Tuesday, June 23, 2009

17 Efficiency In Inefficiency

Cycling is said to be an efficient mode of transport, when compared to running or driving a motor vehicle. Agreed. Mile for mile, far lesser calories and energy is spent, far lesser pollution emitted. But might that idea topple upside down when the road heads uphill?

When road grade rises, there is a seesaw effect in the amount of resistance wind and gravity play. Wind drag now goes down resisting less, and gravity comes up slowing you considerably. All that matters now is how much weight you carry and what gearing you have on the bike. The same gearing that perhaps tripled your speed output on a given rotational crank input on flats will plunge on a steep climb. If you choose to go with a lower gearing, your speed drops. So there is an apparent tradeoff there.

But it stands out, I guess, that one of the obvious elements of cycling athleticism - this notion of how good a cyclist someone is - is by assessing how well they can climb steep roads. Some of us may have this thinking that we're a real cyclist if we climb, and climb steep. I think there's a certain attractiveness in this tiring act. It gives one a sense of accomplishment, and sets a certain level of worth among the people he or she rides with. Bragging rights, yeah that's what it is. Besides, there's always a great view or a downhill to be earned at the other end, isn't there?

Top races in the world are most often won on the steep climbs, when a competitor can easily put time on his rivals. Stars who often showoff their talent on the climbs gets us all motivated to climb, and do it without getting off the bike. Getting off the bike and walking is somehow regarded shameful, powerless. You're no good. You aren't born to do it. Now where a cyclist does show mettle and talent on high gradient climbs, I think more can be said about his physiology and mental faculties than about the efficiency of his activity.

Its interesting that throngs of cycling fans line up steep cobbled roads and alpine climbs in Europe to see their favorite hero drag along the climb at close to walking speeds. Say one casual observer stepped back for a moment and asked : 'How efficient is cycling uphill compared to doing the same on flatland?', what do you think he'd tell himself?

I think the above observer could determine that this cyclist, riding past him on such a steep hill at 3mph, heaving from side to side zigzagging across the road like a detracked choo-choo train, will be more efficient if he got off his bike and pushed it uphill. There's no shame in this. Its just the clever thing to do, for this observer could jog up faster than the cyclist dragging along uphill! I would think much lesser energy is wasted simply caressing the ground with your feet than having to go through the complex motion of pedaling in circles with a chain and derailleur system that ultimately transmits some power to the rear wheel after losses through friction and deformation of rubber tires.

But sporting activity wouldn't have that, would it? Its not considered sporting otherwise. There might be booing from the crowd. There's no athleticism is walking your bike uphill...c'mon now. You're a sissy. You lack mental prowess.

Cycling does have its inefficiencies (perhaps that is why our early ancestors didn't swim out of the ocean carrying bikes to land). But it is the level of efficiency inherent in the cyclist which he applies to get past the natural inefficiencies that come into play in this mechanical activity that ultimately determines his outcome in a race, a training goal or the worthiness and respect he has among his peers. But I'm not the guy is the white lab coat so I can't credibly tell you where this bodily efficiency lies or how to attain it.


Transport Efficiency

* * *


  1. Great post. About the sentence about our ancestors not born as bike riders..I think man is considered a tool making creature, which is what sets him apart from other creatures. Now this can apply even to a bike, if you would consider it a tool of transport. But like all tools have their disadvantages in places, the bike does too. That doesn't reduce my liking for cycling however! I save far more money on gas and putting lesser crap into the air through my bike.

  2. Anonymous12:58 AM

    damn why you think so deep? :)

  3. Interesting post!

    As a mountain biker, and an engineer/scientist, I reckon I have experimented with this a number of times. Using a speedo and HRM, or just by comparing yourself to others, it's possible to empirically work out if it's more efficient to walk or ride a hill. If you are in a group riding (at 3mph all over the road like you describe) and then you get off and walk past them all, then you could day that it is inefficient to ride.

    So I have done exactly that in many different races. My finding is almost always the same: it feels better to walk initially, but it is faster to ride no matter how slowly you are riding.

    However, it gets complicated as the climb goes on. The walkers tend to get this hunched shoulder, head down, depressed, trudging posture - and that is usually reflected in their mood. They might be saving energy by walking, but they are spending it in being grumpy. Again from experience, you can pass a lot of people walking, by walking too, but keeping an upright posture and a positive attitude. Weird I know, but it works.

  4. Anonymous2:44 AM

    Why do you think that slope has anything to do with efficiency? The work required to climb is just the vertical height of a climb, times the weight of you and your bicycle; slope is not a factor. Efficiency is just the amount of work you can do for a given metabolic input. Slope is not a factor there either. Things that rob your efficiency on a bicycle are wind and rolling resistance; those rob less power the slower you go, so for the same rate of vertical climb, the steeper slope, which is slower rolling, will be _more_ efficient (that's why climbing is viewed as such the test of athleticism-- it's all power to weight ratio and no aerodynamics or finesse). Climbing mainly becomes inefficient when you run out of gearing, and are not able to operate at a good cadence for your chosen rate of vertical climb; so get a lower gear, adn you get your efficiency back.

    In one example, as you write you often see spectators running up alongside their heroes in the Tour de France. They can do this because they give up running after about ten meters! No one since the first year derailleurs were permitted on the bikes has ever run up the whole climb alongside the contestants.

    In a second example, the road up Mount Washington in NH is raced by both cyclists and runners, and the cyclists post significantly better times.

    In a third example, someone made a hundred ascents of Fargo Street in Los Angeles in eight hours. Another person established a Guinness record for most stairs climbed in 24 hours. Both made roughly the same vertical ascent, but the stair climber took three times as long to do it.

    In a fourth example, after I take the ferry home after a day mountain biking, I am on a bike that offers a very low gear, so I just point the thing up James St, which exceeds 20% grade for several blocks, rather than the less direct route home. I pick an easy pace because I've throughoughly tired myself out and am out of food, and yet pass everyone walking up the same slope, and make it home sooner than if I'd detoured down to Jackson St.

    Our ancestors were not born as bike climbers, _nor_ were they born to climb steep slopes on foot! As anthropologists have shown human's best claim to specialty evolved athletic ability is to be able to sweat away heat while pursuing prey for great distances over _flat_ terrain. Bipedal locomotion, especially our wierd flat-footed implementation of bipedalism, is really suited to flatland (ever see a mountain ostrich? Ever wonder why we have to build stairs to give our feet purchace on the same slopes that four-legged creatures just scramble up?)

  5. Okay, you are definetly over thinking.
    The way to suck the life out of any thing is over analyze it. That includes riding a bicycle.

    Here is a quote I like.

    ‘A Zen teacher saw five of his students returning from the market, riding their bicycles. When they arrived at the monastery and had dismounted, the teacher asked the students, “Why are you riding your bicycles?”

    The first student replied, “The bicycle is carrying this sack of potatoes. I am glad that I do not have to carry them on my back!” The teacher praised the first student. “You are a smart boy! When you grow old, you will not walk hunched over like I do.”

    The second student replied, “I love to watch the trees and fields pass by as I roll down the path!” The teacher commended the second student, “Your eyes are open, and you see the world.”

    The third student replied, “When I ride my bicycle, I am content to chant nam myoho renge kyo.” The teacher gave his praise to the third student, “Your mind will roll with the ease of a newly trued wheel.”

    The fourth student replied, “Riding my bicycle, I live in harmony with all sentient beings.” The teacher was pleased and said to the fourth student, “You are riding on the golden path of non-harming.”

    The fifth student replied, “I ride my bicycle to ride my bicycle.” The teacher sat at the feet of the fifth student and said, “I am your student.”’

    Zen Buddhist Parable

  6. Anonymous10:20 AM

    Efficiency is a lot in genetics for sure. Back some while ago, I told my self I wasn't born with that extra gas power to do ridiculous things. Its interesting I say this, as I have wasted much time not doing the things I'm not good at while discovering what I am good at. And climbing hills is definitely not one of that. But I've won plenty of Master's time trials in the area.


  7. Anon at 2:44 : Good comment. So let me ask you this. At what grade do you think it becomes stupid to ride a bike and just step down and push it uphill? My feeling is that unless you have ultra low gearing and a well maintained drivetrain, you're putting forth considerably more energy to just pedal up a few inches (on grades>20%) than you could do the same walking. At apeeds less than 5mph, considerable balancing has to occur to keep the bike stable, all the while trying to focus on climbing. I don't know..but it does seem to me as if walking the bike might be a more efficient move than running. Obviously, as a biker, some of us may be biased to say that it 'feels' more easier to bike uphill than to run or walk, but it'll be interesting what a marathoner or an uphill runner would say to that. Ofcourse, but there will be folks who can hammer uphill like you mention. That's where the theme of my post come in. Their bikes are well set up sure, but their bodies can also do ridiculous things like going up and down Fargo St. a thousand times. Not a lot have that innate talent.

  8. Sanish Fernandez12:58 PM

    Don't kill me... but I heard cycling increases the need for human food consumption to keep up with the expending of physical energy. In other words cycling to work may be "green" but it's actually building us up for a massive food shortage.

  9. Sanish :

    Interesting and bizarre :) Then for the same reasons, simply being indulgent in food may be blamed for an apparent progression to food shortage as well. We don't do that often, do we? But its obvious there is some level of cost burden to society in a person being humungous with all sorts of debilitating medical problems. Compare that with a sustainable mode of transport, and exercise while eating good food..Hey, where's the problem again?

  10. I cant believe that walking uphill is more efficient than cycling on a road. With every step a person raises and then lowers their COG slightly and this energy is lost, similarly with each step the leg is lifted clear of the ground then lowered back using energy in both directions.

    With cycling both up and down movements can be used for propulsion and if you lift your COG overall then it still comes down on the pedal and the energy is used.

  11. Gsport : I'm not sure whether you have climbed any hills greater than 20% gradient. Try it for yourself once. Then try doing the same by jogging up the same road. When do you think your muscles are more "loaded", so to speak? If you are loaded in one activity more than the other, it is obvious you're spending more metabolic energy to do so. Many biomechanics books say that the efficiency of cycling is around 25% and decreases with increasing pedal load, possibly because the activity you are doing goes from aerobic, past your lactate threshold into anerobic, which is not very efficient.

  12. Crusher Joe12:48 AM

    Based on the calculations and some heft assumptions - the maximum angle at which a bicycle can maintain forward motion - I think somewhere in the low 30% range is more likely from personal experience. When the runner takes over is when they can "scramble" by using their arms for an extra point of contact.

    The logical next question is - over what distance?

  13. Of course I have ridden up steep hills, I live on one so most rides involve at least some hill climbing. Sure it feels harder than walking but it is massively faster even when it seems very slow.

    Is there anything in the rules of races like the tour that forbids getting off and walking? Because if there was no restriction and walking is more efficient and they were genuinely only making the same speed, you can bet they would be doing it.

    For a comparison to be reasonable in terms of efficiency, the walker needs to be going the same sort of speed and still have the bike (or the weight of the bike) with them.

    I think that the subjective impression that walking is easier, is skewed by gearing choices, speed and muscle groups. When you try to ride a relatively high geared bike up a steep hill and then get off, my guess is that you slow down and start using different muscles so that will effect how it feels.

  14. Gsport : You did mention something about the bobbing up and down of the CG in a runner, and how it has a more energy cost than cycling. Well then, how about cycling on a grade greater than 20% when you're literally squirming and lung busting, pedaling out of the saddle. I think there must be a grade and power output (load) above which it is wiser to run than sit on the bike, just like at around 2.5m/s, it appears to be more energy efficient to run than to walk. I think what we may need to concentrate more on here is the biomechanical basis for what I'm trying to say, perhaps with some experiements and equations. I think I may be doing a poor job of explaining my point of view.

  15. There was a discussion of exactly the same topic on rec.bicycles.tech. Just search there.

  16. When I lived in Colorado we cyclists (who also liked to climb mountains) had this discussion often. Is it easier to walk or bike up Mount Evans ? The people who've done both say it's much easier to walk up and about as enjoyable.

  17. Anonymous5:17 PM

    Nothing beats the feeling of the wind in your hair going downhill, once you've actually made it to the top of the hill and wheeeeeeeeeeeeeeeeeeeeeeeeeeeeee!


Thank you. I read every single comment.