The flashlight you carry on early morning runs almost didn't exist. Or at least, not in the form we know today. An LED—short for light-emitting diode—is a tiny semiconductor that turns electricity directly into light....

  If you run before sunrise or after sunset, you've probably trusted an LED. It's in your headlamp. It's in your watch. It's in the taillight clipped to your running belt. You probably use LED technology several...

The best scientific ideas are simply the best explanations we have today.

Most runners have two New Years. January 1st and the Summer Solstice.

A story about doing the work for its own sake — something every runner gets.

The people we admire often figure things out as they go.

Some of the most worthwhile pursuits in life don't have finish lines.

The older I get, the more I realize I had the reward backwards.

Three words from a 1962 film. Still the best running advice I've heard.

He looked at me like I was crazy. I get it now.

Last week, I finished my training cycle and my marathon. I ran it with a long-time friend, and it was one of those days you’re grateful for. Weeks of work, long runs—all of it leading...

Fourteen marathons. Every single one of them alone. Not alone in the sense that the roads were empty — marathons are crowded, loud, and chaotic in ways that still surprise me. But alone in the sense that I never knew the person running next to me.

This past weekend, that changed.

A longtime friend and I signed up for a race I'd always wanted to run. We trained separately, flew in, met up, and toed the line together. I was nervous — not about the race, but about him. What if his running style drove me crazy three hours in? What if my nose dripping every half mile drove him crazy?

Here's what happened instead.

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I read an article this week in the The New York Times (Visible Abs and the Millennial Midlife Crisis) about midlife and fitness. The headline leans into abs, which is the hook, but the article...

This week I’ve been working on a YouTube video about something I never used to think about: the surface I run on. When I was younger, it didn’t matter. Road, sidewalk, trail—I just ran. My...

Big news in the science world. Physicists are rewriting the First Law of Thermodynamics. It’s one of the first things you learn as an engineering student: energy is neither created nor destroyed. It’s only transferred...