I don't travel huge distances, maybe 1.5 hours at most. Normally my DH drives and I am the passenger in a mini van, where the seats are more like chairs and my legs hang down. Yesterday I was passenger in a Sonata, and even though I had the seat all the way back, my legs were extended out in front of me. When I got to the destination my lower back and knees were screaming pain at me. duh.... I realized that by extending my legs it puts more pressure on my lower back, thus the immediate pain once out and walking. I guess the moral to my story is, the more like a chair that a car seat is, the less pressure and stress on the lower back, and virtually no lower back pain. I actually never considered that before and suddenly I realized car seat type makes a difference for my back and knees.