dear knees..

[forufes]

which would use up less energy, going up the stairs one at a time or two at a time?

[Tugrul]

To calculate how mutch enerygy is needed just do this.

 

Mass of object moving x the force needed for movement= work done

 

so Force(n)xdistance(m)=work done

 

w=FN

[Mokele]

I suspect that two at a time will require more energy, because the greater excursion of the limb puts the muscle off the plateau of the length-tension relationship (muscles generate less force if too short or too long). Thus, to generate the same force, more motor units will have to be activated, resulting in greater metabolic cost.

[Mr Skeptic]

Both will get the same amount of work done, but I guess your question is which if done by a human will result in less energy wasted as heat. I frequently go up stairs quickly, taking advantage of the "bounce" in my tendons. I think the answer to your question may depend on the size of the steps and the size of the person. But it would make sense for stairs to be designed such that going up one step at a time would be the most efficient for a person of average height. Also, old people go one step at a time, right?

[forufes]

To calculate how mutch enerygy is needed just do this.

 

Mass of object moving x the force needed for movement= work done

 

so Force(n)xdistance(m)=work done

 

w=FN

lol i know that, but that's not how you apply it even to a robotic system with pretty linear movements..lots of other small things(which turn out not so small afterwards) come into it..so what do you think a human's movement would be that simple?

i'm looking for a very accurate answer, which sticks to the real life example as much as possible, i know it's a nerdy request, but i find it fun to ponder such small things..

I suspect that two at a time will require more energy, because the greater excursion of the limb puts the muscle off the plateau of the length-tension relationship (muscles generate less force if too short or too long). Thus, to generate the same force, more motor units will have to be activated, resulting in greater metabolic cost.

good input, such simple questions such as the op can only be answered as accurately as much concepts are taken into consideration, with careful labeling of the importance and degree of affection the concept has on the problem(or question)..

 

most concepts i figured out are dependent on an outside factor(depending on person for example), meaning they vary, they aren't fixed, they can be reversed, those will get canceled.

 

so you're saying that two at a time will stretch the tendons to a range where they are less elastic, hence requiring-wasting more energy?

but why can't it be the opposite? maybe taking it one at a time is way under the contraption range of the tendons(muscles) which will then require more energy for them to shrink up to a level they aren't used to, hence needing more energy?

while two at a time might fit the medium or usual contraction of the muscles more?

 

can we say it depends on the type of workout a person one is used to do?

(put simply, the ratio of yellow to red muscle(types 1 and 2 in wiki) fibers might change from one to another, hence one would find one at a time easier and vice versa)

note; if my biological informational basis here is inaccurate my cancellation of this factor would be wrong.

 

the only factor which i found which won't get canceled, is the margin of error in the applied energy by the muscles..because when you raise your leg up to put it on the stair, you don't raise it EXACTLY with the required force, you actually apply a bigger force which will raise your leg higher than wanted, then when it reaches the level wanted, you yet again exert another force to bring it down; example:

 

to raise your leg from one stair to the other you need 10 newtons.

your leg exerts 12 newtons, when your leg starts going overboard, it exerts another 2 newtons to bring it down to contact with the second stair.

 

1 stair up needs 10 newton, two stairs need 20 newtons..

BUT:

i believe that when your body estimates the force needed for two stairs, it will be less off, especially it is continuously against the gravitational force, which will reduce the margin of error..

so your ody will not spend 12x2=24 newtons, but rather 23..less energy wasted..

that's what i feel anyway(literally feel btw:D)..but am open to anyone who'd show me wrong.

 

Both will get the same amount of work done, but I guess your question is which if done by a human will result in less energy wasted as heat. I frequently go up stairs quickly, taking advantage of the "bounce" in my tendons. I think the answer to your question may depend on the size of the steps and the size of the person. But it would make sense for stairs to be designed such that going up one step at a time would be the most efficient for a person of average height. Also, old people go one step at a time, right?

 

it's easier for me two at a time.

for my friend it's easier one at a time..

 

if it varies from one to another no problem, but why and how?

also, is there a factor to it which is absolutely dependent from human differences?

[npts2020]

It seems to me that it depends on how long a persons stride is before leveraging yourself up to the next step becomes more difficult than just overcoming gravity. I don't know about easier but two steps at a time is substantially quicker.

[Mokele]

so you're saying that two at a time will stretch the tendons to a range where they are less elastic, hence requiring-wasting more energy?

but why can't it be the opposite? maybe taking it one at a time is way under the contraption range of the tendons(muscles) which will then require more energy for them to shrink up to a level they aren't used to, hence needing more energy?

while two at a time might fit the medium or usual contraction of the muscles more?

 

can we say it depends on the type of workout a person one is used to do?

(put simply, the ratio of yellow to red muscle(types 1 and 2 in wiki) fibers might change from one to another, hence one would find one at a time easier and vice versa)

note; if my biological informational basis here is inaccurate my cancellation of this factor would be wrong.

 

yeah, it's pretty much completely inaccurate. The simple one first - muscle fiber type differences may affect the cost between individuals, but within an individual it won't account for any difference between 1 stair vs 2.

 

Basically, the leg as a whole is a complex system - you have muscles, which attach in complex ways with moment arms that vary with joint position, with force that depends upon length, contraction velocity, and history, with a few springs (tendons) and pressurized compartments (fascia) thrown in. However, if you move it beyond a certain range, or to certain positions, the muscles will be too stretched or too short to generate much force in a particular action, and may be acting against unfavorable lever arms.

 

Attempting to boil it down to a simple concept, because you're flexing your hip and knee more by going up two stairs, you may be putting your muscles at a serious disadvantage. There will, of course, be variation between humans, mostly due to simple leg length, but on the whole, there will be an "optimum" step that minizimies caloric work, and departures will result in lower muscle efficiency in turning calories into mechanical work.