Final answer:
Active insufficiency in MMT refers to a muscle's reduced ability to generate tension when overly shortened, potentially leading to an underestimation of muscle strength during testing.
Step-by-step explanation:
Active insufficiency refers to the phenomenon that occurs when a muscle becomes too shortened to generate or maintain active tension. In the context of Manual Muscle Testing (MMT), active insufficiency can affect the test outcome as it may prevent the muscle from exhibiting its maximum possible strength during the evaluation. In relation to the provided reference, the concept of active stress can be likened to the tension a muscle can generate, which is influenced by the kinetics of the contractile elements, such as the acto-myosin stress fibers mentioned in the study. These stress fibers contribute to the overall tension a muscle can produce, and their activation level, governed by first-order kinetics, plays a fundamental role in controlling muscle function.
It's important for practitioners conducting MMT to be aware of the potential for active insufficiency, as it may lead to an underestimation of the true strength of a muscle. Observing the position of a joint during testing is crucial, as certain angles may predispose a muscle to a state of active insufficiency, thereby influencing the test outcomes.