Does resistance exercise prevent body fluid changes after a 90-day bed rest?

Abstract

Although various exercise regimens are commonly used as countermeasures to reduce the cardiovascular deconditioning induced by microgravity, the underlying mechanisms are not well understood. In this study we aimed to test whether lower limb resistance exercise with flywheel technology can prevent the fluid homeostasis alterations induced by 90-day head-down tilt bed-rest (HDT), and thus improve orthostatic tolerance. Total body water (TBW, measured by isotope dilution) and plasma volume (PV, calculated from the haemoglobin and the haematocrit) were measured in a control group (Co, n=9) and a countermeasure group (CM, n=9). Simultaneously, plasma atrial natriuretic peptide (ANP), renin (AR), and aldosterone (Aldo), as well as urinary anti-diuretic hormone (ADH), were measured. Orthostatic tolerance was evaluated with a 10 min +80 degrees tilt-test the first day of recovery. After HDT, both groups showed a comparable decrease in orthostatic tolerance [8.2 (0.9) min, Co; 8.0 (0.7) min, CM], PV [-4.7 (1.8)%, Co; -6.2 (2.5)%, CM, P<0.05] and TBW [-6.3 (5.4)%, Co; -3.7 (2.1)%, CM, P<0.05]. AR [97.4 (22.0)%, Co; 117.3 (26.4)%, CM] and Aldo [111.3 (58.4)%, Co; 100.6 (52.0)%, CM] increased significantly in both groups but the countermeasures produced no noticeable effects [data are expressed as mean (SE)]. The drop in ANP was also similar in both groups [-42.0 (15.2)%, Co; -51.1 (27.7)% for the CM]. Surprisingly, urinary ADH declined similarly in both groups during the basal data control period [-25.3 (5.2)%, Co; -26.1 (9.6)%, CM) and was sustained at this level during the 90-day HDT. These results show that, under the conditions described, the flywheel exercise device failed to improve characteristic manifestations of cardiovascular deconditioning and suggest that more frequent and powerful exercise, associated with another device (e.g. LBNP) might be a better countermeasure.

Metabolic and cardiovascular responses during sub-maximal exercise in humans after 14 days of head-down tilt bed rest and inactivity

“…This finding is in good agreement with the results obtained in previous bed rest campaigns (Saltin et al 1968;Fortney et al 1991) and space flight studies (Grigoriev and Kozlovskaya 1987), which imply a down regulation of red cells production (Convertino 1996) due to the inhibition of erythropoietin production (Gunga et al 1996). They are, however, in contrast with more recent findings that failed to confirm a decrease of hematocrit and haemoglobin concentration during 14 days of HDTBR (de Chantemele et al 2004;Gunga et al 1996).…”

WISE-2005: effect of aerobic and resistive exercises on orthostatic tolerance during 60 days bed rest in women

“…A decrease in plasma volume of 10-20% over the Wrst 30 days is a consistent Wnding for HDBR studies ranging from 30 to 90 days in male volunteers (Fortney et al 1988(Fortney et al , 1994Traon et al 1995;Custaud et al 2002;Belin de Chantemele et al 2004a). There have been few previous investigations of the eVects of HDBR on BV in women compared to men, and all such studies were of relatively short duration.…”

“…This exercise showed no beneWcial eVect on orthostatic tolerance (Belin de Chantemele et al 2004a) and did not prevent HDBR-induced reduction in blood volume (Belin de Chantemele et al 2006). It is therefore unlikely that Xywheel resistive exercise plays an important role in orthostatic tolerance in our female subjects.…”

“…Considering the lack of impact of the Xywheel countermeasures in male subjects on orthostatic tolerance (Belin de Chantemele et al 2004a) and the slight eVect of LBNP/ exercise alone (Schneider et al 2002), it is likely that the resting LBNP period after exercise plays a pivotal role for improved cardiovascular responses against an orthostatic stress in EX compared with CON in our study. Mechanisms involved are extensively described in a previous paper from Watenpaugh et al (2007).…”

“…Restoration of blood volume (9-14 days spaceXight) (Buckey et al 1996), moderate levels of aerobic exercise (during 9-16 days spaceXight or a 15-day HDBR, respectively) (Lee et al 1999;Schneider et al 2002), or bouts of maximal exercise (90-day HDBR) (Belin de Chantemele et al 2004a) are not able to maintain orthostatic tolerance at pre Xight or pre HDBR levels. Periods of lower body negative pressure (LBNP) applied during HDBR provide beneWcial eVects on plasma volume, baroreXex sensitivity and lower limb vascular distensibility Traon et al 1995).…”