The short answer: carrying a pack raises the energy cost of walking in rough proportion to the load, which is a real but moderate effect: for typical rucking loads of 10 to 20% of body weight, it is somewhere around 20 to 35% more energy, not "2 to 3 times." The other headline benefits, strength, posture and bone density, have much weaker evidence for rucking specifically than the earlier page suggested.
What the extra load costs
A lab study of load carriage during walking (published in the Journal of Experimental Biology in 2014) found that metabolic energy use rose roughly linearly with load, by about 7.6 watts for each additional kilogram carried in a backpack at 1.25 m/s (4.5 km/h). Converting that for a 75 kg walker (our arithmetic, at one speed), and comparing it with the roughly 262 calories an hour that a 3 mph walk uses in total by the Compendium rating, gives:
| Pack weight (75 kg walker) | Extra calories per hour | Increase over unloaded walking |
|---|---|---|
| 5 kg (7% of body weight) | 33 | about 12% |
| 7.5 kg (10% of body weight) | 49 | about 19% |
| 11 kg (15% of body weight) | 72 | about 27% |
| 15 kg (20% of body weight) | 98 | about 37% |
So a 15 kg pack, a heavy load at 20% of body weight, adds around a third. A later study of heavy military backpacking (Looney and colleagues, Medicine & Science in Sports & Exercise) found that energy use rises nonlinearly with load relative to body mass at the heavy loads they tested, 22% to 66% of body mass, so the cost climbs faster as loads get very heavy, and existing equations underestimate it. The earlier page claimed rucking burns "200 to 300 calories per kilometre" against a casual walk's "100," and that it gives "+100 to 200%" over walking. Those figures don't match the measurements, and the baseline of 100 calories a kilometre was twice what a 70 to 75 kg person uses (calories burned walking), so we've removed them.
Strength and posture
It is plausible that carrying a load on your back works the upper back, core and legs harder than walking without one, and a heavier load will feel harder. But we couldn't find a trial showing that rucking builds strength, so we can't tell you how much, or compare it with a gym program. The claims that it "forces good posture" and fixes rounded shoulders from desk work are also untested, as far as we could find. Walking vs gym covers what the guidelines say about muscle-strengthening activity.
Bone
The earlier page said rucking "delivers strongly" on bone density. The evidence on loaded walking and bone is much thinner. A 2013 meta-analysis found that walking alone had no significant effect on bone density at the spine, forearm or whole body in postmenopausal women (see the same finding in walking vs gym). Studies of weighted vests are mixed. A five-year trial from 2000 (Snow and colleagues) found that postmenopausal women who exercised three times a week with weighted vests, including jumping, maintained hip bone density while controls lost it. A 2025 randomised trial in JAMA Network Open in older adults with obesity found that during weight loss, using a weighted vest did not prevent hip bone loss, with similar losses of about 2% in every group, including weight loss alone. Neither is a trial of walking with a backpack, so we can't say rucking helps your bones.
Impact and injury
The earlier page said rucking has "0 extra impact versus running" and a "low" joint impact. Carrying a load adds to the forces through your legs and spine with every step, so we'd avoid calling it free of impact. If you have back, hip, knee or shoulder problems, speak to your doctor first, and be cautious if you are pregnant or have balance problems, as the page said. We also haven't reviewed the injury research on civilian rucking, which is limited.
Starting out
This part is common coaching practice, not research. Popular guides suggest starting with a pack of about 5 to 10% of your body weight, holding it high and close to your back, and building up slowly, changing only one thing at a time, so your back and shoulders can adapt. We removed the earlier page's detailed progression and its table of "experience levels" up to 30% of body weight, since none of it came from studies. A hip belt helps with heavier loads. Walking with poles is another way to raise the effort; see Nordic walking, and for slope instead of weight, incline walking. For energy cost per distance, see how many steps to lose weight.
Sources
- Mechanics and energetics of load carriage during human walking. Journal of Experimental Biology. 2014;217(4):605-613. biologists.com
- Looney DP, et al. Modeling the metabolic costs of heavy military backpacking. Medicine & Science in Sports & Exercise. 2022. PMC
- Ainsworth BE, Haskell WL, Herrmann SD, et al. 2011 Compendium of Physical Activities: a second update of codes and MET values. Medicine & Science in Sports & Exercise. 2011;43(8):1575-1581. pacompendium.com
- Ma D, Wu L, He Z. Effects of walking on the preservation of bone mineral density in perimenopausal and postmenopausal women: a systematic review and meta-analysis. Menopause. 2013;20(11):1216-1226. NCBI
- Snow CM, Shaw JM, Winters KM, Witzke KA. Long-term exercise using weighted vests prevents hip bone loss in postmenopausal women. Journals of Gerontology Series A. 2000;55(9):M489-M491. PubMed
- Weighted vest use or resistance exercise to offset weight loss-associated bone loss in older adults: a randomized clinical trial. JAMA Network Open. 2025. jamanetwork.com
Correction note: an earlier version of this page said rucking burns 2 to 3 times more calories than walking, 200 to 300 calories per kilometre against 100 for a casual walk, and +100 to 200% in a comparison table; that it forces good posture, delivers strongly on bone density, and has zero extra impact versus running; and gave a progression and an experience-level table of loads up to 30% of body weight. We could not support those, so they were removed or corrected; the calorie effect is now based on measured load-carriage studies. The calorie table is our own arithmetic from a published rate of about 7.6 watts per kilogram at 1.25 m/s and is approximate. The 2014 load-carriage paper is cited by title because we did not see its author list, and we did not read the Snow trial in full. This article is for informational purposes and does not replace medical advice; consult a doctor before rucking if you have back, shoulder or joint concerns. This is general information, not medical advice.