Pitching ask

So I've done a few brews and every recipe I try says to do something different when pitching the yeast. I did a pale ale that said to pitch the yeast and shake the bucket to introduce as much oxygen as possible. But an imperial IPA I just made said stir the yeast in gently and avoid shaking the bucket. Why is this? via /r/Homebrewing https://ift.tt/39yvyFo