I don’t know if this has an answer or if its more of a debate. Maybe someone could help with the question before giving an answer.
Here’s how I’ll post it: What is the most efficient way for a person to move across a smooth, flat surface?
Lets say the distance is long enough so that “start up” is negligible.
I suppose we’d measure it in calories burned per mile.
Is it walking, jogging, bicycling, pogo-sticking, walking in a giant hamster ball?
Is there something fundamentally different about biking because you’re using gears?
What about a pogo stick? Is there something fundamentally different from running or biking with a pogo stick because of the spring in the pogo stick?
Clearly a car is different because it uses another energy source than “human”. Is there some other kind of machine that uses a combination of simple machines to get a human across distances?
It certainly seems like a bicycle is a very efficient human powered machine, essentially being able to turn a “stride” into about 80 inches of movement. Is that a proper way to measure?
It’s a good question, let me add a corollary that I’ve often wondered about.
If you walk a mile, you have to move your legs, expending enough energy to move your own weight. If you cycle the same distance, you have to move your legs expending enough energy to move your own weight plus the weight of the bike. Yet walking seems more tiring than cycling. Why?
Well, don’t forget the bicycle can coast, but your legs cannot. Also, the motion of your legs is different for each. Additionally, most bikes have gears. People tend to set the gear to reduce resistance when going uphill, and maximise stroke when going downhill. In other words, a bike lets you ‘tweak’ a couple of things about your own output.
The most efficient way for a human to move across a smooth flat dry surface, using only their own muscle power, is by bicycle (probably a recumbent – where you lie back to pedal). You’ll notice almost all serious human-powered machines (airplanes, generators or whatever) use the bicycle arrangement – legs moving in a rotary fashion.
I don’t know how the answer would chance on a snowy or icy surface. Skating is certainly far more efficient than walking, but I don’t know how it compares to biking.
Gears, in the sense of something that can trade distance for force, are kind of fundamental to the concept of a ‘machine’. Most bicycles can change gears on the fly, but even a single speed bicycle is more efficient than walking or running or rollerblading.
And most people would consider the most ‘efficient’ method to be the method that uses the least energy to move a given distance. So it depends on how far you go per ‘stride’ but also how much energy it takes to make that stride (compare walking versus sprinting. Running strides are longer, but clearly less efficient).
Sorry I don’t have a cite, but I read years ago that bicycling was the most calorie-efficient method of human transportation, period. In other words, it uses less calories per mile than not only other human-powered means, but also than motorized means. I’m sure this applied to everyday situations rather than specialized ones like sailing or skiiing downhill, which aren’t normally used for ordinary getting around.
The thing to look for is how much of the energy expended is not going into moving you forward. With a bike, there is almost no wasted energy, your leg motion is converted very efficiently into forward motion. There are losses due to friction (as there are in any system) but they are smaller than the losses involved in walking.
The higher pressure tires you can get the better, as that will eliminate more energy loss. A single speed bike without gears would probably be better from an efficiency standpoint as well, the gears introduce lots of places for friction.
So, if it’s true, can we say something about the “naturalness” of the bike as an efficient machine, or have we just not invented something that can translate human power into motion better?
Would you use less calories, say, if something could use your arms and your torso to power it?
What if there was a way to bring the motion of the “elliptical” machine into travel?
If you could balance a geared one-wheeled bicycle (a unicycle), could you get more efficiency than you do with a bike?
I’d be interested in seeing whether a recumbent is more efficient than an upright. 'Bents don’t seem more efficient, simply because the chain travels a much greater distance. That means there’s usually a long sagging chain (which has to waste energy), or multiple chains that travel over several chainrings (which has to add more friction to the system).
I’d guess a kayak or rowing shell would come in pretty high on the list of efficient forms of locomotion, mostly because you also get the “coasting” effect. With little if any conditioning, I can hop in my kayak and paddle 7 miles at pretty much walking speed, using (pretty much) only my arms which are not designed for locomotion.
Rowed boats would be less efficient than a bike because water has a pretty high viscosity, but probably more efficient than walking.
No matter how streamlined your shell, you’re comparing the resistance from water to the resistance of air, and a minor bit of friction with the ground.
I’d put it on par with jogging with a small parachute.
The main benefit of the bike is that you don’t spend any energy supporting your own weight. Walking and running require your legs to constantly compress and expand just to support the motion of your body. Once you get body support off your legs, any other improvements are just incremental.
It would not be more efficient in terms of energy per distance, but it would allow greater power, so you could expend energy faster and cover distance faster.
You mean the cardio machine at the gym? You are still using your leg muscles to support your weight on that machine, though it’s a smoother motion.
Don’t see how.
The lower profile of a recumbent reduces drag, so it would be somewhat more efficient. The other advantage has to do with power rather than efficiency, since you can push against the backrest instead of just using your weight to power it. The length of the chain has nothing to do with efficiency except to the extent that it adds weight. I am not familiar enough with recumbent design to know if the chain travels over more chainrings than a conventional bike.
Another way to increase power (but not efficiency) is toe clips and clipless pedals, allowing power to be applied in the upstroke as well as the downstroke.
In walking you are lifting your weight with every step. A mile is a lot of steps and will expend a many ft-lb of work. In the case of a bicyle you have only to overcome the rolling friction of the entire machine and hence much less work is expended.
Some 'bents have a long chain that runs to the back wheel. The chain will often droop in the middle. It seems to add weight, and there had to be some friction added with all the extra links. Whether that’s negligible or not, I couldn’t guess.
Some, instead of having a long chain, run 2 chains over extra cog wheels, or at least run the one chain over some cogs to get a better alignment. here’s a real clunker
Whether it reduces drag or not, I’m not sure. It’s a lower profile, for sure, but a biker in a racing position can be pretty streamlined whereas a guy on a 'bent usually exposes a lot of his torso, and seat back to the wind. Some even have farings, presumably to reduce this.
Excellent points about not supporting your own weight with your legs. I think that’s a key thing.
Well, until the whole ‘supporting yourself with your legs’ thing, I was gonna say rollerblades.
If you’re not interested in going particularly fast, a VERY minimal side-to-side motion with each foot can propel you quite well on a smoth flat surface with virtually no effort.
But of course, you’re still standing.
And breathing and thinking and metabolizing, so I don’t think ‘standing’ should count as energy expenditure. q;}
Another important benefit is that a bicycle provides an optimal load (impedance) for human legs to handle. Muscles are like gasoline engines; they have a narrow range of speeds (RPM) where they are efficient. Even single-speed bikes are geared so that a comfortable and efficient pedal speed (say 60 rpm) gives you a good cruising speed (say 10 to 15 mph). If you put a very low gear on a bike so that one pedal stroke only moves you forward by 1 ft, I think it would be as inefficient as walking. You would beusing most of your energy moving your legs in a circle, and less energy actually used up for forward motion.
Actually it’s not that bad. IIRC, when the body comes down after each step, it gets converted into forward motion (kinetic energy). This kinetic energy is then used to raise the body again, with the legs acting like a pole vaulter’s pole.
I’m not buying that, at least not 100%. Human leg muscles don’t store energy like a totally elestic device such as a bent pole or rubber band. It takes energy to contract muscles against a load.
Some animals do have ligaments and muscles that return energy this way and I know that somoene has built spring loaded “kangaroo feet” that allow the wearer to run much faster and more efficiently than without because of the returned energy you describe.
Certainly a sprinter who stays on his toes in a run is in this same mode but only because of energy expended to keep muscles contracted not because they are returning stored energy.
