Genetics play a huge role in whether or not the dog will have a pronounced lat muscle. Some dogs no matter how much conditioning you do will never have one show as much as some dogs that it takes very little to show the muscle.
Some people do "condition at the food bowl" and that can lead to a dog appearing somewhat "fit". Thats not a way to achieve a nice lat muscle though, and its not a good idea because you arent actually conditioning you are essentially underfeeding the dog to achieve a thin look.
I have a mutt here who no matter what I do will NOT show a lat muscle at all. Or if I do manage to get it to show its very faint and hardly able to be seen.
I did tons of drag work, running, flirt, spring, etc and it just isnt in his genetics to have that show, he gets killer legs and shoulder muscles, but just no lat.
We also had another dog here who had one popping out with no work at all, all the time! Just depends on genes sometimes.
Just remember that point, but like I was told when I was hell bent on getting a lat muscle on my dog, drag work is great, running up and down hills, and just running in general, and spring pole. I think if you give your dog a balanced workout and stick to a schedule and exercise and feed properly your dog will give you all its genetics allow for.