I have to say - I don't buy this getting old reason for many of the problems cited...i find just the opposite. I can do workouts of pretty high quality and actually put them back-to-back something i don;t think i could do when i was younger because of experience: i know my body so much better. I also don't get sore the way i used to when in college.
I do not accept the conventional wisdom on most things and am willing to try new things in training. There are so many conventional wisdom "myths" that i have never accepted.
- have to take X number off days after a marathon or 1/2
- shouldn't do hard workouts back-to-back
- running on concrete is hard on your legs
- shouldn't bump your milage up by more than X % a week
- should take X amount of time off each year or at the end of each season
- you have to take suppliements
What i do (that may be different than others) or what works for me is:
1) i train in minimalist shoes - i don't think a lot of old timers realize how much shoe have changed over the years - think back to the 70's - the shoes of those days were minimalist in nature - and we put lots of miles on them - didn't we?
2) i lift but not heavy...i like to use weights as a stretching before fast days
3) i have recently added bands and foam roller as well as a few self made sprint drills
4) i build into my workout gradually - if i am doing 16X200 - i may only start out at :40 but may end up at :30-:32...i try not to push/strain the pace, but just let it happen...i focus a lot more on form than effort. I never really did 200 when i was younger - now i do 150, 200 even did 50's one day.
5) i do back-to-back-to-back etc hard days...this is something new...i was talking to a former 4:00 miler who now bikes (he said he does 4 hard days in row and then takes 3 days off)...i decided to experiment a little here.
With the summer heat and frustartion with past summers of just doing milage i wanted to do quality so here is what i did:
Sun - off
MOn - 16X200 or something close to that
Tues - 8 mile tempo (first 4 slowish - last 4 fast)
Wed - 16X200
Thur - 8 mile tempo
Fri - 16X200
Sat - 8 mile tempo
First few weeks of this i would be tired on Thur, then it got to where i was recovering pretty well for each hard day. Usually i would start out tired but end up having a very good quality workout.
The little things are important when you are young, but crucial when you are old - they are:
1) diet
2) sleep
3) effort (train don't strain)
4) flexibility
5) form when running (fast and slow)
6) shoes
7) routine (being consisent - avoid big changes in training) Don't decide to go to the track for the 1st time in forever and attempt all out 200's for example...it took me months to build back into speed workouts.
to the OP: to have such a sudden change is training is not normal - has nothing to do with age - so keep looking for the anwswer - this sounds pretty serious to me (medical in nature).