How to run a sub 4 hour marathon when you’re currently running 4:30’s

Today’s question on the Ask Coach Parry Podcast and it was submitted by Christopher. We shared the secret about how to get faster over a 10km a few weeks ago and how that can then be used to improve your marathon time. Christopher wanted to know how does he run a sub 4 hour marathon, as he is currently stuck running 4:30’s?