Rucking: What the Extra Load Does to Your Joints

Rucking is walking with weight on your back, and weighted vest walking is the same idea with the load held against your trunk. Adding load raises the force going through your knees, and it rises with the weight: in 24 adults walking at a fixed speed, peak knee joint contact force increased directly with loads of 15% and then 30% of body weight. That makes it useful training for legs that tolerate load, and a poor choice for a joint that already complains at walking pace. Nobody has studied recreational rucking, so there is no tested starting weight and no injury rate for people doing it by choice. Every figure on this page comes from military or laboratory load carriage research, most of it in small groups of young men, and it describes what was measured rather than what will happen to you.

What rucking actually is

Rucking is walking with a loaded pack on your back. The name comes from the military ruck march, and so does almost all of the research. That matters when you read a figure. Before the 18th century, foot soldiers on the march seldom carried more than 15 kg (33 lb), and loads have climbed steadily since then as equipment has been added (Knapik and colleagues, 2004).

Weighted vest walking is the same stimulus with the weight held closer to your trunk instead of hanging off your shoulders. The two are not identical in how they press on you, but they ask the same thing of your legs: carry more mass over the same number of steps.

What nobody has studied is people who do this for fitness. No one has counted injuries in recreational ruckers, no one has recorded their hours, and there is no rate per 1,000 hours of rucking to quote. So this page describes what has been measured in soldiers and cadets, and in laboratory volunteers, and says each time how many people that was.

How heavy, and how to start

The loads in the research are heavier than most people imagine, and they were chosen to produce a measurable effect, not to be sensible. The knee loading study used 15% and then 30% of body weight. The Achilles and knee modeling study used a single 20 kg (44 lb) pack. The hip belt study went from 15 kg to 25 kg (33 lb to 55 lb) in three steps, and the pack comparison study used 30 kg (66 lb) over 5 km.

None of those is a starting point, and no study has tested one, so what follows is a clinical judgement and not a dose anybody has measured. Start at 5% of your body weight, which comes to about 3.5 kg (8 lb) for someone of 70 kg (154 lb), and treat 10%, about 7 kg (15 lb), as the top of the first few weeks rather than a place to begin. Keep it to flat ground, 20 to 30 minutes, two or three times a week.

Then change one thing at a time, the minutes or the weight, and leave a week or two between changes. The reasoning behind that band is only this: all of it sits below 15% of body weight, the lightest load used in any study on this page. One change at a time is the only way to tell which change upset something. Your physio will adjust all of it, and will adjust it a long way down if you are returning from a back or knee problem.

One thing worth knowing before you choose boots: weight on your feet is expensive. Each kilogram (2.2 lb) added to the foot raises the energy cost of walking by 7% to 10%, and each kilogram added to the thigh by about 4%, against a much smaller penalty for weight carried close to the center of the body (Knapik and colleagues, 2004). Heavy boots change how hard a walk feels more than the same weight in the pack does.

What the load does at the knee and the Achilles

The clearest finding in this field is also the least surprising. Twenty-four adults, 12 of them women, walked at a fixed 1.4 m/s carrying nothing, then 15%, then 30% of body weight, and peak force inside the knee joint rose directly with the load each time (p less than 0.001). The same study found that the force was not shared evenly between legs, with more on the inner side of the knee on the non-dominant leg and more on the outer side on the dominant one, although those side to side differences were close to the smallest change the method can detect (Jones and colleagues, 2026).

The tendon behind it takes a share too. Sixteen cadets walked with and without a 20 kg (44 lb) pack while a musculoskeletal model estimated the load on three structures that commonly give trouble. Peak Achilles tendon load and peak load on the inner knee joint both rose a long way with the pack, with the Achilles change the largest effect of the set, and the kneecap joint rose moderately (Willy and colleagues, 2019). Those numbers come out of a model, not from inside anybody, so a precise-sounding figure is still an estimate.

That study also tested the advice people give each other on forums. Shortening steps by 7.5% lowered the peak Achilles load but did not lower the total Achilles load per kilometer, because shorter steps mean more of them, and it did not lower peak or cumulative knee loads at all. Lengthening steps raised kneecap joint loads most. The authors concluded that your own preferred step length is the safest one to walk at. In practice: do not mince your stride, and do not stretch it out to keep up with a taller friend.

If a knee has started complaining under the pack, the staged programs are knee osteoarthritis and patellofemoral pain, and a heel and tendon that feel stiff and sore belong with Achilles tendinopathy. Knee pain on stairs is a good place to start if you have no diagnosis yet.

The low back, and what a model can and cannot tell you

The spine is where the evidence thins out, and it is worth being blunt about why. The study most often reached for is a computer model built from scans of one 26 year old man standing still, so it is not a measurement of anyone walking, and the authors say themselves that walking and the speed of loading would change the answer (Zhao and colleagues, 2023).

Two things in it still transfer. The rise in compression through the lumbar discs was larger than the weight of the bag in all three carrying styles, because the muscles that hold you upright have to pull harder as well. And the backpack was the kindest of the three: at a bag of 20% of body weight, shear force at the bottom of the spine came out at 148 N with the pack on both shoulders, against 183 N for a shoulder bag and 291 N for a handbag.

The rule that comes out of it is simple. A symmetrical pack worn on both shoulders is the least demanding way to carry a load, and a bag slung on one side is the most. If your back is the part that objects, the low back pain program comes before any pack, and so does the warning list at the end of this page.

Shoulders and hands that go numb under the straps

This is the part most rucking articles leave out. Thirty-six adults, 18 of them women, walked on a treadmill at 1.1 m/s for 20 minutes in a military-style pack holding 30% of body weight, about 22 kg (48 lb) for the women and 24 kg (53 lb) for the men, with the hip belt done up. Motor responses in the median nerve at the armpit dropped by 8.4% from before the pack went on to the end of the walk (p = 0.025), and sensory responses dropped by 17% (p = 0.007) and stayed about 20% down straight after the pack came off (Hein and colleagues, in print 2026).

The study did not record symptoms at all, so it cannot tell you whether anyone felt pain, tingling or numbness, and it is not evidence that nothing was felt. What it does show is that a single 20 minute walk at a load far heavier than most people start with changes how the nerve conducts. Lower muscle mass and lower body mass index went with larger drops. The measurements were taken straight after the walk and straight after the pack came off, and the authors say the results cannot be stretched to any later point, so nothing here says how long the change lasts.

Taken further, this is the problem that got the name rucksack palsy. It has its place in the standard list of load carriage injuries, alongside foot blisters, stress fractures, back strains, pain in the ball of the foot (metatarsalgia) and knee pain (Knapik and colleagues, 2004).

An arm or hand that goes numb, tingly or weak under a pack is a reason to take the load off, not to finish the route. If it settles once the pack is off, lighten the load and get it looked at if it keeps happening. If there is weakness, or the numbness is still there after the pack has been off a while, see a doctor or physio about it instead of waiting for it to settle on its own. Symptoms that keep coming back with the straps on fit the picture on the thoracic outlet syndrome page, and sore, burning balls of the feet fit metatarsalgia.

Bone is the other thing on that list. Heel or forefoot pain that has built up over a few weeks of loaded walking and hurts more as the walk goes on can be a stress fracture rather than a sore tendon, and walking through one makes it worse. Both have their own warning sign below, with how soon to get them checked, and heel pain in the morning sets out how a stress fracture and plantar fasciitis feel different.

Does the pack itself matter?

Less than the shops suggest, on the one comparison that exists. Twelve soldiers marched 5 km three times at 5.5 km/h carrying 30 kg (66 lb), using a different pack design each time in a balanced order. Heart rate and oxygen uptake were recorded during the march. Jump height and grip strength were measured before and after it, along with how steadily the soldiers could stand. There were no significant differences between the three designs on any measure, and the authors concluded that how much you carry matters more than which military pack you carry it in (Orr and colleagues, 2026).

Hip belt tension has been tested once too, in 9 men carrying 15 kg (33 lb), then 20 kg (44 lb), then 25 kg (55 lb), at a belt tension of 30 N and then 120 N. Tension made no statistically significant difference to walking mechanics at any weight. What the weight itself did was reduce movement: knee bending range through the walking cycle fell by about 2 to 3 degrees between the 15 kg (33 lb) and the 25 kg (55 lb) conditions, from 59.9 to 57.5 degrees at the looser belt setting and from 60.0 to 56.7 degrees at the tighter one, and the pelvis rotated less too (Oberhofer and colleagues, 2018).

Nine men and twelve soldiers are small groups, and both studies used military equipment. So a hip belt is there to spread pressure and keep you comfortable, which is reason enough to use one. Nobody has shown a pack, or a belt setting, that protects a joint.

Hills and pace, if you want it harder

Thirty-one healthy young men were split between three separate experiments, 10 men in one, 11 in another and 10 in the third, so each finding comes from its own small group. The 11 walked at 5 km/h on the flat with vest loads from 0 to 30 kg (0 to 66 lb): metabolic rate rose with the load along a curve, not a straight line, and heart rate rose in a straight line. The 10 in the third experiment kept a 10 kg (22 lb) vest on and changed the walk instead, 3 km/h, 5 km/h and 7 km/h on the flat and then slopes of 0%, 5% and 10% at 5 km/h, and every step up in speed or slope raised the metabolic cost significantly (p less than 0.001). Load position on the trunk made no difference at 10 kg (22 lb) in the first group of 10 (Jing and colleagues, 2025).

Each of those findings rests on 10 or 11 young men in a laboratory, and none of the three experiments tested the same men, so treat the shape of the relationship rather than any single value. The usable bit: a slope or a quicker pace will make a walk harder without another kilogram (2.2 lb) in the pack. Whether that is kinder to a sore knee than extra weight is not something this study measured.

Who should check with a clinician first

If you have had a hip replacement, get the go-ahead from your surgeon or physio before you try rucking. Some operations limit this kind of work for the first months, so the timing depends on your surgery, and the hip replacement rehab page explains how those stages usually run. After a knee fracture or knee surgery, including a knee replacement, follow your surgeon's or physio's plan, and start rucking only when they have cleared you.

With a heart condition or high blood pressure, check with your doctor before you start, because carrying weight raises heart rate and oxygen demand at any given pace. If you are pregnant, check with your midwife or physio before you start. If you have fallen in the past year, or feel unsteady on uneven ground, speak to your physio or doctor first, keep the early walks flat and even, and build the balance and falls prevention program alongside the walking, not instead of it.

If you have been told your bone density is low, ask the clinician who told you before you add load, and start from the osteoporosis program.

Bone density is a separate question

Searches for weighted vests and bone are mostly asking whether the load builds bone, and that question is not answered here on purpose. Bone responds to load differently from joints and tendons, and the right answer for you depends on your own bone density, your fracture history and your medicines. The osteoporosis program is the place to start, with the clinician who gave you the diagnosis.

When to see a physio (physical therapist)

Two weeks of the same ache is the usual trigger, and so is a problem that turns up every time you load the pack and settles when you leave it at home. Go sooner if your arm or hand goes numb under the straps, if a knee swells after a walk, or if you have quietly stopped doing hills to avoid something.

Take the numbers with you: the weight you carry, how far, how often, what changed in the fortnight before it started. Most flares belong to that fortnight, not to the walk you felt them on. The warning list below comes before any of that. Each line sets its own speed, and a physio is not the first call for a single one of them.

See a doctor promptly if

Emergency: if chest pain, pressure or tightness does not ease quickly when you rest, spreads to your arm, neck, jaw, stomach or back, or comes with sweating, feeling sick, feeling light-headed or being short of breath, call emergency services straight away, as this can be a heart attack. If it eases quickly and none of these happen, get medical advice the same day, and do not exercise again until you have been checked.
Emergency: pain, tingling, numbness or weakness in both legs, numbness or altered feeling around your genitals or bottom, or new trouble peeing or controlling your bladder or bowels. The same applies if you lose feeling in one leg. Call emergency services or go to an emergency department straight away. These can be signs of pressure on the nerves at the base of the spine (cauda equina syndrome).
Emergency: you have had a fall or an injury and now have severe hip pain, or you cannot walk or put weight on the leg. Call emergency services or go to an emergency department. This can be a sign of a broken hip (hip fracture).
Same day: back pain that comes on suddenly after lifting, bending, a cough or a sneeze, even without a fall, if you have low bone density (osteoporosis). Get medical advice the same day. This can be a sign of a broken bone in the spine (vertebral fracture). Stop the exercises until you have been checked.
Same day: back pain after a minor fall or strain if you are older, have low bone density (osteoporosis) or have taken steroid tablets for a long time. Get medical advice the same day.
Same day: groin pain that built up with running, marching or jumping, often after you increased your training, and now hurts when you walk, makes you limp, or aches at rest or at night. Stop running and jumping and keep walking to a minimum until it has been checked. Get medical advice the same day and mention your training. If you cannot put weight on the leg, go to an emergency department. This can be a stress fracture in the neck of the thighbone (femoral neck stress fracture), which is easy to miss at first and can become a full break if you keep loading it.
Same day: new hip or groin pain after a fall, even a small one, if you are older, have low bone density (osteoporosis) or have taken steroid tablets for a long time, even if you can still walk. Get medical advice the same day. A broken hip is not always obvious at first.
Same day: a calf or thigh that is newly swollen, warm, tender, red or darker than usual, has swollen veins that are sore to touch, or has a throbbing or cramping pain that does not fit your injury or condition, or that feels different from normal muscle soreness after exercise. This can be a sign of a blood clot (deep vein thrombosis), especially after surgery, an injury, time in a cast or boot, a long trip or a spell of being much less mobile than usual. Get medical advice the same day. If you are also short of breath or have chest pain, call emergency services.
Within a few days: the whole heel hurts when you squeeze it from both sides, especially after a sudden increase in running or walking, or if you have thin bones (osteoporosis). Stop running and jumping, cut down on walking and standing, and see a doctor within a few days, as this can be a stress fracture of the heel bone rather than plantar fasciitis. An X-ray can look normal for the first 2 to 3 weeks, so a normal early X-ray does not rule it out.
Within a few days: the pain sits at one spot over one of the long bones that lead to the toes, and that spot is tender or swollen, especially after a sudden increase in walking, running or standing, or if you have thin bones (osteoporosis). Stop running and jumping, cut down on walking and standing, and see a doctor within a few days, as this can be a stress fracture. An X-ray can look normal for the first 2 to 3 weeks, so a normal early X-ray does not rule it out.

Common questions

How much weight should I start rucking with?

There is no tested answer, because no study has followed people who ruck for fitness. What the laboratory studies used tells you where the measured effects sit rather than where you should begin: 15% and 30% of body weight in the knee loading study of 24 adults, 20 kg (44 lb) in the Achilles and knee modeling study of 16 cadets, and 15 to 25 kg (33 to 55 lb) in the hip belt study of 9 men; those are research conditions, not starting points. The starting point on this page is a clinical judgement and not a tested dose: 5% of body weight, which is about 3.5 kg (8 lb) for someone of 70 kg (154 lb), with 10%, about 7 kg (15 lb), as the top of the first few weeks rather than a place to begin. Keep the early walks to 20 to 30 minutes on flat ground, two or three times a week, and change one thing at a time, the minutes or the weight, with a week or two before the next change. Your physio will adjust all of it, and will start lower than this if you are coming back from a knee, hip, back or Achilles problem.

Is rucking better than running?

Nobody has compared them, so there is no honest winner. A fair comparison needs the same injury definition and the hours each group spent doing each activity, and no study of recreational rucking has collected either. What can be said is that they load you differently: running puts a brief, large force through the leg many times, while rucking puts a smaller force through it for much longer and adds weight to your spine and shoulders at the same time. If running already hurts your knees, rucking is not automatically the gentler option, because the force at the knee rises directly with the load you carry (Jones and colleagues, 2026).

Does rucking build leg strength?

No trial of that kind turned up while this page was written: nobody has strength tested recreational ruckers before and after a block of training, so the claim is untested either way. What has been measured is the load: peak knee joint contact force rose directly with the weight carried in 24 adults walking at a fixed speed (Jones and colleagues, 2026), so the muscles controlling your knee are doing more per step than in unloaded walking. That is endurance work with weight on, which is a real thing to train and is not the same as strength training. If strength is the goal, the sit to stand, step up and squat patterns in the strength program for older adults build it more directly, because you can keep adding load to them.

How long should I wear a weighted vest?

No trial has set a duration, and the measured effects arrive quickly. Thirty-six adults walked on a treadmill for 20 minutes carrying 30% of body weight, about 22 kg (48 lb) for the women and 24 kg (53 lb) for the men, and the electrical responses of the median nerve in the arm had measurably dropped by the end, with a sensory amplitude 17% lower than before they put the pack on (Hein and colleagues, in print 2026). The study did not record whether anyone felt pain, tingling or numbness, so it cannot tell you that symptoms were absent. That is a laboratory measurement at a heavy load, not a warning about every vest. It does say that short and light is the sensible way in, and that an arm or hand that goes numb or weak is a reason to take the load off, not to finish the walk.

Is rucking bad for your knees?

It depends entirely on the knee. Added load raises the force through the knee in proportion to the weight (Jones and colleagues, 2026), which is training for a joint that copes and an aggravation for one that is already sore walking the dog. Knees do not object to load as such, and in knee osteoarthritis the guidelines put exercise first, not rest (NICE NG226), so the question is dose rather than permission. If your knee already hurts on stairs or after sitting, settle that first with the knee osteoarthritis program or the patellofemoral pain program, and add the pack later.

Does a weighted vest help bone density?

That is a separate question and this post deliberately does not answer it, because the bone evidence belongs with the osteoporosis program, not with a fitness trend. Bone responds to load in ways that are not the same as joint loading, and the answer depends on your own bone density, medicines and fracture history. Start from the osteoporosis program, and if you have been told your bone density is low, ask the clinician who told you before you put a loaded pack on.

References

Knapik JJ, Reynolds KL, Harman E. Soldier load carriage: historical, physiological, biomechanical, and medical aspects. Military Medicine. 2004;169(1):45-56. https://doi.org/10.7205/MILMED.169.1.45
Jones BW, Willson JD, DeVita P, Wedge RD. Opposite medial and lateral tibiofemoral joint compartment responses between dominant and nondominant limbs when walking with load carriage. Journal of Applied Biomechanics. 2026;42(1):16-21. https://doi.org/10.1123/jab.2024-0294
Willy RW, DeVita P, Meardon SA, Baggaley M, Womble CC, Willson JD. Effects of load carriage and step length manipulation on Achilles tendon and knee loads. Military Medicine. 2019;184(9-10):e482-e489. https://doi.org/10.1093/milmed/usz031
Hein JL, Saul K, Schmidt DJ. Backpack load carriage affects motor and sensory responses of the median nerve. Military Medicine. Published online 2025; in print 2026;191(3-4):e703-e709. https://doi.org/10.1093/milmed/usaf459
Zhao G, Wang H, Wang L, Ibrahim Y, Wan Y, Sun J, Yuan S, Liu X. The biomechanical effects of different bag-carrying styles on lumbar spine and paraspinal muscles: a combined musculoskeletal and finite element study. Orthopaedic Surgery. 2023;15(1):315-327. https://doi.org/10.1111/os.13573
Oberhofer K, Wettenschwiler PD, Singh N, Ferguson SJ, Annaheim S, Rossi RM, Lorenzetti S. The influence of backpack weight and hip belt tension on movement and loading in the pelvis and lower limbs during walking. Applied Bionics and Biomechanics. 2018;2018:4671956. https://doi.org/10.1155/2018/4671956
Orr R, Rousseau J, Canetti EFD, Schram B. Soldier load carriage: does the type of pack matter? Applied Ergonomics. 2026;134:104733. https://doi.org/10.1016/j.apergo.2026.104733
Jing Z, Han H, Han J, Zhang J. Effect of vest load carriage on cardiometabolic responses with load position, load mass, and walking conditions for young adults. Bioengineering. 2025;12(2):202. https://doi.org/10.3390/bioengineering12020202
National Institute for Health and Care Excellence. Osteoarthritis in over 16s: diagnosis and management (NG226). 2022. https://www.nice.org.uk/guidance/ng226
NHS. Chest pain. Page last reviewed 8 August 2023. https://www.nhs.uk/symptoms/chest-pain/
NHS. Sciatica. Page last reviewed 3 December 2024. https://www.nhs.uk/conditions/sciatica/
NHS. Osteoporosis. Page last reviewed 13 October 2022. https://www.nhs.uk/conditions/osteoporosis/
NHS. DVT (deep vein thrombosis). Page last reviewed 30 April 2026. https://www.nhs.uk/conditions/deep-vein-thrombosis-dvt/

Written and checked by the PocketPhysio editorial team. Last updated 2026-10-01.

This page is general education, not a diagnosis or a personal treatment plan. See a physiotherapist or doctor for advice about your own situation.

Rucking and weighted vest walking: what the extra load does to your joints