Let's not forget about the importance of the conversion process from collagen to gelatin.... Here is snip from one of my articles...
Meat is made of strands of proteins and when you add heat (energy) to a protein you are breaking down it's structure. This relaxes the strands of protein making it more flexable and tender. However, if you add too much heat or too much heat too fast, the protein won't relax the way you had planned, and the meat can be tough. A good example is a steak.... they are pretty tender to start with so they can be cooked at higher temps for a short period of time. As a steak moves from raw to rare to medium rare it gets more tender as the protiens relax. As it passes through the medium, then medium well, then into well done range, the strands of protiens are tightening up, and moisture is getting squeezed out of the meat, so it gets tougher the more it's cooked. The same thing can happen to pork chops or white meat on chickens or turkey.
One thing you will notice when barbecuing heavier meats high in fat like brisket and pork shoulder is a stall in internal temperature during the cook. This "plateau" will happen around 160°, and sometimes takes several hours. Then the internal temperature will begin to rise again. The plateau happens because collagen in the meat is being converted into gelatin. When this happens, we get a tender and moist piece of meat that is worth the wait.
If you are really watching your internal thermometer, you might even notice a drop in the internal temperature. The reason behind the drop in meat temp is basically because the energy from the heat is going into the conversion process instead of into the meat. Think of it this way, the flow of liquefied collagen & fat is stealing heat out of the meat. As the conversion comes to an end, the heat starts going back into the meat.