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Gamefreak is adding a stamina bar to Pokemon.
Basically, "strong" moves take up more stamina and can't be used consecutively (100 bp + or moves like protect. Also, priority moves drain stamina quickly).
After each turn, stamina recovers at a fixed rate that differs per pokemon. Some really bad pokemon will have much higher stamina recovery.
This is the change Gamefreak has been talking about that would alter game mechanics greatly.
Discuss.