Effects of different body positions on the hemodynamics of youths and middle-aged adults / 中华物理医学与康复杂志

ABSTRACT

Objective:To observe the effects of static 70° head-up tilted standing and of repeated body repositioning on hemodynamics in healthy young and middle-aged persons.Methods:The hemodynamics of 24 middle-aged and 23 younger persons were studied. Both groups were requested to perform static 70° head-up tilted standing and to repeatedly change their body position from 0° to 70° of tilt at a velocity of 1°/second for ten minutes in a random order. Before, between and after each test the subjects rested supine for ten minutes. Hemodynamic variables and blood pressure were recorded non-invasively.Results:The average heart rate (HR) increased significantly in both groups when rising from supine to the testing positions. In 70° tilted standing the average HR of the youth group, 84.0±9.5bpm, was significantly higher than that in the other position and that of the middle-aged group in the same position. The average HR of the middle-aged group in 70° tilted standing was also significantly higher than in the other position. Among the middle-aged group, the average stroke volume (SV) in the testing positions was significantly lower than when resting. Significant differences were observed in the average diastolic blood pressure (DBP) between the testing and rest positions for both groups, with the average DBP of the middle-aged group significantly higher than that of the youth group in all three positions. Among the youth group, the average SV, CO and systolic blood pressure (SBP) of the males were significantly higher than among the females in all of the different body positions.Conclusions:Young persons mainly rely on an increased heart rate to maintain cardiac output while middle-aged participants appear to achieve this through increased peripheral resistance. Repeated position changes have less impact on hemodynamics than 70° inclined standing, making it a safer and more stable training method. However, the long-term effects of such intervention need to be confirmed in further studies.