The fact that it feels tiresome is worrying me. That should feel like nothing. 15 kg is not all that much (initially wrote “a joke”, didn’t realize that might sound disrespectful to some), unless you are either 12, 92, or really out of shape.
Have you tried carrying what equates to a toddler by one hand for 3km? Them plastic bag carrying handle bits are going to be digging into your fingers, friend. These days it won’t matter so much of course because the fingers will be frozen anyhow.
Frankly I haven’t used a shopping bag for years because I prefer collapsible cases (approx 40x60 cm) but economically those are even worse to carry farth than, say, 50m.
Why would I carry my groceries in a plastic bag or a collapsible box when I can just use a backpack? I can easily carry 15kg in my backpack.
I mostly go shopping with my bike though. I have huge bags that attach to the carrier and that can fit about a week of groceries for two people. I can transport even more with my bike trailer if I need to.
I might be a bad example indeed. I carry a lot of things in often quite unusual ways. As a male Paramedic working inner-hospital shifts in a 3000 bed hospital complex, well, there is a lot to carry around. And most things don’t have handles either; some resist.
I’m not good with cases, nor shopping bags. I use bags with long handles that I can hang from my shoulders. 12 kg per side won’t even make themselves felt.
Boxes are good to carry to a car.
The talk was about 1 km though, not three I believe? I might be wrong.
Anyhow, a good knapsack with a solid bottom. Two bags with long loops. I can carry 35 kg like that easily. In basic training, we carried that load for 20 km and more.
When I got my new barbells recently, I rented a car. My bench and rack I had delivered.