So I am entering my Senior year, next fall. I am a 5:00 miler and I would love to get my xc 5k times down ( I am a girl). My current pr is 20:12.8. and I would like to break 20:00. I have never done high mileage in the summer, maybe doing like one week of 70. Would getting my mileage up to 90 mpw help me?