What is “sub-failure”? Is that like taking a test and getting a D+?
Sub-failure, when it comes to injury, is common. There is usually pain or discomfort involved, but there is not an acute failure of the tendon, ligament, muscle, disc or bone. It is more of a disruption in the fibers of the connective tissue. This causes a problem in the way these fibers line up and work together.
Imagine a forest full of trees. If a significant portion were cut or burned down, that would be a failure. Now imagine that none of them are cut or burned down, but the ground underneath is so soft and the trees are so big that some of the trees are almost uprooted and are leaning on others. We do not imagine a complete failure here, but we do imagine a major structural and functional problem. This could be considered a sub-failure in the forest system.
Now imagine a muscle full of hundreds of thousands of muscle fibers. You might imagine that a complete failure might include a tear in the muscle or a tear of the tendon. Instead, what if no fibers are torn but are rather pulling each other in different directions, causing pain, spasm and discomfort? An MRI or CT scan would reveal the joint “WNL” or “within normal limits,” but the person might feel pain, discomfort, spasm and decreased strength. We do not imagine a complete failure here, but we do imagine a structural and functional problem. This could be considered a sub-failure injury.