^^ that is the most important question here. If your a long distance runner, I would stay out of the gym. Adding muscle mass will only hinder your distance capabilities.
As a sprinter, I would work plyometrics, dots, foot work, and other intensity type movements. I wouldnt heavy squat,deadlift, or legpress, i've seen many many people slowed down by thier added muscle mass and loss of flexibility.
I don't do this for my family, my friends, women, accolades, pride, or ego. I do it for me and no one else, its just part of who I am.