What is B & F?
when those fucking marathon runners are closing in on a newby runner, you'll often see the newby taking a convenient (and not at all obvious) stretch break.. going back and forth - a.k.a. b & f - from one leg to the other until it's safe to start walking without being noticed by the not-so-newby
"i can hear the fucking marathon runner coming! quick! do the b & f!"