It's a surreal experience: Having all your friends standing at mile 26.2, cheering you on as you cross the finish line. And sure, you're probably in better shape to run a marathon now than you'll be a few decades down the line.
And yet. As Business Insider's Erin Brodwin reported, distance running could be bad for your health. Some research suggests that prolonged, intense exercise is related to reduced immune function and digestive issues.
Brodwin suggests interval training as an alternative to training for a marathon: You work as hard as possible for a few minutes, then rest, then repeat. It may be more beneficial for your health.
If you're still set on those miles, you can do them at 31.