According to the Nine Revolutions Technique left behind by Su Xuansheng back then, in theory, even if he only cultivated the first level of the Nine Revolutions Technique, he could reach the Nine Revolutions Internal Breath.
However, after countless experiments, Chu Nan confirmed one thing. No matter how much his Internal Breath circulated, it would ultimately be limited by the upper limit that his meridians could endure.
Chu Nan had now cultivated to the fifth level of the Nine Revolutions Technique. With the strength of his meridians that had been tempered many times, he could only endure all the Fifth Revolution Internal Breath. It helped his Internal Breath to be powerful enough to be compared to a fifth-stage Internal Breath Martial Artist when it erupted.
As for the Sixth Revolution Internal Breath, Chu Nan had tried it before, but he immediately discovered that the strength of his meridians was insufficient and could only give up.