Abstract
In sixteen healthy individuals the effects of alteration of posture on the heart rate were studied by continuous recording of the instantaneous heart rate by means of Carcliotachograph.
The posture was changed from recumbent to sitting and then standing in one experiment, from squat to standing and then again to squat in an-other experiment.
Blood pressure was also measured and compared with the change of heart rate.
On each of the postural change from reclining to sitting and from sitting to standing the heart rate became immediately accelerated, attained its maximum at ten to fifteen seconds, and with oscillatory fluctuations, came to be stabilized within sixty seconds in a level which was always higher than before.
Similar but more pronounced change was observed in heart rate on changing posture from squat to active standing.
The physiological mechanisms responsible for these changes were discussed: The immediate effect of changing the posture to more vertical from reclining, is the reduction of venous return to the heart, due to the pooling of blood in dependent parts of the body by gravity. Various cir-culatory reactions or adjustments accompanying the postural change were interpreted on this basis and the importance of the cardio-accelerg ating and vago-pressor reflex originating in the venous area (McDowall and Aviado) was stressed.
