Exercise and Arterial Pressure during Simulated Increase of Gravity

Abstract

Heart rate and arterial pressure were continuously recorded in eight healthy young adults in the sitting position at 3 G, acting in the head‐seat direction, before and during leg exercise at 600 kpm/min for 6 min. In spite of the threefold increase of the hydrostatic pressure gradient along the head‐trunk line the arterial mean pressure at the level of the heart was higher at 3 G than at normal gravity, both at rest and during exercise. Exercise at 3 G resulted in a more rapid rise in the arterial mean and pulse pressures, the final increments being similar or somewhat greater than they were at normal gravity. The results emphasize the importance of the leg muscle pump as a booster of the cardiac pump in situations where large hydrostatic pressures in the lower portion of the body would otherwise tend to curtail the effective circulating blood volume.

Differential changes of lung diffusing capacity and tissue volume in hypergravity

“…Nevertheless the data could be compatible with a reduced central blood volume at 3 G zϩ in sitting resting men, which seemed reasonable considering concomitant signs of peripheral venous pooling, such as a 50% reduction in stroke volume. Also, in another study from the same laboratory, Linnarsson and Rosenhamer (15) showed that at 3 G zϩ , sitting resting subjects gradually developed arterial hypotension, which was instantaneously normalized when the subjects started to perform light, dynamic leg exercise, which markedly improved venous return by the action of the muscle pump (6, 13).…”

Microgravity decreases and hypergravity increases exhaled nitric oxide

“…The increased HR levels in hypergravity indicated that subjects were under physiological and probably also psychological stress in hypergravity with arterial hypotension in the head and neck (13) and with associated increases of plasma cathacolamine levels (24,25). Adrenaline infusions have been shown to increase exhaled NO in a rabbit model (2).…”

Gravitational Force and the Cardiovascular System1

“…HR increased as a function ofG z exposure time up to near maximal exposure time when it decreased. Linnarsson [20] has shown that Fa is increased at + G z initially; however, as exposure time increases, there is a decrease of Fa resulting in an inability of the circulatory system to Section 1-ReprJ…”

“…To this end, studying normal subjects in an increased G z environment may provide insight into the feedback mechanisms involved in the prevention of or tolerance to orthostatic hypotension. Many studies of G z tolerance have been conducted; however, relatively few have measured cardiovascular variables during steady state adjustment to increased G z [6,13,20,23,25]. Data from these studies are combined with data from our studies in table II.…”

“…The data from these experiments are presented in table III. The + 2 G z protocol was tolerated for [20][21][22][23][24][25][26][27][28] min, while + 3 G z was tolerated for only [12][13][14][15][16][17][18][19][20] min by which time the subjects developed narrowing peripheral vision. The subjects appeared to maintain their initial adaptations to + G z .…”