Chapter 665
The Body Refinement stages were easier to blaze through but were far more painful. Unlike Qi Cultivation where absorbed energy was stored in the Spirit Root itself, Body Refinement had the energy spread out into your flesh.
When spread into your flesh, it doesn't just sit there but does exactly what it's called, refining your body. Your flesh is destroyed and recreated using the energy you absorbed, perfected bit by bit as you cultivated.
Here, your mileage may vary. If your cultivation was slow, you suffered pain in small bits but over a long period of time. If your cultivation was fast, you suffered a huge amount of pain in a short time and were done with it.
For the fellows here, it was really mild since their Constitution stats were too high to fee;l such a thing. Only if their cultivation reached higher stages would they likely feel it.