I ran a sub 5 mile in 9th grade at age 14. In a couple of years I will be 49, and that year my goal is going to be to make an attempt at breaking 5:00. I really want to be able to say I ran 5:00 miles 35 years apart. Tough getting old, but this is pretty much the last running goal I have on the bucket list.
I am not sure I can do it, as I haven't run a mile for time in at least 15 years. I did do a 5:30 goofing around on a track last year.
Anyway, this thread is really helpful.
My thought is us old guys have to come at it from an endurance and race smarts perspective, rather than from a speed perspective. I feel like I have to do some intervals at maybe 72 pace just so a fast pace feels comfortable. I suspect I'll start as lame as doing some 200m repeats in 36 seconds. Once those get feeling good, I'll move to 300m repeats at the same pace. Once I can do say 8 x 400m at 72 pace, I think I'll be ready.
The other workout I have in mind is to slowly build what I can do at 75 pace. First try it might be 400m. Then 600m. Once I can do 1200m at 75 pace I am probably ready.
Good luck to you.