Glossary
The words, without the jargon
37 terms from the sport and from this site — what a load lifter does, why the Pandolf equation exists, and what a heavy division actually requires.
Measuring the walk
The units this site keeps score in, and the ways a walk gets compared with another one.
- Haulkg·km
- Pack weight multiplied by distance. Sixteen kilograms carried ten kilometres is a haul of 160 kg·km. It exists because distance alone undersells a heavy walk and weight alone ignores the ground covered — the product is the smallest number that respects both.
- lb·mi
- The haul in imperial. The same quantity as kg·km in different units, so a leaderboard never compares the two — everything is stored metric and converted only for display.
- Loadpack weight
- The weight carried, not counting the walker. Convention includes the pack itself, water and everything in it — the number you would see if you put the loaded rucksack on a set of scales.
- Weight class
- A band of average load: under 10 kg, 10 to 20 kg, and 20 kg and up. Here the average is weighted by distance, so a long walk under a heavy pack counts for more than a short stroll under a light one when deciding which band you are in.
- Bodyweight-relative
- Haul divided by the walker's bodyweight. A 60 kg walker carrying 20 kg is moving a third of themselves; a 100 kg walker carrying the same is moving a fifth. Ranking on the ratio asks what the walk cost you rather than how big you are.
- Verified
- A ruck that came off a device or a file rather than being typed in. It is a statement about provenance, not about honesty: hand-entered walks count too, and carry a different mark so nobody has to pretend otherwise.
- Honour system
- A ruck entered by hand. Rucking is unusually friendly to it — distance, time and pack weight is genuinely the whole activity — so refusing manual entry would exclude honest people to inconvenience dishonest ones.
- Streak
- Consecutive weeks with at least one ruck in each, counted on ISO weeks that start on Monday. An empty current week does not break one — there are still days left in it — but a missed past week starts the count again.
- ISO week
- A week that runs Monday to Sunday, numbered by the international standard. Used here so a streak means the same thing to everyone, regardless of where their calendar app starts the week.
The pack and what goes in it
Parts of a rucksack, and the words on the label that are not marketing.
- Ruckrucksack
- Both the bag and the activity. To ruck is to walk with a loaded pack; a ruck is also one such walk, and — from the German Rucksack, 'back bag' — the pack itself. Context does the work.
- Ruck plate
- A flat steel or cast-iron plate sized to sit against the back panel of a pack, usually 10, 20, 30 or 45 lb. Dense and flat, so the weight rides high and close to the spine instead of sagging into the bottom of the bag.
- Sternum strap
- The horizontal strap across the chest joining the two shoulder straps. It stops them splaying outward, which is why a pack feels calmer with it fastened even though it carries no weight itself.
- Hip beltwaist belt
- The padded belt that transfers weight from the shoulders onto the pelvis. On a properly fitted pack it takes the majority of the load. Many rucking-specific packs have only a thin strap instead, which is a deliberate choice to keep the weight on the torso.
- Load lifters
- The short straps running from the top of the shoulder straps back to the frame, ideally at about 45 degrees. Tightening them pulls the top of the pack toward you and takes weight off the front of the shoulder.
- Frame sheet
- A stiff panel inside the back of a pack. It stops the bag collapsing around its contents and gives the hip belt something rigid to transfer weight through.
- MOLLEModular Lightweight Load-carrying Equipment
- The grid of stitched webbing rows on the outside of many packs, and the attachment standard that uses it. Pouches weave through the rows rather than clipping on, which is more secure and considerably more annoying.
- Bladderhydration reservoir
- A flexible water container carried inside the pack with a drinking tube over the shoulder. Three litres of water is three kilograms, so a full bladder is a meaningful part of the load — and it gets lighter as you walk, which changes the balance.
- Centre of gravityC.G.
- The mass-weighted average position of everything in the pack. Higher and closer to the spine keeps you upright; low and far from the back makes the pack pull you backward and your body lean forward to compensate.
Training and technique
How loaded walking is structured, and the vocabulary coaches use for it.
- Ruck marchloaded march, forced march
- A march covering a set distance under a set load, usually against a time standard. The military term; in civilian use it tends to mean any organised long walk under weight.
- Cadence
- Steps per minute. Under load a slightly quicker, shorter step is usually kinder to the knees than a long stride, because it lowers the peak force each footfall has to absorb.
- Ruck shuffle
- A short-stride jog under load, barely faster than walking, with both feet close to the ground. Used to make time on flat ground without the impact of a proper run.
- Progressive overload
- Adding a little more work than last time, repeatedly. In rucking the usual mistake is adding weight and distance in the same week: pick one, and hold the other still.
- Deload
- A deliberately lighter week — commonly every fourth — that lets connective tissue catch up with the muscle that adapted faster. Skipping them is how most people acquire their first rucking injury.
- Time under load
- How long the weight was on your back, as distinct from how far you went. Useful because much of the adaptation from rucking is postural and tendon-related, and those respond to duration rather than pace.
What it costs the body
Why carrying weight costs what it costs, in terms that can be measured.
- Pandolf equation
- The published standard for estimating the metabolic cost of walking under load, from Pandolf, Givoni and Goldman in 1977. It takes bodyweight, external load, speed, grade and a terrain factor, and it is why a good calorie estimate is not a walking figure multiplied by a constant.
- Metabolic cost
- The energy your body spends doing the work, usually quoted in watts or kilocalories per hour. It rises faster than linearly with load, which is why the last five kilograms hurt more than the first five.
- Terrain factor
- A multiplier for the surface underfoot in the Pandolf equation. Tarmac is 1.0; loose sand is roughly twice that. It routinely matters more than pack weight, which surprises people who train only on roads.
- Ground reaction force
- The force the ground pushes back with at each footfall. Rucking raises it modestly — you are heavier — where running roughly doubles it, which is the main reason loaded walking is easier on joints than running at the same energy cost.
- Ascentelevation gain
- The total height climbed over a walk, adding up every rise and ignoring every descent. Going up costs far more than staying level; going down costs more than level too, which is why it is measured separately rather than cancelled out.
Events and standards
Organised marches, and the standards that define a heavy one.
- VierdaagseNijmegen Four Days Marches
- The largest walking event in the world, held every July in Nijmegen in the Netherlands: four consecutive days of 30, 40 or 50 km depending on category, with tens of thousands of walkers. The military category marches under a required load.
- Bataan Memorial Death March
- A marathon-distance desert march at White Sands Missile Range in New Mexico, held in memory of the prisoners of war forced to march on the Bataan peninsula in 1942. Its heavy division requires a pack of at least 35 lb, about 16 kg.
- Star Course
- A GORUCK event format: a team navigates on foot to a set of checkpoints in any order, under load and against a time limit. Distance is typically around 50 km, but the route is the team's to choose.
- Heavy division
- An event category with a minimum pack weight, checked at the start and often again at the finish so nobody sheds it along the way. The threshold varies by event; 35 lb — 16 kg — is the most common.
- Twelve-miler
- The US Army's foot-march standard: 12 miles, about 19 km, carrying a 35 lb pack, inside three hours. It is the benchmark most military rucking training is built backward from.
Files and data
What a watch records, and what survives the trip into a logbook.
- FIT file
- Garmin's binary activity format, and the richest thing a watch will hand over: distance, time, heart rate, ascent and — on watches with a rucking profile — the pack weight you told it about. Uploading one is the easiest way to log a verified ruck.
- GPX
- A plain-text XML track of timestamped positions. Universally supported and far less detailed than a FIT file — distance has to be worked out from the coordinates, and it carries no pack weight, so that gets asked for.
- Moving time
- Elapsed time minus the pauses. Two devices rarely agree on it, because they disagree about what counts as stopped — which is why pace comparisons between apps are worth less than they look.
Something missing?
If you hit a word on this site or in the sport that is not here, tell us and it goes in. The glossary is meant to be the complete list, not a curated one — send it over. Longer explanations live in the know-how library.