If an ordinary martial artist cultivated their Internal Breath cultivation method to a certain extent, their body would naturally be strengthened. Be it their flesh, meridians, or bones, they would be strengthened.
This was the path that martial artists had to take in the first place. Moreover, they would obtain further and greater strength after becoming stronger.
Chu Nan was an obvious and even extreme example.
The degree of tempering of his body far exceeded ordinary standards and the strength of his Internal Breath.