‘’How do I shape up my lower pecs?’’
There are two things to address here, body composition and the shape of the actual pectorals.
If you have man boobs, you don’t have to do more “pecs”, you have to lose the fat over the “pecs”. Man boobs are the result of fat accumulation. This fat is often correlated with hormonal issues such as poor insulin and testosterone management, often due to poor nutritional habits. Once you start to lose fat, these issues usually resolve by themselves. Start by correcting the obvious, which in this case is nutrition.
The shape of the pectorals is a physiological matter. The shoulder girdle influences the look of wider shoulders, which can change the overall look of the pectorals. Some have the V-shape, wide shoulders and narrow waist, and others have the bottle shape, where the shoulders are as wide as the hips (practically impossible but you get the picture). The pectorals can be wide and almost rectangular such as Schwarzenegger or Robby Robinson and others can have more of a V-shape. This is a matter of genetic and overall bone structure.
Training wise, how you train them can have somewhat of an impact on how the “pecs” can look although lean “pecs” will always look more impressive. Before we dig into the subject, biomechanically speaking, it is impossible to isolate one part of the pec. However, you can work certain parts at a greater percentage. For example, the incline bench can recruit more of the upper clavicular fiber but still work at a lesser degree on the mid and lower fibers. Using dumbbells has been shown to involve a greater recruitment than the barbells. But the basic principles of hypertrophy remain. To gain muscle, the time under tension has to be higher than 45 seconds or count a minimum of 8 reps. Your best bet is to use different angles and equipment to work your way towards big “pecs”.