Climbing a hill out of the saddle, standing on the pedals is very tiring and a rider can soon burn himself out. But used sparingly at the right time, an experienced rider can save energy in the long run.
When deciding how to climb a hill on a bicycle, think of it as a work load. Imagine two men, each moving 100lbs. of sand from A to B in five minutes. One man hoists the 100lb. bag of sand on his shoulder, moves it from A to B in one minute, then sits down and rests for four minutes. The other man divides the sand into five, 20lb. loads and takes a minute to move each 20lb. for a total of five minutes.
Now imagine that the two men have to immediately repeat the same task over and over. Who is the fresher? The one who makes a big effort to start with, but then rests, or the man who spreads the work load over the full five minutes? A lot depends on the makeup of each individual.
Often if a road is an undulating series of short steep hills, it is often in the interest of a rider to use the speed and momentum of the descent to carry him half way up the next climb, then without shifting down, he gets out of the saddle and puts in a super human effort to keep the momentum going to carry himself over the crest of the next hill, knowing that even if this effort takes him to the point of exhaustion, he can recover on the following descent.
On a long steep climb it is different, even a long gradual climb. One must still try to keep momentum, and must occasionally get out of the saddle to boost that momentum, but a rider cannot put in those super efforts, when there are no downhill respites where he can recover.
A rider climbs out of the saddle not only to get his full weight over the pedals, but to get his body nearer his hands so he has a direct pull on the handlebars in opposition the downward thrust of his legs. Think of using an elliptical treadmill in a gym. One has to constantly move their body from left to right, so the user’s full weight is directly over the downward stroke of the paddles.
On a bike, instead of moving the body, move the bike. As the rider thrusts down on the right pedal, he pulls upwards on the right side of the handlebar. This not only puts an opposing thrust on the pedals but it moves the bike to the left, effectively using the bike as a lever.
As the right leg pushes down on the right pedal, power is transferred through the crank, chainwheel, and chain to the rear wheel. Meanwhile the bike’s frame is moving to the left and the bottom bracket, is moving upwards on the right side.
There is not just the leverage of the crank arm, but the leverage of the whole bike frame working in the opposite direction. As the pedal moves down towards the bottom of its stroke, the right side of the crank axle is moving towards the top.
When the right pedal gets to the bottom, the rider pulls up on the left side of the handlebars, while pushing downwards on the left pedal. The rider’s body stays vertical, and the bike moves from side to side. (See top picture.) Also as the rider pushes down on one pedal, he pulls upward with his other foot on the opposing pedal.
Obviously climbing out of the saddle like this is very tiring, one is using the whole body. But used sparingly, to increase momentum, it can be very effective. For example if the gradient of a climb starts to level out, a strong rider can shift up a gear, then get out of the saddle to get the cadence back up to a level where he can sit down a pedal again.
It is all a matter of a rider knowing his fitness level, and his recovery time. Knowing his strengths and limitations, and that only comes with hard work, training and experience.