Abstract des Autors

We have studied the main hormonal and urinary variables that control the renin-angiotensin-aldosterone system, both during training as well as at rest at relative normoxia and hypoxia. The sample consisted of 11 subjects (female top-level volleyball players) who trained in normoxia (at an altitude of 640 metres in Granada) for two weeks, in relative hypoxia (at the altitude of 2450 metres, Centre of Top-level Training in Sierra Nevada) during the next two weeks which was followed, once again, by normoxia. This study researches the influence of the altitude in the regulative cardiocirculative mechanisms as well as those that control blood pressure over a long period of time. The hypothesis affirms that being chronically exposed to altitude induces variations in the renin-angiotensin-aldosterone system and adaptations in the system which controls the blood pressure. The design is quasi-experimental with a sample that is natural, descriptive without manipulations, longitudinal with repetitive measures in each phase, reversible and intragroupal in the one group with no modifications in the experimental group. The study is undertaken at a N1 level phase (2 weeks duration), in an A altitude phase (lasting 2 weeks), a N2 level phase (a week long) and a postest undertaken at the end of the month (lasting one week). The dependent variables were biochemical (plasmatic glucose, total of proteins, electrolytes in serum, creatinine, cholesterol HDL, the plasmatic CPK and LDH, the alkaline phosphatase and the acid phosphatase); the hematologics (counting the red blood cells, the hemoglobine and the hematocrite); the hormonals (plasmatic renin and aldosterone); urinary (the total volume of urine and the total intake of liquids, the excretion of renal water, urinary osmolality, urinary electrolytes, the excretionary fraction of urinary sodium and the clearing of urinary creatinine) and the hemodynamics (heart beat and blood pressure) in different phases. The independent variables were altitude in metres or relative hypoxia. While the contaminating variables were subject variables (age) and of the person collecting the experimental data (handling samples, taking blood pressure and heart rate frequency). A descriptive statistical analysis was undertaken using average measurements for position and dispersion, a mixed two-via variance analysis and comparison of couples with the penalization of Turkey. Correlations were studied using the Pearson correlation coefficient penalized by the Bonferroni method. The results showed a significant increase in heart rate and blood pressure at rest, as well as in postraining diastolic blood pressure in hypoxia, since in altitude there is a reduction in plasmic renin, while there is an increase in urinary volume in relation to the excretion of renal water. Aldosterone, which is reduced in the first hypoxic phase, is influenced by other variables. The mechanisms for adapting to altitude condition an increase of the fraction of sodium excretion by an inhibition of renin and an inhibition of renal clearing. Verf.-Referat