centre of gravity
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cen·ter of grav·i·ty(COG) (sen'tĕr grav'i-tē)
Synonym(s): centre of gravity.
centre of gravity; CG point within a body through which gravitational force acts; each body segment has an individual CG, but the overall CG of the static human body lies just superior to the navel, with the line of gravitational force directed downwards between the medial malleoli and just anterior to the ankle joint (through talonavicular joint); thus the erect body is stable; CG position changes continuously in relation to body movements; forward body motion is initiated when the CG is projected forward and the line of gravitational force falls beyond the body outline
trajectory of CG body CG follows a smooth up/down and side-to-side trajectory during gait (5 cm up/down, 5 cm side/side at normal walking speed [60 strides per minute; 1 m/second] in adults, reflects the magnitude and direction of the ground reaction forces); low point of CG trajectory coincides with double support phase; upper point of CG trajectory coincides with midpoints of single support phases; CG trajectory moves to the right from the midpoint of the single support phase of the left leg to the midpoint of the single support phase of the right leg, and vice versa, maintained by postural reflexes