I went to the gym, next to the mirror there was a weight tower, I took a 3 pound weight in each hand and started moving my arms around ...
After 5 minutes, I had to stop because I was hurting.
Everyday, I carry my Small Cafe Bag full to the brim in addition to a Packing Cube for Aeronaut which is equally full.
Last summer, I used a Large Cafe Bag and Swift combo, both full.
Every plane trip is taken with a packed Brain Bag.
On one of my trip, I took a wrong turn and barely made it to the plane on time, they called my name and I ran as fast as I could with a full Brain Bag and a full Large Cafe Bag.
I also used the Brain Bag with very heavy books, the books were part of a package that included a bag, that bag can hold all the books but I can't carry it, I can carry the very same books with the Brain Bag.
Besides being good looking and making me look good, Tom Bihn bags are giving me a workout (with all my stuff I know they weight more than 3 pounds) without hurting.
It is important for me to keep doing weight strengthening, it is way more fun to carry my stuff and the library loot in my TB bags without hurting than try to bear with the 3 pounds weights at the gym