I need to spend a lot more time on maintaining my flexibility, especially my hamstrings and calves. I think the lack of a good stretching routine is the root cause of my sore and stiff lower back. I felt much better today, and I plan to continue easy aerobic running for at least one hour. I hope to add one longer run (up to two hours) on the weekend and a speed workout midweek - something like 6 X 1/2 mile @ 6:20 pace.