Sweet spot training

[street]

I have a tentative theory that bodybuilding exercises have a sweet spot.That is a spot in the range of motion that if enough weight is applied growth will occur.For example in my own experience if I squat or leg press a bit past parallel the exact depth is hard to describe but i feel a good stretch in my hammies at the bottom of the movement anyway if I squat to this point and gradually increase the weights I get a great pump and my legs grow quite fast.If I squat short of this the pump and growth is much less.For back the sweet spot is the fully contracted portion of the pulldown or row.On bodyparts that tend to lag I have a problem finding a sweet spot in the movements range of motion for example standing calf raises I can't find that spot.
Has any one else noticed any sweet spots on exercises?