What were they doing?

Went to a baseball game the other day and was watching the players stretch and run in the outfield before the game. Some guys were doing running drills (backwards, frontwards, laterally) with resistance bands around their ankles.

Anybody know what this was about?

My guess is playing catch gets boring after a bit.

Agreed but were they stretching, strenghtening, both? One of the guys doing it was Jose Reyes the 21 year old phenom who pulls his hammy walking to the bathroom.