Northwestern University, Feinberg School of Medicine, Department of Physiology, Chicago, USA.
ETH Zurich, Sensory-Motor Systems Lab, Institute of Robotics and Intelligent Systems, Department of Health Sciences and Technology, Zurich, Switzerland.
Sci Rep. 2019 Feb 26;9(1):2804. doi: 10.1038/s41598-019-39360-6.
The physiological processes underlying hemodynamic homeostasis can be modulated by muscle activity and gravitational loading. The effects of leg muscle activity on cardiovascular regulation have been observed during orthostatic stress. Here, we evaluated such effects during head-down tilt (HDT). In this posture, the gravitational gradient along the body is different than in upright position, leading to increased central blood volume and reduced venous pooling. We compared the cardiovascular signals obtained with and without leg muscle loading during HDT in healthy human subjects, both at rest and during recovery from leg-press exercises using a robotic device. Further, we compared such cardiovascular responses to those obtained during upright position. Loading leg muscles during HDT at rest led to significantly higher values of arterial blood pressure than without muscle loading, and restored systolic values to those observed during upright posture. Maintaining muscle loading post-exercise altered the short-term cardiovascular responses, but not the values of the signals five minutes after the exercise. These results suggest that leg muscle activity modulates cardiovascular regulation during HDT. This modulation should therefore be considered when interpreting cardiovascular responses to conditions that affect both gravity loading and muscle activity, for example bed rest or microgravity.
生理过程基础的血液动力学稳态可以通过肌肉活动和重力加载来调节。在直立应激期间已经观察到腿部肌肉活动对心血管调节的影响。在这里，我们在头低位倾斜（HDT）期间评估了这些影响。在这种姿势下，身体沿重力梯度不同于直立位置，导致中心血容量增加和静脉池减少。我们比较了在健康人体中使用机器人设备进行 HDT 时腿部肌肉加载和不加载时的心血管信号，无论是在休息时还是在腿部按压运动恢复期间。此外，我们比较了这些心血管反应与在直立位置获得的反应。在 HDT 休息时加载腿部肌肉比不加载肌肉导致动脉血压值显著升高，并将收缩压值恢复到直立姿势观察到的值。在运动后保持肌肉加载改变了短期心血管反应，但运动后五分钟的信号值没有改变。这些结果表明，腿部肌肉活动在 HDT 期间调节心血管调节。因此，当解释影响重力加载和肌肉活动的条件对心血管反应时，应考虑这种调节，例如卧床休息或微重力。
