Listened to my body while I walked/jogged 1.5 miles

For the past couple of jaunts on the 1.5 mile roundtrip on the Jorden River Parkway I've used my GPS to mesure how much jogging I was doing. Tonight I left my GPS home and jogged until my legs told me it was time to walk. My legs didn't feel painful; they just felt stressed, enough so that it was easy to detect the change from how they felt during my walking. After a recovery walk of 100 feet or so, I jogged again. This sequence was repeated during the 1.5 miles. I can tell that my body is getting stronger, because I don't feel as tired at the end of my jaunt as I felt when I first started to do the 1.5 miles. My legs feel fine while I walk, but after jogging 200 - 300 feet, they feel stressed.