If they want to be picked up, they will have their arms and legs around you in a way that balances.
If they are not conscious, or actively trying to not be picked up, their balance is either off to one side or constantly changing.
You can hold two hammers of equal weight, but if you held one closer to the hammerhead, and one closer to the tip of the handle. You can imagine the same object requiring different amount of effort to carry.
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