Then calves and quads started tightening up bad. I'd pull over to stretch them out, walk a ways, stretch them out some more, walk some more then jog again but could only get a little way before they'd feel like they were threatening to lock up again. Had a hydration pack with electrolytes to keep up on the hydration so I don't think it was that. Granted, I had been a sick with a cold a couple weeks before, so I fell behind on my running to build up to that distance, but decided to go for it anyways. I ran a couple marathons over a decade ago, but even then, I had similar issues with leg muscles tightening up and threatening to full on lock up with cramps by the time I hit about 18 miles.