Evidence is insufficient because of: 1  The limited number or size of studies. 2  Important flaws in study design or methods. 3  Inconsistency of findings across individual studies. 4  Gaps in the chain of evidence. 5  Findings not generalizable to routine primary care practice. 6  Lack of information on important health outcomes.
Definition of jerk for English Language Learners. : 1  a stupid person or a person who is not well-liked or who treats other people badly. : 2  a quick pull or twist. : 3  a sudden sharp movement.
A study at the University of Colorado has suggested that a hypnic jerk could be an archaic reflex to the brain's misinterpretation of muscle relaxation with the onset of sleep as a signal that a sleeping primate is falling out of a tree.