Look into the Hobbs Kessler/ Bryce Hoppel approach! I don’t know if the specifics are very available publicly, but It pretty much looks like
1 weekly top end speed session
2 weekly double threshold sessions
1 weekly race specific session (hoppel might do 6x300m, while Kessler might do 10x400m)
And daily easy mileage varies between 10-14 miles in doubles.
Kessler has improved A TON in the 800m using this approach, and Hoppel has also made the huge leap from 1:43 to 1:41 using this approach, which goes to tell me it’s probably effective at developing raw speed and speed economy.
If you don’t want to dedicate 3-4 hours of your day to running like they do it could look something like
Monday: 6x flying 50s, 3x150m, OR 6x50-100m hills with full rest, with a longer cooldown or an easy double
Tuesday: AM 5x4:00 off of 2:00 jogging rest, PM 30 minutes of 1 minute on, 1 minute off, OR just do a single threshold session of 6x5:00
Wednesday: 6-10 mile recovery run depending on mileage goals
Thursday: 5x3:00 @Vo2Max off of 3:00 jogging recovery, + 6x200m @1000m pace
Friday: 6-10 mile recovery run
Saturday: 3x10 minutes @threshold or 20 minutes @threshold
Sunday: 4-6 mile easy run and/or cross train for 30 minutes to an hour.
If you have the tendency to overcook your threshold work and run too fast, this schedule will cook you so make sure to play it safe if you choose to do something like this, threshold days should feel moderate not hard.