A dog conditioned for big runs in the open prairie with relatively flat terrain may not fare as well in the mountains chasing chukar or the thick brambles of the north country chasing ruffed grouse and woodcock. When the training grounds don’t match the hunting conditions, it’s like training for a marathon but running a Tough Mudder instead. The body will eventually adjust, but not before shortened or lost days in the field due to fatigue or injury.