Breathlessness and being "fit"

Hi apparently being breathless means that you don’t have enough oxygen in your blood… if you got more oxygen in your blood either with an oxygen mask or maybe having it pumped into your blood, would you never get breathless? Also what does being “fit” mean in terms of breathlessness… does it mean your heart is good at pumping oxygen into your blood? Why do unfit people get breathless easily while fit people have a lot more endurance? How does being “fit” work? Stronger heart muscles? Enough glucose in the blood?

As a very unfit (and overweight) person trying to get fit and being breathless when going for a morning walk, I am very interested to read the answers to your question.

Multiple factors: lung function, heart function and circulatory function are all closely inter-related.

As you become more fit, many of the pieces work more efficiently, and you develop better aerobic capacity. Some of this is due to better lung function, some by a ‘stronger heart’, and some by just being stronger and more efficient.

If you have a chronic heart or lung condition, you will reach a lower peak fitness than someone who is otherwise healthy.

‘Breathlessness’ in healthy people is predominantly due to hypercapnia (accumulation of carbon dioxide in the bloodstream and tissues), although hypoxia (low oxygen) will also contribute to a much smaller degree.

‘Dyspnea’ is commonly experienced as breathlessness or shortness of breath. There are myriad causes for dyspnea; what they often have in common is a subjective sensation that the results of breathing seem less effective than they should be for the effort expended. This subjective sensation can often be confirmed objectively with one test or another.

For example, an overweight person may have to work harder than a lean person just to expand the chest and pull down the diaphragm. This means extra work for the same result. In addition, the heavier person has to move more mass and do more work for the same walk. Someone more accustomed to walking or running distances will have developed a more efficient circulatory system within the musculature; they also are likely to have a more efficient stride as well (‘practice effect’).

This is assuming no underlying heart or lung disease.

Your blood is already saturated at close to 100% O2 anyway so increasing the oxygen delivered to your lungs would make a minimal difference. When you exercise the muscles in your body demand more fuel and the heart pumps faster to deliver the oxygen to your muscles and to deliver de-oxygenated blood to your lungs for a refill. Your lungs have to have a higher flow of air to maintain the supply of oxygen to your blood, hence the heavy breathing.

Even fit people get breathless doing moderate exercise it’s just that they can do more for longer because their system is more efficient and if they weigh less their muscles don’t need to work as hard to achieve the same outcome as a heavier, less fit person.

Hi apparently being breathless means that you don’t have enough oxygen in your blood.

Nope. Your body doesn’t have oxygen sensors and doesn’t know if you have any oxygen at all in your system. Being breathless means your body is producing excess CO2 and you’re trying to get rid of it. It’s the presence of CO2 in your blood that makes you feel like you need to breathe. If you breathe pure nitrogen, for example, you will suffocate and never feel like anything is wrong as long as you’re breathing out CO2.

Also what does being “fit” mean in terms of breathlessness… does it mean your heart is good at pumping oxygen into your blood?

Your heart does not pump oxygen into your blood. Oxygen enters your blood in the lungs and CO2 is eliminated in the lungs. When you hold your breath, it’s the buildup of CO2 that makes you feel the need to breathe, not a lack of oxygen.

As for fitness, it’s a whole body situation that involves way more than you would imagine. For example, your ability to contract your muscles is tied to how many neurons you can get to fire and that ability is tied to how much work your muscles are used to doing and your available levels of neurotransmitters. If your muscles are used to do doing very little work, then neurons will atrophy and your levels of neurotransmitters will fall. When you exercise, it stimulates your complete neuromuscular system to produce more of everything you need from thicker muscle bundles to more neurons to higher levels of neurotransmitters.

If you have two people who weigh the same, they both need to do the same amount of work to climb a set of stairs, but the fit person will be less tired at the top because their body is adapted to a higher level of work. They have more of everything they need.

So if you were hooked up to a machine that got rid of the CO2 in your blood would you stop being breathless?

What does being more efficient mean exactly? That the lungs can breathe more deeply? Stronger heart muscles?

Your point that CO2 is the driver is correct in that it is by far the main driver, but we do also have oxygen sensors and there is in fact actually a “hypoxic drive” as well. Again, though, mostly CO2 levels drive it.

Really that’s just a quibble.

The other points, especially that cardiorespiratory fitness is an issue of how the whole system works efficiently both the individual parts and the way in which they coordinate, is the key take-away.

What does that mean exactly though? Do the lungs get better at extracting CO2 from the lungs? Also it only takes me a few seconds of sprinting to start to get breathless… does the CO2 in my blood really build up that fast?

Yes it does. But some response comes even before the CO2 builds up in anticipation based on messages from the muscles to the brain and from there to the muscles that power the lungs to give the lungs a head start on working harder.
Exactly what that (how the parts and how they coordinate improve) means is a chapter in a physiology textbook. I can briefly sketch it out some …

A more fit person’s heart is able to pump more blood with each beat (referred to as “stroke volume”) and thus is able to move more blood through the lungs and the rest of the system for any given number of heartbeats. It fills bigger and empties fairly well.

A more fit person’s vascular system reduces resistance more in response to exercise allowing the blood to get around with the pump not having to work quite as hard. That occurs both in the tissues, like the muscles, and in the lungs, allowing for more efficient gas exchange in addition to the heart having to work less hard. These changes occur in a coordinated manner with increases in cardiac output (which happen by way of more heart beats and increased stroke volume per beat both). The coordination is key.

The muscles are more efficient at getting oxygen out of the blood and into the tissues. (Mostly by changes in the number, size, and function of the cells’ powerhouses, the mitochondria. But also by growing more capillaries in the muscles so there is more surface area for exchange. That increase in capillary number also occurs in the lungs as a chronic adaptation to endurance exercise.)

With more vigorous exercise the muscles release more of something called lactic acid (lactate) into the blood. It mainly happens when muscles are working with less oxygen than need to work “aerobically” so they switch to “anaerobic” metabolism, which makes more lactate. Up to a certain point of production it can be removed as fast as it produced. Once it exceeds that level the blood lactate increases quickly and makes some particular breathing receptors start going more nuts and respiratory rate increases dramatically. That point is called the lactate threshold. A more fit individual takes longer to produce enough lactate to do that. More oxygen getting into the muscles means less lactate production and a higher lactate threshold. Many endurance training programs are focused on increasing that lactate threshold.

To clarify the yes it does. Partly yes it does because it takes very little upward change in blood CO2 levels to trigger those central receptors. It is tightly bound.

I guess to get fit quicker I’d need to put up with extended lengths of uncomfortable breathlessness but normally I stop jogging after it starts to get uncomfortable.

Getting fit and maintaining fitness necessarily involves putting your body under a certain amount of stress. If you’re not getting breathless and feeling uncomfortable then you’re not doing it right. This doesn’t change no matter how fit you are. The trick is to find an activity that you actually enjoy doing so you don’t mind feeling uncomfortable. Do it enough and you will start to associate the uncomfortable feelings of physical exertion with the enjoyment you get from the activity. This is a personal thing, some people enjoy running, some hate it. some, like me, enjoy having gone for a run but don’t actually enjoy doing it. Running is not my ideal activity. Currently my ideal activity is mountain biking, because I really enjoy it. I look forward to being able to get out on the bike, I am naturally motivated.

Find an activity you enjoy, whether it be bush walking, rock climbing, road cycling, mountain biking, swimming, rowing, or whatever. Ideally find something that has minimal barriers to entry. Walking is very good because the only thing you need is your body, a pair of shoes, and 30 minutes of spare time. Rowing is not so good because you need access to a boat, you need to get out to the water, etc etc.

I am getting breathless and uncomfortable when I jog for the a while… but I soon stop and walk for a while to get my breath back. An alternative would be to keep on jogging and put up with increasingly unpleasant breathlessness for 30 seconds or more at a time… it could even become almost unbearable if I kept on jogging… I think my approach is causing me to become fitter just more slowly than I could be…

I would like to climb a mountain I used to live near. BTW when I am getting short of breath I am a bit worried that it could be medically dangerous if I kept it up for too long. I mean maybe I might collapse or something.

Lately I’ve been walking for 30-60 minutes at a time… but I never felt breathless… then lately I’ve started jogging or sprinting for some of the time. Sore muscles also stop me from jogging as often as I’d like.

Doing something is certainly better than doing nothing. My point was just that you shouldn’t expect it to be easy or get easy. As you get fitter you will still feel breathless and a bit uncomfortable but you will be going further and/or faster. If you like walking and running there is a program called “couch to 5k” that you can download for free from the Internet. It is a structured way to build up from being able to jog for 30 seconds at a time to being able to run for 30-35 minutes. All you need is a pair of running shoes and a watch.

It would be a good idea to go and see a doctor and just make sure it is ok for you to do strenuous physical activity

See above about the couch to 5k program. As you gain fitness different bits of your body will hold you back. Sometimes it will be your muscles, then they will get better and for a while and it’ll be your heart/lungs, it might flip flop a bit. You just have to stick with it. Give yourself achievable goals. Don’t feel that all is lost if you suffer a set back. Don’t go too hard to soon. You’re better off repeating a week of the C25K program and stretching it out a bit than sticking rigidly to it and risking an injury.

Richard Pearse:
At the moment I’d have trouble jogging for 30 seconds especially after I’ve done a few cycles of it. The first day involves about 8 minutes of jogging within 20 minutes…
http://www.coolrunning.com/engine/2/2_3/181.shtml
I don’t expect it to be easy but I don’t want it to be almost unbearable either. BTW it talks about jogging 60 seconds at a time - not 30 seconds. BTW I think I normally jog faster than it seems to be talking about. They talk about jogging 10 km/h…


easy walk is 5 km/h, racewalkers are 8-10 km/h
Since I set myself a short distance goal for jogging I guess I don’t pace myself so much

Some medications can interfere with the whole process. I take antihypertensives, which interfere with normal physiologic responses during exercise. When we hike uphill, I struggle to keep up because my heart rate doesn’t increase as it ideally should.

John Clay; there’s a long way from breathlessness/panting to collapse. Along the way you’d feel dizzy/lightheaded.

By a very long shot. Inactivity is a killer. The difference between no exercise and walking briskly for 20 minutes a day (or half an hour 5 days a week) on mortality rates (risk of death in some defined next period of time) is large, most estimates placing it as cutting those rates in half.

If you are interested in making more progress than that then you do tolerate some degree of breathing harder. But you do not need to push it to an uncomfortable place to make progress. You make substantial progress while keeping your level of hard breathing to the point at which you can still talk easily and in complete sentences, it would just be a bit hard to sing a whole song. That’s “the breath test” and that level marks the “moderate exercise intensity” level. If you are breathing hard enough that you cannot say more than a couple of words without pausing for breath then you are up into “vigorous exercise intensity” level. Most general plans are built around first developing a base at the moderate activity level and then adding in bouts of vigorous level, gradually increasing their duration and/or their frequency … again though, even without any vigorous level exercise huge health benefits are gained.

A few years ago, I started training for a Tough Mudder, which is one of those muddy obstacle courses. Tough Mudders run 10-12 miles (fortunately not all at once :slight_smile: ), so running is an important part of training. I hadn’t run in many years, but I had run in my youth and I did work out fairly regularly on an elliptical (while watching TV). How hard could it be?

I swear, on my first run, after one or two blocks, I was DYING! Every few blocks or so I was drinking from my water bottle- I felt really thirsty, but I think it was my brain fastening on any excuse to stop or slow down.

I did get better with some work. One strategy for pushing yourself (both mentally and physically) is to go “just a little farther”. A bit farther than where you really wanted to stop, a bit farther than last time, etc. Some people keep going by “moving the goalposts”- they think to themselves, "I’ll make it to that next tree, … I mean to the corner, … I mean to that building, … etc, until they have run their goal.

A lot of this is mind over body. Nothing wrong with taking things slow, but as others have said, you will have to push a bit at some point.

If the distress feels unnatural (and I know it is hard to tell that if you are unfit), a checkup is not a bad idea at all. (One of the hidden health benefits of exercise is that being accustomed to using the ‘machinery’ near peak demand gives you better knowledge of what your body is capable of; when it doesn’t respond “right” to stress, it may be an early sign of disease. On the flip side, you get used to mentally powering through all kinds of discomforts, so probably it helps build up a bigger cushion for denial. )