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Recensione di G.C. Ferretti, G. Iannuzzi, "Storie di uomini e di libri. L'editoria letteraria italiana attraverso le sue collane".
Full text linkNote de lecture de G.C. Ferretti, G. Iannuzzi, "Strie di uomini e di libri. L'editoria letteraria italiana attraverso le sue collane", parue dans OBLIO, 14-15, 2014, p. 104-106.Note de lecture de G.C. Ferretti, G. Iannuzzi, "Strie di uomini e di libri. L'editoria letteraria italiana attraverso le sue collane"
The effects of microgravity exposure on maximal oxygen consumption in humans
No full textAfter a short summary of the multifactorial models of maximal O2 consumption (VO2max) limitation, microgravity exposure is discussed as a convenient experimental condition to test these models. The following points are highlighted: 1) The decrease of (VO2max) in microgravity concerns specifically exercise performed in upright posture upon resumption of gravity exposure; 2) The decrease of (VO2max) after microgravity exposure has two components: one is fast and is related to cardiovascular adaptation, the other is slow and is related to the development of muscle atrophy; 3) (VO2max) does not decrease during microgravity or in supine posture upon resumption of gravity exposure, if the time in microgravity is sufficiently short; 4) cardiovascular oxygen transport accounts for 70% of (VO2max) limitation also after microgravity exposure
Effects of short term bed – rest on exercise response in humans
No full textExposure to real (space flight) or simulated microgravity (e.g., head–down tilt bed rest) induces remarkable alteration of maximal aerobic exercise capacity in humans. Maximal oxygen uptake (V'O2max) drops rapidly during the first 3-6 days to decrease more gradually up to 22 – 17 % of the control values after 30 – 42 days of bed rest (Convertino DA, 1996, Ferretti G et al, 1997, Fortney SM et al, 1996, Saltin B et al, 1968).
The prompt decay of V'O2max is mainly the consequence of the cardiovascular deconditioning ensuing during real and artificial microgravity. The shift of blood and body fluids occurring toward the head and thorax at the onset of microgravity is sensed as a volume overload signal and triggers an integrated cardiovascular-neuro-endocrine response leading to an immediate reduction of total peripheral resistance and to an increased water excretion by the kidney. The consequence is a rapid reduction in circulating volume, which may range from 8.4 % to 16 % in comparison with pre – flight conditions during 4-84 days missions (Convertino DA, 1996).
The observed reduction of circulating blood volume has a detrimental impact on cardiac haemodynamics. Indeed, the decay of and SV seem to be mainly caused by the following cascade of events: the increased elimination of plasma water brings about the reduction in circulating blood volume. This leads, through its effect on venous return, to the reduction of the heart chambers volume and, on longer periods of microgravity exposure, to cardiac atrophy and re–modelling (Levine BD et al, 1997, Perhonen MA et al, 2001), which, in turn, may alter the mechanical functions of cardiac pump in vivo. As a consequence of this chain of events, the volume of blood pumped by the heart at each cardiac cycle drops.
Bed rest campaigns commonly aimed to investigate, in a single group of subjects, the effect of this sort of intervention without considering the possible cross-linked effects of bed-rest and inactivity and/or confinement. In the Short Term Bed Rest – Integrative Physiology (STBR-IP) study, organised at the DLR Institute of Aerospace Medicine in Cologne (D), an experimental protocol was planned to take into considerations the weakness characterising the other similar studies carried out in the past.
To this aim, the same group of subjects was studied before and after confined ambulatory and bed rest periods of identical duration. This allowed us to disentangle the effects of restricted physical activity in a confined environment from those due to bed-rest.
In this paper, the results obtained during sub maximal and maximal exercise in the study at stake are reported. Data deal with oxygen uptake and cardiac output at maximal exercise assessed, in the very same subjects, before and after 14-days of head down bed-rest and ambulatory periods
Limiting factors to oxygen transport on Mount Everest 30 years after: a critique of Paolo Cerretelli's contribution to the study of altitude physiology
Full text linkIn 1976, Paolo Cerretelli published an article entitled "Limiting factors to oxygen transport on Mount Everest" in the Journal of Applied Physiology. The paper demonstrated the role of cardiovascular oxygen transport in limiting maximal oxygen consumption (VO2max). In agreement with the predominant view of VO2max limitation at that time, however, its results were taken to mean that cardiovascular oxygen transport does not limit VO2max at altitude. So it was argued that the limiting factor could be in the periphery, and muscle blood flow was proposed as a possible candidate. Despite this suggestion, the conclusion generated a series of papers on muscle structural characteristics. These experiments demonstrated a loss of muscle oxidative capacity in chronic hypoxia, and thus provided an unambiguous refutation of the then widespread hypothesis that an increased muscle oxidative capacity is needed at altitude to compensate for the lack of oxygen. This analysis is followed by a short account of Cerretelli's more recent work, with a special attention to the subject of the so-called "lactate paradox"
La teologia contemporanea. Introduzione e brani antologici
No full textAA.VV., Marietti, Torino (ha collaborato come autore ai capp.: La nuova ermeneutica, Romano Guardini, Karl Rahner, Edward Schillebeecks, Hans Kung, come con-autore alla Introduzione generale)
ANALISI DELLA CAPACITA' INNOVATIVA DELLE IMPRESE OPERANTI NEL SETTORE DELL'IMPIANTISTICA ALIMENTARE
No full textA revision of maximal oxygen consumption and exercise capacity at altitude 70 years after the first climb of Mount Everest
Full text linkOn the 70th anniversary of the first climb of Mount Everest by Edmund Hillary and Tensing Norgay, we discuss the physiological bases of climbing Everest with or without supplementary oxygen. After summarizing the data of the 1953 expedition and the effects of oxygen administration, we analyse the reasons why Reinhold Messner and Peter Habeler succeeded without supplementary oxygen in 1978. The consequences of this climb for physiology are briefly discussed. An overall analysis of maximal oxygen consumption (VO2max) at altitude follows. In this section, we discuss the reasons for the non-linear fall of VO2max at altitude, we support the statement that it is a mirror image of the oxygen equilibrium curve, and we propose an analogue of Hill's model of the oxygen equilibrium curve to analyse the VO2max fall. In the following section, we discuss the role of the ventilatory and pulmonary resistances to oxygen flow in limiting VO2max, which becomes progressively greater while moving toward higher altitudes. On top of Everest, these resistances provide most of the VO2max limitation, and the oxygen equilibrium curve and the respiratory system provide linear responses. This phenomenon is more accentuated in athletes with elevated VO2max, due to exercise-induced arterial hypoxaemia. The large differences in VO2max that we observe at sea level disappear at altitude. There is no need for a very high VO2max at sea level to climb the highest peaks on Earth. imageAbstract figure legend Maximal oxygen consumption (VO2max) shows a non-linear fall with altitude that is a mirror image of the oxygen equilibrium curve. Di Prampero and Ferretti were the first to associate the non-linear behaviour of the respiratory system to the oxygen equilibrium curve. On the other hand, Wagner constructed his convective curve accounting for the effects of the oxygen equilibrium curve. The decrease is more accentuated in athletic subjects with elevated VO2max compared to those who are non-athletic, so that the large differences in VO2max that are observed at sea level disappear at altitude. Such consequences are due to the effect of ventilatory and pulmonary resistances to oxygen flow in limiting VO2max, which becomes progressively greater while moving toward higher altitudes compared to that of the cardiovascular resistance. On top of Everest, the pulmonary resistances provide most of the VO2max limitation and the respiratory system provides linear responses. imag
LFT-based identification of lateral vehicle dynamics
Full text linkThis paper presents a novel estimation and identification approach for lateral vehicle dynamics. The algorithm leverages on a Linear Fraction Transform (LFT) reformulation of vehicle and tyre models, allowing for a simple and computationally efficient inclusion of complex and nonlinear dynamic models, like, for example, two-wheels, four-wheels or single-track as vehicle model, and Pacejika, brush or Fiala as tyre model. As a result, this technique can be easily adopted in the development of an online identification system, able to run on a standard embedded device, implementing a flexible identification procedure that can handle different driving conditions, up to the limits of handling, different vehicle modelling approaches, and different input measurements. Experimental results demonstrate the effectiveness of the proposal, either in a persistent excitation and in a non-persistent excitation scenario
Physiological determinants of best performance in marathon running - Commentary on viewpoint: the two-hour marathon: who and when?
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