Rucking is disarmingly simple: put weight in a backpack and walk. It comes from military training, where soldiers have marched under load for millennia, and it has become the rare fitness trend whose core claim is basically true — loading a walk makes it substantially harder without turning it into running.
The energy math
Load-carriage research (the Pandolf equation, developed for the US military) predicts that walking with 15–20 kg at normal pace costs roughly the energy of slow jogging for many adults — commonly estimated at two to three times the calories of the same walk unloaded, depending on load, speed and terrain. It is low-impact compared with running (one foot stays grounded; peak joint forces are far lower), which is precisely its appeal for heavier beginners and ageing joints — with the caveat that load itself is a joint stress, addressed below.
What it trains
Rucking is honest Zone 2 work for most people (see our Zone 2 guide): sustained, conversational, aerobic. It adds a posture and strength-endurance demand through the trunk, hips and calves that plain walking lacks, and load-bearing activity is a reasonable bone-density stimulus. What it is not: a replacement for progressive strength training — the loads are too light and static to build maximal strength or muscle the way lifting does.
Loading rules that keep it friendly
Start at about 10 percent of body weight (or 5–10 kg), 2–3 walks of 20–30 minutes a week, and add roughly 10 percent load or distance per week — not both. Cap most training at 20–33 percent of body weight; beyond that, gait degrades and shoulder/knee complaints climb. Use a pack with a hip belt and keep the load high and close to the back; water, sandbags or purpose plates all work. Footwear with real support, and softer surfaces when available, complete the setup.
Who should be careful
Existing knee osteoarthritis, back problems, or shoulder/neck issues deserve a clinician’s or physio’s input before loading — and rucking through pain is not toughness, it is how a cheap exercise becomes an expensive problem. Progress patiently and it stays what it promises to be: the hardest easy exercise you own.
Bottom line: rucking doubles down on walking’s benefits at walking’s impact — start light, progress slowly, respect the joints, and it earns its place beside lifting and intervals.
