Hey :D
In artistic gymnastics (the one with the bars, beam, floor, vault) we do lots of cardio and conditioning, build lots of muscle and also build flexibility too. Just stretch really well before running and also after, and also do kicks - to the front, side, and back on each leg - that really helps a lot too, and to have long muscles, not short and tight. I just posted a youtube video here:
http://www.gymchat.com/messageboards/viewtopic.php?p=39464#39464 - at around :10 in the video I guess you would call that rhythmic gymnastics kicks!!
In any sport there's the stereotypical body type, and there's also those who win and are really good at their sport who don't fit that. Have fun!