1,721,066 research outputs found
On-Earth evaluation of Neuro-verstibular tolerance to centrifuge simulated artificial gravity in Humans
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Oxygen cost of dynamic leg exercise on a cycle ergometer: effects of gravity acceleration.
No full textA model of the metabolic internal power (Ė(int)) during cycling, which includes the gravity acceleration (a(g)) as a variable, is presented. This model predicts that Ė(int) is minimal in microgravity (0 g; g = 9.81 m s-2), and increases linearly with a(g), whence the hypothesis that the oxygen uptake (V̇O2) during cycling depends on a(g). Repeated V̇O2 measurements during steady-state exercise at 50, 75 and 100 W on the cycle ergometer, performed in space (0 g) and on Earth (1 g) on two subjects, validated the model. V̇O2 was determined from the time course of decreasing O2 fraction during rebreathing. The gas volume during rebreathing was determined by the dilution principle, using an insoluble inert gas (SF6). Average V̇O2 for subject 1 at each power was 0.99, 1.21 and 1.52 L min-1 at 1 g (n = 3) and 0.91, 1.13 and 1.32 L min-1 at 0 g (n = 5). For subject 2 it was 0.90, 1.12 and 1.42 L min-1 at 1 g, and 0.76, 0.98 and 1.21 L min-1 at 0 g. These values corresponded to those predicted from the model. Although resting V̇O2 was lower at 0 g than at 1 g, the net (total minus resting) exercise V̇O2 was still smaller at 0 g than at 1 g. This difference reflects the lower Ė(int) at 0 g
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Determinants of oxygen consumption during exercise on cycle ergometer: the effects of gravity acceleration
No full textEffects of gravity acceleration on Oxygen consumption during submaximal exercise in Humans
No full textOxygen uptake at the onset of step-exercise before and after short duration bed rest in humans
No full textV′O2 kinetics was investigated before and after 14 days of head-down tilt (-6°) bed rest (HDT) and of control ambulatory period (AMB) in 11 healthy males at two sub-maximal workloads testing the hypothesis that the altered cardiovascular response to exercise ensuing after bed rest could make it slower. Breath-by-breath oxygen uptake (V′O2) was measured during square-wave cycling exercise calculating it from respiratory gas fractions and ventilatory flow recorded at the mouth. Exercise was performed at two exercise intensities (W1, W2) ranging from: i) W1: 53.6 % of V′O2max ±8.3 % to 58.9±16.9 % and W2: 83.6±15.6 % to 84.7±13.3 % before and after HDT respectively, and; ii) W1: 55.2±9.7 % to 58.9±6.2 % and W2: 83.3±4.2 % to 84.2±7.7 %, before and after AMB. V′O2 data were fitted by means of a bi-exponential model. In HDT and AMB, V′O2max values decreased: from 3.0 1 min-1 ±0.41 to 2.6 ± 0.32 (HDT), and from: 3.0±0.55 to 2.8±0.21 (AMB). Phase II time constants of V′O2 kinetics (τ2) in HDT equalled to: i) 24.8 s ± 4.65 (W1 and 22.2 s±3.65 (W2) before bed rest and; ii) 26.5 s±5.00 and 24.3 s±4.26 after bed rest. In AMB, τ2 turned out to be: i) 25.2 s±4.35 (W1) and 23.9±4.34 (W2) before and; ii) 26.0 s±4.21 and 24.3 s±4.22 after AMB. These data indicate a significantly slower V′O2 kinetics after HDT (by 6.9 % and 9.5 % at W1 and W2, respectively). Oxygen pulse at the two relative workloads turned out to be by 13.9 % and 17.6 % lower after HDT, but it decreased only by 1.9 % and 6.1 % after AMB, thus suggesting a remarkable decrease of the stroke volume during sub-maximal exercise in HDT as compared with AMB
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