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, an increase in iliacus activity may decrease gluteus maximus activity, and an increase in tensor fascia latae activity may decrease gluteus medius activity.

• Note: Reciprocal inhibition is likely dictated by innervations between nerve cells, and may not always reflect "perfect opposites". For example, an increase in erector spinae activity may result in reciprocal inhibition of the transverse abdmoinis, and not the rectus abdominis.

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.

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.