Sun Siwen agreed to practice martial arts, so the next steps became much simpler.
Lu Yuan began to tailor a Cleansing Marrow plan according to his body, and then started to implement it.
Because his best friend had never practiced martial arts and was indeed old in age, it wasn't realistic to forcefully infuse him with Inner Strength like in the novels, directly expelling all impurities from his body.
It could be done, but it's highly likely that the impurities within his friend's body wouldn't be expelled yet, and he would start to transform, being unable to endure the infusion and dying from his body exploding.
Therefore, after understanding these situations, Lu Yuan had no choice but to take it one step at a time.
First, remove some of the impurities and toxins from the body, improve part of the physical condition, and remove some more after the body adapts to it.