Is it more efficient to move to a lot lower gear and remain sitting, or not change the gear as much and stand for more force?
My experience is that you can go faster uphill standing on the pedals, but at the cost of more energy. It is more efficient to sit.
be careful about standing; the chain can slip (or break) and that would be quite bad-- as I found out just before I broke both elbows and both wrists.
I can’t figure how sitting would help anything. If you stand, you use your own body weight to push the petal down. That’s got to be more efficient than just your leg muscles, right?
It’s not that simple. You can’t use your body weight as an energy source. You’re still using your legs to lift your body, and that’s where the energy comes from.
Sitting and spinning (i.e. pedaling at high RPM) is good because human legs have peak power output at a pretty high pedal cadence, somewhere between 90 rpm and 120 rpm IIRC. On the other hand, there’s also benefit to using different muscle groups, so they can take turns resting. Standing on the pedals uses more muscle groups (even your arms are contributing to some extent), so there is benefit to this style of pedaling.
Well, not necessarily, because if you stand your pelvis isn’t supported by the saddle, so you’re using your hips/abs/back muscles a lot more to steady yourself.
There’s also a tendency when standing to shift so that you’re putting more weight on your arms, which at best does no good at all, and at worst reduces your efficiency. You want to keep your weight over what’s producing the movement, not the wheel that’s just getting pushed along. Pressing yourself down onto the saddle can feel kind of counter-intuitive, but can give you much more usable power*.
Plus - as Cagey Drifter mentions - standing can put all sorts of different pressure on the chain. A common problem (which I’ve done more than once myself) is trying to shift into a higher gear once you’re already standing; that can cause your chain to pop right off, and even if you don’t take a tumble because of it there are still greasy fingers and many obscenities in your future.
If you do stand up, then you want to kind of ‘rock’ your bike side to side as you pedal (good explanation here); it increases the usable power of the motion.
*Unless you’re mountain biking on a trail way beyond your capabilities, in which case part of you will desperately want to stand up to get up the damn hill, but part of you will want to lean backwards to keep traction. And then - if you’re me - you wipe out.
I believe I would take the word of this gentleman!
The question of which is more “efficient,” in a technical sense, is extremely difficult to answer, and probably not the one you want answered. A different question, which is more “powerful,” is maybe easier to answer, but again not what you’re looking for (since high power = tire quickly).
So just answer it yourself… which do you find more comfortable? Most of it, in fact, depends on your bike. (Height of your seat determines how well you’ll pedal sitting, and the position/shape of your handle bars determine how comfortable you’ll be standing up.)
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If you have a properly configured and maintained drive train and use proper shifting technique you don’t have to worry about slipping or busting the chain. Just watch a Tour de France sprint finish. Those guys are putting down more power than you or I can dream of while throwing the bike all over the road and they rarely blow up the drive train.
As for whether to sit or stand, I do both. It gives me a chance to switch up muscle groups and/or use them in a different way.
A question I have debated with a fellow rider is if pulling up on the handlebars while standing increased traction at the rear wheel when climbing. Big. Mountain Biking. Issue. around here.
Sitting down when climbing is the most efficient way to use your energy, change down to a low gear, get into a rhythm and spin the pedals at a high cadence. This uses about 11% less energy than standing. Not such a big deal on a quick commute to work, a big deal on a 100 or 200k ride.
Standing however has benefits, gives you a burst of power for corners, short steeper bits and changes in road surface. It also has the befit that you use different muscle groups, enabling you to use your upper body strength and glutes to drive the bike forward and giving your quads a rest for a few seconds.
Watch what Tour de France riders do. They try to sit as much as possible to save energy (stage racing is all about who uses their energy the most efficiently) with short periods of standing to stretch their legs. They save full on standing attacks for when it really counts, knowing that it will empty out their “gas tank” pretty quickly knowing that it will leave them venerable to a counter attack.
In saying all this there is a degree of the right tactic for the right climb (I generally just power up short 200m or so climbs standing) and what suits some people may not be best for others.
Standing up is not so much efficient as it is effective - it allows you to expend more energy, but not for a very long time. Just sitting and pedalling gets you much further. FWIW, the riders in races such as the Tour de France sit down until they cannot take it anymore and they have to muster all their strength, for instance to chase an escaping competitor. Then, and only then, do they stand up to gain more speed. If they get up from their seat in any other situation this is generally seen as a sign that they can’t keep up and will be dropping out shortly.
On a steep hill (and especially off road) you also have to factor in traction. I generally find I can get up a hill easier by standing and leaning forward with most of my weight on the handlebars - unless the surface is loose or slippery, in which case the back wheel tends to lose traction. In that case, it’s better to stay in the seat, with more weight on the driven rear wheel. But then again… when the hill gets *really * steep, you have to stand up and lean forward again, otherwise you tip over backwards.
So the answer is … it depends!
It depends on the hill doesnt it?
Long shallow slope, sit, short steep, stand.
Otara
Not really. You can be faster climbing out of the saddle on any hill. If you’re fit enough, you can stay that way all the way to the top of any hill. The slope of the hill will dictate how long you can keep up the harder effort of standing up, but the same tradeoffs apply.
Note: I am a touring cyclist.
The answer depends on, obviously, a variety of factors. Primarily, however, the answer lays in the length of the hill. If it is a long hill then standing up will only result in your burning yourself out halfway up. Exhausted and halfway up a hill means you spend the rest of the climb essentially walking your bike up. If it is a short hill, however, a quick burst puts you up and over the hill and in many cases you get to recharge on the downhill.
This is pretty much how I approach it. But, as others have said, it’s often good to just switch from one method to the other in order to give certain muscle groups a rest.
Just a guess here, but one good way to answer this question would be to watch the climbs on the Tour de France.
Only if your objective is to compete with the riders in the TdF. 
Seriously, those guys aren’t like you and me, and what they do doesn’t apply to us mere mortals.
Maybe, but it would answer the question posed by the OP: which is the most efficient way to climb a hill on a bike. I can assume without much fear of contradiction, that the racers have figured out the most efficient way to bike up a hill, and apply it regularly.
FWIW I bike about 16 miles round trip on a hilly route to work about 3 days a week. So I was thinking more along the lines of practical mid-distance biking as opposed to the pros. As a parallel, some pro runners won’t touch their heel to the ground for distances up to 10,000 meters, but that probably wouldn’t be a good running stance to recommend to a beginner.