This is the stated goal.
Originally Posted by Jay Guindon
I only want to sprint enough for health/longevity and a little bit for performance.
If that's all you want, go to a junior high or high school track.
One day you can sprint the curves and walk the straights for about 20 minutes.
On another day you can run a 400, rest 8 min., run another 400, rest another 8 minutes, and run another 400. Or just do a couple of them.
On a third day, you could sprint 20x50 or 10x100 or 5x200. Go all out or run build ups. Recover awhile between sprints.
It's not big deal. And, for the love of God, quit worrying about cortisol. It's like you've been reading some CFer's blog. Get a reasonable amount of good food, exercise, and rest, and everything will take care of itself.