Fig. 5.

Heart rate plotted as a function of left ventricular stroke volume during tilt test before and after 4–215 days of spaceflight in astronauts who completed 10 min of tilt test (non-presyncopal) and those who could not stand for the entire 10 min (mean ± SE). Values are plotted regardless of flight duration, and values during 6 min after the onset of tilt are plotted (drawn from data in Ref. [72]). The relationship between stroke volume and HR in presyncopal subjects is maintained, similar to that in non-presyncopal subjects after spaceflight