It depends on the dog and also where you ride. There is no easy answer to this. Just google and read and see what others do and then decide what works for your dog at this stage of its life. I built the dogbike for my dog and he would jump in and out of it without me leaving the bike Just stopped and strapped him in. You soon learn how much your dog can run and when he need to rest. My dog would bark once if he was bored and wanted to run. I alsoo used trailers as he got older, among others also a Carry Freedom Y trailer small with an open box strapped on.
https://flic.kr/p/Gjd4Mt