RESUMEN
The nervous system controls eccentric exercise in a special way. During eccentric exercise, excitability increases in cortex, and inhibition decreases, causing excitability decrease in spinal cords. In another hand, increased cortical excitability results in extra excitatory compensation for spinal inhibition. The excitability of the corticospinal pathway depends on the balance between excitability and inhibition of the spinal cord level finally, which usually decreases. Many factors, such as the intensity of contraction, can affect the balance of corticospinal excitability. There is a cross-over effect in eccentric exercise, which promotes corticospinal excitability in untrained limbs. However, the effects and mechanisms of muscle length, fatigue and training duration are still unclear, and current researches have focused in the healthy populations. More researches are needed to explore the effects of eccentric exercise on ill populations.