In our last session, a character decided that he wanted to run and jump off a 3-story building, land and use might to prevent damage, and then continue running. I’m not entirely convinced it really should have happen that way. How should a character jumping off a building be handled?
Rules for handling falling are on page 319 of Dresden Files: Your Story. The short version is that stress is inflicted for hitting the ground and a skill check can provide armour against it.
The rules use Athletics, not Might, and I don't think there is a good case for switching in Might here (not without a Mortal Stunt anyway) as the skill lies in being able to land at the right angle, bend your legs the right way, and so on. Strength is not much of a factor.
I would rule that if the character wants to keep running, then the normal rules for movement apply and each zone inflicts a -1 supplemental action penalty against the Athletics check to reduce damage.
There is also the temptation to compel one of the new consequences the character has, almost certainly, just acquired to leave them flat on their face for a round.
I guess that just using might to boost athletics as in Combining skills(YS213) isn't cutting it for you.
You can allow the character to maneuver using might and place the aspect