Efficiency of walking v riding up a hill

[pharmaboy]

Hi guys, I'm interested to know at what point it becomes easier to walk up a hill rather than ride - 10%, 15%, 20%?

What I observe in the shared trails I ride, is that I can comfortably ride at maybe 5 times the speed of a jogger on a flattish fire road when approaching from behind, but when I get to a 10% grade and see the jogger pretty much walking up the hill! it takes many many minutes for me to finally catch him. So at some point that jogger is going to go the same speed as me or faster .

The other example of this is in the convict 100 first hill, where walking is not much different from riding - single speeders should also have experience of walking next to a guy in 22,36?

Input?

 

[Jeffgre_6163]

I posted a very similar question on MTBR a couple of years ago [I looked but could not find the thread], my question was which was more efficient purely from a calorific usage point walking or riding a very steep grade.
The conditions I put were that every thing was equal with the two subjects, this is not possible, but assume identical twins with identical bikes and gear/clothing etc working up the same slope. One is riding in granny gear, the other walking and pushing their bike, both at the exact same speed. Assume the slope is very steep, just rideable.
Who burns the most calories? the rider or the pusher?
I was looking for an answer from a qualified physiologist but that never came but I did get varied and multiple answers that generally seemed to fall in one direction from the replies that had thought it through based on physics and physiology:

Everything is equal, the grade of slope, the rider and pusher are identical, the bike and gear [I.E. the MASS they have to move] is the same and, very importantly, the speed and distance they travel is the same.
The general consensus was that both rider and pusher would use exactly the same number of calories getting themselves and the bike to the top of the hill, logic being the they both have moved the same MASS at the same speed over the same distance.
The only difference would be the muscle groups used to do the work.

Comments and opinions welcome.

Personally I think this is correct, I am sure we have often been on rides where someone will bail on a climb and push while you ride beside them or vice versa. It always seems that we both get to the top knackered with very little difference in energy expenditure you just give the aching leg muscled used for riding a rest but the heart, lungs and muscles used for walking still have to do the work.

 

[SlowManiac]

I think it would only be true if walking and cycling were the same efficiency.

look at riding down a hill - you are again moving the same mass the same distance but riding is more efficient downhill.

As a really stupid example - what about a pogo stick that weighed the same as the bicycle. Same mass and distance but pogo sticking is way less efficient that either riding or walking.

I'm not sure of the answer by the way - I assume at a really steep grade walking become more efficient.

 

[Jeffgre_6163]

I think it would only be true if walking and cycling were the same efficiency.

look at riding down a hill - you are again moving the same mass the same distance but riding is more efficient downhill.

QUOTE]

Sorry but this is not a good example to explain the problem, riding/walking up is self evidently vastly different to riding/walking down from an energy usage stand point. The bicycle going down is going to be far more efficient obviously, for a start the rider does not have to do a thing except sit there [less some very minor calorific expenditure to do with maintaining balance etc] and let the bike roll with gravity doing 100% of the work. The walker, who quickly turns to runner if they ley themselves go has to use energy to control his rate of descent or he will face plant.

Uphill and downhill the situations have to be looked at completely separately.

I still think the bottom line is this:
The same mass up the same slope at the same constant speed covering the same distance in the same amount of time = the same energy expenditure. Walk or ride take your pick cause you will be just as knackeredd at the top

 

[cokeonspecialtwodollars]

look at riding down a hill - you are again moving the same mass the same distance but riding is more efficient downhill.

This is a key point I think, the bike while you are riding it naturally want's to go down the hill and when you're climbing you are required to put in the effort to not only counter this but also generate forward momentum. When you are standing on the ground even with the extra weight of a bike there is less tendency for your feet to "roll" down the hill as they are flat on the bottom, you still have to produce the force required to move the mass up the hill but you don't have to counter the tendency to want to roll down.

In regards to the OP's question I don't know what grade it would correspond to but I would think that once you are moving at walking pace and you cannot maintain forward momentum, i.e. you immediately start to roll backwards once you stop pedalling that's when it's time to get off and push.

 

[pharmaboy]

I think it would only be true if walking and cycling were the same efficiency.

look at riding down a hill - you are again moving the same mass the same distance but riding is more efficient downhill.

As a really stupid example - what about a pogo stick that weighed the same as the bicycle. Same mass and distance but pogo sticking is way less efficient that either riding or walking.

I'm not sure of the answer by the way - I assume at a really steep grade walking become more efficient.

One of the reasons I read about this was to do with energy expended versus gravity. Eg at the top of a hill, the cyclist requires almost no energy to travel down it - he just sits and the bike rolls down. The jogger however still has to expend energy to go down a gentle slope.

Going up a gentle hill on a bike staying balanced, if you stop you roll backwards, and in fact have to push against the pedals just to maintain your position. For a walker /jogger, you just stand and gravity doesn't push you back down the hill.

So here goes my out there conclusion. The efficiency of the bicycle doesn't change per se, BUT: the energy expended going up the hill is increasingly stored as gravitational potential ( for want of a better descriptor) at a cost to forward motion. You get that back once you go back downhe hill.

I think it's somewhere around a 15% gradient that I can keep up with similarly fit riders by getting off walking - I lose on the remounting though.

 

[SlowManiac]

I think it would only be true if walking and cycling were the same efficiency.

look at riding down a hill - you are again moving the same mass the same distance but riding is more efficient downhill.

QUOTE]

Sorry but this is not a good example to explain the problem, riding/walking up is self evidently vastly different to riding/walking down from an energy usage stand point. The bicycle going down is going to be far more efficient obviously, for a start the rider does not have to do a thing except sit there [less some very minor calorific expenditure to do with maintaining balance etc] and let the bike roll with gravity doing 100% of the work. The walker, who quickly turns to runner if they ley themselves go has to use energy to control his rate of descent or he will face plant.

Uphill and downhill the situations have to be looked at completely separately.

I still think the bottom line is this:
The same mass up the same slope at the same constant speed covering the same distance in the same amount of time = the same energy expenditure. Walk or ride take your pick cause you will be just as knackeredd at the top

OK - imagine you had a sphere and a cube the same mass and you have to push them up a hill - which one will you expend more energy?

Simply saying its the same mass covering the same distance is not correct.

Also - physics don't just break down just because you are fighting gravity versus going with it.

 

[oldstinky75]

Interesting topic.

I would guess regardless of whether you push or ride your bike up a hill it would require the same amount of force, just like lifting 20kg 5 times or 5kg 20 times, you still exert the same amount of energy.

Even though there is definite mechanical advantage in a geared bike I think walking at a comfortable pace rather than mashing the pedals in a low gear makes sense.

 

[Jim Junkie]

Interesting topic.

I would guess regardless of whether you push or ride your bike up a hill it would require the same amount of force, just like lifting 20kg 5 times or 5kg 20 times, you still exert the same amount of energy.

Even though there is definite mechanical advantage in a geared bike I think walking at a comfortable pace rather than mashing the pedals in a low gear makes sense.

I have read in an article in the past that cycling up a hill is the most efficient way to get up, from a total energy expenditure perspective. The catch is, the rate of energy expenditure is typically higher (when you're moving faster), hence you'd get more tired.

This makes sense when you consider the amount of work done. Walking is pretty inefficient, and you are bobbing up and down on your legs, moving your total body mass around. On a bike, you're just spinning the pedals, transferring most of your energy to the wheel and from there to the ground. I think a standard derailleur setup operates around the 90%-95% efficiency mark, depending on which gear your in (don't quote me on that though). So, when you consider total work done, walking would cost you more energy, just like it costs more energy to run without a bike that it does to ride the bike on flat ground.

I think the article was just a piece about climbing skills in Mountain Bike Australia magazine, so not high science, but the logic makes sense.

Edit: Second year engineering also taught me that there is an ideal gear to be in to apply maximum efficiency & power output given an amount of force input, so there's correct gear selection to consider as well.

 

[cooki_monsta]

I think it would only be true if walking and cycling were the same efficiency.

look at riding down a hill - you are again moving the same mass the same distance but riding is more efficient downhill.

QUOTE]

Sorry but this is not a good example to explain the problem, riding/walking up is self evidently vastly different to riding/walking down from an energy usage stand point. The bicycle going down is going to be far more efficient obviously, for a start the rider does not have to do a thing except sit there [less some very minor calorific expenditure to do with maintaining balance etc] and let the bike roll with gravity doing 100% of the work. The walker, who quickly turns to runner if they ley themselves go has to use energy to control his rate of descent or he will face plant.

Uphill and downhill the situations have to be looked at completely separately.

I still think the bottom line is this:
The same mass up the same slope at the same constant speed covering the same distance in the same amount of time = the same energy expenditure. Walk or ride take your pick cause you will be just as knackeredd at the top

I would agree with this except for gearing. That makes it tricky as the rider can apply a lighter load more often then the walker and that will affect the calories burnt

 

[No Skid Marks]

Im going to say in most cases walking will be more efficient. Te bike still stabilizes you and your not exerting as much energy making bike and rider as one(bars straight, body position etc). The difference would be small and vary with terrain. By the end of the ride the walking would have allowed better oxygen supply to starved riding muscles etc and de lactated better too. I favor having my lowest gear just above walking pace. I either have to man up and smash it up the hill in a hard but fast gear(time to recover at top, or walk at same speed and recover.

not sure how it'd balance out over longer rides or racing. Has always worked for me. I don't know the dynamics of manning up an smashing up a hill in a higher gear and how costly it my be energy wise, you do get recovery time as you got up quicker.

 

[Jim Junkie]

Im going to say in most cases walking will be more efficient. Te bike still stabilizes you and your not exerting as much energy making bike and rider as one(bars straight, body position etc). The difference would be small and vary with terrain. By the end of the ride the walking would have allowed better oxygen supply to starved riding muscles etc and de lactated better too. I favor having my lowest gear just above walking pace. I either have to man up and smash it up the hill in a hard but fast gear(time to recover at top, or walk at same speed and recover.

not sure how it'd balance out over longer rides or racing. Has always worked for me. I don't know the dynamics of manning up an smashing up a hill in a higher gear and how costly it my be energy wise, you do get recovery time as you got up quicker.

This last paragraph is what I was getting at with the gearing thing. If you try and take the case of the walker & rider moving at the same pace, you're not taking into account that the rider is probably not in the ideal gear for the amount of force that could be applied to the pedals (probably because they're shagged). In this case, it could very well be that the walking is more efficient, however if the rider was fit enough to input the ideal amount of energy & move at the higher pace, then the efficiency would always be higher for the rider.

That however doesn't take into account any of the points you raised in the first paragraph regarding the ability of the body to efficiently produce the energy in the first place. That's a whole other bag of chips.

 

[brisneyland]

I still think the bottom line is this:
The same mass up the same slope at the same constant speed covering the same distance in the same amount of time = the same energy expenditure. Walk or ride take your pick cause you will be just as knackeredd at the top

This is absolutely and definitively untrue. The same amount of work is done but energy expenditure is something entirely different.

 

[SlowManiac]

I just want it known that that quote is not from me! haha

I also completely disagree.

 

[Jeffgre_6163]

This is absolutely and definitively untrue. The same amount of work is done but energy expenditure is something entirely different.

Not saying your are wrong but can you elaborate based on the Wiki entry you supplied?

OK - imagine you had a sphere and a cube the same mass and you have to push them up a hill - which one will you expend more energy?
Simply saying its the same mass covering the same distance is not correct.

You have missed the fact that in the bike example the mass we are trying to get up the hill in both cases [riding and walking] has the mechanical advantage of being under wheels
In your example the mass of the cube and the sphere may be the same but the sphere clearly has an advantage when you are pushing/rolling it up the hill because you are not fitting the friction that the cube has just sliding

 

[Jeffgre_6163]

This is great, just what I expected, gotta love a good, sensible debate
A great many varying opinions and theory's but no definitive answer.

There has to be some out there who would know for sure?

I'm sticking to same mass [this includes the total mass of both the bike and the engine], same speed, same incline, in the same time = same energy expenditure

Hang on I just had a thought......
Maybe not.

When you ride the bike the total mass [rider and bike] has the mechanical advantage of being under wheels but uses the same engine [you] to get it up the hill.
When you push the bike the engine [you] is not under wheels, only the weight of the bike has the wheeled advantage.
This should result in riding the bike being slightly more efficient as it takes advantage of the entire mass being under efficient wheels.

I dunno....

 

[pharmaboy]

Double post

 

[pharmaboy]

Just for interests sake I just searched up a couple of offroad strava segments for both Mtb and running and looking at the same athletes that I know. Up an 8% grade! one was 7min running and 6,30 riding and the other was 7, 50 running, and 5, 30 riding.

I think it's reasonable that 8% there is still an advantage for riding! though it's slimmer than general trail on the flat. On a 30 minute loop, a friend of mine has completed it running in 35, we are pretty similar on the bike and I have done it under 25 min

 

[SlowManiac]

Not saying your are wrong but can you elaborate based on the Wiki entry you supplied?



You have missed the fact that in the bike example the mass we are trying to get up the hill in both cases [riding and walking] has the mechanical advantage of being under wheels
In your example the mass of the cube and the sphere may be the same but the sphere clearly has an advantage when you are pushing/rolling it up the hill because you are not fitting the friction that the cube has just sliding

That's completely untrue - when your are walking you mass is not on wheels! I am just giving extreme examples but the principle is the same.

You said same mass + same distance = same energy expenditure. That is obviously not the case.

 

[pistonbroke]

Why are you asking? Are you looking for the most efficient way to the top as far as calories go? Or are you racing and looking for the fastest way to the top?