原因其实跟上一篇的“DRAWING-IN MANEUVER”是一样的，不过到底什么是“Bracing (绷紧)”呢？书中的介绍：

Bracing is referred to as a co-contraction of global muscles, such as the rectus abdominis, external obliques, and quadratus lumborum. Bracing is also commonly referred to as a “bearing down” or tightening of the global muscles by consciously contracting them.

( 绷紧被称为全面肌肉的共同收缩，像是腹直肌、腹外斜肌、腰方肌，以有意识的收缩/紧绷全面的肌肉群。)

Research has shown that muscular endurance of global and local musculature, when contracted together; create the most benefit for those with LBP compared with traditional LBP training methods. Bracing focuses on global trunk stability, not on segmental vertebral stability, meaning that the global muscles, given the proper endurance training, will work to stabilize the spine.

( 研究显示，在全面肌肉与局部肌肉一起进行收缩时，相较于传统的下背疼痛训练的方法，肌耐力会获得最大的受益。绷紧是将焦点放在全面的躯干的稳定度上，而不是片段的嵴椎稳定度。)

因此在进行核心的训练时，首先要缩紧腹部，接着要绷紧周围所有的肌肉群。所以当你在进棒式时，不是只有腹部紧缩，背部、胸部、臀肌等全面的肌群群也同时一起紧缩啰。