Event Abstract

Back to Event

PERSONALIZED EXERCISE TRAINING PROGRAM AS A COUNTERMEASURE TO ORTHOSTATIC INTOLERANCE AFTER SPACE FLIGHTS.

Ferdinando Iellamo1, 2*, Maurizio Casasco3, Chiara Fossati4, Giuseppe Caminiti2 and Maurizio Volterrani2
  • 1 Università degli Studi di Roma Tor Vergata, Italy
  • 2 IRCCS San Raffaele Pisana, Italy
  • 3 Federazione Medico Sportiva Italiana (FMSI), Italy
  • 4 Foro Italico University of Rome, Italy

NTRODUCTION Approximately 83% of astronauts experience pre-syncope and even fainting during upright position on landing days after long-term space flights. The inability to adequately elevate peripheral vascular resistance (i.e. vasoconstriction) along with the hypovolemia occurring during flight are considered the main factors of post-flight orthostatic intolerance 2,3,10 . Among the countermeasures tested against orthostatic intolerance, in-flight physical exercise has been the most obvious, because of its predictable capability to positively affect exercise capacity, autonomic nervous system regulation, muscle strength, and power, all of which are impaired as a consequence of weightlessness. Accordingly, 2-3 hours per day are devoted by astronauts to physical activity during flights. Yet, despite widespread in-flight utilization, physical exercise has proven only partially effective in counteracting orthostatic intolerance after space flights. It is arguable that most of the inconsistencies about the effectiveness of exercise reflect the poor knowledges that exist on the optimal dose of exercise (i.e. intensity and volume) to be performed to achieve a given physiological benefit, in this case orthostatic tolerance. To date, physical activity of astronauts during space flights has been mainly self-selected using conventional levels of dynamic exercise (according to general recommendations) in addition to some forms of resistance exercises. Recently, a new training method, referred to as the “individualized TRaining IMPulses” (TRIMPi)8, which is an individually determined, integrated measure of responses to physical load, that permits to account, in a single term, for both intensity and volume effects of endurance exercise training, has been developed. By this method, the dose of exercise has been repeatedly reported to affect neural cardiovascular regulation in on-ground studies.5 We report the case of an astronaut who performed a TRIMPi-based training program on board of the ISS during the expeditions 52/53 of the NASA/ASI-sponsored “Missione Vita” in order to investigate the feasibility and effectiveness of this structured, individually tailored, exercise training program in preventing/improving space flight-induced orthostatic intolerance and its underlying neural mechanisms. A 60 years old astronaut who took part to the NASA/ASI-sponsored Missione Vita for 139 days performed a TRIMPi-based training program during the last two months of permanence on the ISS (according to the time-schedule allotted by NASA to this experiment). Spectral analysis of heart rate (HR), blood pressure (BP) variability and baroreflex sensitivity (BRS, by mean of the sequences technique) were used as consolidated methodologies to assess the neural control of the cardiovascular system 9 during orthostatic stress before and after flight. The astronaut performed an active orthostatic test (10 min supine rest followed by 20 min of unaided standing-up with continuous one-lead ECG and continuous non-invasive BP recording (by Finometer device) before flight and 4 days after landing (time-constraints by NASA). The astronaut underwent a pre-flight progressive exercise test on a treadmill with continuous ECG monitoring and intermittent capillary sampling for blood lactate determination in order to establish the personalized exercise program by TRIMPi.8 The TRIMPi-based exercise training program was performed on alternate days. Each 30-min exercise session consisting in treadmill running, at pre-flight determined training loads as calculated by the TRIMPi, was performed during astronaut’s usual scheduled physical activity time so as to not disturb his daily routines. The astronaut’s HR was monitored by a cardiotachograph during the whole exercise training sessions and downloaded periodically to the Earth. N adverse effects were reported during exercise training. In comparison to pre-flight, the orthostatic tolerance test (OT) performed after flight showed a greater decrease in BP on going from supine to standing position (SAP: -30 vs – 10 mmHg; DAP – 10 vs -5 mmHg). This was accompanied by a greater increase in HR (+17 vs +8 b/min). No change in BRS was observed between pre-flight and post-flight OT. After-flight, OT showed a greater increase in the Low-Frequency (LF) component of HRV (indicator of mainly sympathetic modulation) and a greater decrease in the High-Frequency (HF) component of HRV (indicator of vagal modulation) (Fig. 1) with a shift in the sympatho-vagal balance toward a greater cardiac sympathetic activation (as expressed by the LF/HF ratio, Fig.2, left panel).9 The LF component of systolic BP variability (reflecting the sympathetic activation at peripheral vascular level) in response to changing posture from supine to upright was less after-flight than pre-flight (Fig. 2, right panel), paralleling the greater decrease in BP. These findings suggest that prolonged exposure to actual microgravity induces an impairment of neural sympathetic mechanisms controlling peripheral vasoconstriction resulting in a greater decrease in blood pressure on the assumption of the upright posture. This greater post-flight decrease in blood pressure is opposed by an increase in sympathetic activation at cardiac level that induces a greater HR response, possibly preventing an excessive decrease in BP, and (likely) the appearance of symptoms of orthostatic intolerance. Exercise training by TRIMPi might be involved in inducing these autonomic responses. DISCUSSION This report is in agreement with several previous studies indicating the central role of sympathetic nervous system in affecting orthostatic tolerance. Blaber et al.1 used HRV to investigate the differences in autonomic regulation of the heart in a group of 29 astronauts who did (non-finishers) or did not (finishers) experience post-flight orthostatic intolerance. Finishers and non-finishers had an increase in sympathetic activity with stand on pre- flight, yet only finishers retained this response on landing. Non-finishers also had lower sympatho-vagal balance and higher pre-flight supine parasympathetic activity than finishers. These results suggest that post-flight impairment in autonomic control of the heart and vasculature may contribute to orthostatic intolerance. Moreover, it has been reported that during Lower Body Negative Pressure (LBNP), Muscle Sympathetic Nerve Activity (MSNA) was lower before symptoms of pre-syncope in orthostatic intolerant subjects, whereas the activation of MSNA was preserved in tolerant subjects after short-term bed rest.7 These results support the hypothesis of reduced peripheral sympathetic activity in subjects with orthostatic intolerance, as indirectly confirmed by our experiment. The TRIMPi-based exercise training employed in this case during a long-lasting space flight might have acted as a physiological stimulus for increasing sympathetic cardiac activity on standing up after flight. Indeed, Iellamo et al.5 have reported that very intensive endurance training shifted the cardiovascular autonomic modulation from a parasympathetic toward a sympathetic predominance in elite athletes. The same group6 reported a curvilinear dose-response relationship between individualized training load (by TRIMPi) and autonomic nervous system functioning parameters with an increase in the LF component of HR variability, at peak exercise training load in patients suffering from chronic heart failure, who shares several pathophysiological changes with humans exposed to prolonged weightlessness. In keeping with this concept, a study performed by Iellamo et al.4 during the tragically ended STS 107 spacelab mission, suggested that dynamic exercise in microgravity environment might potentiate some sympathetic activity-enhancing mechanisms, such as the muscle metaboreflex. Overall, the findings of the present report indicate the feasibility of an on ground-determined, individually tailored, training protocol as an exercise-based countermeasure to be employed during prolonged space manned missions to counteract post-flight orthostatic intolerance. Further researches on a larger number of individuals would be mandatory for a better understanding of the role of TRIMPi methodology in reducing orthostatic intolerance after space flights CAPTIONS FOR FIGURES Figure 1: : Low-frequency and High Frequency components of Heart Rate Variability recorded during pre-flight and post-flight orthostatic tolerance test. LF r-r=Low-frequency, HF r-r=High-Frequency, nu=normalized units Figure 2: cardiac LF/HF ratio and low-frequency component of systolic blood pressure variability recorded during pre-flight and post-flight orthostatic tolerance test. LF-SAP= Low-frequency component of systolic blood pressure variability

Acknowledgements

This work has been supported by Italian Space Agency (ASI) grant n° 2013‐039‐I.0

References

REFERENCES (1) Blaber AP, Bondar RL, Kassam MS. Heart rate variability and short duration spaceflight: relationship to post-flight orthostatic intolerance. BMC Physiol 2004; 27:4–6 (2) Convertino VA. Carotid-cardiac baroreflex: relation with orthostatic hypotension following simulated microgravity and implications for development of countermeasures. Am J Physiol Heart Circ Physiol 2002; 282:2210-2215. (3) Convertino VA. Mechanisms of microgravity induced orthostatic intolerance: implications for effective countermeasures. J Grav Physiol 2002; 9:1-14. (4) Iellamo F, Di Rienzo M, Lucini D, Legramante JM, Pizzinelli P, Castiglioni P, et al. Muscle metaboreflex contribution to cardiovascular regulation during dynamic exercise in microgravity: insights from the STS-107 Columbia Shuttle Mission. J Physiol 2006; 572, 829-838. (5) Iellamo F, Legramante JM, Pigozzi F, Spataro A, Norbiato G, Lucini D, et al. Conversion from vagal to sympathetic predominance with strenuous training in high performance world class athletes. Circulation 2002; 105:2719-2724. (6) Iellamo F, Manzi V, Caminiti G, Sposato B, Massaro M, Cerrito A, et al. Dose-response relationship of baroreflex sensitivity and heart rate variability to individually-tailored exercise training in patients with heart failure. Int J Cardiol. 2013;166:334-339. (7) Kamiya A, Michikami D, Fu Q, Iwase S, Hayano J, Kawada T, et al. Pathophysiology of orthostatic hypotension after bed rest: paradoxical sympathetic withdrawal. Am J Physiol Heart Circ Physiol 2003; 285:1158-1167. (8) Manzi V, Castagna C, Padua E, Lombardo M, D'Ottavio S, Massaro M, et al. Dose-response relationship of autonomic nervous system responses to individualized training impulse in marathon runners. Am J Physiol Heart Circ Physiol 2009;296:H1733-H1740. (9) Task Force of The European Society of Cardiology and The North American Society of Pacing and Electrophysiology: Heart rate variability: standards and measurements, physiological interpretation, and clinical use. Circulation 1996;93:1043–1065. (10) Zhang LF. Vascular adaptation to microgravity: what have we learned? J Appl Physiol 2001; 91:2415-2430.

Keywords: microgravity, orthostatic intolerance, TRIMP method, autonomic control, heart rate variability, microgravity, orthostatic intolerance test, TRIMP method, heart rate variability,, microgravity, orthostatic intolerance, TRIMPi method training, autonomic dysfunction,, microgravity, orthostatic intolerance, TRIMPi method training, autonomic dysfunction, long-lasting flight

Conference: 39th ISGP Meeting & ESA Life Sciences Meeting, Noordwijk, Netherlands, 18 Jun - 22 Jun, 2018.

Presentation Type: Extended abstract

Topic: Analogues and Countermeasure Research

Citation: Iellamo F, Casasco M, Fossati C, Caminiti G and Volterrani M (2019). PERSONALIZED EXERCISE TRAINING PROGRAM AS A COUNTERMEASURE TO ORTHOSTATIC INTOLERANCE AFTER SPACE FLIGHTS.. Front. Physiol. Conference Abstract: 39th ISGP Meeting & ESA Life Sciences Meeting. doi: 10.3389/conf.fphys.2018.26.00039

Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters.

The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated.

Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed.

For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions.

Received: 02 Dec 2018; Published Online: 16 Jan 2019.

* Correspondence: Prof. Ferdinando Iellamo, Università degli Studi di Roma Tor Vergata, Roma, Lazio, 00173, Italy, iellamo@uniroma2.it