I used to have two springer spaniels, who hated running with me.
They could run all day, but would only do so on their terms, which meant they wanted to roam wherever they liked and not have to follow me in a straight line at a boring uniform pace.
The times we did run together they would either intentionally get lost for a few minutes, which would mean I had to stop, or lag behind, badly pretending they couldn't take the modest pace.
Sure enough, I gave in and stopped trying to run with them. Sadly one of them died a couple of years ago, but the other, now twelve and a half but still pretty nippy, is snoring at the foot of our bed as I write.
Glad it's working out better for you Splodge!