xena wrote:"So your legs and body are not doing the exact same movement are they"
But you have to put the force down earlier i.e. because the bigger chainring is closer to your body , your leg is going to be a bit higher when you engage[ use force] the big ring i.e. the difference of the height of the rings.
What do you think ? It may not be a huge difference but surly there is a both physical and mechanical difference?
That is completely nonsensical. It only makes a difference if you have somehow welded your cranks directly to the chainrings instead of having them connected to the bottom bracket. The position of your cranks, pedals and thus your legs is EXACTLY the same whether you have a 30, 34, 50, or 104T chainring.