This trick is performed in pre-cathedral room, using 1 reserve tank, x-ray, speed booster, and CF ammo.
You must have at least 70 energy in the reserve tank, and it must be set to auto. 60 is near death, 100 gives more breathing room, more than 100 is a time loss.
Energy must be below 20, so that one hit from a sova will trigger reserves.
- Position Samus as deep in the doorway as possible without triggering the transition. Holding angle and tapping forward to move a pixel at a time is a good way to get into position.