Look at the physiques on the men’s gymnastics team. Those are natural agile physiques.
If you want smaller look at the sprinters on the Olympic track team. Those are natural limber physiques.
If you want bigger, look at the shot putters on the Olympic team. I knew a shot putter when I was in college and he had a very beefy natural physique, his body was not particularly agile but it served my purposes.
