Little bit of a story. I'm 22 years old and have been a runner for years but only started running serious mileage this year. I'd always done 30-35 MPW and had a 5k PB in the low 17's. After a summer of averaging 65-70 MPW I time trialled a 10k on the track in high 32's. I think it's realistic to say I'd be in the 15:40 - 15:50 range for 5k. I recently got a new coach as I want to improve further and he's adamant that I can be sub-15 (and sub-4 1500) NEXT SUMMER! I'm aware that there's an enormous gap from 15:40 to 15:00. I like to think that sub-15 is an ambitious goal for my entire running career, is it really realistic that I could do it in a few months time?