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1 Faculte de Medecine, EA 2992, Dynamique des Incoherences Cardio-Vasculaires, Nimes, France
2 Faculte des Sciences, UPRES, Physiologie des adaptations Cardiovasculaires a l'exercice, Avignon, France
* To whom correspondence should be addressed. E-mail: philippe.obert{at}univ-avignon.fr.
This study questioned the effect of living and training at moderate altitude on cardiac morphological and functional adaptations and tested the incidences of potential specific adaptations when compared to aerobic sea level training on maximal left ventricular performance. Sea level native rats were randomly assigned to N (living in normoxia), NT (living and training 5 days per week for 5 weeks in normoxia), CH (living in hypoxia, 2800 m) and CHT (living and training 5 days per week for 5 weeks in hypoxia, 2800 m) groups. Cardiac adaptations were evaluated throughout the study period using Doppler-echocardiography. Maximal stroke volume (LVSVmax) was measured during volume over-loading before and after the study period. Finally, at the end of the study period, passive pressure-volume relationships on isolated heart and cardiac weighing were obtained. Altitude training resulted in a specific left ventricular (LV) remodelling when compared to NT, characterised by an increase in wall thicknesses without any alteration in internal dimensions. These morphological adaptations associated with hypoxia-induced alterations in pulmonary outflow and preload conditions, led to a decrease in LV filling and subsequently no improvement in LV performance during resting physiological conditions in CHT compared to NT. Such a lack of improvement was confirmed during volume over-loading which simulated maximal effort (LVSVmax pre-test: NT= 0.58±0.05; CHT= 0.57±0.08 ml; post-test: NT= 0.72±0.06; CHT= 0.58±0.07 ml, NT vs CHT in post test session: p<0.05). Maximal aerobic velocities increased to the same extent in NT and CHT rats despite marked polycythemia in the latter. The lack of LVSVmax improvement resulting from altitude training-induced cardiac morphological and functional adaptations could be responsible for this phenomenon.
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