Reciprocal inhibition describes the relaxation of

muscles Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of musc ...

on one side of a

joint A joint or articulation (or articular surface) is the connection made between bones, ossicles, or other hard structures in the body which link an animal's skeletal system into a functional whole.Saladin, Ken. Anatomy & Physiology. 7th ed. McGraw- ...

to accommodate contraction on the other side. In some

allied health Allied health professions are health care professions distinct from optometry, dentistry, nursing, medicine, and pharmacy. They provide a range of diagnostic, technical, therapeutic, and support services in connection with health care. Definitio ...

disciplines, this is known as reflexive antagonism. The central nervous system sends a message to the

agonist An agonist is a chemical that activates a receptor to produce a biological response. Receptors are cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an antagonist blocks the action of the ag ...

muscle to contract. The tension in the

antagonist An antagonist is a character in a story who is presented as the chief foe of the protagonist. Etymology The English word antagonist comes from the Greek ἀνταγωνιστής – ''antagonistēs'', "opponent, competitor, villain, enemy, ri ...

muscle is activated by impulses from motor neurons, causing it to relax.

Mechanics

Joints are controlled by two opposing sets of muscles called

extensors In anatomy, extension is a movement of a joint that increases the angle between two bones or body surfaces at a joint. Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extendin ...

and

flexors A flexor is a muscle that flexes a joint. In anatomy, flexion (from the Latin verb ''flectere'', to bend) is a joint movement that decreases the angle between the bones that converge at the joint. For example, one’s elbow joint flexes when o ...

, that work in synchrony for smooth movement. When a muscle spindle is stretched, the

stretch reflex The stretch reflex (myotatic reflex), or more accurately "muscle stretch reflex", is a muscle contraction in response to stretching within the muscle. The reflex functions to maintain the muscle at a constant length. The term deep tendon reflex is ...

is activated, and the opposing muscle group must be inhibited to prevent it from working against the contraction of the homonymous muscle. This inhibition is accomplished by the actions of an inhibitor interneuron in the spinal cord. The afferent of the muscle spindle bifurcates in the spinal cord. One branch innervates the

alpha motor neuron Alpha (α) motor neurons (also called alpha motoneurons), are large, multipolar lower motor neurons of the brainstem and spinal cord. They innervate extrafusal muscle fibers of skeletal muscle and are directly responsible for initiating their co ...

that causes the homonymous muscle to contract, producing the reflex. The other branch innervates the inhibitory interneuron, which then innervates the

that synapses onto the opposing muscle. Because the interneuron is inhibitory, it prevents the opposing

from firing, thereby reducing the contraction of the opposing muscle. Without this reciprocal inhibition, both groups of muscles might contract simultaneously and work against each other. If opposing muscles were to contract at the same time, a muscle tear can occur. This may occur during physical activities such as running, during which opposing muscles engage and disengage sequentially to produce coordinated movement. Reciprocal inhibition facilitates ease of movement and is a safeguard against injury. However, if a "misfiring" of motor neurons occurs, causing simultaneous contraction of opposing muscles, a tear can occur. For example, if the

quadriceps femoris The quadriceps femoris muscle (, also called the quadriceps extensor, quadriceps or quads) is a large muscle group that includes the four prevailing muscles on the front of the thigh. It is the sole extensor muscle of the knee, forming a large ...

and

hamstring In human anatomy, a hamstring () is any one of the three posterior thigh muscles in between the hip and the knee (from medial to lateral: semimembranosus, semitendinosus and biceps femoris). The hamstrings are susceptible to injury. In quadrupe ...

contract simultaneously at a high intensity, the stronger muscle (traditionally the quadriceps) overpowers the weaker muscle group (hamstrings). This can result in a common muscular injury known as a

pulled hamstring Straining of the hamstring, also known as a pulled hamstring, is defined as an excessive stretch or tear of muscle fibers and related tissues. Hamstring injuries are common in athletes participating in many sports. Track and field athletes are ...

, more accurately called a muscle strain.

Duration

The phenomenon is fleeting, incomplete, and weak. For example, when the

triceps brachii The triceps, or triceps brachii (Latin for "three-headed muscle of the arm"), is a large muscle on the back of the upper limb of many vertebrates. It consists of 3 parts: the medial, lateral, and long head. It is the muscle principally respon ...

is stimulated, the

biceps The biceps or biceps brachii ( la, musculus biceps brachii, "two-headed muscle of the arm") is a large muscle that lies on the front of the upper arm between the shoulder and the elbow. Both heads of the muscle arise on the scapula and join ...

is reflexively inhibited. The incompleteness of the effect is related to postural and functional tone. Also, some reflexes

in vivo Studies that are ''in vivo'' (Latin for "within the living"; often not italicized in English) are those in which the effects of various biological entities are tested on whole, living organisms or cells, usually animals, including humans, and p ...

are

polysynaptic A reflex arc is a neural pathway that controls a reflex. In vertebrates, most sensory neurons do not pass directly into the brain, but synapse in the spinal cord. This allows for faster reflex actions to occur by activating spinal motor neurons ...

, with entire muscle groups responding to noxious stimuli.

Application in physical therapy

Reciprocal inhibition is the basic original notion behind indirect

muscle energy technique Muscle Energy Techniques (METs) describes a broad class of manual therapy techniques directed at improving musculoskeletal function or joint function, and improving pain. METs are commonly used by manual therapists, physical therapists, occupationa ...

s. While this notion is now understood to be incomplete, the clinical mechanism of reflexive antagonism continues to be useful in physical therapy. Muscle energy techniques that use reflexive antagonism, such as rapid deafferentation techniques, are

medical guideline Medicine is the science and practice of caring for a patient, managing the diagnosis, prognosis, prevention, treatment, palliation of their injury or disease, and promoting their health. Medicine encompasses a variety of health care practic ...

techniques and protocols that make use of reflexive pathways and reciprocal inhibition as a means of switching off inflammation, pain, and protective spasm for entire synergistic muscle groups or singular muscles and

soft tissue Soft tissue is all the tissue in the body that is not hardened by the processes of ossification or calcification such as bones and teeth. Soft tissue connects, surrounds or supports internal organs and bones, and includes muscle, tendons, ...

structures.

References

*1. Fryer G 2000 Muscle Energy Concepts –A Need for a Change. Journal of Osteopathic Medicine. 3(2): 54 – 59 *Fryer G 2006 MET: Efficacy & Research IN: Chaitow L (Ed) Muscle Energy Techniques (3rd edition) Elsevier, Edinburgh *Ruddy T 1961 Osteopathic rhythmic resistive duction therapy. Yearbook of Academy of Applied Osteopathy 1961, Indianapolis, p 58 *Solomonow M 2009 Ligaments: A source of musculoskeletal disorders. J Bodywork & Movement Therapies 13(2): IN PRESS *Smith, M., Fryer, G. 2008 A comparison of two muscle energy techniques for increasing flexibility of the hamstring muscle group Journal of Bodywork and Movement Therapies 12 (4), pp. 312–317 *McPartland, J.M. 2004 Travel trigger points - Molecular and osteopathic perspectives

Journal of the American Osteopathic Association ''Journal of Osteopathic Medicine'' (JOM) is a monthly peer-reviewed open access medical journal published by the American Osteopathic Association. The journal primarily publishes original research publications and editorial articles. The edito ...

104 (6), pp. 244–249 *Hamilton, L., Boswell, C., Fryer, G. 2007 The effects of high-velocity, low-amplitude manipulation and muscle energy technique on suboccipital tenderness International Journal of Osteopathic Medicine 10 (2-3), pp. 42–49 *McFarland, J.M. 2008 The endocannabinoid system: An osteopathic perspective Journal of the American Osteopathic Association 108 (10), pp. 586–600 *Magnusson M Simonsen E Aagaard P et al. 1996a Mechanical and physiological responses to lengthening with and without pre-isometric contraction in human skeletal muscle Archives of Physical Medicine & Rehabilitation 77:373-377 *Magnusson M Simonsen E Aagaard P et al. 1996b A mechanism for altered flexibility in human skeletal muscle. Journal of Physiology 497(Part 1):293-298 *

Anatomical terms of muscle Anatomical terminology is used to uniquely describe aspects of skeletal muscle, cardiac muscle, and smooth muscle such as their actions, structure, size, and location. Types There are three types of muscle tissue in the body: skeletal, smooth ...

Bibliography

* {{cite journal , pmid=8299401 , volume=40 , issue=5 , title=Reciprocal inhibition in man , year=1993 , journal=Dan Med Bull , pages=571–81 , last1 = Crone , first1 = C * Neuroscience Online, Chapter 2: Spinal Reflexes and Descending Motor Pathways. James Knierim, Ph.D., Department of Neuroscience, The Johns Hopkins University http://nba.uth.tmc.edu/neuroscience/s3/chapter02.html Muscular system Motor control

Mechanics

Duration

Application in physical therapy

References

Further reading

Bibliography