energy required to clmb a hil....

richymcp

Hi,

Me and some of my riding buddies have been having a bit of a debate/disagreement about the amount of energy required to climb a hill/mountain and if it’s the same for every rider (if you discount variables such as weight of bike etc.).

If you have 2 riders of similar weights riding similar bikes do they use the same amount of energy (and burn the same amount of calories) when climbing an identical mountain?

Also does it make any difference if one is extremely fit and the other is not (in terms of the amount of energy required) is it the same for both?

Any answers to this puzzle would be appreciated!

gwebb118

Same weight, same bike, same energy. But one is likely stronger than the other.

sirmol

If one rider is fitter they will use less energy as they are not being 'pushed' as hard i.e. their heart isn't pumping faster.

gwebb118

Its not that a fitter rider uses less energy, its that they have more power, and output the same energy, just faster than the other rider. It still takes the same energy for two riders of equal weight to go up the same hill (assuming that they both are as aerodynamic as each other and there bikes are identical)

rstabler11

The same weight going up the same mountain will require the same total gain in gravitational potential energy (which would be the argument for both riders using the same amount of energy).

However, a fitter / better rider will be more efficient and so they will burn less energy in order to gain the same amount of gravitational potential energy (rise in altitude). Therefore two people will not use the same amount of energy.

For example - 72kg cycling from sea level to the top of Col du Galibier:
Gain in potential energy = gravitational constant x mass x height gain
= 9.81 x 80 (72kg rider + 8kg bike) x 2645m
= 2075796 Joules
= 496 kcal
= 2 mars bars.

I would use a lot more energy / need to eat a lot more than 2 mars bars to cycle the Galibier (if I made) it - it's all about efficiency!

TakeTurns

The more experienced rider would use less energy.

richymcp

rstabler11 wrote:

The same weight going up the same mountain will require the same total gain in gravitational potential energy (which would be the argument for both riders using the same amount of energy).

However, a fitter / better rider will be more efficient and so they will burn less energy in order to gain the same amount of gravitational potential energy (rise in altitude). Therefore two people will not use the same amount of energy.

For example - 72kg cycling from sea level to the top of Col du Galibier:
Gain in potential energy = gravitational constant x mass x height gain
= 9.81 x 80 (72kg rider + 8kg bike) x 2645m
= 2075796 Joules
= 496 kcal
= 2 mars bars.

I would use a lot more energy / need to eat a lot more than 2 mars bars to cycle the Galibier (if I made) it - it's all about efficiency!

So let’s say that me and Andy Schleck go for a ride up Alp Dhuez (we're presuming I've lost 2 stone in weight to get down to his body weight and we're on identical bikes etc.) Andy gets up there is 40 minutes (him being the professional cyclist) and I get up there in 85 minutes (me being the middle aged bloke in dodgy lycra), I know he’s gets up there faster but you’re saying I’d need more mars bars than him? (guess my next question is how many more mars bars…?)

gwebb118

The only reason a more experienced rider would use less energy is due to technique. Which really I missed out from my arguement. But physically speaking, 2 riders with same techniques, weight, bike, aerodynamics, but one with greater fitness would both use the same energy. However the fitter rider gets up faster as they produce more power (by having more muscle (one of the riders may be more fat less muscle to be the same weight) or a better muscle composition, potentially other factors too) and power is how much energy can be produced per unit of time. So fitter rider, more power, faster up a hill, but same energy used.
This is confusing because the less fit rider will feel like they have to have worked harder, but it still takes the same energy to go up the hill.

rstabler11

Sorry, the mars bar example wasn't really meant one type of rider necessarily needs more energy than the other. The point was more to demonstrate that no-matter who it is going up, you or Andy Schleck, you are both going to need to eat a lot more than 500 calories to get to the top, so human cyclists are very inefficient in terms of using energy to gain altitude.

So, there is no reason I can see to suggest it will take everyone the same amount of energy to reach the top (ie everyone is 'equally inefficient'). I would suggest professional riders will be more efficient, and so burn less calories in doing so. But even the same rider could probably become more efficient by travelling at a slower pace for longer, and doing interval sprints the whole way up is likely to use more energy than not doing so.

So basically, am I trying to say human cyclists do not have a fixed inefficiency, so I don't think there is any reason to suggest everyone uses the same amount of energy to get up the same hill.

Lycra-Byka

Two words experience = efficiency.

gwebb118

Sorry, I'm not trying to say an experienced rider uses less energy, just that physically speaking, it requires the same energy. Obviously the more experienced rider would use less energy in reality due to technique differences (efficiency). I was just trying to put a scientific perspective on what I thought the OP wanted.
But with ideal control its the same energy, but reality is a different thing, with many many different variables to consider.
So I guess the answer to the OP's question is yes and no.

smidsy

Lycra-Byka wrote:

Two words experience = efficiency.

Technically thats 3

Lycra-Byka

That's a symbol in written form.

Your forgiven.

diy

The bit is that is being missed is the process of converting food to energy. two objects need the same amount of energy to move them from the top of the hill assuming the same weight etc. But two riders will not necessarily require the same amount of food and effort to produce the same amount of force to achieve the same result.

Different finesses, age and even different genetics will determine how much effort is required to produce the same force. Things like the efficiency of their lungs, quality of their blood, ability of their heart to deliver the blood to the muscle, ability of the body to process food in to energy etc will all be different.

You could also have differences in muscle mass. Rider A could have massive legs and be a skinny feck everywhere else, rider B could have skinny legs and a massive upper body - giving the same overall mass but hugely different requirements/abilities.

Then on top of that we have all the hormones in the body, hydration etc, which will change efficiency.

Lastly the guy with the pointy face will be more aerodynamic.

So no. All things can never be equal. or to put it another way, would you expect two different steam trains of the same weight to run the same distance at the same speed on the same amount of coal and water.

TakeTurns

Lycra-Byka wrote:

That's a symbol in written form.

Your forgiven.

You're also forgiven.

Froomes Edgar

Jesus, there is a lot of bolleaux above.

1. Same weight, same bike, same aero profile and same speed = same energy. Efficiency doesn't tend to vary much between riders (from bronze medal Sportive numptys to TdF winners), varies between 21%-27% from memory (although 25%+ results are disputed), and is largely unresponsive to training - but its a potential source of difference. However - to be clear - there is little evidence that efficiency is trainable - Lance was tested at 23.12%, which is decidedly average (and regardless of doping blah blah he's practically as good as it gets).

2. If you go faster you burn more energy for the climb. Whilst most of the resistance when climbing a mountain is gravitational, a small proportion is to move air out of the way, and the faster rider will have more to do because its not a linear relationship.

3. rstabler11 - The Galibier doesn't start from sea level. And you've forgotten air resistance (which is relatively small but not immaterial).

4. Going off piste to areas I barely understand, one potential reason that, all else being equal, a fitter cyclist might need less energy is because anaerobic glycolysis is much less efficient than via the aerobic pathway. However, even for a Contador/Rasmussen track stand/sprint fest, climbing a bit mountain is predominantly an aerobic endeavor so this can probably be disregarded.

Let the swamping of the above by ignorance commence

Lycra-Byka

TakeTurns wrote:

Lycra-Byka wrote:

That's a symbol in written form.

Your forgiven.

You're also forgiven.

Teh keyboard warrior and grammar nazis r out 2nitez.

Go away fickle topic digressors.

Mikey23

I would assume that mental toughness a factor? There are those who seem to be able to deal with the pain of climbing and those, like me who are a little wimpy

Froomes Edgar

Mikey23 wrote:

I would assume that mental toughness a factor? There are those who seem to be able to deal with the pain of climbing and those, like me who are a little wimpy

Mental toughness a factor in energy used? You think?

bigpikle

yep - surely mentally tough, holding a calm facial expression etc while flat out up the Galibier and suffering, uses less facial muscles and hence less energy is required to get to top while appearing to be out for an easy recovery ride....

amaferanga

Fat, unfit feckers just assume they burn more energy cos it feels harder for them and so they can justify eating even more pies.

Strith

Ha!

rstabler11

Froomes Edgar wrote:

3. rstabler11 - The Galibier doesn't start from sea level. And you've forgotten air resistance (which is relatively small but not immaterial).

This was hardly the central point of my argument... a standard Mars Bar also doesn't have exactly 248 calories in it either...

Froomes Edgar wrote:

1. Same weight, same bike, same aero profile and same speed = same energy. Efficiency doesn't tend to vary much between riders (from bronze medal Sportive numptys to TdF winners), varies between 21%-27% from memory (although 25%+ results are disputed), and is largely unresponsive to training - but its a potential source of difference. However - to be clear - there is little evidence that efficiency is trainable - Lance was tested at 23.12%, which is decidedly average (and regardless of doping blah blah he's practically as good as it gets).

This is the bit I'm interested in / trying to talk about. I don't have the numbers on efficiency like you do as I've never read about this before - I'm just thinking about it theoretically - but let's say I am 21% efficient and Chris Froome is 27% efficient. This means he is 29% more efficient than me. I think that is going to make a substantial difference to the total energy used, all else being equal.

Furthermore, if I rode up a mountain under identical conditions at the same speed as Chris Froome (and we were identical weights etc.) I'm confident my heart rate would be much higher than his. This implies (although not necessarily true) I am delivering more oxygen to my muscles, and so my muscle fibres will be converting more glucose to CO2.
Clearly, if we were at a speed where I was respiring anaerobically and him aerobically he would be much more efficient, but I think even if I was in my aerobic zone I would have a higher HR and so be burning more calories. This isn't always the case but the few times I have been on an exercise bike that does HR and calories think link between HR I am exercising at and calories burned has been fairly apparent.

The reason I have said 'not necessarily true' is that if someone has a smaller heart they can have the same Cardiac Output despite a higher heart rate. In addition, some people (eg with atherosclerosis or diabetes) may have worse control of blood flow (ie the ability to direct almost all of the blood being pumped to active muscle when needed).
Some people's arterial blood oxygen content will be lower (eg a mild lung disease, lower haematocrit levels). However, I still believe the oxygen delivery to muscles can be different in different riders, but you could argue against this for any of the reasons I just stated.

Froomes Edgar

Yes, indeed - IF Froome is 27% efficient and you are 21% efficient then you're clearly right - but as I've said, there is no evidence to support elite riders being better in this regard - so it could well be the case that Froome is 21% and you are 27%. Or, statistically far more likely, you're both about 23% which I believe is the about the mean.

Your HR being higher might indeed make a difference. A quick bit of googling suggests that the heart uses about 2w of power at full tilt, which surely even for the most shamefully unfit would be less than 1% of useful power output, and <0.27% of total power output. Obviously the difference between your heart at say 180 and Froome's at say 120 would be considerably less. NB there might be more than just the power of the heart to consider, but I suspect we're not going to see an order of magnitude difference which is where it might become material. The fact that riders fall into a narrow range of efficiency makes this clear.

Secondly, your HR being higher than Froome's doesn't imply that you are deilvering more oxygen. It implies that your aerobic system is working harder to deliver the same amount of oxygen because you're not as fit. Regarding exercise bikes and calories - I'm sure you do realise that at best they're random number generators and any correlation between the readout on the screen and the number of calories actually being burned is purely coincidental? Your Froome/chipper comparison makes this patently obvious.

rstabler11

OK.

My intuition would still be that someone with a much lower HR will use less calories. However, I can see what you're saying, its possible that what aerobic training achieves is the ability to deliver much more O2 to muscles, as opposed to making muscles work more efficiently.
This would mean Froome could go much quicker than me (and deliver more O2) if his HR reaches 180, but if he sits at 120 he might only be delivering the same amount of oxygen as me at 180.

So I guess you've convinced me that: "for two riders of the same bike/weight/aero profile going at the same speed, energy usage is approximately the same assuming they are both working aerobically".
(I would say at a HR of 180 you would have started developing lactate, so the HRs would have to both stay below this, probably only up to around 150).

The approximately is for the variations in measured efficiency, which as you've said for most people (not the extremes) will be small. Do you know how this was measured?

ShutUpLegs

Froomes Edgar wrote:

Your Froome/chipper comparison makes this patently obvious.

diy

rstabler11 wrote:

So I guess you've convinced me that: "for two riders of the same bike/weight/aero profile going at the same speed, energy usage is approximately the same assuming they are both working aerobically".

but that wasn't the exam question.

richymcp wrote:

If you have 2 riders of similar weights riding similar bikes do they use the same amount of energy (and burn the same amount of calories) when climbing an identical mountain?

Also does it make any difference if one is extremely fit and the other is not (in terms of the amount of energy required) is it the same for both?

@Froomes Edgar - you talked a lot of "science" but you didn't answer the question from what I can see. If you did and I missed it and if you said its broadly the same, then you are going have to explain the difference in actual performance between a newbie and an elite athlete of the same weight etc.

YIMan

Ultimately, if there are two people weighing 80kg, of exactly the same size and shape to climb 1000 vertical metres on exactly the same bikes, the energy required to move their 80kg mass 1000m vertically is exactly the same i.e. they both have to expend energy to gain the potential energy of being 1000m higher. So the energy output (which equals the potential energy gained) is exactly the same.....even if one does it in 1 hour and the other in 3 hours.

I guess the question is then, how much energy input does each person have to put in to secure the same energy output. I presume the fitter one will be much more efficient at turning stored "food" energy via the cardiovascular and muscular/skeletal system....into the force on the bike pedals that secures the potential energy gain?

Froomes Edgar

rstabler11 wrote:

The approximately is for the variations in measured efficiency, which as you've said for most people (not the extremes) will be small. Do you know how this was measured?

I don't I'm afraid.

diy wrote:

@Froomes Edgar - you talked a lot of "science" but you didn't answer the question from what I can see. If you did and I missed it and if you said its broadly the same, then you are going have to explain the difference in actual performance between a newbie and an elite athlete of the same weight etc.

What part of the question do you think I've missed?

RE elite athletes, whats the problem? An elite athlete will expend the same amount of energy climbing the hill as the chipper, assuming he climbs at the same speed. That doesn't mean he couldn't climb faster if he wanted to.

Froomes Edgar

YIMan wrote:

Ultimately, if there are two people weighing 80kg, of exactly the same size and shape to climb 1000 vertical metres on exactly the same bikes, the energy required to move their 80kg mass 1000m vertically is exactly the same i.e. they both have to expend energy to gain the potential energy of being 1000m higher. So the energy output (which equals the potential energy gained) is exactly the same.....even if one does it in 1 hour and the other in 3 hours.

No, because air resistance isn't zero

YIMan wrote:

I guess the question is then, how much energy input does each person have to put in to secure the same energy output. I presume the fitter one will be much more efficient at turning stored "food" energy via the cardiovascular and muscular/skeletal system....into the force on the bike pedals that secures the potential energy gain?

No, the answer is exactly the same, unless you dispute the principle of the conservation of energy.

That said, the fitter rider will generally burn a greater proportion of fat compared to the chipper and thus save glycogen because he's riding at a lower proportion of his FTP. Since glycogen is a limiting factor for cycling but fat is not, if you made these two hypothetical riders ride up this hill repeatedly without any food, the chipper would collapse first.

vinnymarsden

So, Let me get this right...if what some of the pseudo scientists are saying is to be believed........ everyone should be going up there using the same energy/calories regardless of fitness/technique etc!!!

So why do you see people hanging off their bars on big climbs when others simply fly past them??
Methinks the scientists trying to answer this one have maybe tried to overcomplicate the answer...it is in my opinion quite straightforward/simple......if you put in the work/hours/training, then you will be better than the Lardilicious lads/lasses that think its all genetic and come what may they are going to be alright!!
No they're not...its an age old saying...No pain...No gain...its not just for cycling..you can use it for anything sport related...I come from a distance running background and overall did quite well before injury forced me to admit it was insane in the first place!! But I KNEW that training was the only way to get better...not some scientific mumbo jumbo about energy spent etc etc..that only gets you so far....there's a line in the dirt....and everyone can get to that line...it's how far you want to go over it that dictates how hard you are willing to train!!!!
Just my thoughts...I'm not looking for an argument or to be shot down, albeit I accept I will no doubt be in someones sights before long!!!