Rapid Heal is a Prayer that doubles the rate at which the user's life points are restored.
Rapid Heal does not drain the user's prayer points quickly, but this prayer is nevertheless not commonly preferred among players who are in combat, since the replenishing rate of LP is rather slow even with it activated. Using food or a healing familiar such as a Bunyip is recommended and generally preferred.
Training: turn it on the moment you start training, along with various prayer boosting equipment, such as an Amulet of Glory. This may provide you with 300+ life points, depending on how long you stay in the area, your prayer level, and whether or not you use other prayers.