Ok, I do use a backpack, but when I have to carry over 40 lb I use the cart. Today we walked the 6 miles down to the train station on the way to buy dog food, The bags are 25 kilo bags and that is 2.2 * 25 = 55 lb. too much for me to carry up from my local train station. So we use the cart:-). What can I say I am Old. Puppy works for his food on shopping day, he will help me pull the cart up the hill. This is how I get my exercise.