Babies: Kids' posture in jogging strollers

Hi,

I am looking to buy a jogging stroller for my 1 and 3 year old boys. The most popular stroller out there is the BOB, for example:
http://www.bobgear.com/strollers/stroller.php?product_id=6

As all other strollers out there, the seats in this stroller are reclined a little and they are a little soft and cushy. How does this affect the babies and kids in them? Is there anything that can be done to improve the kids' posture in these strollers or are there any out there that are more appropriate than others for kids in terms of proper posture?
thanks in advance for your help! (I didn't find much info in the baby-gear section),

Yaga