How inspiratory muscle training (IMT) improves performance…in a nutshell

You can obtain more information about breathing training at www.breathestrong.com, where you can also find out about my comprehensive guide to breathing and exercise “Breathe Strong, Perform Better” (published by Human Kinetics Inc.). Scroll to the bottom of this page to visit the ‘Breathe Strong’ Amazon store.

So, having cleared the air in my previous Blog, this second instalment provides an introduction to how IMT improves performance, and explains why it has nothing to do with maximal oxygen uptake (VO2max), or inhaling more oxygen (a common misconception).

Let’s start by returning to the question of what people believe they know about the role of breathing in exercise limitation, and why it’s only half of the story. We’ll begin by considering a factor that is synonymous with training and improved performance – maximal oxygen uptake (VO2max). Most lay people  ‘buy into’ IMT because they [incorrectly] assume that IMT increases the amount of oxygen in the blood, thereby increasing VO2max. It’s therefore a surprise to learn that breathing more DOESN’T do any of this (find out why below). On the other hand, sport scientists know that breathing more doesn’t increase VO2max, so they find it hard to understand how on earth IMT can possibly improve performance. So for many people who know about VO2max, the ‘knee-jerk’ response to the concept of IMT is to conclude that it can’t possibly work, i.e., because there is no obvious underlying mechanism. However, IMT improves performance via an entirely different mechanism to VO2max, but one that is, nonetheless, linked to oxygen delivery. I’ll provide more detail in a later Blog, but what follows is the ‘abridged’ version of how IMT improves performance. If you want to know the nitty-gritty detail, then please revisit my Blog, as I’ll be discussing this in due course. In the meantime, you can also find out more in my book, “Breathe Strong, Perform Better” (see www.breathestrong.com or scroll to the bottom of this page to visit the ‘Breathe Strong’ Amazon store).

How IMT improves performance

Over the course of the past decade, an important cardiovascular reflex has been discovered. The reflex originates from the breathing muscles, and when it’s activated, it causes blood flow to the limbs to be restricted (a process known as vasoconstriction). Impairment of blood flow to exercising muscles reduces the delivery of oxygen and nutrients, as well as impairing the removal of metabolic by-products such as lactic acid. The reflex is activated when the breathing muscles are forced to work hard, or for prolonged periods, and it’s triggered by build-up of metabolic by-products in the breathing muscles (for this reason, it’s called a metaboreflex). The impairment of blood flow and oxygen delivery to limb muscles resulting from activation of the metaboreflex causes them to fatigue more quickly, thereby impairing performance. Research has now shown that the intensity of breathing work required to activate the metaboreflex can be increased by IMT. In other words, athletes can work harder, and longer before the metaboreflex causes blood flow to be directed away from their limbs. The result is that IMT improves performance in a wide range of sports and exercise modalities because it preserves oxygen delivery and metabolite removal from exercising muscles. It’s that simple, and that profound.

In addition to influencing the metaboreflex, IMT also makes breathing feel easier. Because the inspiratory muscles are stronger and more powerful after IMT, they are able to undertake the work of breathing more ‘comfortably’. In other words, the muscles are operating at a lower percentage of their maximum capacity, which makes the activity feel easier. For the same reason, being stronger also increases the endurance of the inspiratory muscles, delaying fatigue, and making breathing feel easier. Finally, because breathing feels easier, and because the limb muscles are better supplied with blood (delivering oxygen and removing metabolites), leg discomfort, and the sense of effort associated with exercise (perceived exertion) is also lower – athletes feel as though they are not working as hard.

Now you know how IMT does work, let’s finish by explaining why IMT does not increase VO2max.

Why breathing doesn’t limit VO2max

The transport of oxygen to the working muscles involves four stages:

1. Alveolar ventilation—Delivery of atmospheric air to the alveoli (breathing).

2. Pulmonary diffusion—Transfer of oxygen from the alveoli to the capillary blood.

3. Transport by the blood—Collection and delivery of oxygen in combination with the blood from the lungs to the muscles.

4. Tissue diffusion—Transfer of oxygen from the muscle capillary blood to the muscle cells.

There is no active transport of oxygen at any point in its journey from lungs to tissues. The entire journey occurs via a process of passive diffusion. During diffusion, oxygen moves from an area of high concentration (the atmosphere) to one of lower concentration (the muscle). The rate and efficiency of diffusion are directly related to the size of the gradient. Think of a river flowing downhill; the steeper the gradient of the hill, the faster the water flows.

In theory, any one of the four listed stages could limit the transport of oxygen. In practice, for people with healthy lungs who are at sea level (not at an altitude where the oxygen gradient is reduced), steps 1 and 2 operate with almost 100 percent efficiency in terms of their purpose, which is to oxygenate the blood fully before it leaves the lungs. Steps 1 and 2 are the only steps in the transport of oxygen that can be influenced by breathing, and because the blood is almost 100 percent saturated with oxygen when it leaves the lungs, increasing breathing cannot improve oxygen transport (the oxygenation of the blood is already almost 100 percent). In other words, breathing more cannot increase maximal oxygen uptake, and this is why people sometimes incorrectly jump to the conclusion that IMT cannot possibly improve performance. This is incorrect, so spread the word!

If you found my first blog interesting, please come back for further articles and news, as well as my musings on all things breathing and sport related. Also, don’t forget that you can obtain more information about breathing training at www.breathestrong.com, where you can also find out about my comprehensive guide to breathing and exercise “Breathe Strong, Perform Better” (published by Human Kinetics Inc.). Scroll to the bottom of this page to visit the ‘Breathe Strong’ Amazon store.

Clearing the air - Some myths about breathing training research

You can obtain more information about breathing training at www.breathestrong.com, where you can also find out about my comprehensive guide to breathing and exercise “Breathe Strong, Perform Better” (published by Human Kinetics Inc.).

Let’s start by defining what we mean by “breathing training”. In my definition, breathing training is the application of established principles of training science to the muscles of respiration, i.e., the breathing pump muscles. These muscles are of two types, inspiratory and expiratory.. I use the term “breathing training” as an overarching term as I would if I were referring to, say interval training. However, the term “inspiratory muscle training” (IMT), has a specific definition, i.e., resistance training of the inspiratory muscles. Similarly, EMT refers to resistance training of the expiratory muscles. The majority of research has been undertaken on IMT, and in a later Blog I’ll summarise the evidence relating to each type of training, and explain why the focus has been on IMT.

Although most people take the scientific evidence relating to IMT at face value, there are still a few misinformed “IMT deniers” whose scepticism does a huge disservice to a legitimate, evidence-based training method. In fact, IMT has more scientific credibility than most other products that are vying for the attention of enthusiastic sports people.

For this reason, I wanted to start my Blog on the front foot by exploding some common myths about breathing training research, as well as setting the record straight about my involvement in it. That way, we can begin with a clean slate, and readers can put behind them all of the misinformation that has been propagated by people who don’t know as much about sport science as they believe they do. Over the years, I’ve seen some pretty outlandish comments about breathing training on Blogs and forums (e.g., “it’s a scam”) from people with just enough knowledge to be dangerous, and too little to provide an accurate, insightful opinion on the scientific facts. Lots of people believe they know about the role of breathing in exercise limitation, but the truth is, they only know half of the story, and that’s why their opinions fall short of being useful (see my next Blog for an explanation of why).

As well as misinformation about the science, there’s also been some [reasonable] scepticism about IMT created by my involvement in the commercialisation of the POWERbreathe® inspiratory muscle trainer (www.powerbreathe.com). As a leading scientist in the area, I’ve played a pivotal role in the development of research on breathing training, but I also have a commercial interest in its results, and this creates an obvious potential conflict – the old, “well she would say that wouldn’t she” scenario. It has even been suggested that an entire area of scientific research has been fabricated in order to create a market for POWERbreathe®. What an extraordinary feat that would have been; to have hoodwinked so many reputable scientists into replicating my “made up” research. The truth is, it’s simply not possible to do this, and I have always been open and honest about my connection with POWERbreathe®. This being the case, it’s up to the readers of my research to draw their own conclusions about the veracity of the data and its interpretation.

In addition, it’s worth pointing out that I never set out to develop a breathing training product - POWERbreathe® came into being some 20 years ago because I needed a ‘tool’ to test a research hypothesis. The hypothesis was simple – does training the inspiratory muscles influence breathlessness and exercise tolerance in older people? Why older people? Because they are more breathless, have lower exercise tolerance, and weaker inspiratory muscles than younger people. The hypothesis seemed logical and worthy of exploration, but I needed to create a training device to test it, i.e., I need to create a ‘dumbbell’ to overload the inspiratory muscles, thereby training them. The resulting device was a little “Heath Robinson”, but it imposed a reliable inspiratory resistance, and became the precursor to the POWERbreathe®.  To cut a long story short (an entire PhD in fact), the research showed that making the inspiratory muscles of older people stronger, reduced their breathlessness and improved exercise tolerance. However, what I was to discovered next surprised even me. The results in older people led me to wonder what effect the training might have upon exercise tolerance in young, physically active people. To satisfy my curiosity, I suggested the question as a final year dissertation project for a BSc student. The results were, to say the least, surprising – performance also improved in people with perfectly normal inspiratory muscles. Why did this surprise me? Because everything I’d been taught as an exercise scientist led me to believe that breathing did not limit exercise performance. So the study was run again, but this time as part of a PhD research programme - the results were the same. So the study was run again, as part of a different PhD research programme – again, the same results. We found repeatedly that athletes got faster by doing nothing more than strength training their inspiratory muscles. Convinced the finding was real, the next step was to dig deeper to find out how this was happening….but that’s another Blog.

My first studies of inspiratory muscle training (IMT) took place in the early 1990s, and their results propelled me on a quest that I have pursued ever since. As for the commercialisation of POWERbreathe®, the finding that we could make people less breathless and improve their exercise performance by doing something as simple and quick (five minutes per day) as IMT got me thinking that I might have created something of some medical and sporting significance. After fruitless efforts to interest existing commercial companies in exploiting the POWERbreathe® patent, I came to the conclusion that the only way my innovation would see the commercial light of day was to take it to market myself. I might add that this was also the only way that the research could be perpetuated and proliferated; creating a commercial product, also created the opportunity for other scientists to undertake their own studies, which they have done in their hundreds.

I’ve spent the past 20 years of my professional life seeking an understanding of how breathing limits exercise performance, as well as figuring out how to overcome those limitations through training. Along the way, I have worked with a number of PhD students, all of whom were independent thinkers, and some of whom even started their research with the firm belief that IMT “did not work”. The result of our research speaks for itself – IMT does work. Furthermore, our findings have been replicated by completely independent scientists, many of whom were also “IMT sceptics” before they undertook their own studies. In common with all high quality published research, our research papers have been peer-reviewed by world-class, independent scientists whose role it is to ensure that only the best research is published. As mentioned above, in seeking publication for my research, I have always been meticulous about declaring my commercial interest in a breathing training product, because the potential conflict of interest that this creates is something readers of the research have a right to know. Despite all these ‘hurdles’, my research has been published in the top international scientific journals, and has also been highly cited by other scientists. That’s why it rankles me when I read comments suggesting that my research “is a scam”.

The purpose of this first Blog was to clear the air for what is to come. In doing so, I hope I have created an atmosphere of open mindedness in which to explore the fascinating, unfolding story of breathing training, and of breathing-related research. In the next instalment of my Blog I’ll address how IMT improves performance, and why, as is commonly assumed, it has nothing to do with maximal oxygen uptake (VO2max).

If you found my first Blog interesting, please come back for further articles and news, as well as my musings on all things breathing and sport related. Also, don’t forget that you can obtain more information about breathing training at www.breathestrong.com, where you can also find out about my comprehensive guide to breathing and exercise “Breathe Strong, Perform Better” (published by Human Kinetics Inc.).

Breathe Strong Blog Coming Soon

The Breathe Strong Blog is coming soon. I'll be posting regular articles, news, research and 'top tips' on breathing training. In the meantime, you can visit www.breathestrong.com for free information about breathing training, as well as a link to my newly published, comprehensive book on performance enhancement through breathing training - "Breathe Strong, Perform Better". The book is packed with scientifically based information, as well as giving practical guidance on getting the most from breathing training. With just 5 minutes of daily training, you can achieve a laboratory-proven increase in time trial performance of as much as 4.6% (www.ncbi.nlm.nih.gov/pubmed/12166881). To find out more, visit www.breathestrong.com, and follow the Breathe Strong Blog.