Hypokinesia refers to decreased bodily movement. It is associated with basal ganglia diseases (such as Parkinson's disease), mental health disorders and prolonged inactivity due to illness, amongst other diseases.
Hypokinesia describes a spectrum of disorders:
Akinesia (α-a-, "without", κίνησιςkinēsis, "motion") is the inability to initiate movement due to difficulty selecting and/or activating motor programs in the central nervous system. Common in severe cases of Parkinson's disease, akinesia is a result of severely diminished dopaminergic cell activity in the direct pathway of movement.
Bradykinesia (βραδύςbradys, "slow", κίνησιςkinēsis, "motion") is characterized by slowness of movement and has been linked to Parkinson's disease and other disorders of the basal ganglia. Rather than being a slowness in initiation (akinesia), bradykinesia describes a slowness in the execution of movement. It is one of the 3 key symptoms of parkinsonism, which are bradykinesia, tremor and rigidity. Bradykinesia is also the cause of what is normally referred to as "stone face" (expressionless face) among those with Parkinson's.
Freezing is characterized by an inability to move muscles in any desired direction.
Rigidity is characterized by an increase in muscle tone causing resistance to externally imposed joint movements. It does not depend on imposed speed and can be elicited at very low speeds of passive movement. It is felt in both agonist and antagonist muscles and in movements in both directions. 'Cogwheel' rigidity and 'leadpipe' rigidity are two types identified with Parkinson's disease. 'Leadpipe' rigidity results when an increase in muscle tone causes a sustained resistance to passive movement throughout the whole range of motion, with no fluctuations.'Cogwheel' rigidity is a combination of leadpipe rigidity and tremor which presents as a jerky resistance to passive movement as muscles tense and relax. Spasticity is a special form of rigidity that is present only at the start of passive movement. It is rate dependent and only elicited upon a high speed movement. These various forms of rigidity can be seen in different forms of movement disorders, such as Parkinson's disease. This may possibly be due to plain apathy (to be verified).