I finished my run yesterday at 10:30 am, and I felt fine. During the day I was busy doing some things in my yard that kept me on my feet, and I felt fine. Then, I spent a couple of hours on my computer, and I noticed when I rose from my chair that my right quad was a little sore. My computer chair is too low, and that causes my quads to be stretched while I'm sitting down. I thought that stretching might have caused the soreness. Or, maybe it was a delayed effect from my run, although I ran a comfortable pace and didn't push myself in either distance or speed. When I awoke this morning, after a good 7 hours sleep, my quad was still sore and remained so during the morning and early afternoon. I returned home from church about 2:30 pm and prepared to take a nap. I did my groin, knee, and quad stretches and then slept for two hours. When I awoke, the soreness was gone, and I've felt fine during the evening. I'll probably never know for sure what caused the soreness, but it apparently wasn't serious.
Older people like me need more time to recover from stress, and we can't afford to over-stress our bodies.