I rested a day and most numbness went away. Came back on next workout and has been present since. My initial thought was that it was the extended time I did on the treadmill Christmas (an hour at about 3.5 mph with varying incline up to 4). I bought new shoes. Still problem. Moved from the treadmill to the recumbant bike. OK, NOW it is localizing to the midpoint IN on both legs. On Christmas I also added hip adductor (3 x 10 @ 130 which feels easy) and hip abductor (3 x 10 @ 80 lb) exercises to my routine.
The rest of my weight work has been upper body and I'd been doing that for a month with no problems.
I've researched online and talked to a couple of friends who are massage therapists and work with sports teams (actually, I have too). IMO, this is not sciatica--there is no radiating, no pain, and no problems elsewhere. It more closely matches (anterior tibialis) compartment syndrome, but that is normally accompanied by problems with foot/ankle flexion which I don't have. I *do* have a history of shin splints, but this is NOT shin splints (certainly not as I've ever experienced them).
Any thoughts/ideas? My next move is to stick with the recumbant bike for my aerobic warm-up and to drop the hip add/ab exercises and see if I experience full return of sensation. Then I'll SLOWLY add back the treadmill time and/or at least try to isolate what the problem is. BTW, I don't use elliptical machines (in case anyone was going to suggest) because they set my bunions on fire

