Superhuman Strength With Normal Weight.... Plausible or Pure Fantasy?

[AeroGav]

I studied a bit of biochemistry a while back,  so from that angle :

Heat - human metabolism is only about 20% efficient converting the chemical energy into mechanical work.  The other 80% ends up as heat.

So,  when i'm on my bike I can do a 1000 watt sprint (just under one and a half horsepower) for a few seconds.   During that time I'm generating 4000w of heat.    My aerobically sustainable output is 220W.   That's a mere 900w of space heater boiling my blood.

Fat is our most energy dense fuel source,  and gram for gram it stores almost as much energy as petrol/diesel products.      Unfortunately our bodies have trouble burning it quickly.  Much over 100w and and the energy starts to come from Carbohydrate instead.   Why is this ?  Well,  it probably doesn't help that fat is not water soluble, and our metabolic reactions are things that happen to stuff thats dissolved in our body fluids, for the most part.      

Second,  carbohydrates are made into fats by stripping off their oxygen molecules.    Carbohydrates have a roughly equal number of oxygen , hydrogen and carbon atoms in them.   But oxygen is in the air all around you,  so get rid of them to improve the density of your fuel.    Except that   oxygen atoms have a stronger affinity for electrons that carbon and hydrogen, resulting in that end of the molecule becoming "polarised" with a slight negative charge.   This makes it easier for enzymes to latch onto and react with them, and allows them to dissolve in water.

Third reason, we're not a migratory species.   

So what about carbohydrates as a fuel source ?   Well,  they only give 4 calories per gram unlike fat which does 9 calories.  In practice, they are even less dense, because they are hygroscopic (attract water).  Your body only stores about a kilogram of carbohydrate (enough to last about 90 minutes) but that kilogram attracts 3 or more kg of water weight.   Still more energy dense than batteries though.

So,  our super human could be engineered to not store energy in the form of fat at all,  and store all of their excess calories as glycogen.   Or we could somehow invent a way to make fat burn as fast as glycogen, then happy days.

The other thing you could do is jack up our body temperature.  This will make heat dissipation more efficient,  and should also increase the rate of the chemical reactions in our body.  However you'd have to redesign all our enzymes and proteins to not break down in the heat.   There's no such thing as a free lunch either.    Enzymes that are more stable at higher temps tend to suck at lower ones.   These super soldiers would have to maintain this higher body temperature permanently or else suffer hypothermia.    Nature already does this - birds have a higher body temperature than mammals.

So to summarise - super soldier with no fat storage, all excess calories stored as glycogen,  and higher body temperature would do much better than a normal human if asked to run as far as possible in 24 hours with a heavy backpack.      However, owing to their less efficient energy storage, and higher basal metabolic rate to maintain the higher core temp,  they'd do terrible at surviving a famine.

[kerbiloid]

Afair, sumo wrestlers eat up to 10 000 kilocalories/day, i.e. ~40 MJ/day.
So, a human can be as mighty as a motorcycle. If not throttling it too much.

Edited October 30, 2019 by kerbiloid

[magnemoe]

 

Shadiversity did an video anlyzing this. 
https://www.youtube.com/watch?v=zS9xBLVA6zM&list=PLWklwxMTl4sxf_Yvz8ePW7tcpDnhGpKV_&index=32&t=0s

He is looking at physic with an focus on melee weapon and not about how you got you strength. 

[Spacescifi]

12 hours ago, AeroGav said:

I studied a bit of biochemistry a while back,  so from that angle :

Heat - human metabolism is only about 20% efficient converting the chemical energy into mechanical work.  The other 80% ends up as heat.

So,  when i'm on my bike I can do a 1000 watt sprint (just under one and a half horsepower) for a few seconds.   During that time I'm generating 4000w of heat.    My aerobically sustainable output is 220W.   That's a mere 900w of space heater boiling my blood.

Fat is our most energy dense fuel source,  and gram for gram it stores almost as much energy as petrol/diesel products.      Unfortunately our bodies have trouble burning it quickly.  Much over 100w and and the energy starts to come from Carbohydrate instead.   Why is this ?  Well,  it probably doesn't help that fat is not water soluble, and our metabolic reactions are things that happen to stuff thats dissolved in our body fluids, for the most part.      

Second,  carbohydrates are made into fats by stripping off their oxygen molecules.    Carbohydrates have a roughly equal number of oxygen , hydrogen and carbon atoms in them.   But oxygen is in the air all around you,  so get rid of them to improve the density of your fuel.    Except that   oxygen atoms have a stronger affinity for electrons that carbon and hydrogen, resulting in that end of the molecule becoming "polarised" with a slight negative charge.   This makes it easier for enzymes to latch onto and react with them, and allows them to dissolve in water.

Third reason, we're not a migratory species.   

So what about carbohydrates as a fuel source ?   Well,  they only give 4 calories per gram unlike fat which does 9 calories.  In practice, they are even less dense, because they are hygroscopic (attract water).  Your body only stores about a kilogram of carbohydrate (enough to last about 90 minutes) but that kilogram attracts 3 or more kg of water weight.   Still more energy dense than batteries though.

So,  our super human could be engineered to not store energy in the form of fat at all,  and store all of their excess calories as glycogen.   Or we could somehow invent a way to make fat burn as fast as glycogen, then happy days.

The other thing you could do is jack up our body temperature.  This will make heat dissipation more efficient,  and should also increase the rate of the chemical reactions in our body.  However you'd have to redesign all our enzymes and proteins to not break down in the heat.   There's no such thing as a free lunch either.    Enzymes that are more stable at higher temps tend to suck at lower ones.   These super soldiers would have to maintain this higher body temperature permanently or else suffer hypothermia.    Nature already does this - birds have a higher body temperature than mammals.

So to summarise - super soldier with no fat storage, all excess calories stored as glycogen,  and higher body temperature would do much better than a normal human if asked to run as far as possible in 24 hours with a heavy backpack.      However, owing to their less efficient energy storage, and higher basal metabolic rate to maintain the higher core temp,  they'd do terrible at surviving a famine.

I really like your analysis, but I think you may be leaving something out significant.

 

The fuel budget will be much greater than that of an ordinary human to compensate for the superhuman feats.

Thus I do not know if it can work as a scifi concept at all, if a superhuman has to spend time eating large meals constantly throughout the day to both maintain body temperature and energy levels.

It really depends on how often he/she has to eat large meals to maintain that body temperature. How hot we talking? Like hot enough for a human to be sweaty, although they must get hotter still before they sweat? Hot enough to burn stuff sounds not likely.

EDIT: On the other hand, if their homeworld is naturally frigid, being really hot blooded could be a boon, though on Earth they would need a cryosuit to survive so they could literally not overheat due to the warmer temperatures.

Edited October 30, 2019 by Spacescifi

[wumpus]

13 hours ago, AeroGav said:

Third reason, we're not a migratory species.  

I'm not sure being a persistence hunter is all that different from being a migratory species.  And most of the reason we aren't a migratory species is simply too many humans to allow that (humans are too territorial to allow *other* migrant humans to waltz through).  It is entirely possible that humans were pretty migratory back when evolutionary forces on human strength levels stabilized.  Granted, I wouldn't expect anything intercontinental: during such huge migrations somebody would get the bright idea of fortifying obvious passes and demanding tolls from migrants.

Human internal carbohydrate sources are good for running ~14-18 miles (this becomes painfully obvious while running a marathon).  Expect to walk large parts of longer distances, all the while consuming food (so humans would have to forage while migrating).  Backpackers likely go much further than this, but there is a reason that when you think of nomadic tribes you think of people on horseback (I suspect most of the horses are pack animals).