orthostatic
(adjective)
 Of, or relating to upright posture.
Examples of orthostatic in the following topics:
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Chronic Fatigue Syndrome- Persons with CFS may report additional symptoms such as muscle weakness, increased sensitivity to light, sounds and smells, orthostatic intolerance, digestive disturbances, depression, and cardiac and respiratory problems.
 
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Adrenal Gland Disorders- Symptoms may also include weakness, tiredness, dizziness, low blood pressure that falls further when standing (orthostatic hypotension), cardiovascular collapse, muscle aches, nausea, vomiting, and diarrhea.