| 1. |
- Jacobs, Robert A., et al.
(author)
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Twenty-eight days of exposure to 3,454 m increases mitochondrial volume density in human skeletal muscle
- 2015
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In: Journal of Physiology. - : Blackwell Publishing. - 0022-3751 .- 1469-7793. ; 594:5, s. 1151-1166
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Journal article (peer-reviewed)abstract
- The role of hypoxia on skeletal muscle mitochondria is controversial. Studies superimposing exercise training with hypoxic exposure demonstrate an increase in skeletal muscle mitochondrial volume density (MitoVD ) over equivalent normoxic training. In contrast, a reduction in both skeletal muscle mass and MitoVD have been reported following mountaineering expeditions. These observations may however be confounded by negative energy balance, which may obscure the results. Accordingly we sought to examine the effects of high altitude hypoxic exposure on mitochondrial characteristics, with emphasis on MitoVD , while minimizing changes in energy balance. For this purpose, skeletal muscle biopsies were obtained from 9 lowlanders at sea level (Pre) and following 7 (7 Days) and 28 (28 Days) days of exposure to 3454 m. Maximal ergometer power output, whole-body weight and composition, leg lean mass, and skeletal muscle fibre area all remained unchanged following the altitude exposure. Transmission electron microscopy determined intermyofibrillar (IMF) MitoVD was augmented (P = 0.028) by 11.5 ± 9.2% from Pre (5.05 ± 0.9%) to Day 28 (5.61 ± 0.04%). On the contrary, there was no change in subsarcolemmal (SS) MitoVD . As a result total MitoVD (IMF + SS) was increased (P = 0.031) from 6.20 ± 1.5% at Pre to 6.62 ± 1.4% on Day 28 (7.8 ± 9.3%). At the same time no changes in mass-specific respiratory capacities, mitochondrial protein or antioxidant content were found. This study demonstrates that skeletal muscle MitoVD may increase with 28 days acclimation to 3454 m.
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| 2. |
- Keiser, Stefanie, et al.
(author)
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Detection of blood volumes and haemoglobin mass by means of CO re-breathing and indocyanine green and sodium fluorescein injections
- 2017
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In: Scandinavian Journal of Clinical and Laboratory Investigation. - : Taylor & Francis. - 0036-5513 .- 1502-7686. ; 77:3, s. 164-174
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Journal article (peer-reviewed)abstract
- The main aim of the present study was to quantify the magnitude of differences introduced when estimating a given blood volume compartment (e.g. plasma volume) through the direct determination of another compartment (e.g. red cell volume) by multiplication of venous haematocrit and/or haemoglobin concentration. However, since whole body haematocrit is higher than venous haematocrit such an approach might comprise certain errors. To test this experimentally, four different methods for detecting blood volumes and haemoglobin mass (Hb(mass)) were compared, namely the carbon monoxide (CO) re-breathing (for Hb(mass)), the indocyanine green (ICG; for plasma volume [PV]) and the sodium fluorescein (SoF; for red blood cell volume [RBCV]) methods. No difference between ICG and CO re-breathing derived PV could be established when a whole body/venous haematocrit correction factor of 0.91 was applied (p=0.11, r=0.43, mean difference -340 +/- 612mL). In contrast, when comparing RBCV derived by the CO re-breathing and the SoF method, the SoF method revealed lower RBCV values as compared to the CO re-breathing method (p<0.05, r=0.95, mean difference -728 +/- 184mL). However, compared to the ICG and the SoF methods, the typical error (%TE) and hence reliability of the CO re-breathing method was lower for all measured parameters. Therefore, estimating blood volume compartments by the direct assessment of another compartment can be considered a suitable approach. The CO re-breathing method proved accurate in determining the induced phlebotomy and is at the same time judged easier to perform than any of the other methods.
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| 3. |
- Gejl, Kasper D., et al.
(author)
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Changes in metabolism but not myocellular signaling by training with CHO-restriction in endurance athletes
- 2018
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In: Physiological Reports. - : Wiley. - 2051-817X. ; 6:17
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Journal article (peer-reviewed)abstract
- Carbohydrate (CHO) restricted training has been shown to increase the acute training response, whereas less is known about the acute effects after repeated CHO restricted training. On two occasions, the acute responses to CHO restriction were examined in endurance athletes. Study 1 examined cellular signaling and metabolic responses after seven training-days including CHO manipulation (n = 16). The protocol consisted of 1 h high-intensity cycling, followed by 7 h recovery, and 2 h of moderate-intensity exercise (120SS). Athletes were randomly assigned to low (LCHO: 80 g) or high (HCHO: 415 g) CHO during recovery and the 120SS. Study 2 examined unaccustomed exposure to the same training protocol (n = 12). In Study 1, muscle biopsies were obtained at rest and 1 h after 120SS, and blood samples drawn during the 120SS. In Study 2, substrate oxidation and plasma glucagon were determined. In Study 1, plasma insulin and proinsulin C-peptide were higher during the 120SS in HCHO compared to LCHO (insulin: 0 min: +37%; 60 min: +135%; 120 min: +357%, P = 0.05; proinsulin C-peptide: 0 min: +32%; 60 min: +52%; 120 min: +79%, P = 0.02), whereas plasma cholesterol was higher in LCHO (+15-17%, P = 0.03). Myocellular signaling did not differ between groups. p-AMPK and p-ACC were increased after 120SS (+35%, P = 0.03; +59%, P = 0.0004, respectively), with no alterations in p-p38, p-53, or p-CREB. In Study 2, glucagon and fat oxidation were higher in LCHO compared to HCHO during the 120SS (+26-40%, P = 0.03; +44-76%, P = 0.01 respectively). In conclusion, the clear respiratory and hematological effects of CHO restricted training were not translated into superior myocellular signaling after accustomization to CHO restriction.
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