Human body under pressure

[Shadow]

Hi all,

 

as far as I know, it's a long established fact that when the human body is under stress (ie. someone is chasing you with a gun), it will be able to accomplish physical (and mental?) feats impossible under normal circumstances. I haven't read up on this or anything, so I am unaware if there are other factors to be considered, but I am under the impression that adrenaline plays the biggest role in this. However, there are differences. For example, you might be under stress to catch a train for work you can't afford to miss, so you'll run faster than you normaly would. But if a killer with a 9 mil was chasing you, I think we'd all agree you'd be running a lot faster. So the burst of speed, or strength, or whatever, varies depending on the situation. My question is, how fast, strong, etc. are we really? I realize that depends on the individual, but is there any common limit beond we simply can't go?

 

Also there is such a thing as adrenaline overdose....I was wondering if the body could overdose itself.

 

Cheers,

 

Gabe

[Mr Skeptic]

We are strong enough to physically damage ourselves (eg break our own bones). I suspect that the reason we don't function at the limit is because we would destroy ourselves if we did.

[katcongrave77]

Yes adrenaline does play a huge role in allowing the human body to do things that are normally not possible. But there is more!

 

When we are faced with stress, like trying to catch a train or running away from being shot the brain receives that in the form of stress. The stress and emotions we are feeling, like fear or anger stimulate the hypothalamus in your brain. This controls your stress and relaxation in your body. When the hypothalamus recieves the message of stress then it sends out messages to the adrenal glands causing the sympathetic system to react by sending adrenaline (epinephrine) and noradrenaline (norepinephrine), hormones to cause the body to react stronger than it would in a normal everyday situation. These hormones cause these hormones raised heart rate, increased respiration, dilation of the pupils, slowed down digestion and allow muscles contraction.

Adrenaline comes from the adrenal medulla a region of the adrenal glands that is above your kidneys it allows blood to flow easier than normal in your body allowing a higher percentage of oxygen to be in your blood, thus allowing your muscles to be able to function and be stronger to out run someone, or in some amazing cases allow people to lift cars off hurt people and allow humans to fight for their lives against bears and survive. Also when adrenaline is released it speeds up the the conversion of the body's fuel source glycogen into its fuel glucose faster than normal, allowing the body to be stronger yet.

 

The strength of the person depends on many factors, like age, gender, ethnically, physical fitness, and the ability of their body to react. A body builder would be able to react better to adrenaline than a small child would. There is many factors that would determine the strength of a person feeling adrenaline.

 

There is no set limit really to what human strength can do with the help of adrenaline. Unfortunately no one has bothered to really test the limit of the human body. Obviously harm to the body, like breaking of bones, tendon damage, ect would be a limit, but no one has really tested the idea. Someone really should.

 

In theory adrenaline overdose could happen, because too much of anything is bad for the body, but there has been no recorded cases of death or harm caused by adrenaline overdose as far back as 1900. Before they didn't keep very good records that I could get to.

 

Hope that answers your questions. =]

[Shadow]

So they don't know how much epinephrine one can inject without harming themselves? That's strange, I though you had to be real careful when introducing adrenaline to the body. I'm astounded no research has been done in this field. But thanks for your answers.

 

Is it possible, with enough mental discipline, to control how much adrenaline get's released into your blood, or even release it at will? As in, has anybody tried? People can slow their hearts down, so why not this...it's certainly a lot more useful

[Mokele]

We are strong enough to physically damage ourselves (eg break our own bones). I suspect that the reason we don't function at the limit is because we would destroy ourselves if we did.

 

Um, no. I have never heard any verified report of bones being broken solely due to muscle contractions without some *major* confounding factor (such as osteoporosis). Bones are VERY strong, and most muscles are not oriented in a direction which would make it easy to break them.

 

Adrenaline comes from the adrenal medulla a region of the adrenal glands that is above your kidneys it allows blood to flow easier than normal in your body allowing a higher percentage of oxygen to be in your blood, thus allowing your muscles to be able to function and be stronger to out run someone, or in some amazing cases allow people to lift cars off hurt people and allow humans to fight for their lives against bears and survive. Also when adrenaline is released it speeds up the the conversion of the body's fuel source glycogen into its fuel glucose faster than normal, allowing the body to be stronger yet.

 

Actually, blood flow and nutrient levels won't increase strength at all. They'll increase the length of time you can function at maximum levels, but not the actual maximum force. Maximum force is strictly a property of the muscle proteins and the cross-sectional area of the muscle.

 

There is no set limit really to what human strength can do with the help of adrenaline. Unfortunately no one has bothered to really test the limit of the human body. Obviously harm to the body, like breaking of bones, tendon damage, ect would be a limit, but no one has really tested the idea. Someone really should.

 

Actually, yes, there is. Muscles have a well-known maximal force per unit cross-sectional area, which is very consistent across all animals (including humans), with only a few variations and influences. Adrenaline *does* increase maximum force, but not to an unlimited extent (it appears to depend upon a wide variety of factors, including muscle fiber type).

 

Mokele

 

So they don't know how much epinephrine one can inject without harming themselves? That's strange, I though you had to be real careful when introducing adrenaline to the body. I'm astounded no research has been done in this field. But thanks for your answers.

 

In 3 seconds of googling, I was able to find that it can be done (via injection), and the lethal dose in rats is 1.0 mg / kg

 

Is it possible, with enough mental discipline, to control how much adrenaline get's released into your blood, or even release it at will?

 

You could theoretically release it at will via stimulating the 'fight or flight' reflex, but I don't think it's physiologically possible to control the amount.

 

Mokele

[Shadow]

You're right, I should have Googled that before asking. But thanks for the information ;-)

 

So, since there is a lethal dose, it is possible for the body to kill itself by releasing too much adrenaline into the bloodstream?

Also, I was wondering, is artificiality the sole difference between adrenaline and epinephrine ?

[hell0o7]

You're right, I should have Googled that before asking. But thanks for the information ;-)

 

So, since there is a lethal dose, it is possible for the body to kill itself by releasing too much adrenaline into the bloodstream?

Also, I was wondering, is artificiality the sole difference between adrenaline and epinephrine ?

 

Adrenaline and epinephrine are equivalent terms.

[blike]

Also there is such a thing as adrenaline overdose....I was wondering if the body could overdose itself.

Mokele has done an exellent job with your questions, just want to point out pheochromocytomas as an example of an endogenous 'overdose' of adrenaline.

[John Cuthber]

I have heard that strychnine poisoning can cause the muscles to contract so vigorously that the bones break. If that's true then the muscles are strong enough to break the bones but the body normally doesn't use that potential.

[Mokele]

I highly doubt that - bone is very strong, and we actually *do* maximally recruit muscles during extreme but voluntary events (long jump, weight lifting, sprinting, etc.). Indeed, most vertebrates have at least a safety factor of 3 for their bones in terms of the maximal forces, both from muscles and external influences (impacts with the ground, etc.).

[Mr Skeptic]

Um, no. I have never heard any verified report of bones being broken solely due to muscle contractions without some *major* confounding factor (such as osteoporosis). Bones are VERY strong, and most muscles are not oriented in a direction which would make it easy to break them.

 

http://www.health.state.ny.us/diseases/communicable/tetanus/fact_sheet.htm

What are the complications associated with tetanus?

Complications include spasm of the vocal cords and/or spasms of the respiratory muscles causing interference with breathing.

Other complications include fractures of the spine or long bones from stiff muscles

, elevated blood pressure, abnormal heartbeats, coma, generalized infection, clotting in the blood vessels of the lung, and pneumonia. Death occurs in about 11 percent of all cases, especially in persons 60 years of age and older and unvaccinated individuals.

 

Tetanus prevents the relaxation of muscles, resulting in severe and incremental contraction of the muscles. That under these circumstances, the muscles can break bones (the bones are not weakened, nor the muscles strengthened) seems to indicate that the muscles are physically capable of breaking your own bones. I've also heard of bones being broken during electroshock therapy, but I don't know if that is due to swinging/impact or muscular strength. I've also heard of people breaking their bones arm wrestling, though that might be their opponent's fault.

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I highly doubt that - bone is very strong, and we actually *do* maximally recruit muscles during extreme but voluntary events (long jump, weight lifting, sprinting, etc.). Indeed, most vertebrates have at least a safety factor of 3 for their bones in terms of the maximal forces, both from muscles and external influences (impacts with the ground, etc.).

 

I think that part of the reason we hardly ever break our own bones is because we are not normally capable of contracting them in damaging ways. We can use dozens or hundreds of muscles to aid an action, but they are used cooperatively.

 

It is difficult for us to move muscles in certain ways, for example many people have trouble doing a circular motion with one hand and a patting motion with the other. An even harder one to do, that I've never seen anyone who can do is to have their arms in front of them (like when crossing arms) and then to move them in a circular motion in opposite directions (like one arm over the other, but with one arm moving in the opposite direction). Same with twiddling your thumbs in opposite directions. The point being that even though our muscles may be strong enough to break our bones, we can't normally contract them in opposition to actually do so, barring unusual circumstances.

[Shadow]

I've also heard of people breaking their bones arm wrestling, though that might be their opponent's fault.

 

I once saw a video depicting just that, but as you said, I think it's much more probable it's the fault of the opponent. I mean, if someone had the ability to clench his muscles that hard, I think it would be reasonable to assume he'd have won the game before his bones snapped. And at least in the video I saw, they were pretty much equal in strength, and the game had been going on for more than a minute.

 

An even harder one to do, that I've never seen anyone who can do is to have their arms in front of them (like when crossing arms) and then to move them in a circular motion in opposite directions (like one arm over the other, but with one arm moving in the opposite direction). Same with twiddling your thumbs in opposite directions.

 

Can you describe that a different way?, I'm having trouble understanding it, and I'd love to try.

 

EDIT: Never mind, I just remembered what "crossing arms" means Anyway, I also didn't have much trouble doing this motion, although I admit it was more difficult than the thumbs.

 

Same with twiddling your thumbs in opposite directions.

 

This didn't really take much effort. A much harder one is have your arms stretched out in front of you, and draw a square with one and a triangle with the other at the same time (repeatedly). I only manage that for two-three seconds at a time, unless I slow way down.

[Mokele]

Tetanus prevents the relaxation of muscles, resulting in severe and incremental contraction of the muscles. That under these circumstances, the muscles can break bones (the bones are not weakened, nor the muscles strengthened) seems to indicate that the muscles are physically capable of breaking your own bones. I've also heard of bones being broken during electroshock therapy, but I don't know if that is due to swinging/impact or muscular strength.

 

Both electroshock and tetanus result in spasms, not just sustained contractions. I did some searching, but was unable to find anything clarifying whether the fractures due to tetanus were from muscles alone, or, more likely, due to impacts associated with powerful spasms. I did also find many refs on bone fracture during epileptic seizure, again due to impact.

 

I think that part of the reason we hardly ever break our own bones is because we are not normally capable of contracting them in damaging ways. We can use dozens or hundreds of muscles to aid an action, but they are used cooperatively.

 

That would be applicable, if I was just thinking of what happens normally, but I'm thinking in absolute terms, gleaned from in-vitro data.

 

The maximum force a muscle can produce is 30 N /cm2

The failure stress of trabecular bone is 655 N /cm2

The failure stress of compact bone is 16500 N/cm2

 

So, a muscle pulling on a bone (since all they can do is pull) would have to be 550 times the size of the bone in order to break it, a condition which not only does not occur in the human body, but doesn't occur anywhere in the bony vertebrates.

 

This also leaves out muscle failure - muscles themselves rip and fail at around 1.5-2 times their maximal force. The muscles would be destroyed long before they broke bone.

 

Bones aren't minimally designed, either. Even in birds, bones tend to be built to widthstand 3-5 times the maximal load they could face even in the most strenuous possible situation.

 

The numbers just don't add up.

[Mr Skeptic]

How about this one:

 

http://www.jbjs.org.uk/cgi/reprint/37-B/3/466.pdf (warning: pdf)

Fracture of the spine is a recognised complication of tetanus (Quinlan 1954). In this case

there were several unusual features. The tonic spasm of the muscles of the neck, trunk,

abdomen and lower limbs remained intense for a long time, even remaining in the calf

muscles of the right leg forty-seven days after the onset. In addition the occurrence of the

paroxysms for twenty-four days is unusually prolonged.

When the acute exacerbations of the spasm occurred it was noted that there was little

head-retraction. The spasms appeared to cause vertical compression of the spine, the head

being drawn down towards the thoracic inlet. It appears likely that the compression fractures

of the vertebrae were caused as much by the powerful, continued, tonic spasm as by the

paroxysmal exacerbations. The latter caused very little actual movement of the trunk, the

muscles being almost fully contracted in their tonic state. The fracture of the manubrium

was undoubtedly caused by the acute flexion of the thoracic spine.

 

Remember that we have many muscles, and working together they can have a lot of strength. In this case, it seems that several muscles were responsible for the fracture.

[John Cuthber]

Comparing anything to the compressive strength of bone is a bit misleading since things (not just bones) seldom fail in straight compression.