There are large groups of techniques in patterns that are very similar to one another. It makes sense to practice them together, as the use much the same muscle groups and trajectories, with only a few differences in tool, height and stance. This group, the bent armed blocks and strikes, bring the attacking or blocking tool inwards or outwards across the body. In the outward versions the movement is begun by the upper back muscles and stopped by the chest muscles. The opposite is true for the inward strikes and blocks. This makes it quite important to do upper back exercises as well as the usual push ups. See my other videos for ideas.