The Human Body: A Heater Rather Than an Engine?

and a GA! Pretty funny.

Maybe we should have a FA button for funny answer. There are a lot of them, but they don't really contribute in any meaningful way....... Never mind, I just had a flash of the circus that could occur if everyone was competing for FA's, not pretty! Moderators would be jumping from bridges! Best just leave it alone, since most FA's are responses to FUQ's, (funny unintelligible questions). What did you think I meant?

I remember a BBC programme on the design of the Concorde. In the mock up to check heat balance, they used 100 watt bulbs to simulate the people except, one or two were resistors to generate 115 watts to allow for those who had been partaking of alcohol.

They should have also had a few Molotov Cocktails, to simulate people that had been drinking for several days. I'm kidding, making light of the subject because I can't figure out what the OP is looking for.

At rest 100 Watts. Hunter in tree freezing his ----- off. Burns just 80 Watts to keep warm, don't believe it.

You are a true sportsman!

The sums are correct but I don't think they are the right sums.

The relay runner is not accelerating the whole way. Or at all?

If you can do similar calculations for a marathon runner,a weight lifter(snap),swimmer, pole vault jumper etc it will illustrate the ratings of a human body similar to ratings of an electric cable having four current ratings(steady state,cyclic,emergency,short circuit).

What about what i overheard " Of course Usain Bolt broke the world record ! i would have done too, if i had a big guy called Gay running after me!" .. can we factor in 'incentivised acceleration' in the formula?

CR4 Admin Deleted Post

This post was deleted because it did not adhere to the behavioral policies of the site. Please review Section 14 of the CR4 Site FAQ and the CR4 Rules of Conduct.

My understanding is a fit cyclist can maintain about 300 watts, top end guys about 500W.

I think rowers have the highest sustained output, about 1kW, they get to use every muscle - I know from limited experience.

One fatal flaw behind that 3.5 Hp human engine. Sustainability.

Short burst peak power is not the same as continuous run power.

Given the standard for a 2000 calorie a day diet that 2000 calories is the same energy as 2.32 Kilowatt hours per day or just under 100 watts per hour. Some people use more some use less but thats the overall agreed upon average.

The average human is estimated to be able to maintain a continuous work load of around 1/10 Hp or roughly 75 watts load on top of their basal metabolic rate needs. And again that still has a working time limit based on how many hours a day a healthy person can maintain that load. Since the average person needs around 8 hours of sleep and several more hours a day of low effort time as well very few people would even be able to sustain that 75 Watt output for more than a few hours under normal conditions without the need for a rest period.

And again this are the average numbers based on the life of Joe average who is of average physical condition, physical health, and diet.

Fat slob Bob is obviously going to be far less capable of sustaining that 75 watt load for any length of time. But super athlete Fred could probably push that number at double or triple the 75 watt average for many hours on end and likely could do short bursts into the tens of times more peak capacities during momentary bursts.

This is basic high school level health and fitness information most everyone should have learned at one point in their life. Who actually paid attention that day is however is a different matter.

Since the OP posted his question in the form of an answer, my question to guest is, How can I slow down Usain Bolt to the point that he can sustain power to my trolling motor for an entire day? And if that's possible, what do I feed him to keep him from getting fidgety and jumping off the boat? Please don't tell me that "Guest" is posting erroneous google answers! That is, by far, the weakest way to attain a GA.

kramarat, you are justt pissed off because you dumb ass Guru's could not work out what the Guest worked out.

Right you are. Since I couldn't figure out what the OP was after, there was no way I could figure out how guests formula pertained to it.

On a dare when I turned 60 two falls ago, I built this 1200 frame house on top of the concrete basement walls completely by myself, cutting, carrying up and nailing together the entire frame second floor, walls, roof trusses, sheathing, siding, porch decking, wiring, doors and windows in 800 hours. Roughly 3000 calories a day averaging 6 hours of labor a day because of travel time.

Beautiful work! Is 60 when reality kicks in? I've got a little way to go. Thanks for sharing your awesome project with us, keep us posted. Don't forget, finishing is the hardest step of all!

Oh, yes, sorry for the old pic, it's done...designed it all too, by the way.

Awesome!!! I've accomplished a couple of projects also that I need to sneak in here, nothing to compare to yours, a little boat restoration and a workshop, but, I can say I did it! Wait a minute, I'll post them now if you don't mind. Be right back.

I can't get the pictures to come up. I will do it tomorrow.

where are the pictures of the f&%kin boat and workshop. I need something to help me sleep.

Here you are guest, hope these can help you get to sleep.

Horse Power.

HP.

A horse is capable of lifting a 550 lb. weight one foot in one second. That's the definition of this particular unit of power. Now, as a human, you couldn't come close to this power output (750 watts approx.), but you probably could raise a 55 lb. weight one foot in one second (75 watts).

http://www.businessdictionary.com/definition/horsepower-hp.html

Horses weigh in at around 2000 lbs. and humans, lets say, 200 lbs. so the power to weight ratio is similar.

Now this sportsman, whether hardly working or working hardly, is producing energy via mitochondria mainly to vibrate (imperceptibly) their muscles to maintain body temperature and to feed the brain, which uses the majority of the body's oxygen and energy supply.

To get an additional 80% , or 800% under extreme conditions for a few hours for muscle exertion is pretty good.

So to answer your question, humans are not really designed to perform physical work efficiently but to think and keep warm.

Orangutans, on the other hand, will kick any humans butt even if the weight ratio is 4:1. They are very strong.

So, avoid pissing off orangutans if you can

I once made the mistake of hiring the best mason I've ever know to lay up some concrete block walls on Labor Day, ironically the only day he could get off from his regular job.

He didn't bring a laborer so I had to lift and stack the 500 35 pound blocks for him onto the 6' high scaffolding he was working on. Plus shovel the 3000 pounds of mortar mix up onto the scaffold also. We worked 10 hours straight.

If my math is right that is 3000+35x6x500=108000ft.#/550=196.4/10=19.64hp per hour/60=0.33hp per minute/60=0.0055hp per second or 4 watts per second sustainable work.

I was pretty much maxed out. I remember reading a research paper on the optimum size of a hand shovel used to unload coal cars was one that held 5# of coal, shoveled every 2 seconds which allowed a worker to work and entire 12 hour day, non-stop with only a lunch break (circa 1910). This comes to only 10800 pounds of coal per man. Union scale I guess. :)

"Now this sportsman, whether hardly working or working hardly, is producing energy via mitochondria mainly to vibrate (imperceptibly) their muscles to maintain body temperature and to feed the brain, which uses the majority of the body's oxygen and energy supply." Two inaccuracies here. The muscles do not spend their time imperceptibly vibrating at any stage of rest or activity. Either they are at rest or they are actively contracting, either in the form of active exercise or in shivering when the body temperature drops. The body keeps warm by chemical processes, notably the breakdown of ATP, which occur both in muscles and elsewhere, which generate heat. The second inaccuracy is in the oxygen consumption of the brain, which is about 50 ml/min, or roughly 1/5 of the total body oxygen consumption. However, it is true that the body generates, even at rest, about 100 watts to maintain the body temperature.

When I was power lifting I would regularly do reps(2-5) on a leg sled of 1000 lbs +. The distance traveled was more than a foot.

You are right about an orangutan; an average one could pull Arnold Scwarzenegger's arms off like wings on a fly.

So, what's the output of a marathoner ot ultra-marathoner?

Seems like I saw what Scott Macready's output was on the Gossamer Albatross' flight across the English Channel, and I was pretty flummoxed by how much power that guy could, and had to, sustain for 22 miles or so. I'll look it up and see if I can find it.

Come to think of it, I'm not sure that was the right name, either. I think I'm confusing the team lead on the project and the pilot, and combining their names.

Back in a few.

Dr. Paul McReady was the design driver for the Gossamer Albatross. Bryan Allen was the pilot and power source. Still can't find the data on power output during the flight, though.

Back in a few. I hate these piece-meal postings.

Can't find any data on the Gossamer Albatross, but since Bryan Allen was preceded on the project by a marathon bicyclist, and Wikipedia had this:

"In lab experiments an average "in-shape" cyclist can produce about 3 watts/kg for more than an hour (e.g., around 200 watts for a 70 kg rider), with top amateurs producing 5 watts/kg and elite athletes achieving 6 watts/kg for similar lengths of time. Elite track sprint cyclists are able to attain an instantaneous maximum output of around 2,000 watts, or in excess of 25 watts/kg; elite road cyclists may produce 1,600 to 1,700 watts as an instantaneous maximum in their burst to the finish line at the end of a five-hour long road race." at the URL:

http://en.wikipedia.org/wiki/Human-powered_transport

That will probably go a ways toward answering the question, in comparing known values for defined levels of capability in a well-known sport, with well-observed requirements.

Help any?

Thanks. Interesting that a body at rest is producing 80 watts and in full, sustained motion only jumps up to 200-300 watts. At least on a bike. I'm an avid mountain runner and go out on 1-2 hour runs covering 10-20 miles with, up to, 14,000 feet of elevation change. I would have thought power output for this kind of endeavor exceeds 300% the resting state of the body.

Ignoring the distance covered (which I know does use a lot of energy), just raising 75Kg over the 14000 foot in an hour requires a sustained 872 Watts.

Walking up the stairs is a good way of burning energy:-

mgh= 75X10X3= 2250. I reckon 4 seconds is reasonable so that's about ½ a KWatt

Both answer 7

"Burns just 80 Watts to keep warm, don't believe it"

and answer 15

"producing energy via mitochondria mainly to vibrate (imperceptibly) their muscles to maintain body temperature and to feed the brain, which uses the majority of the body's oxygen and energy supply"

touch on parts of the answer to your question.

First, DO believe answer 7. We MUST produce heat to warm our bodies under any circumstances, since we are "warm blooded" beings. And we were designed to produce that heat by self-contained processes. (And yes, I do, personally, believe that God designed us that way, since I know SOMEONE will ask.)

Second, answer 15 provides one of the ways we warm ourselves.

Finally, and this is also a power source for the "vibrating muscles" (yep, we hum like small dynamos even when we AREN'T singing to ourselves. or, alternatively, listen in a very quiet place and time to the swish-thump of your own pulse. Your heart requires power to beat, as every muscle in your body requires power to operate) we are fascinatingly complex laboratories of exo-thermic (net balance, because we have both exo- AND endo-thermic reactions ongoing) chemical reactions that run continuously, doing such things as converting oxygen, water, carbon, hydrogen, etc., including many trace materials, to usable compounds, while at the same time removing many deleterious materials via our waste products. And all of those processes combined have a net-exothermic value.

So, our bodies at rest produce some resting energy state, approaching 100 watts. Anything we produce above that is a combination of work performed, and the increase in the metabolic chemical processes, with attendant net gain in total exothermic output needed to support muscles working at increased output.

Our brains, though, don't seem to require measurably greater amounts of energy whether working or "at rest" (another subject entirely, but brains really don't ever "rest", until we die).

My question arose after one of the Discoveries channel's programm which was telling about a discovery and then the reconstruction of a medieval Venetian big galley. Among anything else they wanted to find out how quick the galley had moved so they measured the power a professional rower can produce (for a time, probably hours) - it turned out 80 Watts (so the ship with 150 rowers should have the total constant pushing power of 12 KW and the galley may have the speed of 11 km per hour).

The power mentioned surprised me a bit : if JUST the heat human bodies produce could be utilised then there should not be the need for so many men - toiling hard !

Except that you have to understand the difference between total power output, and applied power output. In this case, the total power output would be the 80 watts per rower plus the 100 watts (at least, I'll bet they were working up a sweat, too!) of heat output per body (where rower equal "body doing the rowing" and body equals "any human body present whether rowing or not"), so the 80 watts they cite per rower does NOT include, nor is it a fractional part of, the 100 watts a body at rest produces just staying alive. Hence, at least a 180 watt output for that rowing session, per person.

I'll bet that was one stinking, wet, humid, hot oarsman's gallery.

I'm glad I wasn't a sailor then, anyway.

The Discovery said it were the galleys that had brought plague to Europe in 1348.