1.
Hormonal changes during long-term isolation.
Custaud, MA, Belin de Chantemele, E, Larina, IM, Nichiporuk, IA, Grigoriev, A, Duvareille, M, Gharib, C, Gauquelin-Koch, G
European journal of applied physiology. 2004;(5-6):508-15
Abstract
Confinement and inactivity induce considerable psychological and physiological modifications through social and sensory deprivation. The aim of the SFINCSS-99 experiment was to determine the cardiovascular and hormonal pattern of blood volume regulation during long-term isolation and confinement. Simulation experiments were performed in pressurized chambers similar in size to the volumes of modern space vehicles. Group I consisted of four Russian male volunteers, who spent 240 days in a 100-m(3 )chamber. Group II included four males (one German and three Russians) who spent 110 days in isolation (200-m(3) module). The blood samples, taken before, during and after the isolation period, were used to determine haematocrit (Ht), growth hormone (GH), active renin, aldosterone, and osmolality levels. From the urine samples, electrolytes, osmolality, nitrites, nitrates, cortisol, antidiuretic hormone (ADH), aldosterone, normetanephrine and metanephrine levels were determined. The increase in plasma volume (PV) that is associated with a tendency for a decrease in plasma active renin is likely to be due to decreased sympathetic activity, and concords with the changes in urinary catecholamine levels during confinement. Urinary catecholamine levels were significantly higher during the recovery period than during confinement. This suggests that the sympathoadrenal system was activated, and concords with the increase in heart rate. Vascular resistance is determined by not only the vasoconstrictor but also vasodilator systems. The ratio of nitrite/nitrate in urine, as an indicator of nitric oxide release, did not reveal any significant changes. Analysis of data suggests that the duration of the isolation was a main factor involved in the regulation of hormones.
2.
High VO2max with no history of training is primarily due to high blood volume.
Martino, M, Gledhill, N, Jamnik, V
Medicine and science in sports and exercise. 2002;(6):966-71
Abstract
PURPOSE To investigate the high VO2max observed occasionally in young men who have no history of training. METHODS VO2max, blood volume (BV), maximal stroke volume (SVmax), maximal cardiac output (Qmax), and related measurements (reported as mean +/- SEM) were studied in six men (mean age 20.0 +/- 0.5 yr) with no history of training, who all had a VO2max below 49 mL.kg-1.min-1 (LO group) and six age- and weight-matched men (mean age 19.5 +/- 0.5 yr) with no history of training, who all had a VO2max above 62.5 mL.kg-1.min-1 (HI group). RESULTS Compared with the LO group, the HI group had a higher SVmax (149 +/- 5 vs 102 +/- 5 mL), higher Qmax (28.9 +/- 0.9 vs 20.0 +/- 1.0 L.min-1) and higher BV (88.1 +/- 3.8 vs 76.7 +/- 0.9 mL.kg-1). The BV of four participants in the HI group (mean = 92.3 +/- 4.3 mL.kg-1) was substantially higher than the BV of all participants in the LO group, but two participants in the HI group had a BV (mean = 79.7 +/- 0.8 mL.kg-1) that was similar to the mean BV of the LO group. CONCLUSION The primary explanation for the high VO2max observed occasionally in young men who have no history of training is a naturally occurring (perhaps genetically determined) high BV that brings about a high SVmax and Qmax. However, some young men with no history of training have a high VO2max, SVmax, and Qmax possibly because a greater portion of their BV is hemodynamically active.