# Would a suit that acts as extra-cardiovascular system allow you to run indefinitely?

Generally, when you run a long distance or do something particularly strenuous, you start breathing heavily because of a decrease of oxygen in your blood. Your gasping and weezing is in an effort to replenish that oxygen that you used up while you were working hard.

So let's say that there exists a suit that contains extra blood and a pump of sorts that adds oxygen and nutrients to your blood. It's basically an external cardiovascular system that constantly filters out your used up blood and replenishes it with the oxygenated and nutrient rich blood. Now you have two systems working at keeping your blood refreshed.

Would this help you run farther distances without feeling winded? What would be the most effective way to incorporate this addition to your current cardiovascular system? (I was thinking lots of needles, but ickkk).

• You gasp and wheeze because you are unfit. If you train at running (or any aerobic activity) you'll increase your cardiovascular capacity, and be able to run long distances at a reasonable pace - e.g. marathons and ultramarathons - at which point you'll discover that it's not the CV system that's the limiting factor, but muscle fatigue. – jamesqf Jan 3 '17 at 18:06
• I think you might want to look up "blood doping", of the kind that has been such a controversial occurrence in various sports. It's very close in effect to what you want, and doesn't even have to be physically on a person, and this requires no new technology. You could use that as a basis to extend into a more high-tech future, while still remaining science-based. – BrianH Jan 3 '17 at 18:59
• @Faulkner: Marathon runners are out of breath because it's a race, and so they typically finish by putting everything they can into one last sprint to the finish line. If you're just out for fun - trail running, for instance - you don't do that big finish. My point is that JUST improving the CV system with artificial assistance isn't going to do much, because then you run into the next weak point. Just as, to turn things around, doing pure strength training doesn't do a lot for CV endurance. – jamesqf Jan 3 '17 at 21:06
• Probably not. At some point the joints in your feet, knees, possibly hips, and back are going to be so swollen and painful that you will wish to be put out of your misery. I cannot imagine that the body's healing process would outpace the deterioration caused by running. I am not an expert though so I am completely open to being corrected. – MonkeyZeus Jan 3 '17 at 21:27
• If you want to compare with a fictional version of this, Peter F. Hamilton's standalone novel "Fallen Dragon" has the main character wearing a "skin suit", a biomechanical power armour suit which plugs into the wearer's circulatory system, so that both blood supplies become symbiotic during use. To answer your question, this allows the wearer to run faster, swim deeper, jump higher, and so on - but only to the limits of body+suit blood combined. It's like having two bodies to draw from; you'll still run out of energy eventually, and be forced to stop and recharge (suit and person both). – flith Jan 4 '17 at 10:35

The process of getting winded is actually quite complicated! There's more to it than just oxygenation.

Stanford developed a prototype to extend one's capacity for exercise. They didn't need an external cardiovascular system. All they needed was a fist. It turns out that a surprisingly large amount of what makes us fatigue is temperature. Our body decides to stop exerting itself if it thinks it can overheat to the point of damaging itself. They developed a heat exchanger that work with the palm of the hand, and it showed dramatic effects for increasing our endurance.

Oxygen actually has less to do with exercise than you might think. We're actually more concerned with getting CO2 out than oxygen in. CO2 levels in the blood make the blood more acidic, and that can cause serious issues for many metabolic processes. Meanwhile, hemoglobin is very good at its job. Generally speaking, even in extreme exercise, oxygen saturation doesn't dip below 95%. Below 90% is consider hypoxia, and below 55% is typically considered fatal (though there was some awesome data gathering done on Everest which showed climbers not only surviving at 40% saturation, but climbing. Just shows how much it's mind over matter!)

In fact, where you really run into issues with long distance running is energy. As it turns out, the brain is a bit of a conundrum for evolution. If you put enough energy storage (i.e. sugars) in the brain, it actually spreads things out too much and the brain doesn't do its job as well. The body has to store sugars for the brain elsewhere. The solution is marvelous, and centers around the hormone insulin. The brain actually subsists entirely on energy stored in the liver as glycogen (the animal equivalent of starch), and the liver releases that into the blood stream as glucose to be consumed. Of course, glucose feeds other parts of the body too, like muscle. If you were running too hard, your muscles might try to rob the brain of glucose, which could be bad.

The solution is insulin. All skeletal muscles and adipose tissue, which together make up 2/3 of the body's mass, are not permitted to pull glucose out of the blood unless there is insulin present. When you eat, your body recognizes that there's sugars/starches in the food, and releases insulin to permit the muscles to capture their share of it. When the food has been consumed, the body stops producing insulin, and the liver starts emitting the glucose it picked up during the feast. The only muscles that are allowed to pick up that glucose are the cardiac muscles and the smooth muscles which line hollow organs (essential for processing more food when it arrives... we also find smooth muscle lining the cardiovascular system to control blood pressure).

When doing long distance running such as marathons, runners experience what is known as the "bonk." It's a wall that occurs, for most people, around the 18 mile mark. What has actually happened is that the liver only stores about 4 hours of sugars to work with, and runners hit 18 miles around the 4 hour mark. At this point, your brain starts running into trouble. It literally lacks the fuel to keep making good decisions. The muscles still have plenty of glycogen to keep themselves going, but the brain has run out!

The solution is simple: a sports drink. The little bit of sugar in the drink quickly hits the blood stream and perks you right back up.

In the end, a suit may not be needed at all. Enter the world of Ultra-marathoners and the infoamous the iron man triathalon. Iron man is a 2.4 mile swim, 112 mile bike ride, and a 26.2 mile run, done over the course of a day. These individuals clearly can keep functioning for long runs, but there is a limit: sleep. At some point, you have to stop running to sleep. Any run which tries to avoid sleeping is going to have new problems that aren't solved by a mere cardivascular suit. For some sense of what those look like, consider looking at the demands of the military, where making it to the correct location is literally a matter of life and death. Even there, sleep is prized.

In the end, long distance endurance is a lot more than just oxygen content. There's a vast multitude of interconnected factors which all line up to form endurance. We are one complicated machine indeed!

• +1 for explaining a very complicated system in simple terms! Although I guess I'd say that for the simplest form of OP's question, the answer is actually No. I'm curious, though, could you think of a solution that would boost performance in the way he's wanting? Might require some more info from OP first though. – automaton Jan 3 '17 at 19:45
• @automaton I think the level of effort would have to be expanded upon. If you wanted to be able to run at a dead sprint for 10 minutes, external muscles may be the most effective way to maximize endurance. For the longer term solutions, a system which promotes cooling and provides a feed of glucose could permit some very long runs, but I'm not too familiar with the side effects of a continuous glucose source like that... there may be nasty ones. – Cort Ammon Jan 3 '17 at 20:08
• One small point: triathlons are, I think, different from ultramarathons, which are just running longer than marathon distances - typically 50 or 100 km or miles. – jamesqf Jan 3 '17 at 21:12
• Any run which tries to avoid sleeping is going to have new problems that aren't solved by a mere cardivascular suit although there was that story a few years back about this guy who won a cross-country foot race because he (apparently?) didn't realize he was supposed to get a bit of sleep at night... completely changed how that race is now run. – Michael Jan 4 '17 at 5:21
• One thing you missed is the muscular fatigue due to lactic acid accumulation that will impar muscular function (i.e. movement). But I +1'd your A all the same. – Mindwin Jan 4 '17 at 12:18

I see two ways to look at this problem. You have in mind either some form of hardened suit or exoskeleton, or you're thinking of a lightweight jogging suit-style apparel. I'll discuss both of these for completeness.

## Exosuit

First off is the hardened suit/exoskeleton option, which I will simply call the exosuit. The biggest problem I see with this is the weight issue. According to this medical catalog, a heart-lung machine has a shipping weight of 500 lb. (226.8 kg). Even if we supposed we could improve that technology such that the weight is reduced by half, it'd still be unreasonable to attempt to run with it. You may as well make the suit fully mechanized, which also significantly reduces the stresses on the human occupying it and increases performance. With this setup, oxygen infusion happens constantly with minimal maintenance.

## Soft Suit

The soft suit, on the other hand, might be more workable. I'd see it coming equipped with a backpack of sorts that contains a power supply, a pair of small pumps, and a reservoir of oxygen-laden microparticles. Probably also a sensor to detect the wearer's blood oxygen level. When the suit detects your oxygen levels getting low, it turns on the two pumps, one to add microparticles and the other to remove excess fluid to offset what is being pumped in (it's not much). With this setup, oxygen infusion lasts only until the reservoir is depleted, at which point you're lugging around an extra 20 lb. (9 kg) of dead weight.

## Injection

Adding oxygen to a person's bloodstream via a machine isn't an easy process. The most efficient way would be to inject directly into a major vein, such as the femoral vein. However, doing this is hazardous to health as the femoral artery and vein occupy the same part of the body and severing either is an effective means by which to kill someone. This activity is not conducted outside of clinical settings except in emergencies.

## Conclusion

So it can be done, there's existing research to support it, and it would improve oxygen-related performance, but there are significant risks that might make it infeasible.

• I was picturing more of a soft suit, but thanks for covering both options. – Faulkner Jan 3 '17 at 17:52
• Do you think it would be possible to avoid injecting directly into the femoral vein by having multiple smaller insertion points? – Faulkner Jan 3 '17 at 17:55
• @Faulkner It could be possible. There would need to be injection points somewhere in the bloodstream before the femoral, as that's the vein that collects it all and sends it to the heart. The farther back in the system you go, the more points you could use. I'll leave it to someone else to figure out the optimal balance. – Frostfyre Jan 3 '17 at 17:58

You'll not be surprised to learn the the US military has looked at exoskeletons to help soldiers on the battlefield. With current technology, the results show clearly that using the exo-legs is more strenuous for the soldier. Rather than easing their burden, it makes it worse! This says something pretty clearly about 3 billion years of evolution being pretty good at optimizing us, and the difficulty in improving on it. Your scenario assumes that more blood means more oxygen will be available to the muscle cells AND that the limiting metabolite is O2. I direct you to Wikipedia/Muscle fatigue for more information. You'll note that it doesn't mention O2 as a factor. So, I think your question's answer boils down to: for someone with poor physical conditioning, it would probably help a lot. For someone in excellent physical condition, it would probably help marginally. You'd be supplying more nutrients - such as phosphcreatine - and I assume removing more metabolic wastes. The question is, where do you put the shunts? Well there's two obvious choices: into the femoral artery (and vein). Gosh, you better hope nothing goes wrong: you can bleed out in seconds if you cut your femoral artery. The other "obvious" choice is splicing into the aorta or iliac artery (and vein). If this doesn't also sound dangerous, then you're not paying attention. It's believed that body armor has increased femoral exsanguination rates, I don't know why. It seems to me that in theory two hearts (if properly coordinated, a big if) could be better than one - and that's part of what we're talking about. Whether in real world practice, they'd be well enough coordinated is a different question. And you'd need the extra weight of the pump, filter, nutrients, control and monitoring circuitry - built in such a way as to be as efficient as a system developed (by trial and error) over 3 billion years. But let's say we grow a human heart, lungs, kidneys, liver (all no doubt genetically modified/augmented) and put them in a box on your back then hook you into them via a serious hole in your abdomen (bacterial infections, anyone?) and you get maybe double your current stamina - hey, why not triple? This begs the question: for what reason? We're not the best running animals anyway. Would you start with a Fiat 500 to design the fastest car in the world?

• > We're not the best running animals anyway That depends. Take a look at persistence hunting. True, humans are not fastest runners around, but outrunning someone in the long run is kinda what we can do and what OP asks about. – Daerdemandt Jan 3 '17 at 22:45
• @Daerdemandt: Take a look at sled dogs, though. Run a thousand mile race, then go out and start running another one the next day. As long as it's decently cold, they leave humans, and probably everything else, way back in the powder snow. – jamesqf Jan 4 '17 at 18:29

The main reason you feel cardiovascular fatigue when running (especially when beginning) is clearing carbon dioxide, not lack of oxygen. Your blood O2 levels are usually easily enough maintained on the inhale, what you're feeling is CO2 buildup forcing you to exhale more often. Try focusing on a stronger exhale if you're feeling fatigued when running.

As others have said, low glycogen levels are probably next, and that can be in as little as 2-3 hours. And then real muscle fatigue after that.

No. Oxygen is only one factor in producing energy to run. The other is fuel. If you can't keep up the fuel level in your body (see articles on how to fuel for long distance running to avoid "bonking"), it doesn't matter how much oxygen you have - there's nothing for it to burn.

It's all about lactic acid accumulation...

As Laurent Messonnier from the University of Savoie explains, the difference is that your aerobic capacity is a measure of your cardiovascular system performance, while your lactate threshold is your ability to clear lactate from your blood and convert it back into energy.

Perhaps your suit can somehow offload the lactic acid so that the body's muscles can continue to perform at peak efficiency?