Posted: 06/09/2016 at 12:22
I'll leave it to others with more knowledge to guide you on training. You should be able to do sub-40, but it's not always a linear affair - I've done, in my late 40s (I'm now 53) sub-20 parkruns, but the nearest I've got to a sub-40 10k is just over 41 minutes. It's possible you'll bust it easily, and I should have done it I guess, but the longer distance can be deceptive: quite possibly, because you're running longer you feel able to coast some of the middle miles a bit more than you can in the 'long sprint' of the 5k. A first thing to say is that running hard all the time will probably, counter-intuitively, hold you back - easy runs should be just that, run at what for you is an easy pace. Others will have wider advice.