First, when doing it, bend your knees so that your feet cross behind your body. This can focus the body's center of gravity on the middle of the trunk? Are you sure you don't rely on your body to move up and down?
Second, every movement must be done slowly? Especially when you lower your body? Try to lower your body slowly to a depth that won't hurt your shoulders (folding your feet is also to let tall people lower their bodies)?
Third, the interval between groups should be short? This action needs to be divided into 3-4 groups? Do 8- 12 (exhausted) in each group? The most important thing is that the time interval between each group can only be 30-40 seconds? This will greatly stimulate the lower outer edge of the pectoral muscle.
Other equipment you mentioned? Including horizontal bar pull-ups, most of which are aimed at back exercises? But please keep training, okay? The back is far more important to the body shape than the chest muscles? When the latissimus dorsi develops to a certain extent, the outline of the pectoral muscle will also increase, become stiff and present a more square outer edge.
Back to your question? Flexion and extension of parallel bars arm is definitely the best way to shape the lower outer edge of pectoral muscle? There is another practical method? Can I buy a spring Zhang Liqi or a rubber band Zhang Liqi in a sporting goods store or online (it's better to buy two)? Fix the handle on the end of the spring tensioner slightly above the head after buying it? Hold the other ends of the two tensioners in each hand so that the tensioners pass through the chest? You can find many pictures online. Is this a simple way to replace the rope tensioner in the gym at home? )? This action is also good for shaping the outer edge? But also greatly stimulated the suture of chest muscles when crossing the chest.
About the suture of chest muscles? Dumbbell bird is also a good idea? The pictures are also easy to find, so I won't go into details? In addition, it can be strengthened by doing narrow push-ups? Is to keep your hands as close to your body as possible when you do it? Doing so will greatly stimulate the middle seam of the pectoral muscle and triceps brachii (in fact, try to constantly adjust the distance between your hands when doing push-ups? Location? What about the height of the feet? This can stimulate all parts of the upper body)
Word for word? All my practical experience in fitness activities over the years? I hope it helps you.