Sprint Nading is the act of throwing a grenade whilst sprinting.
Original Author: Pimgd
When: Whilst throwing a grenade.
What: Moving and throwing a grenade at the same time.
Why: Throwing a grenade takes time. It's almost like reloading - you can't fire until the weapon is ready. As such, you want to stay in cover for as long as you can.
How: Stand in cover, and start throwing a nade. Once your character pulls the pin out, get out of cover. It may take a few tries, but soon you'll be able to exactly time when to move out of cover to be exposed for as little time as possible. Important here is that you need to start throwing your nade first, THEN start sprinting. Otherwise this won't work.
Bonus: You can sprint and jump whilst throwing a nade. With doing so, you can throw grenades in a low arc over boxes in Warehouse - if done properly at the begin of the match, you can hit 5 people or more in a medium/mega server.
How to practice: Try figuring out the exact moment when you toss the nade. Simply do so by finding a fixed measure of distance (like boxes in Warehouse) and count how much boxes you walk past before you toss the grenade. Then practice starting at that amount of boxes away from a corner of the box maze in Warehouse, throwing the nade as you pass around the corner. Try some other locations as well, mapping the distance mentally in seconds instead of boxes.