The Spine (背脊)
Han Xiong Ba Bei, or 'contains the chest and raises the back,' are Taijiquan terms. Being able to contain the chest enables raising the back; thus, these two actions are interconnected. When the chest is slightly drawn inward, the muscles of the back relax and sink downward, and the spine between the shoulders seems to be raised and pulled upwards naturally, which is referred to as raising the back. It should occur naturally and should not use force to raise it up intentionally, as this could lead to developing a hunchback.
Taijiquan is about the transformation of storing and releasing (Xu Jin and Fa Jin), and the key lies in containing the chest and raising the back. The function of containing the chest is conducive to neutralizing Jin (storing Jin), and the function of raising the back is conducive to Juan (rolling back) Jin and Fang Jin (releasing Jin). The saying "force is released from the spine" is the result of raising the back. In the technique of Fa Jin, raising the back cooperates with the waist, allowing the Nei Jin (internal Jin) to rise from the heel, pass through the spine, and manifest in the fingertips.
Taijiquan places great emphasis on training the spine and back because the back houses the Governor Vessel (Du Mai), which contains important acupoints that are the convergence centers for the body's Qi and blood. The Qi of the organs and meridians is interconnected through the acupoints. Practicing the form helps stretch and activate the muscles around the shoulders and back, giving the spine strength and elasticity, harmonizing qi and blood, opening blockages, and having a good effect on digestion, absorption, and metabolism, playing a significant role in overall health and wellness.
From 《太极拳谱内外功研几录》or 'Treatise on the Internal and External Practices of Taijiquan,' by master Shi Chengzhi.