然而練筋易而練膜難，練膜難而煉氣更難也
However, it is easy to train the tendons but harder to train the membranes; and as hard as it is to train them, it is still harder to train vapours*
If you are to meet two sharpshooters and one comes with a weapon that seems a bit shady and especially not well taken care of while the other person with a perfectly maintained one, you may not know who shoots best but you will definitively know who is the professional. In the old days, the body was an essential machine for a Martist, it had to be kept fit and in perfect health.
