[Reflex examination. Neurophysiologic and biochemical status].

The neural network excites when a stretch reflex is elicited during a physical examination. It is important to be aware that the stretch reflex depends on the contraction level of the muscle before stretch, and on the amplitude and velocity of the muscle stretch. A changed resistance from passive tissue or muscle fibre them self has to be taken into account when evaluating the size of the stretch reflex. A weak contraction compared with no contraction in the stretched muscle decrease the variation in the size of the stretch reflex. Influence from other types of receptors and synergistic and antagonistic muscles can also contribute to the stretch reflex.