Humans Were Born to Carry Weight on Our Backs
Carrying weight for distance — or rucking — is part of the human design and it can keep us fit and healthy
Last fall I found myself standing on the Arctic Tundra, about 120 miles from civilization. One hundred pounds of caribou filled my pack. I had to hoof the weight back to camp, which was five miles away. All uphill and across the tundra. And the tundra is a savage landscape comprised of dirt that exists in an ice-cream-like state: spongy layers of dense moss, mucky swamp, and basketball-sized tufts of grass called tundra tussocks. A mile out there is like five on a regular trail.
I was in the Arctic for more than a month on a backcountry hunt while reporting my new book, The Comfort Crisis, which investigates the shocking downsides of our overly comfortable (first) world and reveals how we can leverage the power of a handful of evolutionary discomforts that will dramatically improve our fitness, health, and happiness. The Arctic is one of many places around the world I embedded myself in while investigating the upsides of getting out of our comfort zones.
My career as a human health and performance journalist has sent me to train inside some of the world’s most hardcore gyms and undertake 24-hour endurance challenges. But packing out my caribou was the hardest thing I’ve ever done.
Yet it felt oddly primal — and emerging scientific evidence suggests there was probably a good reason for my notion.
Why we’re born to carry
After the Arctic, I traveled to meet researchers at Harvard, who told me that, compared to most other mammals, humans are “athletically pathetic.” We’re slow and weak. But we are damn good at endurance running and carrying. We can’t go fast. But we can go far — especially in hot weather. On a hot day, a relatively fit human will beat most other mammals in a distance race — lions, tigers, bears, dogs, etc. And we’re also the only animal that can carry well.
Endurance running and carrying are, quite literally, acts that made us human. The human body is built the way it is so that we could slowly but surely run down prey for miles and miles in the heat until the animal toppled over from exhaustion. Then we’d kill it and carry it back to camp. This is why we have two legs, springy arches in our feet, big butt muscles, sweat glands across our body, no fur, short torsos, and strong grips.
But as we evolved, running was relatively rare. It was reserved mostly for hunts. Modern-day tribes like the Tarahumara, for example, never run for the fun of it. Running is reserved for rare hunts and religious ceremonies, the Harvard anthropologists (who’d embedded themselves with the Tarahumara) explained.
Carrying, on the other hand, is something we humans did all the time as we evolved. So all the evidence suggests that we were more so “born to carry.”
Why we stopped carrying
For the vast majority of time, humans lived as hunter-gatherers. To gather we’d saunter away from camp and then carry back what we found. Most of these loads were small, likely 10 to 20 pounds. But scientists in Spain say gatherers sometimes carry weights equal to half of their total body weight. After a successful hunt, we’d hoof heavy animal limbs home. The hindquarter of a zebra — an animal still today pursued by African hunter-gatherers — for example, typically weighs about 80 pounds.
Then the Industrial Revolution happened. And like its brother running, our need to carry was largely rendered unnecessary thanks to new technologies. We have shopping carts, wheeled suitcases, strollers, and Amazon Prime dropping anything and everything off at our doors. But unlike running, most of us never reengineered carrying back into our days.
There is, however, one modern tribe that hasn’t forgotten it. They’ve embraced it. Their lives depend on their ability to move loads. And it’s helped them maybe become the fittest band of humans to ever walk the earth.
Why we should ruck
After the Arctic, I traveled to Jacksonville, Florida, to spend a few days with Jason McCarthy, a former Green Beret who founded GORUCK, a company that makes beautiful backpacks built to military specs.
“You never run in war without weight. Never,” said McCarthy. “But you’re always rucking. No matter what. Always. Rucking is the foundational skill of being a Special Forces soldier. Any soldier for that matter.”
“Ruck” is both a noun and a verb. It’s a thing and an action. It’s military speak for the heavy backpack that carries all of the items a soldier needs to fight a war. And “to ruck” or “rucking” is the act of marching that ruck in war, or as a form of training for soldiers or civilians to get really, really fit.
One morning Jason and I each loaded about 45 pounds into his GORUCK packs and rucked into GORUCK HQ. It worked my lungs and muscles. He described rucking as, “cardio for people who hate to run, and lifting for people who hate the gym.” It corrects for body type. If you’re too big, it’ll lean you out. Too skinny? It’ll add muscle to your frame. This, he explained, is why carrying is the foundation of military fitness training. It builds humans who one hour can hike 75 pounds of gear up a mountain and the next powerfully breach an enemy cell.
And this makes sense from an evolutionary perspective. The scientists at Harvard told me that early humans weren’t buff like today’s gym rats — back then, having extra weight, even in the form of muscle, was a liability. We needed enough strength for day-to-day tasks and were “extreme” in our ability to hoof heavy items from point A to B, according to a study in PLOS One.
The Harvard scientists think we can find enhanced fitness by doing the physical acts we evolved to do.
The benefits of rucking
It burns lots of calories. A casual ruck burns somewhere between two and three times the calories of walking, according to scientists at the University of South Carolina. And that’s just on an evening stroll with a 20- to 50-pound weight in a pack.
But declassified data presented at a summit on military physiology suggests it can burn even more. The data shows the caloric burn of rucking unsurprisingly rises or falls based on a variety of factors: speed, load, and the type and slope of the terrain. The estimates suggest what McCarthy did in Green Beret training burned between 1,500 and 2,250 calories an hour. It also suggests that what I did, packing 100 pounds of caribou across the steepest pitches of the tundra, burned between 1,850 and 2,150 an hour.
It can prevent and relieve back pain. About 80% of people will suffer from back pain. We can thank our modern, comfortable environments for this.
Most of us spend most of our days sitting in a soft office chair, slumped over a keyboard. This trains us to have a poor spinal position and weakens our core. The weight of the ruck pulls your torso backward and more upright, into a better position, while actively working your core.
The result: A stronger, more bulletproof back and core.
It builds endurance safely. Running is a go-to for cardio. But one analysis found, “27% to 70% of recreational and competitive distance runners sustain an overuse running injury during any 1-year period.” Our comfortable environments seem to mess up our movement patterns and cause muscular imbalances. These often lead to injury when people start pounding the pavement.
Scientists at the University of Pittsburgh investigated what activities most often injure special forces soldiers. Running was the top offender. The injury rate of rucking, meanwhile, was minimal (running caused six times more injuries than rucking). Yet rucking delivers equivalent cardio benefits, according to researchers at the University of South Carolina.
It builds functional strength. What is more functional than moving items from point A to B? One source I spoke to, a famed strength coach, explained that rucking strengthens your “tactical chassis.” The Tactical Chassis is everything between the shoulders and knees: hamstrings, quads, hips, abs, obliques, back, shoulders, etc.
It gets you outside. Humans now spend about 95% of our time indoors. In reporting The Comfort Crisis, I traveled to Boston to meet a neuroscientist who is discovering that time in nature is one of the best ways to tame burnout and stress and increase happiness and productivity. She’s discovered specific doses that work the magic.
Rucking gets us outside. Exercise in the outdoors also provides a better brain stimulus compared to indoor exercise, according to researchers I spoke to at the University of Southern California. This can enhance and protect brain function.
After my time in the Arctic and Jacksonville, I not only had a freezer full of caribou, I was also in the best shape of my life, despite not running or touching a single dumbbell or barbell for more than a month. I could zoom up mountain trails that once slowed me, and all of my lower body lifts were up significantly. Backaches? Gone. One friend described me as looking like, “a human weapon” (which makes sense, given the role of carrying and rucking in military training).
If you want to learn more about the science and anthropology of carrying and rucking — why it’s so damn important for our species and exactly how to do it better (for example, the perfect weight to use for your body size)—along with what I learned about rucking from doctors at the Mayo Clinic, check out my book, The Comfort Crisis. It covers nine more beneficial evolutionary discomforts we’ve removed from our lives and tells us how to add them back for improved fitness, health, and happiness.