Active stretching eliminates force and its adverse effects from stretching procedures.

Before describing the principles on which active stretching is based, the terms agonist

Agonist (muscle)

Agonist is a classification used to describe a muscle that causes specific movement or possibly several movements to occur through the process of its own contraction. This is typically a term designated for skeletal muscles...

 and antagonist

Antagonist (muscle)

Most muscles work in pairs, and when a muscle works it needs to have an agonist and an antagonist, unless the muscle's natural state is opposite to that which is produced by the muscle, example Sphincter ani externus muscle....

 must be clarified. Agonist refers to actively contracting muscle or muscles while their opposing muscles are termed antagonists.

The neuromechanisms conceptualized by Sir Charles Sherrington (1857 - 1956), “the philosopher of the nervous system”, as applied to active stretching are:

1. Reciprocal inhibition — While agonist muscles contract, contraction of the opposing antagonist muscles is inhibited. (Such as when alternately flexing and extending one's elbow.)
2. Muscle spindles — Sensory nerve endings in muscle detect the change in length of the muscle and its rate of change.

Force applied to a muscle stimulates the muscle spindles which activate protective reflexes resulting in contraction of that muscle. (Such as the knee jerk response of neurological testing procedures.)

While necessary for sports and ordinary motions, this protective reaction is counterproductive for stretching, i.e., lengthening muscles.

A history of active stretching

1. Sir Charles Sherrington conceptualized the principle of reciprocal innervation circa 1904 and demonstrated it circa 1913.
2. A. D. Munrow's work proposed these principles for ‘active’ mobilizing exercises. 1962
3. While H. A. DeVries, L. E. Holt and others wandered from this course, P. Williams (1937) utilized procedures for his flexion exercises back program. Peters and Peters (1975) further adapted Sherrington's principles into their program of ‘active stretching’, departing from the popular static stretching designed for specific sports, to address mobility of the entire body.
4. EMG (Electromyographic) studies by S. Blackburn and others have validated Sherrington's principle of reciprocal innervation. Audiovisual electromyography by Peters and Peters supports Sherrington's principle of reciprocal innervation (inhibition) and his description of the reaction of ‘muscle spindles’ to force. These two principles are the basis of ‘active stretching’ procedures.
5. There currently are other stretching methods utilizing ‘active’ components in conjunction with force, the use of which Munrow does not concur.

6. Invented in 1998 By Thomas Sheehan of Columbia University.