Blood pressure and heart rate responses to sudden changes of gravity during exercise

Linnarsson, Dag; Sundberg, Carl Johan; Tedner, B.; Haruna, Y; Karemaker, John M.; Antonutto, G.; Prampero, P. E. di

doi:10.1152/ajpheart.1996.270.6.h2132

Cited by 41 publications

(68 citation statements)

References 17 publications

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“…phases before and after microgravity and marked increases during microgravity (Johns et al 1994). Also, for MAP the time course is in agreement with the previous results of Linnarsson et al (1996) with an initial peak at the 1.8 G z? to 0 G z?…”

Section: Part Ii: Parabolic Flight Experimentssupporting

confidence: 91%

“…Sudden increases of venous return caused by a decrease of G z? were associated with transient increases in SV and MAP (Johns et al 1994;Linnarsson et al 1996).…”

Section: Introductionmentioning

confidence: 95%

“…In part II, we introduced an additional stimulus in addition to hiP and/or BH, namely large and rapid changes of central blood volume (Linnarsson et al 1996) induced by transitions between normal gravity (1 G z? ), hypergravity (up to 1.8 G z?…”

Section: Part Ii: Parabolic Flight Experimentsmentioning

confidence: 99%

“…Also during steady state exercise, Linnarsson et al (1996) studied cardiovascular responses to sudden changes of gravity in the head-to-foot direction (G z? ) by exposing subjects to tilts between upright and supine and to gravity transients during parabolic flight.…”

Section: Introductionmentioning

confidence: 99%

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Influence of combined exercise and gravity transients and apnea on hemodynamics

et al. 2009

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Hemodynamic responses to combined heavy dynamic leg exercise (hiP), breath holding (BH) and gravity-induced blood volume shifts direction were studied. Thirteen subjects were studied at normal gravity and 12 during parabolic flight, performing 20 s hiP or combined hiP&BH (stimulus period) from a baseline of 30 W at normal gravity (1 G(z+)). Heart rate and mean arterial pressure responses to BH were similar between gravity conditions, but stroke volume (SV) differed markedly between gravity conditions: at 1 G(z+) SV was higher [112 +/- 16 ml (mean +/- SD)] during BH, than during eupnea [101 +/- 17 ml (P < 0.05, N = 13)]. In weightlessness the corresponding SV values were 105 +/- 16 and 127 +/- 20 ml, respectively (P < 0.05, N = 6). Transthoracic electrical conductance (TTC) was used as index for intrathoracic volume. TTC fell significantly during BH. This decrease was attenuated in weightlessness. It is concluded that the transient microgravity temporarily reduces the efficiency of the muscle pump so that the deep inspiration at the onset of the high-intensity exercise and breath-hold period cannot augment venous return as it could during identical manoeuvres at normal gravity.

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Section: Part Ii: Parabolic Flight Experimentssupporting

confidence: 91%

“…Sudden increases of venous return caused by a decrease of G z? were associated with transient increases in SV and MAP (Johns et al 1994;Linnarsson et al 1996).…”

Section: Introductionmentioning

confidence: 95%

Section: Part Ii: Parabolic Flight Experimentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Influence of combined exercise and gravity transients and apnea on hemodynamics

et al. 2009

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“…A delay in the latency of the peak cardiac baroreflex response has previously been reported during dynamic exercise in young individuals (193,325), although this has not been a universal finding (256). Sundblad and Linnarsson (327) proposed that this delay resulted from an exercise-induced increase in sympathetic activation.…”

Section: Ex (Moderate)mentioning

confidence: 91%

Autonomic Adjustments to Exercise in Humans

Fisher

Young

Fadel

2015

Comprehensive Physiology

232

253

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Autonomic nervous system adjustments to the heart and blood vessels are necessary for mediating the cardiovascular responses required to meet the metabolic demands of working skeletal muscle during exercise. These demands are met by precise exercise intensity-dependent alterations in sympathetic and parasympathetic nerve activity. The purpose of this review is to examine the contributions of the sympathetic and parasympathetic nervous systems in mediating specific cardiovascular and hemodynamic responses to exercise. These changes in autonomic outflow are regulated by several neural mechanisms working in concert, including central command (a feed forward mechanism originating from higher brain centers), the exercise pressor reflex (a feed-back mechanism originating from skeletal muscle), the arterial baroreflex (a negative feed-back mechanism originating from the carotid sinus and aortic arch), and cardiopulmonary baroreceptors (a feed-back mechanism from stretch receptors located in the heart and lungs). In addition, arterial chemoreceptors and phrenic afferents from respiratory muscles (i.e., respiratory metaboreflex) are also capable of modulating the autonomic responses to exercise. Our goal is to provide a detailed review of the parasympathetic and sympathetic changes that occur with exercise distinguishing between the onset of exercise and steady-state conditions, when appropriate. In addition, studies demonstrating the contributions of each of the aforementioned neural mechanisms to the autonomic changes and ensuing cardiac and/or vascular responses will be covered.

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Parasympathetic heart rate modulation during parabolic flights

Beckers¹,

Seps²,

Ramaekers

et al. 2003

Eur J Appl Physiol

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During parabolic flight short periods of microgravity and hypergravity are created. These changes influence cardiovascular function differently according to posture. During the 29th parabolic flight campaign of the European Space Agency (ESA), the electrocardiogram (ECG) was recorded continuously in seven healthy volunteers in two positions (standing and supine). Five different phases were differentiated: 1 g (1 g=9.81 m/s(2)) before and after each parabola, 1.8 g at the ascending leg of the parabola (hypergravity), 0 g at the apex, 1.6 g at the descending leg (hypergravity). We assessed heart rate variability (HRV) by indices of temporal analysis [mean RR interval (meanRR), the standard deviation of the intervals (SDRR), and the square root of the mean squared differences of successive intervals (rMSSD) and coefficient of variation (CV)]. In the supine position no significant differences were shown between different gravity phases for all HRV indices. In the standing position the 0 g phase showed a tendency towards higher values of meanRR compared to the control and to the other phases ( p=NS). SDRR, rMSSD and CV were significantly higher compared to control ( p<0.05). Significantly higher values for meanRR in the supine position at 1 g and hypergravity ( p<0.05) were found when compared to standing. SDRR was significantly higher at 0 g in the standing position compared to supine [95 (44) ms vs. 50 (15) ms; p<0.05] and lower in other phases. rMSSD and CV showed the same trend ( p=NS). We confirm that, during parabolic flights, position matters for cardiovascular measurements. Time domain indices of HRV during different gravity phases showed: (1) higher vagal modulation of the autonomic nervous system in microgravity, when compared with normo- or hypergravity in standing subjects; and (2) no differences in supine subjects between different g phases.

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Blood pressure and heart rate responses to sudden changes of gravity during exercise

Cited by 41 publications

References 17 publications

Influence of combined exercise and gravity transients and apnea on hemodynamics

Influence of combined exercise and gravity transients and apnea on hemodynamics

Autonomic Adjustments to Exercise in Humans

Parasympathetic heart rate modulation during parabolic flights

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