1,721,093 research outputs found
Metabolic myopathies: functional evaluation by analysis of oxygen uptake kinetics.
No full textPURPOSE: The aim was to identify additional noninvasive tools allowing to detect and to quantify the metabolic impairment in patients with mitochondrial myopathies (MM) or McArdle's disease (McA). METHODS: Kinetics of adjustment of pulmonary oxygen uptake (V̇O2 kinetics) during transitions to constant-load moderate-intensity cycle ergometer exercise were determined on 15 MM, 8 McA, 21 patients with signs and/or symptoms of metabolic myopathy but a negative biopsy ("patient controls"; P-CTRL), and 22 healthy untrained controls (CTRL). RESULTS: V̇O2 kinetics were slower in MM and in McA versus P-CTRL and CTRL, slower in McA versus MM, and not significantly different between P-CTRL and CTRL. The time constants (τ) of the monoexponential function describing the V̇O2 kinetics were (X̄ ± SE) 59.2 ± 8.5 s in MM, 87.6 ± 16.4 s in McA, 36.9 ± 3.1 s in P-CTRL, and 35.4 ± 1.9 s in CTRL. In a subgroup of the patients (eight MM and seven McA), τ of V̇O2 kinetics were negatively correlated with two variables determined in a previous study (Grassi B, Marzorati M, Lanfranconi F, et al. Impaired oxygen extraction in metabolic myopathies: detection and quantification by near-infrared spectroscopy. Muscle Nerve. 2007;35:510-20): a) a muscle oxygenation index, obtained by near-infrared spectroscopy, estimating the peak capacity of skeletal muscle fractional O2 extraction; and b) V̇O2 peak. CONCLUSIONS: In MM and McA patients, analysis of pulmonary V̇O2 kinetics during moderate-intensity exercise allows to identify and to quantify, noninvasively, the impairment of skeletal muscle oxidative metabolism. In these patients, the slower V̇O2 kinetics can be considered a marker of the impaired exercise tolerance. The present data could be useful for clinicians who need an objective, quantitative, and longitudinal evaluation of the impairment to be used in the follow-up of these patients as well as in the assessment of therapeutic interventions. © 2009 by the American College of Sports Medicine
Estimation of muscle oxidative capacity by nearinfrared spectroscopy: Does exercise intensity matter?
No full text
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
Comparison between slow components of HR and VO2 kinetics: Functional significance
No full textPurpose Aerobic exercise prescription is often based on a linear relationship between pulmonary oxygen consumption (VO2) and heart rate (HR). The aim of the present study was to test the hypothesis that during constant work rate (CWR) exercises at different intensities, the slow component of HR kinetics occurs at lower work rate and is more pronounced that the slow component of VO2 kinetics. Methods Seventeen male (age, 27 ± 4 yr) subjects performed on a cycle ergometer an incremental exercise to voluntary exhaustion and several CWR exercises: 1) moderate CWR exercises, below gas exchange threshold (GET); 2) heavy CWR exercise, at 45% of the difference between GET and VO2 peak (Δ); 3) severe CWR exercise, at 95% of Δ; 4) "HRCLAMPED" exercise in which work rate was continuously adjusted to maintain a constant HR, slightly higher than that determined at GET. Breath-by-breath VO2, HR, and other variables were determined. Results In moderate CWR exercises, no slow component of VO2 kinetics was observed, whereas a slow component with a relative amplitude (with respect to the total response) of 24.8 ± 11.0% was observed for HR kinetics. During heavy CWR exercise, the relative amplitude of the HR slow component was more pronounced than that for VO2 (31.6 ± 11.2% and 23.3 ± 9.0%, respectively). During HRCLAMPED, the decrease in work rate (14%) needed to maintain a constant HR was associated with a decreased VO2 (10%). Conclusions The HR slow component occurred at a lower work rate and was more pronounced than the VO2 slow component. Exercise prescriptions at specific HR values, when carried out for periods longer than a few minutes, could lead to premature fatigue
Improved exercise tolerance after enzyme replacement therapy in pompe disease
No full textPurpose: Enzyme replacement therapy (ERT) has recently became available for Pompe disease. Data on the effects of ERT on physiological variables related to exercise tolerance have never been published. Methods: Pulmonary gas exchange, cardiac output (by impedance cardiography), and vastus lateralis muscle O 2 extraction (by near-infrared spectroscopy) were determined during cycle ergometer exercise in a 50-yr-old patient before and after 1, 12, and 24 months of ERT. Results: At the same constant-workload submaximal exercise, RPE, R, pulmonary ventilation, and HR were lower during ERT versus before, suggesting an increased exercise tolerance. Peak oxygen uptake (V̇O 2peak) increased by ∼35% from before (0.64 L•min -1 or 11.4 mL•kg -1•min -1) to 1 month (0.88 L•min -1 or 15.7 mL•kg -1•min -1) of treatment and did not significantly change thereafter. Also, peak cardiac output significantly increased during ERT, whereas peak skeletal muscle fractional O 2 extraction was unchanged compared with before. Conclusions: Improvements of peak exercise capacity and exercise tolerance at submaximal workloads were observed in a patient with Pompe disease after 1 month of ERT, with no further changes during the ensuing treatment period (up to 24 months). © 2012 by the American College of Sports Medicine
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Exercise intolerance in patients with mitochondrial myopathies: perfusive and diffusive limitations in the O2 pathway
No full textMitochondrial myopathies are a heterogeneous group of disorders characterized by genetically determined defects that impair oxidative phosphorylation at the mitochondrial level. Exercise intolerance is a clinical hallmark in most of these patients, who present fatigue and dyspnoea during low levels of exertion, including moderate activities of daily living. This review aims to discuss the principal limiting factors of muscle oxidative metabolism during exercise in patients with mitochondrial myopathies, investigating the effects of perfusive and diffusive impairments along the O2 transport pathway from ambient air to muscle mitochondria. Possible therapeutic effects of exercise training will be also highlighted
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