Rajon Rondo has been pretty active during the summer of the lockout in the NBA. This video was posted by fellow University of Kentucky alumni Nazr Mohammed, and shows Rondo doing various drills on the track to strengthen the legs, while also improving speed, agility, balance and quickness. There is no sound, but it's always interesting to see the various workouts that players use to train.
In this second video, we see Rondo and company doing a classic training exercise: Stadium Sprints:
(h/t to @sanabeans for posting this on her Twitter timeline)