Short 400 meter training block for distance runner

7/5 morning workout, in the rain:

2x200m, 600m, 2x200m:

30.1, 30.3 (2 minutes rest in between)

4 minutes rest

1:29.9

7 minutes rest

28.7, 28.7 (5 minutes rest in between)

Use a five-paces block. 14 day cycle repeated 3-4 time (6-8 weeks)

Day 1: 1500m pace (300m-600m reps) (3k-4k total volume), recovery interval: 2x rep time
Day 2: Recovery pace or Base pace run 30 min
Day 3: Max Sprints (30m-50m reps) (300m-500m total volume), recovery interval: 1 min per 10m of rep
Day 4: Base pace run 30 min
Day 5: Recovery pace run 15 min
Day 6: 400m pace (120m-300m reps) (1200m total volume), recovery interval: 8x rep time
Day 7: Recovery pace run 60 min
Day 8: 800m pace (200m-400m reps) (2k-2400m total volume), recovery interval: 4x rep time
Day 9: Recovery pace or Base pace run 30 min
Day 10: 200m pace (80m-120m reps) (800m-1k total volume), recovery interval: 16x rep time
Day 11: Base pace run 30 min
Day 12: Recovery pace run 15 min
Day 13: 400m pace (120m-300m reps) (1200m total volume), recovery interval: 8x rep time
Day 14: Recovery pace run 60 min

- If you race, that replaces the 400m pace workout.
- For meets sign up for three races: 100m or 200m, 400m, and 800m or 1500m. You want to race below, at, and above the target race distance.
- Progress the rep distances from shorter reps to longer reps as you progress through each 14 day cycle.

This seems like a reasonable sprint-focused block for a distance runner - especially one looking to maintain fitness for 800 and 1500. How close would this sort of plan come to maximizing pure 400 meter fitness? With no longer races planned for a while, I don't mind sacrificing long-distance fitness to see how fast of a 400 I can run.

I feel like my 800 meter fitness currently is certainly as good as it was before starting this training block - even focusing solely on the 400. Not sure about my 1500. I might still be able to run a halfway decent 1500 but it would probably feel horrible compared to when I am in good 1500 shape.

Workouts this week:

7/8: Planned to run 400/200/200 pretty fast, but not all out. In the 400, I felt a twinge in my hamstring around 300 meters. It didn't feel bad enough to stop, but I eased off and coasted in. Time was 57.3, and it felt relatively easy except for my hamstring. Didn't run any 200s - they probably would have been slow and only hurt my leg more.

Middle of the week I just did some easy strides and drills.

7/12: Ran 8x100m strides, followed by 800m pretty hard. Hamstring feeling much better, but I didn't want to run a 400 meter time trial today. Ran 2:05.6, splitting 62.x/63.x. Was decently happy with that time, and especially happy that my hamstring didn't protest.

I will probably aim for a time trial at the end of the month - too much travel in the next week and a half to count on consistent training.