sprinting. It was sooooo much fun. But I'd done a ton of work leading up to it.

Guys, if you're just starting out, DON'T DO THAT!!! Especially if you're a middle-aged dude just getting back to training. The risk of injury to tendons, muscles, bones, etc. is too high. Start slowly. Maybe very slowly. Roll out beforehand if ya can. Walk at a comfortable pace. Stretch -gently -afterwards (preferably before you go to bed). Repeat. Build up your pace and your distance over time. Your capacity will grow rapidly. Then bask in the physical and mental health benefits. You're gonna feel good.

Official legal disclaimer thingy: I ain't no trainer. And I surely ain't no doctor. Walk/jog/run/sprint at yer own risk.