At this level, muscle control over the lower sternocostal part of the pectoralis major is mastered.
The performer has total control over that part, can interchange the contractions between his two pecs fast and readily and can accelerate their contractions at impressive speeds WITHOUT changing to pec shake (meaning they can reach the highest possible frequency before the muscles really have no time to fully relax), all of that without any other muscles on the body facilitating the performance.
The generated bounce effect at this level appears extremely smooth and flawless when compared to other levels of pectoral control. This happens because the waves generated by a mastered and powerful lower pec control spread on the upper chest just at the time of the next bounce of the lower pec, resulting to a visually spotless and aesthetically synergetic animation.
Performers at this level are also qualified to perform pec dances, which is a special pec bounce performance that synchronizes the contractions to an audio beat.
Another distinctive characteristic of this level of control is how pec bounces reach incredible speed, yet they still don't transition to pec shake, as the starting point of each bounce still is the relaxed position. That indicates mastered level of pec control, as the performer has the ability to reach the maximum potential pec bounce frequency. Any greater speed than that without changing to pec shake would be physically impossible.
Our Youtube playlist of this control may be found here.
Justooraw is a characteristic performer of mastered lower pec bounce control, praised by many for one of, if not the smoothest pec bounce performer. Notice how his contractions start from the lower sternocostal part of his pecs and spread upwards just at the time of the next.
Justooraw performs a powerful yet extra-smooth, ever-accelerating pec bounce while also being able to casually move the rest of his body without interrupting the bouncing sequence in the slightest. In this example, the movement of only the lower sternocostal head is even more apparent and how it spreads upwards the rest of the pec.