LOL Lola's habits not mine

I am wondering if this is a common thing for dogs that normally potty outside. Lola can hold herself for a good 6 plus hours and only poops about once a day. But on days we walk it's like tripled.
Today for instance she did a big healthy poop about a half hour before we went for a walk. We are not even 8 houses from home and there she goes with a another poop about the same size as the one she did a half hour ago, then halfway into a short mile walk she poops again, this time a small and not so great one so now some is stuck on her hair. She never get's anything on herself when we are home, only on walks. I can bet if we did not go for walk today she might not have pooped again all day. I can't help but wonder if she is making herself go to the point that it is messy. Of course she also has to wet at every other house we walk by. I have gotten to the point that we walk down the middle of the street and I try to keep her away from the grass, otherwise it would take and hour or longer to go a mile.
My last dog pottied on pads, and LOL just like I would as soon as he knew we were leaving the house he would run and use his piddle pad. So I am wondering if this is something common among dogs that do their business outside