How do bonds rotate in pericyclic reactions?

In Pericyclic reactions, it is shown that the terminal bonds rotate (conrotation or disrotation) to allow for allignment of the FMO's, thereby forming the sigma bond


[![Pericyclic bond formation](https://i.stack.imgur.com/kS9G7.png)](https://i.stack.imgur.com/kS9G7.png)


However, a detail that most of my textbooks and references miss out on is **how is the double bond rotating about it's axis**? As far as I know, pi bonds are restricted in their rotation which is what gives rise to cis-trans isomerism. If this is the case, how are the bonds rotating about their axis to align the orbitals?


One possibility I can think of is that the double bond is broken before/during rotation, but I haven't seen this explicitly mentioned anywhere. Any insights are appreciated.


