Lets say my best event is the marathon , 2:35, and my speed is lacking - 16:55 5k and 35:00 10k. To be onest I've built backwards from most, starting in Ultra's and moving into marathons with no real running background. It seems like this coming 2020/2021 winter and spring without racing is a great time to really hone is on building some actual speedy pace with 800/mile/5k work.
Is this a a stupid idea? I'd imagine most of the work is intervals at sub-mile and sub-800 pace? How would you all go about building speed from this direction?