Decent miler, 5ker and 10ker trying to increase 400 speed...

Keep doing drills. Do shorter hills, steep ones. 10-12 by 8-10 sec all-out with full rec. Do all-out 40m sprints on the track in spikes. 4 sets of 4 by 40m, with the first set being done at 85% max speed and then 90, 95, 100% max speed for the next sets. Always take full rec. (like 2min between reps, 8min between sets.)

Let me think though, 16 flat in the 5k? Is your 400m pr around 58? If its faster then that, I'd guess that you haven't reached your "limits" in terms of aerobic development.

So if you are a decent miler, are you a lot better at the 5k and 10k? 400m speed is way more important in predicting your mile time "limit" than it is for 5k-10k.

thanks for the advice... yes you are right on the money, i am much better at the 5K and 10K then the mile... all i know though is that the guys i train with beat up on me in the 800s and 400s, i start to be able to hang int he 1200s and miles i am fine. (ironically, probably because of lack of training i start to fade in much longer distances though)

my 400 pr to date is 60.5 (my own watch), doing the 100m strides i've been timing myself and I can get down to about 13.0

More speed will help as will the hills.