Quantification of muscle volume by echography: comparison with MRI data on subjects in long-term bed rest.

The objective of this study was to determine the accuracy of an echographic method for measuring the change in leg muscle volume against the gold standard, magnetic resonance imaging (MRI). Leg muscle volume was measured using an echographic scanner, which consisted of two metallic rails on which a probe holder moved via an electric engine. Ten to 20 transverse muscle views were collected along the area scanned, and the muscle cross-sectional area (CSA, cm2) was measured on each of them.

WISE-2005: adrenergic responses of women following 56-days, 6 degrees head-down bed rest with or without exercise countermeasures.

We tested the hypotheses that women completing 56 days, 6 degrees head-down bed-rest (HDBR) would have changes in sensitivity of cardiovascular responses to adrenergic receptor stimulation and that frequent aerobic and resistive exercise would prevent these changes. Twenty-four women, eight controls, eight exercisers (lower body negative pressure treadmill and flywheel resistance exercise), and eight receiving nutritional supplement but no exercise were studied in baseline and during administration of the beta-agonist isoproterenol (ISO) and the alpha- and beta-agonist norepinephrine (NOR). In the control and nutrition groups, HDBR increased heart rate (HR) and reduced stroke volume (SV), and there was a significantly greater increase in HR with ISO after HDBR.

Portal vein cross-sectional area and flow and orthostatic tolerance: a 90-day bed rest study.

The objective of this study was to evaluate the changes in the portal vein cross-sectional area (PV CSA) and flow during a stand test associated with orthostatic intolerance. Eighteen subjects underwent a 90-day head-down tilt (HDT) bed rest at 6 degrees: 9 controls (Con) and 9 with flywheel exercise countermeasures (CM). At post-HDT, nine subjects (5 CM, 4 Con) were tolerant, and nine were intolerant.