Abdomen stretch

Yesterday when doing the standing meditation I felt a stretch on the front sides of the abdomen. It felt a little like a balloon type feeling like there was a tissue being stretched over an expanding inner object. Normally all the other stretching feelings I've felt  in past, e.g. foot couple, transverse, stretch on the back, they've all felt more linnear but this felt like the stretch was being stretched over a more round shape. I also felt like the round feeling stretch a little in my legs as well. This only happened once so not sure if this will happen again or not. I'm curious if this is okay or if this is disconnected. Is this at all related to peng? I feel like I've heard or read people say that peng is sort of like an inflated ball. 

It also felt like the feeling of stretch on the front sides was somewhat related to the stretch on the back, if the stretching on the back changed it would affect the front stretch slightly.

Standing FBD