rigi-, rig-

(Latin: stiff, hard, numb; to be frozen, to grow stiff with cold, to be chilled)

acid rigor
The coagulation of muscle protein which occurs in acid conditions.
cadaveric rigidity (s) (noun), cadaveric rigidities (pl)
1. The stiffening of the muscles that occurs several hours after someone has died: The medical examiner noted the degree of cadaveric rigidity or rigor mortis that was present as part of the estimation of the time of the victim's death.
2. The hardening of the muscular tissues of the body, from one to seven hours after death as a result of the coagulation of the myosinogen and paramyosinogen: The cadaveric rigidity disappears after one to five or six days, or when decomposition begins.

Sometimes the rigor mortis, or cadaveric rigidity in the corpse, makes it difficult to fit the body into the coffin for burial.

3. The postmortem stiffening of the voluntary and involuntary muscles of the body present a board-like situation for the entire body: The development of cadaveric rigidity may be poor or incomplete in elderly, very young, or severely debilitated individuals.
calcium rigor
Stopping the heart in the fully contracted state as a result of poisoning with calcium.
catatonic rigidity (s) (noun), catatonic rigidities (pl)
Associated with psychotic conditions in which all muscles exhibit "flexibilitas cerea" or "cerea flexibilitas", a rigidity of the body in which the patient maintains whatever position he or she is placed in, the limbs having a heavy waxy malleability, which is the rigidity of catalepsy that may be overcome by slight external force, but which returns at once, holding the limb firmly in the new position: Catatonic rigidity is a condition of diminished responsiveness usually characterized by a trancelike state with constantly maintained immobility, often with flexibilitas cerea or a waxy rigidity of muscles.

A patient with catatonic rigidity may remain in one position for minutes, days, or even longer.

cerebellar rigidity
Stiffness of the body and extremities resulting from a lesion of the middle lobe of the cerebellum.
clasp-knife rigidity, clasp-knife effect, clasp-knife spasticity, clasp-knife phenomenon
1. A condition in which passive flexion of a joint causes increased resistance of the extensors.

This gives way abruptly if the pressure to produce flexion is continued.

2. An initial marked resistance to passive movement, which then suddenly gives way.

This variety of increased muscle tone is characteristic of spasticity as a result of disease or dysfunction of the pyramidal tracts.

cogwheel rigidity
A type of rigidity seen in parkinsonism in which the muscles respond with cogwheel-like jerks with the use of constant force when bending the limbs.

The term parkinsonism is any of a group of nervous disorders similar to Parkinson's disease, marked by muscular rigidity, tremor, and impaired motor control and often having a specific cause; such as, the use of certain drugs or frequent exposure to toxic chemicals.

It is also called Parkinson's syndrome or it may actually refer to having Parkinson's disease.

de rigueur (Latin phrase)
Extensive translation: "Required by fashion, custom, etiquette, essential, socially obligatory, and strictly required."
decerebrate rigidity, decerebrate state
A change in posture which takes place in some comatose patients, consisting of episodes of opisthotonos (a condition, caused by a tetanic spasm of the back muscles, in which the trunk is arched forward while the head and lower limbs are bent backward), rigid extension of the limbs, internal rotation of the upper extremities, and marked plantar flexion (turning the feet or toes toward the plantar surface or bottom) of the feet.

This can be produced by a variety of metabolic and structural brain disorders.

heat rigor
1. Coagulation of muscle protein as a result of heat.
2. Etymology: from Old French rigor, from Latin rigorem, rigor, "numbness, stiffness", from "heat" + rigere, "to be stiff".
hysterical rigidity
Increased resistance to passive movement resulting from hysteria (neurotic disorder characterized by violent emotional outbreaks and disturbances of sensory and motor functions) and not from organic nervous disease.
instantaneous rigor mortis
Instantaneously developing muscular stiffening that occurs at the moment of death in individuals who are engaged in strenuous physical activity immediately prior to their demise.

The detection of this phenomenon is important because the body maintains the postion it was in at the time of death and this positioning continues until true rigor mortis develops.

lead-pipe rigidity
1. Constant resistance to a passive movement of a limb throughout the entire range of movement, as when trying to bend a lead pipe.
2. The generalized nervous disorder marked by symptoms of trembling limbs and muscular rigidity as seen in parkinsonism (a syndrome similar to Parkinson disease; for example, as a side effect of an antipsychotic drug).

Parkinson disease: a slowly progressive neurologic disease characterized by a fixed unexpressive face, a tremor (shaking) when at rest, slowing of voluntary movements, walking with short fast steps, a peculiar posture and muscle weakness, caused by degeneration of an area of the brain called the basal ganglia, and by low production of the neurotransmitter dopamine.

Most patients are over fifty, but at least ten percent are under forty. It is also known as paralysis agitans and shaking palsy.

muscular rigidity
1. Increased muscle tone.
2. The increased muscular tension and shortness that cannot be released voluntarily and prevents lengthening of the muscles involved.
mydriatic rigidity
A fixed and dilated condition of the pupil of the eye that is unresponsive to light or other stimuli to which the pupil normally reacts.