Reciprocal Inhibition

Reciprocal Inhibition: When a muscle's activity increases, the activity of the functional antagonist decreases. For example, an increase in biceps brachii activity may decrease triceps brachii activity, and an increase in psoas activity may decrease gluteus maximus activity.

• Note: Reciprocal inhibition is likely dictated by innervations between nerve cells and may not always reflect "perfect opposites." For example, an increase in the tensor fascia lata's activity may decrease the gluteus medius's activity (both muscles perform hip abduction).
  

For a lecture discussing reciprocal inhibition and related human movement science concepts, check out Lesson 20: More on the Human Movement Systems

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 of 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 have led 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.

1. Descartes, Rene (1648). La description du corps humaine (The Description of the Human Body ). Published posthumously by Clerselier in 1667
2. Sherrington, Charles Scott (1906). The integrative action of the nervous system (1st ed.). Oxford University Press: H. Milford. pp. xvi, 411 p., [19] leaves of plates.