Invigorating

If a creature has training in Endurance, it gains temporary hit points equal to its Constitution modifier when it hits with a power that has the invigorating keyword. No invigorating power grants temporary hit points more than once during a turn, even if the user hits more than once with that power.

Published in Player's Handbook 2, page(s) 220, Martial Power, page(s) 7, Rules Compendium, page(s) 313.