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Search: WFRF:(Calbet J)

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2.
  • Boushel, Robert, et al. (author)
  • Maintained peak leg and pulmonary VO2 despite substantial reduction in muscle mitochondrial capacity.
  • 2015
  • In: Scandinavian Journal of Medicine and Science in Sports. - : Wiley. - 0905-7188 .- 1600-0838. ; 25:Suppl 4, s. 135-143
  • Journal article (peer-reviewed)abstract
    • We recently reported the circulatory and muscle oxidative capacities of the arm after prolonged low-intensity skiing in the arctic (Boushel et al., 2014). In the present study, leg VO2 was measured by the Fick method during leg cycling while muscle mitochondrial capacity was examined on a biopsy of the vastus lateralis in healthy volunteers (7 male, 2 female) before and after 42 days of skiing at 60% HR max. Peak pulmonary VO2 (3.52 ± 0.18 L.min(-1) pre vs 3.52 ± 0.19 post) and VO2 across the leg (2.8 ± 0.4L.min(-1) pre vs 3.0 ± 0.2 post) were unchanged after the ski journey. Peak leg O2 delivery (3.6 ± 0.2 L.min(-1) pre vs 3.8 ± 0.4 post), O2 extraction (82 ± 1% pre vs 83 ± 1 post), and muscle capillaries per mm(2) (576 ± 17 pre vs 612 ± 28 post) were also unchanged; however, leg muscle mitochondrial OXPHOS capacity was reduced (90 ± 3 pmol.sec(-1) .mg(-1) pre vs 70 ± 2 post, P < 0.05) as was citrate synthase activity (40 ± 3 μmol.min(-1) .g(-1) pre vs 34 ± 3 vs P < 0.05). These findings indicate that peak muscle VO2 can be sustained with a substantial reduction in mitochondrial OXPHOS capacity. This is achieved at a similar O2 delivery and a higher relative ADP-stimulated mitochondrial respiration at a higher mitochondrial p50. These findings support the concept that muscle mitochondrial respiration is submaximal at VO2max , and that mitochondrial volume can be downregulated by chronic energy demand.
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3.
  • González Henríquez, J J, et al. (author)
  • A new equation to estimate temperature-corrected PaCO2 from PET CO2 during exercise in normoxia and hypoxia.
  • 2015
  • In: Scandinavian Journal of Medicine & Science in Sports. - : Wiley. - 1600-0838 .- 0905-7188. ; 26:9, s. 1045-1051
  • Journal article (peer-reviewed)abstract
    • End-tidal PCO2 (PET CO2 ) has been used to estimate arterial pressure CO2 (Pa CO2 ). However, the influence of blood temperature on the Pa CO2 has not been taken into account. Moreover, there is no equation validated to predict Pa CO2 during exercise in severe acute hypoxia. To develop a new equation to predict temperature-corrected Pa CO2 values during exercise in normoxia and severe acute hypoxia, 11 volunteers (21.2 ± 2.1 years) performed incremental exercise to exhaustion in normoxia (Nox, PI O2 : 143 mmHg) and hypoxia (Hyp, PI O2 : 73 mmHg), while arterial blood gases and temperature (ABT) were simultaneously measured together with end-tidal PCO2 (PET CO2 ). The Jones et al. equation tended to underestimate the temperature corrected (tc) Pa CO2 during exercise in hypoxia, with greater deviation the lower the Pa CO2 tc (r = 0.39, P < 0.05). The new equation has been developed using a random-effects regression analysis model, which allows predicting Pa CO2 tc both in normoxia and hypoxia: Pa CO2 tc = 8.607 + 0.716 × PET CO2 [R(2) = 0.91; intercept SE = 1.022 (P < 0.001) and slope SE = 0.027 (P < 0.001)]. This equation may prove useful in noninvasive studies of brain hemodynamics, where an accurate estimation of Pa CO2 is needed to calculate the end-tidal-to-arterial PCO2 difference, which can be used as an index of pulmonary gas exchange efficiency.
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5.
  • Boushel, Robert, et al. (author)
  • Low-intensity training increases peak arm VO2 by enhancing both convective and diffusive O2 delivery.
  • 2014
  • In: Acta Physiologica. - : Wiley. - 1748-1708 .- 1748-1716. ; 211:1, s. 122-134
  • Journal article (peer-reviewed)abstract
    • AIM: It is an ongoing discussion the extent to which oxygen delivery and oxygen extraction contribute to an increased muscle oxygen uptake during dynamic exercise. It has been proposed that local muscle factors including the capillary bed and mitochondrial oxidative capacity play a large role in prolonged low-intensity training of a small muscle group when the cardiac output capacity is not directly limiting. The purpose of this study was to investigate the relative roles of circulatory and muscle metabolic mechanisms by which prolonged low-intensity exercise training alters regional muscle VO2 .METHODS: In nine healthy volunteers (seven males, two females), haemodynamic and metabolic responses to incremental arm cycling were measured by the Fick method and biopsy of the deltoid and triceps muscles before and after 42 days of skiing for 6 h day(-1) at 60% max heart rate.RESULTS: Peak pulmonary VO2 during arm crank was unchanged after training (2.38 ± 0.19 vs. 2.18 ± 0.2 L min(-1) pre-training) yet arm VO2 (1.04 ± 0.08 vs. 0.83 ± 0.1 L min(1) , P < 0.05) and power output (137 ± 9 vs. 114 ± 10 Watts) were increased along with a higher arm blood flow (7.9 ± 0.5 vs. 6.8 ± 0.6 L min(-1) , P < 0.05) and expanded muscle capillary volume (76 ± 7 vs. 62 ± 4 mL, P < 0.05). Muscle O2 diffusion capacity (16.2 ± 1 vs. 12.5 ± 0.9 mL min(-1)  mHg(-1) , P < 0.05) and O2 extraction (68 ± 1 vs. 62 ± 1%, P < 0.05) were enhanced at a similar mean capillary transit time (569 ± 43 vs. 564 ± 31 ms) and P50 (35.8 ± 0.7 vs. 35 ± 0.8), whereas mitochondrial O2 flux capacity was unchanged (147 ± 6 mL kg min(-1) vs. 146 ± 8 mL kg min(-1) ).CONCLUSION: The mechanisms underlying the increase in peak arm VO2 with prolonged low-intensity training in previously untrained subjects are an increased convective O2 delivery specifically to the muscles of the arm combined with a larger capillary-muscle surface area that enhance diffusional O2 conductance, with no apparent role of mitochondrial respiratory capacity.
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6.
  • Calbet, J. A. L., et al. (author)
  • A time-efficient reduction of fat mass in 4 days with exercise and caloric restriction
  • 2015
  • In: Scandinavian Journal of Medicine and Science in Sports. - : Wiley. - 0905-7188 .- 1600-0838. ; 25:2, s. 223-233
  • Journal article (peer-reviewed)abstract
    • To determine whether a fast reduction in fat mass can be achieved in 4 days by combining caloric restriction (CR: 3.2kcal/kg body weight per day) with exercise (8-h walking+45-min arm cranking per day) to induce an energy deficit of approximate to 5000kcal/day, 15 overweight men underwent five experimental phases: pretest, exercise+CR for 4 days (WCR), control diet+reduced exercise for 3 days (DIET), and follow-up 4 weeks (POST1) and 1 year later (POST2). During WCR, the diet consisted solely of whey protein (n=8) or sucrose (n=7) (0.8g/kg body weight per day). After WCR, DIET, POST1, and POST2, fat mass was reduced by a mean of 2.1, 2.8, 3.8, and 1.9kg (P<0.05), with two thirds of this loss from the trunk; and lean mass by 2.8, 1.0, 0.5, and 0.4kg, respectively. After WCR, serum glucose, insulin, homeostatic model assessment, total and low-density lipoprotein cholesterol and triglycerides were reduced, and free fatty acid and cortisol increased. Serum leptin was reduced by 64%, 50%, and 33% following WCR, DIET, and POST1, respectively (P<0.05). The effects were similar in both groups. In conclusion, a clinically relevant reduction in fat mass can be achieved in overweight men in just 4 days by combining prolonged exercise with CR.
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7.
  • Larsen, Filip J, 1977-, et al. (author)
  • Mitochondrial oxygen affinity increases after sprint interval training and is related to the improvement in peak oxygen uptake.
  • 2020
  • In: Acta Physiologica. - : John Wiley & Sons. - 1748-1708 .- 1748-1716. ; 229:3
  • Journal article (peer-reviewed)abstract
    • AIMS: The body responds to exercise training by profound adaptations throughout the cardiorespiratory and muscular systems, which may result in improvements in maximal oxygen consumption (VO2 peak) and mitochondrial capacity. By convenience, mitochondrial respiration is often measured at supra-physiological oxygen levels, an approach that ignores any potential regulatory role of mitochondrial affinity for oxygen (p50mito ) at physiological oxygen levels.METHODS: In this study, we examined the p50mito of mitochondria isolated from the Vastus lateralis and Triceps brachii in 12 healthy volunteers before and after a training intervention with 7 sessions of sprint interval training using both leg cycling and arm cranking. The changes in p50mito were compared to changes in whole-body VO2 peak.RESULTS: We here show that p50mito is similar in isolated mitochondria from the Vastus (40 ± 3.8 Pa) compared to Triceps (39 ± 3.3) but decreases (mitochondrial oxygen affinity increases) after 7 sessions of sprint interval training (to 26 ± 2.2 Pa in Vastus and 22 ± 2.7 Pa in Triceps, both p<0.01). The change in VO2 peak modeled from changes in p50mito was correlated to actual measured changes in VO2 peak (R2 =0.41, p=0.002).CONCLUSION: Together with mitochondrial respiratory capacity, p50mito is a critical factor when measuring mitochondrial function, it can decrease with sprint interval training and should be considered in the integrative analysis of the oxygen cascade from lung to mitochondria.
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9.
  • Sala, M. M., et al. (author)
  • Contrasting effects of ocean acidification on the microbial food web under different trophic conditions
  • 2016
  • In: ICES Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; 73:3, s. 670-679
  • Journal article (peer-reviewed)abstract
    • We investigated the effects of an increase in dissolved CO2 on the microbial communities of the Mediterranean Sea during two mesocosm experiments in two contrasting seasons: winter, at the peak of the annual phytoplankton bloom, and summer, under low nutrient conditions. The experiments included treatments with acidification and nutrient addition, and combinations of the two. We followed the effects of ocean acidification (OA) on the abundance of the main groups of microorganisms (diatoms, dinoflagellates, nanoeukaryotes, picoeukaryotes, cyanobacteria, and heterotrophic bacteria) and on bacterial activity, leucine incorporation, and extracellular enzyme activity. Our results showed a clear stimulation effect of OA on the abundance of small phytoplankton (pico- and nanoeukaryotes), independently of the season and nutrient availability. A large number of the measured variables showed significant positive effects of acidification in summer compared with winter, when the effects were sometimes negative. Effects of OA were more conspicuous when nutrient concentrations were low. Our results therefore suggest that microbial communities in oligotrophic waters are considerably affected by OA, whereas microbes in more productive waters are less affected. The overall enhancing effect of acidification on eukaryotic pico- and nanophytoplankton, in comparison with the non-significant or even negative response to nutrient-rich conditions of larger groups and autotrophic prokaryotes, suggests a shift towards medium-sized producers in a future acidified ocean.
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10.
  • Cardinale, Daniele A., 1982-, et al. (author)
  • Muscle mass and inspired oxygen influence oxygen extraction at maximal exercise : role of mitochondrial oxygen affinity.
  • 2019
  • In: Acta Physiologica. - : Wiley-Blackwell. - 1748-1708 .- 1748-1716. ; 225:1
  • Journal article (peer-reviewed)abstract
    • AIM:We examined the Fick components together with mitochondrial O2 affinity (p50mito ) in defining O2 extraction and O2 uptake during exercise with large and small muscle mass during normoxia (NORM) and hyperoxia (HYPER).METHODS:Seven individuals performed two incremental exercise tests to exhaustion on a bicycle ergometer (BIKE) and two on a one-legged knee extension ergometer (KE) in NORM or HYPER. Leg blood flow and VO2 were determined by thermodilution and the Fick method. Maximal ADP-stimulated mitochondrial respiration (OXPHOS) and p50mito were measured ex vivo in isolated mitochondria. Mitochondrial excess capacity in the leg was determined from OXPHOS in permeabilized fibers and muscle mass measured with magnetic resonance imaging in relation to peak leg O2 delivery.RESULTS:The ex vivo p50mito increased from 0.06±0.02 to 0.17±0.04 kPa with varying substrate supply and O2 flux rates from 9.84±2.91 to 16.34±4.07 pmol O2 ·s-1 ·μg-1 respectively. O2 extraction decreased from 83% in BIKE to 67% in KE as a function of a higher O2 delivery, and lower mitochondrial excess capacity. There was a significant relationship between O2 extraction and mitochondrial excess capacity and p50mito that was unrelated to blood flow and mean transit time.CONCLUSION:O2 extraction varies with mitochondrial respiration rate, p50mito and O2 delivery. Mitochondrial excess capacity maintains a low p50mito which enhances O2 diffusion from microvessels to mitochondria during exercise. This article is protected by copyright. All rights reserved.
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  • Result 1-10 of 38
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journal article (25)
conference paper (13)
Type of content
peer-reviewed (33)
other academic/artistic (5)
Author/Editor
Calbet, J A L (13)
Holmberg, Hans-Chris ... (11)
Holmberg, Hans-Chris ... (10)
Calbet, JAL (9)
Boushel, Robert (9)
Perez-Suarez, I. (8)
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Morales –Alamo, D (7)
Losa-Reyna, J (7)
Jensen-Urstad, M (6)
van Hall, G. (6)
Calbet, José A L (5)
de la Calle Herrero, ... (5)
Santana, A (4)
Saltin, B (4)
Larsen, Filip J, 197 ... (4)
Boushel, R (4)
Morales-Alamo, David (4)
Calbet, J (4)
Cardinale, Daniele A ... (3)
Saltin, Bengt (3)
Ørtenblad, Niels (3)
Willis, Sarah J. (3)
Ekblom, Björn, 1938- (3)
Martin-Rincon, M (3)
Zinner, Christoph (3)
Larsen, Filip J (3)
Martinez, A (2)
Granéli, Edna (2)
Rosdahl, Hans (2)
Jakobsson, J. (2)
Catalán, Núria, 1985 ... (2)
Rullman, E (2)
Calbet, A. (2)
Ara, I (2)
Gelabert-Rebato, M (2)
Robach, P. (2)
Gnaiger, E (2)
Helge, J W (2)
González-Alonso, J (2)
Søndergaard, H (2)
Raven, John A. (2)
Negoita, F. (2)
Calbet, Albert (2)
Ponce-Gonzalez, J. G ... (2)
Schiffer, Tomas A (2)
Tillmann, Urban (2)
Flynn, Kevin J (2)
Stoecker, Diane K (2)
Mitra, Aditee (2)
Glibert, Patricia M. (2)
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The Swedish School of Sport and Health Sciences (14)
Karolinska Institutet (11)
Luleå University of Technology (10)
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