breathing devices. I’ve also included the transcripts which have been edited for clarity.
Studies:
Devices:
Transcripts
Maryann: Thanks for coming on this interview series! Just to let our listeners know, you’re Daniel Craighead assistant research professor of integrative physiology of aging lab at the University of Colorado Boulder. Can you start off with what got you into this line of work?
Daniel Craighead: Yeah, absolutely. I got my bachelor's degree in exercise in sports science from Ithaca college. I've always had this interest in how exercise can be used as a tool to improve health. After completing my undergraduate work, I wanted to go on to grad school. I had some research experience and really wanted to become a professor and do research on ways that exercise could be helpful for us and kind of as I was progressing through my studies.
I got really interested in the barrier to adherence that we have with exercise. I don't think there's anyone out there that would argue that we shouldn't exercise. We all know exercise is good for us. But despite that over fifty percent of adults in the United States don't perform enough exercise to meet current public health guidelines meaning they're not as healthy as they could be if they would just exercise a little more. So, I got really interested in why that might be and came up with evidence-based exercise interventions to improve health that also overcome those barriers to adherence so when we look at common barriers one of the big ones is time availability. People just don't have enough time in the day to fit exercise into their schedule. And if you need to say, go to a fitness center or buy expensive exercise equipment, those can be barriers as well.
I got really interested in this intervention called high resistance inspiratory muscle strength training (IMST) which involves breathing against resistance through a handheld device performing only 30 resistive breaths per day which takes little time (over five minutes). So it's something that's very time efficient that can be done in the comfort of your own home and for that reason I suspected it would promote excellent rates of adherence and there was some research coming out of the University of Arizona from Dr. Fiona Bailey's laboratory she was testing this respiratory intervention in patients with obstructive sleep apnea so it makes some intuitive sense sleep apnea is a condition where people stop breathing at night. So, a respiratory intervention may improve their sleep apnea symptoms. And what Dr Bailey's laboratory was seeing was not actually really much of a change in sleep apnea or sleep quality but a surprising reduction in blood pressure when people did high resistance inspiratory muscle strength training 30 breaths a day for six weeks. That really got me interested in this as a potential lifestyle and intervention that could have cardiovascular benefits in sort of the broader population while also promoting adherence. That's how I got interested in studying this.
I got really interested in this intervention called high resistance inspiratory muscle strength training (IMST) which involves breathing against resistance through a handheld device performing only 30 resistive breaths per day which takes little time (over five minutes). So it's something that's very time efficient that can be done in the comfort of your own home and for that reason I suspected it would promote excellent rates of adherence
Maryann: Yeah, it's really interesting. Can you touch on the significance of nitric oxide, oxidative stress, and endothelial function in relation to aging and midlife women's health?
Daniel Craighead: Yeah, so the endothelial cells form the inner lining of our blood vessels are critically important for preventing cardiovascular diseases and healthy endothelial cells produce a compound called nitric oxide. Nitric oxide causes our blood vessels to dilate or get wider when we need to increase blood flow throughout our body, and it also prevents atherosclerosis. We need nitric oxide for our blood vessels to stay healthy. However, as we get older the availability of nitric oxide in our blood vessels goes down. And that's in large part due to increased oxidative stress. So, when we have oxidative stress those reactive oxygen species that our body starts naturally producing at higher levels react with Nitric oxide and actually reduce it, so we no longer have as much nitric oxide available. To maintain blood vessel health. So that deleterious change tends to happen with aging in all adults including women. Women are generally protected from this until they go through menopause. There is something about estrogen which seems to prevent oxidative stress from damaging the cardiovascular system and impairing endothelial function. But as you go through that menopause transition, because there's less estrogen available, that protective effect goes away and we see a pretty rapid change in cardiovascular disease risk in postmenopausal women and that corresponds with a reduction in nitric oxide availability and impaired health of those endothelial cells.
Maryann: I actually do talk a lot about this on my Substack so it's nice for people to hear it from someone else because it's not really talked about a lot, right? I mean nitric oxide isn't mainstream. Aerobic exercise is one way to enhance endothelial function with age. But with midlife women especially as they go through menopause, some studies show that they don't always get that boost from aerobic exercise. Can you touch on that.
Daniel Craighead: Yeah, so pretty consistently if you take a midlife or older man and have them do an exercise training intervention for let's say three months and you measure their endothelial function before and after that exercise training, they'll see an improvement in endothelial cell health. When women go through the same exercise intervention, we don't as consistently see those improvements. For some reason not all the benefits of aerobic exercise seem to be accrued by women who are postmenopausal. And part of this, we think has to do with time sense menopause so as we're learning more about this phenomenon. If you have a woman who is in perimenopause or only slightly postmenopausal and have her start an exercise intervention at that time point, there’s a window where they can exhibit that improvement in endothelial health and function. But if you take someone who's late postmenopausal, the ability to respond to aerobic exercise fully seems to go away unless you supplement estrogen back. Our laboratory has shown that you can restore that beneficial effect from aerobic exercise so women who take hormone replacement therapy and do an exercise intervention see an improvement in endothelial cell health. But of course, there are some potential contraindications to taking exogenous estrogen when you're postmenopausal so it's not a perfect solution for everyone. So that means for postmenopausal women, there's really a need to look for other interventions that can improve their endothelial cell health and prevent cardiovascular disease risk. And aerobic exercise is not always as effective for them.
pretty consistently if you take a midlife or older man and have them do an exercise training intervention for let's say three months and you measure their endothelial function before and after that exercise training, they'll see an improvement in endothelial cell health. When women go through the same exercise intervention, we don't as consistently see those improvements. For some reason not all the benefits of aerobic exercise seem to be accrued by women who are postmenopausal.
Maryann: Let's say you have a perimenopausal woman who's been participating in aerobic exercise for a long time. If she continued to exercise through her menopause transition, would she still be getting the benefit? Or is that question not answered yet.
Daniel Craighead: I think the question isn't answered yet. This is an area that's only started to become studied more recently and there's definitely a need for more investigation. It seems like if you start it in the perimenopause or early postmenopause period you can see the same benefits, but I don't think the studies have not gone on long enough to know that. We don't know the long-term effects. We only know in the short term that they seem to get the same benefits. When we look at master athletes these are women who have been exercising at a really high intensity for a number of years.
When we look at them in the post-menopausal age, they tend to have endothelial cell health and function similar to their sedentary peers. So that would suggest that maybe at older ages farther away from menopause the effect could be lost. Regardless of whether you started exercising during perimenopause or not, I think that's still a question that needs to be fully answered.
Maryann: Yeah, and I'm really interested in other ways women can boost their endothelial health since it's a key risk factor and that's where the IMST research fits in. I know you're running a trial right now that maybe you can talk about how it might help midlife women.
Daniel Craighead: Yeah, so we did an initial study comparing six weeks of IMST compared to a low resistance kind of sham control group and we found that in a mixed group of midlife and older men and women. Six weeks of IMST improved endothelial function by about 45% which is a very robust response and clinically meaningful and when we looked at only the subset of postmenopausal women in the study, it seemed like their endothelial function improved as well. But one thing I want to caution people on is this was a small pilot trial. So, when we look only at the women we're now down to a really small group of people but at least it was a promising trend that has spurred further investigation for us.
Six weeks of IMST improved endothelial function by about 45% which is a very robust response and clinically meaningful and when we looked at only the subset of postmenopausal women in the study, it seemed like their endothelial function improved as well.
Maryann: What’s the mechanism?
Daniel Craighead: That’s still something we're trying to figure out. Our initial hypothesis was that when you perform a resisted deep inspiration that you would be changing blood flow throughout your body as your sort of core blood volume changes with the deep breath. In subsequent work, it really hasn't played out that that's the likely stimulus. Instead, I now think it's most likely substances released from tissues during exercise that go into the bloodstream and then have effects throughout the body. I suspect when your diaphragm contracts very forcefully to do this resisted breath in, it's releasing some sort of helpful compound that's interacting with endothelial cells and causing them to function better. That's where our data at least are pointing right now though we have more mechanistic research ongoing to try to figure out exactly if that's the stimulus or not.
Maryann: Do you think it could be that the diaphragm gets weaker with age and when you strengthen those breathing muscles, people are breathing better? Kind of like these hidden muscles that now are getting stronger and help people get the oxygen they need. I know in that study there was a decrease in CRP (inflammation) which helps increase nitric oxide. Do you think that could play a role?
Daniel Craighead: You know it's certainly possible. I like to point out that for this type of exercise there's likely multiple mechanisms at play. Like if you go for a walk or a run there's tons of different ways that that's helpful for you working through different pathways and IMST is a type of exercise as well, that’s also working through multiple pathways. So, I think improved function of the respiratory muscles could certainly be one as well. There are also connections between deep breathing and sympathetic nerve activity or that kind of fight or flight response. I think there's a lot of pathways likely involved working together in a complex manner for how we're seeing these improvements in cardiovascular health.
Maryann: Yeah, I think it's usually a variety of mechanisms. Were you surprised with the results of that 2021 study, such as the decrease in blood pressure. I mean in a review with IMST it was found to decrease systolic blood pressure by an average of 9 points. It's a significant amount.
Daniel Craighead: Yeah, so we saw a reduction in systolic blood pressure of nine millimeters mercury and a two millimeter mercury reduction in diastolic blood pressure that was about in line with what we were expecting based on Dr. Bailey's work and patients with obstructive sleep apnea. But it was helpful to see that in a generally healthy group of midlife and older adults that had higher blood pressure that suggested it was a more broadly applicable intervention that could help lots of people and not just specifically patients with sleep apnea. I think the improvement in endothelial function that we've been discussing was the more exciting and novel part. No one had looked at that as an outcome yet. So, we didn't really know if we would see a benefit or not. To see this more sort of comprehensive impact of IMST on cardiovascular health was very exciting.
Maryann: Yeah, I'm also excited about your latest not-yet published study that's comparing this high resistance IMST to standard care of aerobic exercise in postmenopausal women. Can you share what information you expect to gain from the study?
Daniel Craighead: I mentioned before that that small group of postmenopausal women in our pilot trial did see an improvement in endothelial function and that inspired us to now do a larger study where we are taking postmenopausal women who are not on hormone replacement therapy, and we're randomizing them to either three months of IMST (30 resisted breaths per day for three months) or they're doing one hundred and fifty minutes per week of brisk walking at a moderate intensity, which is the minimum current public health guidelines for aerobic exercise. And we will be comparing the two groups to see how much blood pressure goes down and endothelial function goes up. If the previous work from our laboratory holds, what we expect to see with IMST is a significant reduction in blood pressure, and a significant improvement in endothelial function. However, we don't expect to see that same improvement in endothelial function in the aerobic exercise group. This study will also let us get a little bit of a look at adherence to the intervention compared to other known healthful forms of exercise.
We suspect that IMST promotes high rates of adherence because it's so time efficient. But now we'll get to directly compare it to aerobic exercise to see if people do it more frequently and regularly.
If the previous work from our laboratory holds, what we expect to see with IMST is a significant reduction in blood pressure, and a significant improvement in endothelial function. However, we don't expect to see that same improvement in endothelial function in the aerobic exercise group. This study will also let us get a little bit of a look at adherence to the intervention compared to other known healthful forms of exercise.
Maryann: In your studies you guys use the Power Breathe device, right?
Daniel Craighead: Yes, we’ve using a device called the PowerBreathe K3. It's a handheld device that provides resistance when you inhale, and you can program in a range of resistances so we can set you know the appropriate training intensity for people in our studies. We've been using that device because it has a data storage system so we can objectively document that everyone trained at the appropriate intensity and how many training sessions they did. It is a very expensive device. I think it's up to somewhere between five hundred and six hundred dollars that you know we used for research purposes. But for sort of home use as someone who wanted to try this on their own, there are much more affordable devices out there that don't have the same digital data recording system, but you could get a comparably effective device for something closer to 60 or $70. The main thing I recommend is that a lot of the cheapest devices you can find out there don't go to a very high resistance so you couldn't replicate our research. We have people perform each breath at basically 75% of their one rep max. If you get the cheapest device, it won't go up to a high enough intensity. So, it's just important to make sure you're getting past just the sort of base level and into a slightly higher quality device so you can perform inhalation at a higher effort.
Maryann: Are there any brands you recommend? There’s one I found that’s called Expand a Lung which is around $30 Amazon but it's both inspiratory and expiratory where you breathe in and out and you can change the resistance.
Daniel Craighead: Yeah, so along with Power Breathe I've also been doing some work now in a study using the Aerofit device which is sort of comparable. I don't have any sort of financial arrangement with any of these companies and pay for their devices to use them in our research. So far, we've been seeing a lot of benefits with the Power Breathe so I've been sticking with it. But I think really anything that can provide a high enough level of resistance while you're doing a quick and powerful inhale, will get the job done.
Maryann: I would assume if more people started buying these that the prices would go down, right? How much more research will it take for a doctor to recommend IMST for someone who is seeing an increase in blood pressure?
Daniel Craighead: Yeah, so my hope is that we move sort of past these small laboratory-based clinical trials soon that show us the physiology of what's happening and start moving into large conventional physical trials. This is a clinical trial where you're looking at hundreds of people over a number of years and I think if we do that, and we see positive health outcomes then we're getting to a place where now maybe insurance will reimburse for these devices so they can be used really at low or no cost by people who need them to improve their cardiovascular health. That's my long-term hope if the research continues to have positive health outcomes. I think there already are physicians who at least recommend IMST as an additional therapy for people to try out and you can get generally affordable devices in our work so far, we haven't seen any real serious adverse events. We've seen a little bit of soreness in the neck muscles and a little bit of transient dizziness when people first start the training. So, It appears to be fairly safe. That being said, we do always recommend people check with our physician before starting it because it might not be right for everybody. But overall, you know you have a lot of potential benefits without a lot of real risks.
Maryann: Yeah, I mean I think that's what's so nice like the side effects with breathing exercises. I mean I guess if you’re really straining you have to be careful but you know it's not like a drug where there's always going to be unwanted side effects. I think it's really exciting and there have been other benefits to IMST such as sleep improvements. Are there any other benefits you've seen from your studies?
Daniel Craighead: Yeah, so we had people in our initial study perform a maximal treadmill exercise test until exhaustion, people in our IMST group were able to stay on the treadmill longer after their six-week intervention and we didn't see any change in our control group. So that suggests that people basically have a higher ability to perform aerobic exercise and we think this happens because when you train those respiratory muscles, they become more efficient. If you are exercising at a high intensity for a long duration your diaphragm will start to fatigue, and it'll actually steal blood flow away from your locomotor muscles. So, your legs if you're walking or running on a treadmill as the diaphragm becomes more fatigue resistant, it won't do that same steal of blood flow meaning you have greater oxygen delivering capacity available for the muscles and your legs so seems like for physical function. We did also look at the specific health of some blood vessels in the brain and we found benefits in blood vessel health in the brain. A lot of cognitive decline and dementia has a sort of vascular background meaning the blood vessels in the brain are becoming less healthy and that's contributing to the brain overall being less healthy. So that's something we're looking into more: longer training with IMST and benefits to cognition. You know we're seeing reductions in blood pressure and high blood pressure which is also a risk factor for dementia.
I'm pretty excited about cognitive function as another potential health outcome we'll see in our ongoing studies.
Maryann: Yeah, I mean it's all related, right? Heart disease is linked to brain function. Well, this is super exciting work and I really appreciate you coming on. Is there anything you want our listeners to know before we depart?
Daniel Craighead: I'll tell your audience that I do IMST myself but that's probably not a good reason for them to do it because there's a long history of scientists doing, you know, crazy things. But I think the stronger endorsement is that I have my parents doing it, so I do believe that it's safe and has the potential to be helpful without a lot of downsides. So, we're still investigating, and we'll see where the research leads. But so far it seems like in the studies that we've done, it’s been a very beneficial intervention.
I will point out that all the studies we've done to date are laboratory-based clinical trials, so we are interacting with our study volunteers on a weekly to daily basis. So, one of our next goals is to come up with ways to disseminate this intervention. You know it sounds pretty simple just taking 30 resistive breaths per day, but we've seen people do a little bit of off the wall stuff and not be able to do it on their own as easily as one would imagine. So, we're working on things like smartphone apps as a tool to deliver this to a larger group of people and that's another avenue we're working on.
I think the stronger endorsement is that I have my parents doing it, so I do believe that it's safe and has the potential to be helpful without a lot of downsides. So, we're still investigating, and we'll see where the research leads. But so far it seems like in the studies that we've done, it’s been a very beneficial intervention.
Maryann: Yeah, I think it's so great because people can do it just sitting at their desk. I mean it's pretty easy to fit in for most people.
Daniel Craighead: I often do mine while I'm cooking dinner.
Maryann: Well thanks so much and we'll be sure to follow up. When do you expect the study to be published?
Daniel Craighead: The study we have going on right now is a 5-year clinical trial. So, we still have a few years to go, but we've got some other studies in the works. There might be some other interim findings from.
Maryann: Oh bummer.
Daniel Craighead: Some other institutions are studying this intervention around the country so I don't think you'll have to wait too long before you know information on how this works and other patient groups or other potential benefits come to light.
Maryann: All right. Well, thank you so much for coming on. I appreciate it.
Daniel Craighead: Yeah, my pleasure.
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