Does it take more energy to go downstairs than upstairs?

I just found this website today, and there's some very interesting information here. One thing I do have to comment on, although I'm sure someone has already mentioned it: there are two types of actions your muscles can make--concentric and eccentric. A concentric movement is one where you use your muscle to move a weight e.g. pushing the bar away from your chest in the benchpress or pulling a weight toward your chest in a barbell row. An eccentric movement is one in which you use your muscles to resist a motion e.g. lowering the bar to your chest in a benchpress. Eccentric movements cause the build-up of lactic acid in your muscles, which is what causes soreness. Since walking down stairs is a primarily eccentric movement, it would cause more soreness than walking up stairs, which is where someone would get the idea that wlaking down staris requires more energy.

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Link to the Mailbag Item inserted by CKDextHavn, Board Moderator: http://www.straightdope.com/mailbag/mdown.html



[Note: This message has been edited by CKDextHavn]

Actually, eccentric motions cause soreness for another reason. If you can, imagine your muscle fibers have a series of "hooks". These hooks (upon muscle contraction) grab, pull, and move to the next "hole". This is actually a chemical action, but I'm not going to get into it here. During a concentric contraction, these hooks are climbing in the direction they were meant too.(since muscles can only contract one way) During relaxation phase, these hooks are withdrawn. If you do an eccentric contraction instead of relaxing, these hooks are grabbing and trying to pull up, however, they are moving the wrong way. This tearing motion is what causes the soreness. Lactic acid will build up during any type of muscle movement.
I can get the chemical process for you, but I thought I would explain it like it was taught to me.

Roksez: The hook and hole analogy is utter nonsense. Our muscles are arranged in pairs so that what one muscle cannot accomplish by contraction, another one can. "There is no "reverse gear," so to speak. Anaerobic activity (operating oxygen-starved) and the build up of waste products in the muscle cells is what causes the "burn" (and the later soreness) that signifies the tissue damage that body-builders so crave. You gotta destroy some to get bigger, better ones.

The walking downstairs vs. upstairs is a matter of which muscle group you're using.
Our climbing muscles have been fighting gravity for eons, and are correspondingly bigger and use more oxygen than their coasting-downhill counterparts. Oxygen consumption is a very accurate gauge of how much work a muscle is doing, and anyone who has hiked uphill one day and down the next can tell you, uphill requires more oxygen and downhill cause supreme agony in muscles unused to such nonsense.

Ok simple test to show what I'm talking about. Grab anything in your hand, and do a bicep curl. Now slowly lower it back down, letting it fall naturally, but with some resistance. Your tricep muscle is not contracting, your bicep muscle is. It is resisting the downward motion. It is contracting, but it is moving "backward". This is taught as fact in my human kinesiology book, which I will dig out and get some exact quotes from. Perhaps you have a source for your information??

The eccentric motion does cause more soreness, not from oxygen depletion, but because of the method I described earlier. Unless the body of knowledge on this subject has changed in the last 2 years, I can assure you I am correct. If you doubt me, I will contact my professors to see if I have missed something, but my major is fitness/exercise physiology. I would hope I am not paying to be taught "nonsense". Also, the "hook" thing is an analogy, as I said. It is actually a chemical reaction, which produces a ratcheting effect in the muscle fibers. These only connect in one direction, thus when you do an eccentric contraction (not a relaxion) you tear more of these fibers.

Yes, I understand what you mean by "eccentric" and "concentric," although I have never heard these words used to describe muscle movements, and they really don't make much sense when used as such. I guess the idea is that an "eccentric" muscle movement is one that goes against the "normal, accepted pattern?" (I cannot fathom how "concentric" figures into this. The whole thing sounds like a bunch of body-builder hooey). Anyway, it makes no difference, the muscle is contracting in the same manner - muscle cells move our body parts by making themselves shorter and fatter, regardless of which direction they are moving or whether they are actively or passively effecting movement. I cannot imagine where this idea of a "ratchet" arrangement came from, or maybe I don't understand why you are using a mechanical analogy for what you say is a chemical process. I don't understand how a chemical process can be responsible for the mechanical damage ("tearing"?) you describe. Or are you saying the muscle fibers somehow "let go" of each other and "reattach" in a different position? This I never heard.

Until you can provide me with some physiological basis for your claim - a reverse Krebs cycle, say - I'll stick to Human Anatomy & Physiology 101 and stand by my original statement.

Ok, found the book,(actually my anatomy, this is not as detailed, but I digress). Here goes the technical explanation, and this will take awhile.
First, the structure and organization of a muscle.
1 Muscles are made up of cells known as muscle fibers, which are long cylandrical shapes up to 1 foot long.(Picture a fibreoptic phone line).
2 Each cell is further made up of myofibrils. Myofybrils are composed of units called sarcomeres, which lie end to end. (Again, fibreoptic phone line)
3 Myofibrils are composed of sarcomeres, stacked end to end. Sarcomeres are the contractile units of a muscle.
4 Sarcomeres are composed of two types of myofilaments called (this is real technical here) the thick one and the thin one. The thin one is composed of actin molecules, the thick one of myosin molecules. These filaments overlap, and when the actin molecules are slid past the myosin, contraction results.
Ok, now for the actual contraction.
On each myosin filament, the are myosin heads(which look somewhat like hooks). On each actin filament, there are binding sites, each covered with troponin(negatively charged)
When an impulse is sent to contract a muscle, positive calcium ions are released, which attach to the troponin, and pull it away from the binding sites on the actin.
Once the sites are exposed, the following occurs.
1 The active myosin heads are attracted to the exposed binding sites, and cross bridging occurs.
2 As the head attaches, it bends, pulling the actin filament toward the center of the sarcomere. At this point, adenosine triphosphate(ATP) binds to the head, and returns it to its original position. The actin filament has now been slid slightly towards the center of the sarcomere.
3 The head is now ready for another "step" and it binds to the next site on the filament. Keep in mind there are many, many heads, and some are always in contact with the actin filament. If this were not the case, the filament would simply slide back to its original position.
Now picture all these heads, attaching, bending, releasing, grabbing again, attachin, etc. This is a muscle contraction. Usually, one "pull" generates a shortening of about 1% of the muscles length. Some muscles can perform 30-35% shortening, so many of these cycles are repeated.
side notes:
1 Since dying cells cannot exclude calcium ions, they promote the cross bridging of dead muscle tissue. These contractions are more commonly known as rigor mortis.
2 When ATP is relatively depleted, the heads cannot detach and move on. The muscle is in a continual state of stationary contraction. Writer's cramp is an example of this.
3 There are three types of contractions:
a)isotonic (regular contraction, the vertical lift in a bench press)
b)isometric (contraction, no movement. Push on a wall, your muscle contracts, but does not move)
c)eccentric (contraction with reverse movement. When you bring the bar back down on a bicep curl, you are not pulling it with your triceps, you are contracting your biceps in a way that you slowly let it down. A true eccentric workout is one in which you cannot physically lift the weight. Someone else helps you lift it, you let it fall as slowly as possible.

All this brings us to why eccentric contractions cause more soreness. You are correct in stating that muscles only contract one direction. The heads cannot contract , release, and move backwards. When you do an eccentric motion, the heads are attaching and trying to ratcht to the next site. However, the muscle is lengthening. You are actually tearing the heads away from the binding sites. This causes the extra soreness associated with doing an eccentric workout.
We are taught to use simple explanations so that we can pass them on to people we are doing rehab or workout programs for. Everyone knows how sore you get after the first few times you work out, and there can be several reasons for the soreness. If your job is to make sure this person continues to follow their program, you have to explain the reasons in everyday language.
Thus, the "hook, pull, and ratchet" analogy. I'll try to recall more of the chemical reaction, it involves positive and negative ions, and the signal from the neural net that says "contract"
And yes, it is possible to get sore walking down a hill, as well as up. But who wants to climb a hill and wait two days, see how sore you are, recover, and walk down, and see how sore you are, and compare. If you are out of shape, you're probably going to get sore.

forgot this as well--
Your krebs cycle comment is on the right track, it is the cycle which provides the energy for the above movement. The krebs cycle produces ATP, which is necessary for the above to happen. It is actually the first step in all of this.

I stand by my original explanation. I've attached an abstract from medline that says
(a) Lactic acid is a factor contributing to muscle soreness, and (b)DOMS is biased toward eccentric muscle actions. Sorry it took me so long to respond, especially since I started the thread, but I had some quals. occupying my time.


1.
Miles, MP; Clarkson, PM. Exercise-induced muscle pain, soreness, and cramps.
Journal of Sports Medicine and Physical Fitness, 1994 Sep, 34(3):203-16. (UI: 95131528)
Language: English; Pub type: JOURNAL ARTICLE; REVIEW; REVIEW, TUTORIAL


Abstract: The three types of pain related to exercise are 1) pain experienced during or immediately following exercise, 2) delayed onset muscle soreness,
and 3) pain induced by muscle cramps. Each is characterized by a different time course and different etiology. Pain perceived during exercise is considered to
result from a combination of factors including acids, ions, proteins, and hormones. Although it is commonly believed that lactic acid is responsible for this
pain, evidence suggests that it is not the only factor. However, no single factor has ever been identified. Delayed onset muscle soreness develops 24-48
hours after strenuous exercise biased toward eccentric (muscle lengthening) muscle actions or strenuous endurance events like a marathon. Soreness is
accompanied by a prolonged strength loss, a reduced range of motion, and elevated levels of creatine kinase in the blood. These are taken as indirect
indicators of muscle damage, and biopsy analysis has documented damage to the contractile elements. The exact cause of the soreness response is not
known but thought to involve an inflammatory reaction to the damage. Muscle cramps are sudden, intense, electrically active contractions elicited by motor
neuron hyperexcitability. Although it is commonly assumed that cramps during exercise are the result of fluid electrolyte imbalance induced by sweating, two
studies have not supported this. Moreover, participants in occupations that require chronic use of a muscle but do not elicit profuse sweating, such as
musicians, often experience cramps. Fluid electrolyte imbalance may cause cramps if there is profuse prolonged sweating such as that found in working in a
hot environment. Thus, despite the common occurrence of pain associated with exercise, the exact cause of these pains remains a mystery.

I totally agree with you; the pursuit of a cure for DOMS is of great concern in my profession-to be. You can either decide to go easy when you first work out, and gradually build your intensity, or just blow it all out at once and be sore for a few days. After taking a break from working out, I usually will work out twice at low weight, medium rep, then start working out hard. If I still get DOMS, I just so low weight/high reps for a few days til it's gone. Potassium and drinking water seem to help some people offset the effects.

Not for nothing, kids,but I drink Diet Tonic Water. The Quinine therein not only keeps me from getting wicked leg cramps, but keeps down the Malaria.

More biking, less worrying !!

Typer

I dunno how the science/medicine works, but it definitely takes me more energy to go up than go down. FWIW, though, you are more likely to hurt yourself going down.

Ok, Rok - that explanation makes sense. What threw me was the mechanical analogy for chemical process. The "tearing" you cite is chemical, not mechanical. (I still don't know how this equates to "tissue damage").

I'll stand by every single statement in my original post with the exception of the first sentence.

Sorry, folks, but all this scientific info is quite unnecessary. I know from daily personal experience (not to mention common sense) that it takes more energy to go up stairs than down. Jeeeeeezzzz....gimme a break!

I think the original question should have been: Does walking downstairs result in more soreness than walking upstairs. It obvioulsy does not take more energy. I can answer the following question: will a workout consisting of nothing but eccentric contractions result in more soreness that a concentric workout. Assuming equal levels of intensity, yes.

Geez, you guys obviously aren't physicists. And for that matter you weren't paying much attention in high school. Not counting any special forces from the human body (like one muscle having more friction than another) it takes exactly the same amount of energy to go upstairs as to go down.

When you push a ball down the stairs the energy goes into motion and the ball smashes into something. People (well at least me) don't randomly collide with walls after going down the stairs. You start going down the stairs at a nice pace and the length of the staircase doesn't affect the speed you leave it at. Therefore you have absorbed the energy (mgh whether going up or down).

In a ball all the potential energy goes into speed, and lacking any survival instinct, it doesn't absorb it.

I think that is the most ridiculous application of physics I have ever seen. How does the ball go upstairs??? If your application is correct, then slowing a 100 pound weight as it falls takes as much energy as raising it. Does anyone believe this? I think you are saying if it takes X amt. of energy to go from pt.A to pt.B, then it takes the same amount to go from B to A. Which is fine if you don't account for gravity. When you climb stairs, you are doing concentric muscle contractions of (mainly) the gastocnemius muscle. When you descend, you are doing eccentric contractions of the gastrocnemius muscle. Concentric contractions use more energy than eccentric contractions to control the same amount of weight. However, due to their nature, eccentric contractions cause more soreness. For this reason, you lift higher weights doing an eccentric workout, and will be sorer, but you can do more reps, and actually need to, to use the same amount of energy . (an eccentric workout would be one in which if you were doing bench press, someone else lifts the weight up, and then you slowly lower it back down.)

I think that is the most ridiculous aplication of physics I have ever seen. If your application is correct, then slowing a 100 pound weight as it falls takes as much energy as raising it. Does anyone believe this?

*********************

Boy one would have the knowledge of science had advanced since the middle ages.
First of all I specifically said that I wasn't including any special forces from the human body. So we're assuming that the human body is frictionless here. Besides the original question was what takes more energy not which makes you more sore.

As for your question: Obviously it does! If it didn't where would all the energy go? You raise a brick 1 meter and then lower it back down and it releases less energy, so where does the energy go? By your logic the universe would be doomed to a quick dissappearance from all this "leaking" energy.

Look, simple physics. Potential energy is mgh. You raise a 1 kg mass 1 meter and you use 9.81 joules. You lower same mass 1 meter and you get back 9.81 joules. What's the controversy? Are you going to tell me that there are different laws for going up and down?

Konrad: <<Are you going to tell me that there are different laws for going up and down? >>

Different laws? No. Different effects of gravity? Yes.

I have a ball at rest on a stair in the middle of a stairway. I give it a horizontal push of two inches towards the edge of the stair. The ball bounces down the stairs, pulled by gravity.

Are you telling me that it can fall up?

Or that that same amount of force (the horizontal push) could propel the ball to the top of the stairs?

If you're being serious, Konrad, then you're talking about the total energy of the whole system (or in a gravity-free vaccuum). The rest of us are talking about the additional force needed needed to propel up vs down.

You're not talking about the right energy here. The energy you put into a ball to get it to go down the stairs doesn't even come into consideration because it can be infinately small as long as the ball is right on the edge. The energy that we're talking about is the energy the ball gains as it falls down the stairs. The ball speeds up as it falls down, right? And the longer the flight of stairs the faster the ball is going at the end. But humans are not like a ball, they do not speed up as they go down stairs because they slow themselves down by absorbing the energy of each step down.

Now the proof that the energy is the same:

You should know that if a ball that fell down the stairs then (neglecting friction) went on a ramp that launched it straight up it would reach the same height that is was released at. Therefore the kinetic (speed) energy that the ball gained from going down the stairs is exactly equal to the potential energy lost.

A person will absorb the speed they gain after going down each step so that they don't speed up after each step and break their necks. The energy they must absorbed is equal to the energy it takes to slow them down after each step. This is equal to the potential energy they lost at each step. And the potential energy is *by defintion* the energy it takes to go up the steps.

I realize this is not a very clear explanation but the main point is that (if you want to use the ball analogy) it takes more energy for a ball to go down the stairs then just the initial push. You have to slow it down at the end of those steps so that it is going as fast as it was when it started falling. That way it simulates the way a human goes down.

[[ball. . . the initial push. . . it is going as fast. . . the way a human goes down.]]

I'm sorry, what was the topic again?

Rich

I think the original post related to the amount of energy your body uses to traverse a flight of steps on this planet. When we need to walk around in a vacuum tube, we'll let you know.

I see the confusion here, I think, Konrad. The correct answer is: (c) Boston, MA, in the year 1792.

Here's the link to the original question and answer: http://www.straightdope.com/mailbag/mdown.html ... you might try to read it first?

The question is not the energy amount of the total system, the question is how much energy the human being needs to exert to traverse stairs.

Well, how about that. I just actually read the column in question. Cecil is right, of course, the body will burn more energy going upstairs. However, you can become sorer from walking downstairs. The extra soreness derived from doing the negative or eccentric phase of any motion would make it seem like you had expended more energy, but it isn't so.

Just to clarify, though, rok -- that Cecil is always right is axiomatic. (The word "always" in this context is defined as an item of faith, and ignores the situation of later evidence not known at the time of Cecil's initial statement...)

The Mailbag items, however, are not written by Cecil, but by his loyal staff, the Straight Dope Science Advisory Board, who are a bright and energetic lot, but not infallible. Just wanted to clarify.

Ok, I think this question is really simple. I don't see why you're talking about the "energy of the entire system". My answer is that it takes a human just as much energy to go down as up stairs. That was the question and that is my answer, I don't really see much room for confusion.

Now I'm a first year physics student, and this question seems completely, beyond obvious to me. Now, you haven't actually said what's wrong with my explanation so I can't really rebutt your points. I don't see what air has to do with it anyway, neglecting friction (as I specified) air pressure would not change anything.

Try posting this question on sci.physics if you don't want to take my word for it.

A) That answer is wildly, ludicrously wrong in physics. I suggest you try another major.

B) The answer is also wildly wrong in biology. A human body is not a friction-free 100%-efficient machine. (Or have you never noticed that you can get tired just standing still?)

------------------
John W. Kennedy
"Compact is becoming contract; man only earns and pays."
-- Charles Williams

Well, I am a fourth year fitness therapy/kinesiology student, and I can assure this IS a simple question. Read all my responses. If you live in a frictionless gravity free environment, then yes, it would take the same amount of energy. But till then, trust me. You should find the kinesiology class there and take it. It about applying physics to the human body and its motion.

John:

First of all I specifically said I was not counting any biological factors so either you haven't read my post or you're merely a cretin.

Secondly, it is not sufficient to say "Your answer is ludicrous" to prove a point. But I guess if you can't actually find anything wrong with my explanation you have to try other ways...

RokSez: Yes, but as I said I wasn't counting any friction. And like I said in my last post, I don't see why you are saying my answer only applies when there is no gravity. You haven't actually said what is wrong with my explanation apart from stating that it is wrong.

Your major might be fine if we were arguing what makes you more sore but the question is pretty simple: What takes more energy? So it is strictly a physics question.

Again I invite you to post the question to sci.physics. And remember the question is not whether it takes more energy to walk up stairs than to throw yourself down the stairs which is obviously what you and Ckdexthavn are talking about. It is about walking up/down.

I still don't understand your point, Konrad, so I'm not sure what I'm supposed to "disprove." The question is worded, does it take more energy to walk upstairs or downstairs. We are saying that gravity exerts a force to assist you in going downstairs, whether you are walking or sliding; and that gravitational force opposes you in going upstairs, whether you are walking or sliding.

You seem to be saying that the answer is different for walking than for sliding? That you concede it takes more energy to slide upstairs than to slide downstairs, but you think it is somehow different from walking?

I have asked our unofficial physicist and penguinist to comment on this thread, I'm hoping she will do so soon. I don't visit other sites, my time is way too limited to playing online.

The original post is being read too literally if you take it to mean how much actual energy is being used as it relates to the universe. The poster is asking if your body uses more energy (read-works harder) to go upstairs or downstairs. It has nothing to do with potential or kinetic energy, but how much work your muscles do to go upstairs or downstairs. If someone just ran a marathon, and came up to you and said "gosh, I'm all out of energy." they arent saying they have no more potential for motion. They are saying they are fatigued. Like I said, this has nothing to do with physics, it is ridiculous to apply it here.

roksez: What you have just said about my reasoning is exactly what I'm trying to say about yours. It takes as much energy for your muscles to go up or down the stairs. Not the universe or any of that crap but simple muscle power. What you are talking about is the energy of the entire system.

ck: Exactly, sliding is different from walking. When you slide your clothing absorbs the energy that your muscles would normally take up and that's why it heats up.

Here's an example: You jump out a window. It doesn't take any work at all for your muscles. That's cause at the end of the jump you are moving very quickly and the energy is absorbed by your bones breaking etc etc...

When you walk down the stairs, even if you started at the same heigh as the window, you are not going very fast at the bottom. Why? Because your muscles had to work to slow you down.

So in the case of the jump you did do work but not with your muscles and it was all at the end in the form of friction and breaking. In the case of the slide that same work was absorbed gradually by friction between you and the slide.


Remember, this is like one of those 12 step programs. To see the truth you must first accept you are wrong. You must want to change. In moments of doubt, say to yourself "I think I am right, while Konrad knows he is right." There is still hope for you!

The fact that I abandon discussion of a topic does not mean that I concede, but only that I am tired of banging my head against a wall.

Hey, did you know that banging your head against the wall uses the same amount of energy as.... oh hell, I'm sick of it too. But a great new invention awaits develpment: are you tired of walking upstairs on a stairmaster?? Now you can go downstairs. It's just as good a workout.
Seriously-I will give you that the total energy expended is the same, but your muscles do MORE work to go upstairs than down. This means they expend more energy. On the way down, you have bones, tendons, etc. also absorbing energy, so your muscles don't do as much work.

Roksez: So you're basically agreeing with me? I specifically said not counting any special forces from the human body, ideal human, no friction etc... Yes compression of bones and tendons does absorb some energy which makes it easier to go down. If you want to test just how little energy is absorbed this way try jumping even one inch off the ground and absorbing the impact on your heels with your knees locked... it hurts. And it doesn't hurt that much to walk normally so normal walking absorbs even less than that.

BTW the reason they don't have reverse stair masters is that it would give you almost the same workout but with more likelyhood of knee or ankle injuries.

I'm not agreeing or disagreeing with your argument about total energy consumption(as far as energy in E=MCsquared goes). That argument isn't my bag, baby The problem I have is your literal interpretation of the word energy in the original question. This is not a question having anything to do with physics. If the original post wasnt clear to you, well, sorry, but everyone else understood it. The post should have read,
"Does walking downstairs result in a greater oxygen deficit than walking upstairs?" The answer is NO. However, walking downstairs (the eccentric phase of the exercise) CAN produce more soreness than the concentric phase. This is where the original question comes from. If walking upstairs causes a greater O2 depletion, then why doesnt it necessarily cause a greater soreness. I also addressed this earlier. Like I said, don't take every use of the word energy so literally. If you see an ad for a Powerbar, and it says "get a BOOST of ENERGY", do you get mad because you think they are advertising a bar that increases the total amount of energy in the universe? God I hope not. I know you are eager to spread the knowledge you gained in the past year, but use it in appropriate forums.

It take s more energy to walk upstairs than down stairs. after all, you can slide down the bannister, and the only energy you would use(or lose) would be Heat caused by friction.............anyway.. you cant slide back upstairs........ never mind....

roksez: I understood the question perfectly. I am talking about the same energy you are, why can't you accept this? Oxygen depletion is proportional to energy used since that's where you get your energy from. I keep repeating this but you don't seem to get it: I'm not talking about total energy in the universe, just the energy your muslces use.

I don't know what else to say. I just keep repeating that statement and it's like you're ignoring me and just saying the same thing over and over. Have you actually reread your own posts? It's like you suffer a lapse of memory each time I say I'm talking about the same energy you are.

John: Exactly. But when you slide down a bannister you aren't walking. That's why you don't get tired from sliding down a bannister (except from holding yourself up).

To be simplistic:

When I hike to the top of Camelback Mountain, I'm winded, tired, and need a few minutes of rest. After resting, I hike back to the bottom. I'm not nearly as winded or fatigued when I get there.

when moving upstairs, you have to use enough force to carry your mass in 2 directions, forward, which would be the same as walking normally, and upward, against gravity.
as muscles work in pairs, walking upstairs and downstairs use the same muscle groups,
but because your moving against gravity, walking upstairs uses more energy.

a quick annalogy,

you dont have an excercise machine called a stair-decender. they only go up.

The question it self is bad cause most people (as yourself's) don't understand energy very well!
If your talking about Human energy (calories and that stuff) then even a child knows it takes more enery to go against gravity than with it!!!!
If your talking about real enery then you must realize IT IS EXACLY THE SAME! All you do is change potential to Kenetic (neglecting friction due to the small speeds).
Look up conservative systems in a scientific Encylopedia and you'll get some idea about what is Energy.
As for who ever wrote the question: maybe you should think about the answer first and ask more intellegent questions!

Ok, I hate typing long responses, but I am tired of this topic. So here goes.
Muscle contractions are not all or nothing responses. You only contract as many sarcomeres as you need. This is why you do not slam a can of coke into your face when you lift it. This is also why you cannot hold a weight suspended forever. As your muscles fatigue, more and more sarcomeres are recruited, until there are none available and failure results. Assuming equal weights(your body, in this case) any concentric contraction requires more sarcomeres to be involved than the corresponding eccentric contraction.
Ok point 2-
Energy derived from the food(sugars and starches) that we eat is stored as energy in the form of adenosine triphosphate (aka ATP). As you will remember from my earlier lecture, ATP is the chemical which binds to each myosin head as it release from its binding site during a contraction. Now if we just put 2 and 2 together, we understand that-
any concentric muscle contraction requires more sarcomeres working than any eccentric contraction(assuming equal weight). The more sarcomers you have contracting, the more ATP is needed to bind with the myosin heads as they release. ATP is the chemical in which the body stores its energy. It is the chemical which allows the myosin heads to "reload" and contract again. Since you need more ATP to produce a concentric contraction(assuming equal weight), your body is burning more "energy".

Eddie just summed up everything I have said. And you don't have stairmasters going downhill because there is a negligible aerobic benefit.(Your muscles do less work)

[John W. Kennedy]

Eddie -- roksez -- your "explanation" has the slight practical disadvantage that it gives the same answer for all experiments, practical or gedanken, that do not involve divine intervention or the use of magic. Of course energy is conserved! But when potential energy is entered into the equation, you can say equally well that an ant sneezing uses the same energy as a supernova.

You're arguing like a doctor who answers the question: "Will my wife live or die?" with "Yes." Technically true, but useless and rude.

------------------
John W. Kennedy
"Compact is becoming contract; man only earns and pays."
-- Charles Williams

[Konrad]

Strainger: Hiking is not the same thing as stairs, there's a lot of friction when you walk down an incline but not much when go down stairs. Also read there is the other thing which John Larrigan said:

JohnLarrigan: Actually, that's a good point. I didn't want to bring it in before because it would confuse things but since you brought it up... It does take more energy cause you have to make yourself move forward when you go up but once you make that first initial push forward at the bottom of the stairs you pretty much keep the momentum. When you walk up the stairs you sort of bend forward and push almost straight down. I'm sure you lose some of the forward momentum from friction and stuff but I don't think it's a major effect. (If you have gain .5m/sec horizontal speed each step it takes .125 joules/kilo of body mass whereas going up one step takes 2 joules/kilo.)

roksez: Out of your 2 points how do you get that it takes more energy for concentric than eccentric? I'm not saying it's not true but you just made a statement, not an argument. You have no proof for that. Either way as I said before we're not counting any friction so that point is irrelevant.

What is also irrelevant is the fact that your body uses ATP for energy. I took bio, I know what ATP is. What are you trying to do? Impress me by pointing out an obvious and COMPLTELY irrelevant fact? It wouldn't bloody well matter if your body used goat sperm for energy, it would use just as much goat sperm going up as down if it weren't for friction.

John Kennedy: I think what Eddie is trying to say is that because energy is conserved then all the extra energy you used going up must come back out as friction when you go back down. The whole point is when you go downstairs you spend a whole lot of energy as friction dragging your hands on the rails and so on and that takes the load off your muscles.

[mr john]

A prime exmple of why the original poster needs to post a link. Cecil said every bit of this with a lot less and simpler words.None of that extensor vs. contractor,chemical processes etc has any thing to do with it. In physics you allways assume a perfect enviroment,africtionless,gravityless,vaccuum, then start adding conditions. Sliding down a bannister causes friction which results in heat which is energy.Same amount of energy as heat as it took to climb? Probably in that perfect place with friction and gravity added. A downstairsmaster? What a concept,I'll be in the basement developing that,if Igot the energy to go downthere.(My brother's down there now anyway cussin at the government or something). Any way can I ask you physiology people the question this way? "Do I use different muscles to go upstairs or down? If so, is one set more efficient than the other? If not,are they more efficient one way or the other? In other words, do less efficient muscles take more "energy" to operate? Does my body have to "work' harder? Note the quotes physics people. It takes just as much energy to conteract gravity when raising something as it does to resist it when lowering it at the same speed. Get a rope, pulley,scale, and weight and check it out.Now if i tie the rope off with weight suspeded no energy is being created or used, it is all stored(kinetic) energy. But if I hold the rope in my hand,then for sure my body is expending energy.Ty this stand at the top of the stairs like this and LOOKOUT! OOF BLUHHH WHAP CURSE OOOF YOU OOF NEWTON! OUCH ARGHH KIN AHHHH ETIC OOF POW> BANG

[mr john]

That enough spaces Dex?

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Signitorily yours, Mr John
" Pardon me while I have a strange interlude."-Marx

[Nickrz]

Wow, this whole thing turned into an argument with a moron? Dangit, I miss all the good stuff.

[Konrad]

Do a search on deja news for "Konrad stairs" under sci.physics. Most people agreed with me.

Also the 2 physics Ph.D.'s I asked said I was right, and I think they're a lot more likely to be right than some moderator on a message board.

[C K Dexter Haven]

OK, once more from the top.

IF the question had been whether it takes more energy to lift an object in the air or to lower it gently the same distance, then the argument from physics says that it takes the same amount of energy.

Please note: if the object was not being lowered gently, but was being lowerd most of the way and then dropped.... then it would take less energy (exerted by the person) to lower/drop the object than to lift it.

IF the question was about whether it takes more energy (exerted by the human) to push an object (like a ball) to roll down the stairs, vs throwing it up the stairs, I think we agree that it takes less energy to let the ball roll down the stairs.

Neither of those were the question.

The question was about a human walking down and up stairs. The energy involved in walking is different from the energy involved in lifting an inert body.

I have used the rolling ball as the example, but I probably should have used a person "jumping." If I stand on the top stair and take a little jump, I go down one stair. This takes less energy (I contend) than if I tried to jump (or walk) UP one stair.

The physical process of walking down stairs involves a little "lifting" and a little "jumping" -- letting gravity set your foot down. To that extent, gravity is helping you go down, but does not help you go up.

Does that resolve the seemingly irresolvable differences?

On a further note, Konrad, you can take the gratuitous insults to the BBQ Pit. This is not a question that is resolved by majority vote, not even if two Ph.D.'s vote with you. The author of the Mailbag item has a Ph.D., and he sought (and got) agreement with a physics Ph.D. prior to posting the article. So we're even. I don't think that your attempt at one-upmanship is productive.

I have edited the first posting on this topic to include a link to the Mailbag item.