I am a female, 23 years of age and I want sub 20 by my next birthday. I was just running for fitness up until recently, meaning I was doing a lot of sprints and no miles. Essentially I was running 10 miles a week maximum, all in the form of intervals (400s @ mile pace twoce a week, 200s once a week and 800s once a week - 2.5 miles per workout).
Anyway over the last 2 months I have started running milage to build a base and get used to more time on my legs to make far distances soon short. I have built up to run 25-30 miles per week, 70% easy miles at 9:30-9:45 pace with a long run between 8 and 10 miles. I still do 400s once a week to keep my speed on form and I do 800s or a tempo once a week for endurance. Every now and then I will throw in 3-4 mile run at a moderate pace (for me, 8:30).
Obviously I should build up my miles to around 50 before I can sniff sub 20, I know that. But I’ve never trained seriously before and to be honest, I am nervous because I seem to be in better shape than I thought (just off two months of very low milage - it makes me wonder what I am capable of with more miles) because yesterday, I hopped into a 3.5 mile road race (it was short at 3.4 miles though because I measured the route with mapmyrun and my garmin also measurd it short) and was able to run it in sub 25. I didn’t even think I was in shape to run a 25 minute 5k, let alone 3.5 miles at that pace and to be honest, it felt more like a super hard tempo than an actual race. I plugged these times into a few calculators and the equivalent 5k time for the shape I am in could be anywhere between 22 and 23 minutes, so I’m going with 22:30. I want sub 20 badly, but I am not sure about everything I need to do to get there and was hoping for some advice. My weight is not an issue as I am already very slim.