The harder part

Exercise. I am not fit and havent been for a long time so exercise is hard for me. Todays exercise was a 2 hour Ultimate skills session. I have been doing this for the last 4 weeks. I love getting back into it but the sprinting kills me. I am anything but fast! I am doing the skills sessions in the hope that I will be ready to play in the Fall league but need to do some kind of sprint training if I am going to be serious. Not sure how to do that yet but am open to ideas.