I just finished my freshman year of cross country and was wondering how I could come back next year faster. My PR is 22 minutes and I'm looking at a long term goal of getting sub 18. I think what I need to do is improve my endurance. I'm planning on working my way up to 60-70 mpw all the way until next March. Then I will start incorporating tempo runs, intervals, hills, and long runs. My question is how should I build my aerobic base throughout this winter. Like I said I am looking for 60-70 mpw. I don't have a lot of talent. I'm 5'7", 125 pounds.