Muscle movements are carefully controlled during posture by mechanical impedance. This is an area where neuroscientists can apply the accuracy of control systems analysis to quantitatively analyse how a single neuron matches the mechanical stress on the muscle as relayed by mechanoreceptor input with the maintainence of a movement or posture. To do this cells which control a single reflex will be recorded in the hermit crab and experiments carried out to test the cell response to quantifiable resistances applied to the leg movement. The data will be analysed mathematically. The results will determine which mathematical model best describes the way in which a neuron maintains posture and stiffness in a complete motor reflex. This kind of information has important consequences for the understanding of movement and efficiency of neuronal systems.