at the
5000 m records per age group for masters women.W35: 14:34
W40: 15:04 +30
W45: 15:56 +52
W50: 16:20 +24
W55: 17:42 +82
W60: 18:48 +66
If we look at 35-50, the average increase is 30+52+24, yielding 35 seconds for ~3 miles every five years, or 7 seconds over three miles every year, or 2 s/mile per year courtesy of time.
Yes I recognize this may not be relevant because we are not presuming you were already at maximum fitness previously or other different initial conditions, etc.
I should not be running 3 minutes slower per mile than I did a few years ago. Cannot be related to age.
I might biased but stretching has always been beneficial for me.
Three minutes per mile can't be stretching?!?
What is the baseline for the 3:00/mile? I didn't see any 30:00 5ks? Perceived effort and hr per pace in this muggy weather would do it!
Last weekend, I ran 2 hours at 11:28 per mile and was really feeling it toward the end and slowing down. On trails, I've been seeing 12 and even 13 (!!) minutes per mile even without a pack. My historical "all day" pace a few years ago was 9:30 per mile. Sure, wearing a pack on a lot of workouts makes a difference. It's not THAT muggy. 10 minute miles should be VERY easy. Instead, I find it very difficult. Something is wrong. I've been running distance for 17+ years and I've never slowed down multiple minutes per mile on a hot day (and this summer isn't even very hot - especially in the evenings when I run.) You can't convince me that this is normal. It is not.
PS I haven't run a 5k for over 1.5 years because I couldn't bear to find myself crying at the finish line after a 30 minute 5k.
As an example, look at the first week of September 2013. I did an 18-mile trail run with pack under 10:00/mile.
You are too hard on yourself. Maybe you need to do more sprint training then endurance stuff? Are you wearing your pack for these slower miles? You might just be having a slower year. That has happened to me before. Or you could be over training.