I'm desperately unfit at the moment - that's another story - and after a 45 minute cycle it was slightly hard going pedalling up the hills to our place with about 4kg of shopping on board. Not that the weight made any difference to the bike, her balance or handling; she was very stable and I didn't notice the bag was even there except that the last hill was a real bugger!
Here's my little haul of groceries; there was still plenty of room in the bag but not plenty of use left in my unfit legs so we stopped after getting these essentials. My husband doesn't have a front or rear rack on his bike so the load was all mine. Penelope weighs 20 kg so with the shopping my bike was precisely twice as heavy as my husband's. No wonder he powered up the hill ahead of me. Next time I'm putting a backpack on him so he can have some load too!
How do I know this was 4kg? I didn't do anything scientific such as put it on the scales. That's too much hard work. I used the Animal Method. If we want to get a rough idea of how much something weighs, we compare it to one of our pets. The dog weighs 10kg, the Birman boycat 6.5/7kg and the Birman girlcat 4.5 kg. It felt about the same as the girlcat when I picked her up and then the bag. :-)
As for the unfitness, I might have to head to the gym for a bit as well as ride some more. I caught a bug six weeks ago and felt like crap for almost a month. I still have the cough. Then the weather was either too hot or too wet to go riding. Wimp? Yes, unashamedly. Any fitness I had ran away and joined the circus, where it would have been appreciated. T'other half and I keep muttering that we should ride each morning before breakfast, but so rarely do. It's so hot and humid at nights at the moment we both have broken sleep and wake up late, all bleary-eyed.