Harvard's Running and Rucking Prescription

Mileage to hit each week.

Last Wednesday, we looked at a study led by scientists at Harvard that identified an ideal amount of strength training per week for health.

Today, we’re returning to something I learned while reporting The Comfort Crisis, but didn’t put in the book. It gives us an ideal weekly rucking or running distance.

Most cardio recommendations measure endurance in time. The Federal Exercise Guidelines tell us to get at least 150 minutes of cardio for health. Other research suggests 300 minutes maxes out our benefits.

But measuring in time forces vague terminology like “moderate-to-vigorous exercise.” That can make things more confusing than they need to be (as the researchers in Wednesday’s post noted).

Measuring in distance is simpler. Do cardio on foot—walking, rucking, or running—a specific distance each week. Don’t overthink the intensity.

Then the question becomes: what’s the ideal distance of cardio we should get each week to maintain our health and a lifelong level of fitness?

To answer the question, I’m publishing unreleased material I discovered in a lab at Harvard while reporting The Comfort Crisis.

Before we dive in, a quick word on yesterday’s podcast and some housekeeping.

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Yesterday’s Podcast: World Cup + Why Sports Fandom Is Shockingly Good for Wellbeing

First, professor and journalist Leander Schaerlaeckens, author of The Long Game, explains why this World Cup is the “biggest sporting event in human history.” He shares why Team USA is actually … kind of good?, the players you need to know, and why America took so long to get decent at the world’s game.

Then psychologist Dr. Daniel Wann, who has studied sports fans for 40 years, explains why caring about sports is one of the most underrated and powerful things you can do for your mental health and social connections.

• This link opens the episode in your podcast player of choice.

• This link takes you to the video version.

Quick Housekeeping

• Become a Member of Two Percent to get full access to this post and all three of our weekly posts:

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  • Friday’s Expedition post covered 17 of the best ideas I found last month, including the 5 Enemies of Greatness, a comparison of sleep trackers, a classic Russian exercise everyone should try, and more.

• Check out Momentous, the brand that made me feel good about supplements again. I use Momentous’ Plant Protein Powder, Multivitamin, and Creatine daily. Get a discount through this link.

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The role of endurance in human evolution

In short

The human body is uniquely adapted for endurance exercise.

The details

While reporting The Comfort Crisis, I traveled to Harvard University. This was 2019. I was there to speak with Daniel Lieberman.

Lieberman studies the evolution of the human body and why we’re built the way we are, especially as it relates to human movement and physicality. He’s the guy who discovered just how important running is for humans.

Humans aren’t fast compared to other animals. Many other mammals can beat us in a sprint. Because of this, anthropologists since the discipline’s inception thought that running was something of a useless parlor trick.

But Lieberman found that, no, we can’t go fast. But we can go far—especially in hot weather.

Most other mammals can’t do this. On a hot day, a relatively fit human will beat most other mammals in a distance race. Lions, tigers, bears, dogs, etc.

Humans are “born to run”—and carry

In short

Cardio exercise is likely more important for us than raw strength. Carrying weight is our most unique strength act, and it also works our cardiovascular system.

The details

Humans can run far in the heat, Lieberman’s “Born to Run” Nature¹ paper explains, thanks to a handful of adaptations we developed over millions of years.

We stand on two legs, have springy arches in our feet, long tendons in our legs, big butt muscles, sweat glands across our body, no fur, complicated noses that humidify air before it hits our lungs, and more.

Other mammals gallop quickly for a few minutes, then have to stop and pant to cool down.

Endurance was our killer app—and we used it to kill. We practiced what’s called persistence hunting: slowly but surely tracking and chasing down prey for miles upon miles until the animal toppled over from heat exhaustion. Then we’d spear or club it and have dinner.

Because humans have undergone intense evolutionary selection for endurance and aerobic activity, Lieberman believes cardio exercise is more important for us than raw strength. We also saw this in the study covered in Wednesday’s post—people who did enough cardio had a 26-43% lower mortality risk, while lifters had a 7-11% reduction.

If you read The Comfort Crisis, you know that I agree with Lieberman—with a caveat.

I believe carrying was equally if not more important to us than running.

After we’d speared that animal, we’d have to carry it back to camp.

Carrying is where our strength shined. It wasn’t raw strength. We’d have to engage relatively low levels of total body strength as we covered miles of rough ground.

We’d also carry all day when we gathered food. We’d carry our kids for the first years of their lives (the research on carrying children is fascinating).

We’re the only mammals who can pick up something and carry it for distance². And it shaped us. Humans are, in fact, “extreme” in their ability to move items from point A to B, wrote researchers in a study in PLOS One.

Lieberman’s great insight

In short

While I was at Harvard, Lieberman told me something that forever changed how I view exercise.

The details

I spent the better part of an afternoon at Harvard. Lieberman and I chatted in his office, and he showed me his laboratory (which has all sorts of incredible, lab-grade treadmills).

We talked about how physical activity keeps humans healthy, and how the way we now approach exercise is rather strange in the grand scheme of things.

For example, we both agreed that people in the gym community overhype the benefits of strength training compared to cardio. Meanwhile, people in the running community overhype the benefits of cardio compared to strength. “It’s kind of a Rorschach test,” he told me.

Which, naturally, led me to ask him what exercise he does.

He told me he prefers running. He’s run the Boston Marathon a handful of times.

But he also tries to lift weights a couple of times a week. “I’m really realizing the value of strength training as I age,” he said.

Then he said something I haven’t forgotten. It’s shaped how I approached my own exercise routine. And when I put it to use, I feel better. He told me this: