Hi jenna,
You two could put up a united front. And if you can get other people on the running team to chime in, that would work wonders. Bullies only bully because they can get away with it. If three different people hit him back verbally each three times harder than he bullies your friend, he will stop. Believe me! The social pressure will be too great.
A good line to say to him (in front of everyone) is: “I have two questions. Why are you saying that? And why are YOU saying that?” *you turn to running team* “Am I right??” *Everyone laughs*
*Someone else says* “They’re not laughing with you, they’re laughing at you!”
He will smolder in embarrassment. Let him.
Good Luck!
Inky