400 / 800 TRAINING PLAN Which should i stick to?

This is more of an 800 program, with maybe one 400 session chucked in. You won't reach your potential for 400 training like this.

You need AT LEAST two speed workouts a week to run a better 400.

However I think there is something to the theory that the faster your 400 is, the easier the first lap of your 800 feels. So there is benefit even for 800 specialists to do a fair chunk of 400 training.

By the way for your 400 sessions. Do them fresh. Do some good speed drills at the start, then say some flying 40s at pretty much mx speed, with full recovery.

Then for the speed endurance part of the session afterwards, I think the following are better than 150s or 200s:

- 7 x 100, going round the track, with cones every 50m. So start off running 0-100, jog back 50, then run 50-150, jog back 50, then 100-200 etc. Each of the 100s (except maybe the first) should be flying 100s at 400 speed, so you are hitting pretty much 400 speed at the start of the 100 and then relax and hold it for the 100. It comes out to about 7 x 100 with a 20-30" jog recovery

- 3 x 300 at 400 speed, but with big (8-10') recoveries.