Marinades don't penetrate nor do acids tenderize,except for making the outer mushy. Papain, if not time controlled, will turn the meat to mush also. Sorry to be the bearer of bad news but at least you have something that will tenderize. Nothing is going to make tri tip melt literally like butter.
The diaphragm is the major muscle responsible for breathing. It is a thin, dome-shaped muscle that separates the abdominal cavity from the thoracic cavity. During inhalation, the diaphragm contracts, so that it's centre moves caudally (downward) and its edges move rostrally (upward).
Several muscles located in the neck may also contribute to the work of breathing during exercise. The sternocleidomastoid muscle, which runs from the back base of your skull down to your chest, may be called to action during periods of strenuous exercise.