Increasing leg blood volume during head-down tilt by performing physical exercises, a preliminary study

Alessandro, Cristiano; Tafreshi, Amirehsan Sarabadani; Riener, Robert

doi:10.1109/biorob.2016.7523740

Cited by 3 publications

(4 citation statements)

References 14 publications

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“…earth-like). Similarly, dynamic exercises during HDT can temporarily increase HR and leg blood volume [1]. These findings motivate the development of lower limb wearable devices that can provide astronauts with antigravity muscle loading for extended periods of time, potentially limiting the reduction of blood pressure they experience in the microgravity environment.…”

Section: Discussionmentioning

confidence: 95%

“…The intensity of the exercises was defined as a combination of: (1) resistive force of the leg-press, F; (2) frequency of the leg-press movements, f; (3) duration of the exercise phase, T. We tested two values for each of these factors (see here [1] for details), for a total of eight intensities and corresponding experimental sessions. In these sessions, MARCOS did not apply any force during baseline and recovery, so that no muscle contraction was required to maintain leg extension (i.e.…”

Section: Study Protocolmentioning

confidence: 99%

“…The user is secured to the platforms by means of: (1) shoes that are firmly attached to the foot pedals, (2) a brace that prevents mediolateral movements of the hip, and (3) shoulder straps that prevent sliding in the direction of force. The position of the brace as well as the length of the shoulder straps can be adjusted to the size of the user, allowing us to obtain very similar ranges of motion across subjects (hip: 0 • to 40 • ; knee: 0 • to 70 • ).…”

Section: Marcosmentioning

confidence: 99%

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Cardiovascular responses to antigravity muscle loading during head-down tilt at rest and after dynamic exercises

Alessandro

Tafreshi

Riener

2018

Preprint

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The physiological processes underlying hemodynamic homeostasis can be modulated by muscle activity and gravitational loading. The effects of antigravity muscle activity on cardiovascular regulation has 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 antigravity muscle loading during HDT in healthy human subjects, both at rest and during recovery from leg-press exercises. Further, we compared such cardiovascular responses to those obtained during upright position. We found that loading the antigravity 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 demonstrate that antigravity 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.

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Section: Discussionmentioning

confidence: 95%

Section: Study Protocolmentioning

confidence: 99%

Section: Marcosmentioning

confidence: 99%

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Cardiovascular responses to antigravity muscle loading during head-down tilt at rest and after dynamic exercises

Alessandro

Tafreshi

Riener

2018

Preprint

Self Cite

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“…Other studies conducted simulations on Earth that included the use of Lower Body Positive Pressure (LBPP) (Cutuk, 2006; Evans et al, 2013; Schlabs et al, 2013), parabolic flights (Pletser, 2004; Pletser et al, 2012; Widjaja et al, 2015), and head-down tilt (HDT) and head-up-tilt (HUT) paradigms (Lathers et al, 1990, 1993; Louisy et al, 1994; Pavy-Le Traon et al, 1997; Kostas et al, 2014; Baranov et al, 2016). However, few of these hypogravity simulation experiments have studied the effects of exercise (Richter et al, 2017), and those that did focused on walking and running tasks (Cutuk, 2006; Schlabs et al, 2013; Pavei et al, 2015; Pavei and Minetti, 2016), or anaerobic training (Alessandro et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Cardiopulmonary Responses to Sub-Maximal Ergometer Exercise in a Hypo-Gravity Analog Using Head-Down Tilt and Head-Up Tilt

2019

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After more than 50 years of spaceflight, we still do not know what is the appropriate range of gravity levels that are required to maintain normal physiological function in humans. This research effort aimed to investigate musculoskeletal, cardiovascular, and pulmonary responses between 0 and 1 g. A human experiment was conducted to investigate acute physiological outcomes to simulated altered-gravity with and without ergometer exercise using a head-down tilt (HDT)/head-up tilt (HUT) paradigm. A custom tilting platform was built to simulate multiple gravitational loads in the head-to-toe direction (Gz) by tilting the bed to the appropriate angle. Gravity levels included: Microgravity (-6°HDT), Moon (0.17g-Gz at +9.5°HUT), Mars (0.38g-Gz at +22.3°HUT), and Earth (1g-Gz at +90° upright). Fourteen healthy subjects performed an exercise protocol at each simulated gravity level that consisted of three work rates (50W, 75W, 100W) while maintaining a constant cycling rate of 90 rpm. Multiple cardiopulmonary variables were gathered, including volume of oxygen uptake (VO 2 ), volume of carbon dioxide output (VCO 2 ), pulmonary ventilation (V E ), tidal volume (V T ), respiratory rate (R f ), blood pressure, and heart rate (HR) using a portable metabolic system and a brachial blood pressure cuff. Foot forces were also measured continuously during the protocol. Exercise data were analyzed with repeated-measures ANOVA with Bonferroni correction for multiple comparisons, and regression models were fitted to the experimental data to generate dose-response curves as a function of simulated AG-levels and exercise intensity. Posture showed a main effect in all variables except for systolic blood pressure. In particular, VO 2, VCO 2 , V E , V T , R f , and HR showed average changes across exercise conditions between Microgravity and 1 g (i.e., per unit of simulated AG) of -97.88 mL/min/g, -95.10 mL/min/g, -3.95 L/min/g, 0.165 L/g, -5.33 breaths/min/g, and 5.05 bpm/g, respectively. In the case of VO 2 , further pairwise comparisons did not show significant differences between conditions, which was consistent with previous studies using supine and HDT postures. For all variables (except HR), comparisons between Mars and Earth conditions were not statistically different, suggesting that ergometer exercise at a gravitational stress comparable to Mars gravity (∼3/8 g) could provide similar physiological stimuli as cycling under 1 g on Earth.

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Cardiovascular responses to leg muscle loading during head-down tilt at rest and after dynamic exercises

Alessandro

Tafreshi

Riener

2019

Sci Rep

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Increasing leg blood volume during head-down tilt by performing physical exercises, a preliminary study

Cited by 3 publications

References 14 publications

Cardiovascular responses to antigravity muscle loading during head-down tilt at rest and after dynamic exercises

Cardiovascular responses to antigravity muscle loading during head-down tilt at rest and after dynamic exercises

Cardiopulmonary Responses to Sub-Maximal Ergometer Exercise in a Hypo-Gravity Analog Using Head-Down Tilt and Head-Up Tilt

Cardiovascular responses to leg muscle loading during head-down tilt at rest and after dynamic exercises

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