打拳壯筋骨
Training to strengthen fascias and bones.
寧練筋長一寸，不練肉厚三分
Rather train to lengthen the fascias by one inch than to thicken the flesh by one third.
百折連腰盡無骨
A hundred twists linking the waist, a boneless utmost1.
The first part of internal training was meant to deeply transform the body and its metabolism. Both were trained by deeply stretching the body, though the second one also involved some special breathing and putting physical pressure on the body to make it hotter2.
