A 15 kg toddler is 17–20% of body mass for a 75–90 kg man — and the net energy cost of walking rises in near-direct proportion to load carried at the waist. Carries also train grip strength, lateral trunk, and gait stability in ways lifts don't. Farmer carry, suitcase carry, weighted walk: conditioning already scheduled into your week.
01Is carrying your kid actually training?
A 15 kg toddler is 17–20% of a grown man's body mass, and the net cost of walking rises almost in step with the load [1].
Exercise physiology has measured this, just under a different name. When researchers loaded walkers with 10%, 20%, and 30% of body mass carried at the waist, the net energy cost of walking rose in near-direct proportion to the load [1]. Carry 20% more mass, spend roughly 20% more net energy per step — no gadget, no class, no hack.
Run the dad math: a 15 kg toddler is 17–20% of body mass for a 75–90 kg man. Every zoo lap, every carry-me stretch home from the park, every trip up the stairs with a sleeper on your shoulder is loaded walking at a dose the laboratory literature has actually studied [1].
02Does it matter where the load rides?
Placement sets the price: 1 kg on the foot costs 7–10% more energy; load near your centre of mass is the cheapest carry there is [2].
Enormously. The military literature is the deepest well of load-carriage science there is. It reports that 1 kg on the foot raises energy expenditure by 7–10%, and 1 kg on the thigh by about 4% [2]. Load positioned close to the body's centre of mass keeps the energy cost lowest and posture upright [2].
A kid on your back or shoulders rides near your centre of mass — cheap per kilogram, sustainable for distance. A kid carried out front in both arms costs more. A kid on one hip loads you asymmetrically, which costs the most effort and, as the next section shows, trains the most trunk. Same kid, different workout.
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03What do loaded carries actually train?
Carries train what lifts skip — lateral trunk and steady gait under load [3] — plus grip, by the nature of holding the weight.
When researchers wired up strongman competitors, the carrying events — farmer's walk, suitcase carry, yoke — challenged the body differently than the lifting events did: heavy trunk muscle co-contraction to keep the spine stiff and the pelvis level while walking under load [3]. In the one-sided suitcase carry, the lateral trunk musculature — quadratus lumborum included — worked to hold the torso upright against a load trying to fold it sideways [3].
That's the kid on your hip. The study's authors concluded that loaded carrying would enhance traditional lifting-based strength programs [3]: grip, lateral trunk, hips, and gait stability under fatigue, none of which a bench press touches.
04How does a toddler compare with a rucksack?
A toddler weighs about what a pre-18th-century foot soldier marched with, but squirms — waking up stabilizers a strapped-down pack never asks for [2].
Favourably, as history goes: before the 18th century, foot soldiers seldom marched with more than 15 kg [2] — your toddler, give or take a snack. The differences cut both ways. A rucksack holds still, hugs your centre of mass, and lets you set the dose. A toddler squirms, shifts sides, demands the shoulders, and dismounts without notice — a live load, which is exactly why carrying one wakes up stabilizers a strapped-down pack never asks for.
The catch is progression. The kid's mass creeps up on its own schedule and quits the program around age six. The rucksack — or the twenty-minute dumbbell sessions — is how you keep the stimulus once your training partner outgrows the job.
05How do you build carries into a week?
Farmer carry, suitcase carry, weighted walk — or just stop putting the kid down.
Three moves, zero skill barrier. The farmer carry: a heavy dumbbell in each hand, walk 20–40 m, rest, repeat for 4–6 rounds at the end of a training session. The suitcase carry: one dumbbell, same distances, both sides — the one-sided load that works the lateral trunk especially hard in the strongman data [3]. The weighted walk: a pack loaded to about 10% of body mass — the bottom of the range the lab literature tested [1] — on an ordinary 30-minute walk, building time before load.
Or skip the equipment phase entirely. The school run with a kid on your shoulders, the sleeping transfer up the stairs, the one-trip grocery haul — the training was already scheduled. All you're adding is the decision to stop putting the load down.
Is a weighted vest better than dumbbells for walks?
Which side should I carry my kid on?
Does carrying count as cardio?
General-audience information — not medical advice. How we source and verify. No affiliate links in this breakdown. Last updated 2026-09-05.
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