Running - How to get faster?

[AndStilliRise]

So I have tried running 400s 800s 1ks. Tried 100m, 200m but just can not seem to get much faster. I want to try and break Sub3 for a marathon (pb 3:23) but can seem to get fast at the rate I would like.

What am I doing wrong?

[944fan]

Are you carrying any excess weight? Each pound of fat you can lose is worth a couple of seconds per mile.

Otherwise I suspect your training speeds are wrong. Use this calculator to work out training paces from recent race performances.

https://www.mcmillanrunning.com/

You are already running a pretty decent rate and you will find diminishing returns the faster you get.

I swim mostly these days and start of this year I was chassing 4 seconds off my 400m time to get me below 6mins. Took so much work