- When a muscle's activity increases, the activity of the functional antagonist decreases.
- Example: An increase in iliacus activity may decrease gluteus maximus activity.
Reciprocal Inhibition is also known as Sherrington's Law of Reciprocal Innervation or Sherrington's Law II.
Although Descartes may have been the first to publish an observation of this relationship between muscles as early as 1648 (1), it was Nobel Laurette Sir Charles Scott Sherrington who demonstrated this phenomenon, and proposed a theory synaptic communication of the nervous system in seminal work in 1906 (2). This theory of the "synapse" laid the foundation for our current understanding of central nervous system communication. New technology and research has lead to a far more nuanced understanding of the nervous system, neuromuscular reflex and reciprocal inhibition; however, conceptually, his definition of reciprocal inhibition still holds true.
- Descartes, Rene (1648). La description du corps humaine (The Description of the Human Body). Published posthumously by Clerselier in 1667
- Sherrington, Charles Scott (1906). The integrative action of the nervous system (1st ed.). Oxford University Press: H. Milford. pp. xvi, 411 p.,  leaves of plates.