It's no secret that the Masters of all Terrain 50 mile run is a week before the T3. Some of those currently enrolled in the class are doing this insane run in addition to the T3. As is customary to the T3, those who do extra credit (extra events) close to or immediately before the event will get relief from certain hardships during the event. So let's say you plan on doing 50 miles only one week before the T3. Here are the rewards you can earn:

Finish the 50 mile run: Automatically start the T3 with a stress card
Finish the 50 mile ruck: Your T3 will be entirely ruckless!