Full Run

With suitably flat or ample terrain, a creature can reasonably move or maneuver as fast as possible to cover long distances.

When you Full Run, you can spend your Action & Bonus Action to move up to 4 x your Movement Speed in a straight line.

You cannot Full Run through Difficult Terrain (unless you have features that ignore Difficult Terrain, such as Ranger's 8th-Level Land's Stride feature, and features such as Mobile's "When you use the Dash Action, difficult terrain doesn't cost extra movement on that turn"). Full Run counts as a Dash for some mechanics, but you cannot Full Run as if it was the Dash action (for the purpose's of Rogue's Uncanny Dodge or the Haste spell).

You still have Movement and can use up your movement before or after taking the Full Run action, but not during.

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Couldn't find it. From a D&D 4e Book though, definitely.