After I packed in with the terriers I moved from 4x4's to estate cars. Them old Legacy's being my fave..! Though had a couple of hatchbacks and one Ford Orion inbetween. Never liked jamming 4 big lurchers in an Orion boot, even if the speaker casings in the parcel shelf had no speakers in, to aid ventilation... ?
TBH, looking back, it was bloody tough on dogs being loaded ran, loaded and ran, all night long... But good dogs (and decent callers) will always pull you through...
As for fitness, I keep mine fit all year with daily free running walks, apart from my two week hols and my ma