A little conditioning may be good for them, but they are there to play softball, not run track...
This ^^^ reminds me of our last tournament. Blue came over to our dugout at the end of a big inning for our team, and said, "This is softball. You have a track team out here!" Our girls are runners. I would consider my DD to be average speed for her age. On this team, she's in the bottom 3 or 4.