Not trying to hijack your thread Chris, but I've just been informed by my wife that there's a local 5k at the end of September that we're both doing. I'm in a somewhat similar boat as you being that I'm historically skinny and have spent much of the last 2 years devoted to strength/weight gain with occasional forays back into CF style WOD's. I used to run quite a bit, but was never that fast, running 5k's from anywhere from 22 to 28 min, depending if I'd run at all in the preceding months. My jogging background succeeded in royally messing up my knees with chronic tendonosis and the combo of weighttraining, sprinting and abandoning the heel strike have helped me immeasurably. I've gone from 5'11 lean 160 up to 192 (bulking), now back down to 175 with the same leanness I had at 160 and running definitely feels different with the extra 15.
With only 6 weeks I don't have high expectations but I'd like to prove that I can run in the low 20's w/o any real running program, and with the extra muscle. Here's the plan I've been working on:
M - Lower body strength (I've been using lots of unilateral stuff b/c my sore knees really seem to thrive on this, and at the bottom of a heavy squat I catch myself shifting over to the left b/c of rt. knee wonkiness)
T - Upper body (vert push/pull)
W - 400's, maybe some 800's (but probably not)
Th - off
F - Upper body (horiz push/pull)
S - Roving 5 mile mountain trail loop with the dog. A combo of hill sprints, 2-5 min tempo runs with an unsustainable pace, and lots of walking. Often, I just do what the pooch wants (she hates jogging - smart dog)
Su - off
Again, not trying to hijack, just thought I'd throw this out there. I'm just going to see how this 37 yr old body responds to a moderate ramp up in mileage. Hopefully this will provide a nice break from the SS type training I've done recently, and I'll be able to hit the weights again hard in October/November.
Oh, and in answer to your last post, I don't have any experience in running with a weight vest but I personally wouldn't do it. Then again, my knees are tempermental and I'm not willing to take the risk. YMMV.