What Is Rucking? What a Ruck Is and Why It Matters

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Rucking is walking with weight on your back. That is the whole definition. A ruck is the pack itself (short for rucksack, from the German word for “back”), and rucking is moving on foot while you carry it: around the block, up a mountain, or 12 miles down a dirt road at 4 a.m. because a sergeant said so.

I learned to ruck in the infantry, where nobody called it a workout. It was just how you got places, and how you found out who could be counted on when everyone was tired. Years later it is the training I come back to more than any other, and I think most people who move for a living or for fun should be doing some version of it. Here is what it is, where it came from, what the research actually says about it, and why it still sorts people out in the hardest jobs on earth.

What a ruck is	A backpack built to carry weight, short for rucksack (German: Rücken, the back)
What rucking is	Walking with a loaded pack, usually at a brisk pace, on roads or trails
Typical starting load	About 10% of body weight, often 10 to 20 lb
Classic military benchmark	12 miles, 35 lb, under 3 hours (about 15 min per mile)
Who it is for	Almost anyone who can walk, scaled to their body and health

What is a ruck?

A ruck is a rucksack: a backpack designed to carry real weight for real distances. The English word came over from German in the mid 1800s, built from an Alpine dialect word for “back” plus “sack”. British mountaineers and soldiers adopted it, and the military eventually clipped it down to “ruck.” Today the word does triple duty:

• The noun: “Grab your ruck.” The pack itself.
• The verb: “We rucked 8 miles.” To walk carrying the pack.
• The event: “The ruck is Saturday.” A loaded march, timed or not.

A purpose-built ruck is different from a school backpack in three ways that matter. It holds weight high and tight against your back, it has shoulder straps and usually a hip belt that can actually manage 30 to 60 pounds, and it is tough enough to be thrown, dragged, and rained on. Many people now carry flat iron “ruck plates” in a dedicated sleeve so the weight does not shift. A bag of rice wrapped in a towel works too. I have done worse.

What is rucking?

Rucking is walking (not running) with a loaded pack. The military calls it a foot march, road march, or hump. Civilians call it rucking. Same thing.

It sits in a sweet spot between other activities:

• Versus walking: the load raises the energy cost and adds a strength demand on your legs, hips, core, and upper back.
• Versus running: you keep one foot on the ground at all times, so impact forces are far lower than running at the same effort.
• Versus hiking: hiking is about the destination; rucking is about the load and the pace. Plenty of hikes are rucks and plenty of rucks are on pavement.
• Versus a weighted vest: a vest spreads load around your torso, while a ruck sits on your back. Both count as loaded walking. The ruck is closer to how people actually carry gear in the field.
• Versus ruck running: running with a pack is a different, harder animal with more injury risk. I wrote a whole piece on the truth about running with a ruck. Walk first.

A short history of carrying heavy things

Humans are carriers

Long before anyone sold a ruck plate, people carried water, food, firewood, tools, and children over long distances every day. Biologists still argue about exactly why our ancestors stood up on two legs, and carrying is one of the leading ideas. Lab work from the University of Manchester found that humans carrying an evenly balanced load are more efficient than most mammals, while lopsided loads like a child on one hip cost far more energy. Studies of East African women have found they can carry loads of up to 20% of body mass with no measurable increase in energy cost, likely because their gait adapted to a lifetime of carrying.

So when people say humans were built to carry load, there is a real basis for it. The honest version is that evolution did not leave a receipt, but our bodies are clearly good at it when the load is balanced and close to the spine. That is exactly what a good ruck does.

Marius’ mules

The first army famous for rucking was Rome. Near the end of the second century BC, the general Gaius Marius moved much of the baggage off the mule trains and onto the legionaries themselves, who carried their kit on a pole called a furca. The troops picked up the nickname muli Mariani, Marius’ mules. Historians disagree on the weight. An Australian Army Journal review of the soldier’s load notes estimates from about 50 to 100 pounds, with most landing near 80 pounds, or roughly 55% of a typical Roman’s body weight. Embrace the suck, 2,000 years early.

The modern soldier’s load

Load has been the infantry’s problem ever since. Joseph Knapik, a U.S. Army researcher who has spent decades on this topic, concluded in his landmark review in Military Medicine that foot soldiers rarely carried more than about 33 pounds on the march before the 18th century, and that loads have climbed ever since as weapons, armor, radios, and batteries got heavier. In Afghanistan, his later work reported, U.S. infantry carried an average of about 101 pounds. That is why every infantry unit I know of still trains the ruck march. It is not tradition for its own sake. It is the job.

From the field to the neighborhood

Civilian rucking took off after 2008, when former Green Beret Jason McCarthy founded GORUCK, originally as a backpack company, and then started running team rucking events led by Special Forces veterans. The first GORUCK Challenge ran in 2010, and the company now reports more than 10,000 events hosted and a network of rucking clubs worldwide. CrossFit, obstacle racing, and tactical fitness all picked it up from there, and rucking is now a common sight on greenways at 6 a.m.

Why rucking matters: what the research says

It burns more than walking, and hills matter more than weight

The best-known tool for estimating the energy cost of carrying a load is the Pandolf equation, developed by U.S. Army researchers and published in the Journal of Applied Physiology in 1977. I ran it for a 180 lb walker at 3.5 mph to show what a ruck actually adds.

Two things jump out. First, the load adds less than the internet promises: about 13% more energy for 30 pounds on flat ground. Second, grade is the real multiplier. A modest hill with a light pack beats a heavy pack on a flat track for pure work. Take the exact numbers as estimates: later research found the Pandolf equation under-predicts the cost of contemporary military loads, so real-world rucking likely costs a bit more than shown, especially on soft ground or trails.

It builds the strength that running skips

A load on your back makes your glutes, hamstrings, calves, core, and upper back work for every step. Army research has long found that load-carriage performance improves most when people combine actual load carriage with both resistance and aerobic training, not one alone. A 2021 international review co-authored by Knapik recommends a load-carriage session about every 10 to 14 days alongside strength and aerobic work for soldiers being conditioned or reconditioned, and it points out that speed and terrain are better levers than piling on more weight. That is a far lower dose than most enthusiasts assume, and it is good news for anyone with a busy week.

Bone density: real, but not magic

This is the claim I hear most, so here is the straight answer. Yes, loading your skeleton is a real bone-building signal, and rucking provides some of it. No, rucking alone is probably not enough to build bone, especially later in life.

• The case for: bone adapts to the forces placed on it. British Army researchers scanning infantry recruits found that 13 weeks of arduous basic training increased the density and changed the shape of the shinbone, and a U.S. study found similar adaptive bone formation in the tibia during Army basic combat training. Load carriage is a big part of that training.
• The catch: the British researchers credited the change mainly to unaccustomed, dynamic, high-impact loading. Recruits also run, jump, and climb. Loaded walking is steady and repetitive, which bone tends to tune out over time.
• The weighted vest evidence is mixed: in the 12-month INVEST in Bone Health trial at Wake Forest, older adults losing weight wore a weighted vest about 7 hours a day, and it did not prevent hip bone loss any better than diet alone. A follow-up analysis found that vest wearers who spent more time upright and moving did show positive changes in bone density. Translation: weight that just sits on you does little; weight you move with may help.
• The consensus: bone and sports-medicine guidance consistently pairs weight-bearing activity with resistance training and, where safe, some impact. The UK consensus statement on osteoporosis exercise, for example, recommends resistance and impact exercise to maximize bone strength.

My take: ruck for your bones as one leg of the stool, then lift heavy things and, if your body allows it, add some jumping or hill work. If you already have osteoporosis or low bone density, talk to your doctor or a physical therapist about load before you strap on a pack.

It is low impact and very hard to quit

Walking keeps impact forces low, so many people who cannot run (or should not run much) can ruck. It also gets you outside, works well with a friend, and does not require you to be fast. In my experience that last part is underrated. The best training plan is the one you will still be doing in a year.

The mental side

Rucking is boring, uncomfortable, and slow, and that is the point. Every selection course I know of uses long, heavy movement because it reveals who keeps a steady pace and a decent attitude when it is dark, wet, and nobody is cheering. You can build that same patience on a Tuesday morning loop.

The great equalizer: where rucking is the test

Rucking is one of the few events that strips away most athletic advantages. Sprinters, lifters, and marathoners all suffer under a pack. That is why so many demanding jobs use some version of it to decide who gets in.

U.S. Army Expert Infantryman Badge	12-mile foot march with a 35 lb ruck in 3 hours or less
Wildland firefighters (Arduous Pack Test)	3 miles over level ground with a 45 lb pack in 45 minutes or less
Army Special Forces selection (SFAS)	Multiple timed rucks at unannounced distances, loads commonly 45 lb or more, plus heavy team events
Marine Raiders (MARSOC)	Official prep program builds 45 lb ruck progressions up to long-distance assessments
UK SAS selection	The Fan Dance, a 24 km loaded march over Pen y Fan in the Brecon Beacons

The firefighter test is my favorite example because it is not about combat at all. U.S. federal land agencies require it because, as the Department of the Interior’s wildland fire program explains, the job involves carrying heavy loads over steep ground for long shifts. The Forest Service designed the 45-minute pass time to match the aerobic fitness standard for the job, with enough reserve to handle emergencies.

The EIB march, which you can read about straight from the U.S. Army, works out to roughly 15 minutes per mile for three hours with a pack. Army Special Forces Assessment and Selection includes rucks with weapon and equipment, land navigation under load, team events hauling heavy gear, and a very long final march. MARSOC publishes its own preparation program built around 45 lb ruck sessions.

Plenty of other jobs do not have a formal ruck test, but the job is the test. Mountain guides carry ropes, food, and often a client’s spare layers to altitude. Hunting guides pack quartered elk out of drainages where no truck can reach. Tactical police teams and search and rescue crews move on foot in heavy kit when vehicles cannot. If your career depends on your legs working under weight on a bad day, rucking is the most specific training you can do.

Who can ruck?

Almost anyone who can walk. Teenagers, retirees, new parents, people coming back from injury, and selection candidates all ruck. The difference is the dose.

• Beginners: a light pack, flat routes, short distances.
• Older adults: rucking can be a great way to keep legs strong and stay active outdoors. Start lighter than you think, and get medical clearance if you have heart, joint, spine, or bone density concerns. Orthopedic surgeons note that extra load can aggravate degenerative disc disease.
• Kids and teens: keep it light and fun. A day pack with water and snacks on a family hike is rucking.
• Selection candidates: build a long base first. The people who get hurt are usually the ones who jump straight to heavy and fast.

How to start rucking safely

The research on load-carriage injuries is consistent: the usual suspects are blisters, stress fractures, back strain, foot pain, knee pain, and “rucksack palsy” (numb arms from straps compressing nerves). Almost all of it comes from doing too much, too soon, with a poorly fitted pack. My full walk-through is in my guide to rucking gear and getting started. The short version:

• Start light: around 10% of your body weight, or 10 to 20 lb. Do not start at 45.
• Build one thing at a time: add distance or weight or pace, not all three in the same week.
• Keep the weight high and tight: load against your upper back, straps snug, hip belt on if you have one.
• Take care of your feet: broken-in shoes or boots, good socks, and deal with hot spots at the first sign.
• Walk, do not run: even MARSOC’s own selection prep guide tells candidates to walk as fast as they can and not run with a ruck in training.
• Give it time: the Forest Service tells firefighters to train at least four weeks before the pack test, starting with no pack and adding weight slowly.

The gear you actually need

You need a pack and shoes. Everything else is optional. That said, here is what I would buy if I were starting over:

• A real rucksack: something with a padded frame sheet and a plate sleeve, like a 20 to 26 liter rucking pack. Your old school backpack will tear at the seams around mile three.
• Ruck plates: a 20 lb set of ruck plates keeps the load flat and high. Sandbags and dumbbells wrapped in a towel work if you are on a budget.
• Shoes that can take it: stable trail shoes or light boots like rucking shoes with a firm heel.
• Socks that do not blister: merino hiking socks. Cheap insurance.
• Blister kit: blister bandages and tape in the lid pocket. Every infantryman learns this one the hard way.

Rucking FAQ

What does rucking mean?

Rucking means walking with a weighted backpack, called a ruck. The term comes from military slang for a loaded march.

What is a ruck in the military?

In the military, a ruck is a soldier’s rucksack, and a ruck (or ruck march) is a foot march carrying it. It is used for both training and testing.

How heavy should my ruck be?

Start around 10% of your body weight, often 10 to 20 lb. Many experienced ruckers settle around 20 to 30 lb for regular training. Military standards commonly use 35 to 45 lb as a baseline, but that is a goal, not a starting point.

How many calories does rucking burn?

It depends mostly on your body weight, pace, and terrain. Using the Pandolf equation, a 180 lb person walking 3.5 mph with 30 lb on flat pavement burns roughly 410 kcal an hour, and about 635 on a 5% grade. The hill matters more than the plate.

Is rucking good for bone density?

Partly. Loaded, weight-bearing activity helps maintain bone, and military training with lots of load carriage increases shinbone density. But steady walking is a modest signal on its own. For bone health, combine rucking with strength training and some impact work where safe.

Is rucking better than running?

It is different. Running builds more aerobic fitness per minute. Rucking builds more load tolerance and strength with far less impact. Most people do best with both.

Is rucking safe?

Yes, when you start light and build gradually. Most rucking injuries come from adding too much weight or distance too fast, poorly fitted packs, and neglected feet. Check with a doctor first if you have back, joint, heart, or bone density issues.

Bottom line

A ruck is a pack. Rucking is walking with it. It is one of the oldest forms of training humans have, it is how soldiers, firefighters, and guides prove they can do the job, and it is something you can start this afternoon with a backpack and a bag of rice. Start light, find a hill, and keep showing up. Embrace the suck, a little at a time.

Sources and further reading

• Knapik JJ, Reynolds KL, Harman E. Soldier Load Carriage: Historical, Physiological, Biomechanical, and Medical Aspects. Military Medicine, 2004.
• Knapik JJ. Injuries and Injury Prevention During Foot Marching. Journal of Special Operations Medicine, 2014.
• Knapik JJ and international co-authors. Soldier Load Carriage, Injuries, Rehabilitation and Physical Conditioning: An International Approach. IJERPH, 2021.
• Pandolf KB, Givoni B, Goldman RF. Predicting energy expenditure with loads while standing or walking very slowly. Journal of Applied Physiology, 1977.
• O’Leary TJ, et al. Skeletal macro- and microstructure adaptations in men undergoing arduous military training. Bone, 2019.
• Tibial adaptations to Army Basic Combat Training. JBMR Plus.
• Beavers KM, et al. INVEST in Bone Health trial, JAMA Network Open, 2025, summary from Wake Forest.
• Strong, Steady and Straight: UK consensus statement on physical activity and exercise for osteoporosis.
• Watson JC, et al. The energetic costs of load-carrying and the evolution of bipedalism. Journal of Human Evolution, 2008.
• The History of the Soldier’s Load. Australian Army Journal.
• USDA Forest Service. Work Capacity Test Administrator’s Guide.

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