One thing about standing is that you can/have to do it in a higher gear than sitting. If you are comfortably turning the pedals sitting and then stand- you will almost certainly spin out your legs. So if you want to stand then up a couple of gears or don't bother changing till it gets tough sitting and then stand.
I don't stand often but top of a hill and no gears left and I will stand to give the legs a rest. Top of the hill in large or middle ring and instaed of changing on the front for the last 50 yards and I will stand- Or if the butt needs a rest I will stand.
It does work a different group of muscles and is usefull. Efficient possibly and more tiring- Definitely.
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How long was I in the army? Five foot seven.
Spike Milligan