| 1. |
- Galvan-Alvarez, Victor, et al.
(författare)
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Determinants of the maximal functional reserve during repeated supramaximal exercise by humans: The roles of Nrf2/Keap1, antioxidant proteins, muscle phenotype and oxygenation
- 2023
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Ingår i: Redox Biology. - : Elsevier B.V.. - 2213-2317. ; 66
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Tidskriftsartikel (refereegranskat)abstract
- When high-intensity exercise is performed until exhaustion a “functional reserve” (FR) or capacity to produce power at the same level or higher than reached at exhaustion exists at task failure, which could be related to reactive oxygen and nitrogen species (RONS)-sensing and counteracting mechanisms. Nonetheless, the magnitude of this FR remains unknown. Repeated bouts of supramaximal exercise at 120% of VO2max interspaced with 20s recovery periods with full ischaemia were used to determine the maximal FR. Then, we determined which muscle phenotypic features could account for the variability in functional reserve in humans. Exercise performance, cardiorespiratory variables, oxygen deficit, and brain and muscle oxygenation (near-infrared spectroscopy) were measured, and resting muscle biopsies were obtained from 43 young healthy adults (30 males). Males and females had similar aerobic (VO2max per kg of lower extremities lean mass (LLM): 166.7 ± 17.1 and 166.1 ± 15.6 ml kg LLM−1.min−1, P = 0.84) and anaerobic fitness (similar performance in the Wingate test and maximal accumulated oxygen deficit when normalized to LLM). The maximal FR was similar in males and females when normalized to LLM (1.84 ± 0.50 and 2.05 ± 0.59 kJ kg LLM−1, in males and females, respectively, P = 0.218). This FR depends on an obligatory component relying on a reserve in glycolytic capacity and a putative component generated by oxidative phosphorylation. The aerobic component depends on brain oxygenation and phenotypic features of the skeletal muscles implicated in calcium handling (SERCA1 and 2 protein expression), oxygen transport and diffusion (myoglobin) and redox regulation (Keap1). The glycolytic component can be predicted by the protein expression levels of pSer40-Nrf2, the maximal accumulated oxygen deficit and the protein expression levels of SOD1. Thus, an increased capacity to modulate the expression of antioxidant proteins involved in RONS handling and calcium homeostasis may be critical for performance during high-intensity exercise in humans.
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| 2. |
- Hustvedt, Bo-Egil, et al.
(författare)
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Validation of ActiReg to measure physical activity and energy expenditure against doubly labelled water in obese persons.
- 2008
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Ingår i: The British journal of nutrition. - 0007-1145. ; 100:1, s. 219-26
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Tidskriftsartikel (refereegranskat)abstract
- ActiReg is an instrument that uses combined recordings of body position and motion to calculate energy expenditure (EE) and physical activity (PA). The aim of the study was to compare mean total energy expenditure (TEE) measured by ActiReg and doubly labelled water (DLW) in obese subjects. TEE was measured by the DLW method during a period of 14 d in fifty obese men and women with metabolic risk factors. During the same period ActiReg recordings were obtained for 7 d. RMR was measured by indirect calorimetry and also estimated by standardized equations. Because EE may be disproportionately increased in obese subjects during weight-bearing activities, we established a new set of physical activity ratios (PAR). These ratios were based on oxygen uptake measurements during treadmill walking. The mean TEE according to the DLW was 13.94 (sd 2.47) MJ/d. Mean TEE calculated from the ActiReg data and measured RMR was 13.39 (sd 2.26) MJ/d, an underestimation of 0.55 MJ (95 % CI 0.13, 0.98; P = 0.012) or 3.9 %. RMR derived from standard equations based on weight, age and sex were overestimated while the RMR based on fat-free mass values in addition was underestimated. Despite slight underestimation ActiReg may be used to measure TEE in obese subjects on two premises: RMR should be measured, and the increased EE during weight-bearing activities in obese subjects should be considered.
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| 3. |
- Nilsson, Johnny E, et al.
(författare)
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Effects of 20-s and 180-s double poling interval training in cross-country skiers
- 2004
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Ingår i: European Journal of Applied Physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 92:1/2, s. 121-127
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to investigate the effect of upper body 20-s or 180-s interval training, using a double poling ergometer, on upper body power output and selected physiological and biomechanical parameters in cross-country skiers. Twenty (12 male, 8 female) well-trained cross-country skiers took part. Two intervention groups, a 20-s interval training group (IT20; n=6) and a 180-s interval training group (IT180; n=7), underwent training three times a week for 6 weeks on a double poling ergometer. A third group served as a control (CON; n=7) and followed the same training program as the IT20 and IT180 groups without the double poling ergometer interval training. The IT20 and IT180 groups significantly (P<0.05) increased both peak and mean power in a 30-s test and mean power in a 6-min test after double poling training. There was a significant improvement in work efficiency in both IT20 and IT180 (P<0.05) and, in IT180, a significant reduction (P<0.05) in blood lactate concentration at given sub-maximal workloads. VO(2peak) increased significantly during double poling in IT180 ( P<0.05) only. VO(2max) did not change significantly in either group. There were no significant changes in any of the test variables in CON. In conclusion, this study shows that 6 weeks of 20-s or 180-s double poling interval training, three times a week, significantly increases power output in both 30-s and 6-min tests, as well as in selected physiological and biomechanical parameters in well-trained cross-country skiers.
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| 4. |
- Paulsen, Gøran, et al.
(författare)
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Maximal eccentric exercise induces a rapid accumulation of small heat shock proteins on myofibrils and a delayed HSP70 response in humans
- 2007
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Ingår i: American Journal of Physiology. Regulatory Integrative and Comparative Physiology. - : American Physiological Society. - 0363-6119 .- 1522-1490. ; 293:2, s. R844-R853
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Tidskriftsartikel (refereegranskat)abstract
- In this study the stress protein response to unaccustomed maximal eccentric exercise in humans was investigated. Eleven healthy males performed 300 maximal eccentric actions with the quadriceps muscle. Biopsies from vastus lateralis were collected at 30 min and 4, 8, 24, 96, and 168 h after exercise. Cellular regulation and localization of heat shock protein (HSP) 27, alpha B-crystallin, and HSP70 were analyzed by immunohistochemistry, ELISA technique, and Western blotting. Additionally, mRNA levels of HSP27, alpha B-crystallin, and HSP70 were quantified by Northern blotting. After exercise (30 min), 81 +/- 8% of the myofibers showed strong HSP27 staining (P < 0.01) that gradually decreased during the following week. alpha B-Crystallin mimicked the changes observed in HSP27. After exercise (30 min), the ELISA analysis showed a 49 +/- 13% reduction of the HSP27 level in the cytosolic fraction (P < 0.01), whereas Western blotting revealed a 15-fold increase of the HSP27 level in the myofibrillar fraction (P < 0.01). The cytosolic HSP70 level increased to 203 +/- 37% of the control level 24 h after exercise (P < 0.05). After 4 days, myofibrillar-bound HSP70 had increased approximately 10-fold (P < 0.01) and was accompanied by strong staining on cross sections. mRNA levels of HSP27, alpha B-crystallin, and HSP70 were all elevated the first day after exercise (P < 0.01); HSP70 mRNA showed the largest increase (20-fold at 8 h). HSP27 and alpha B-crystallin seemed to respond immediately to maximal eccentric exercise by binding to cytoskeletal/myofibrillar proteins, probably to function as stabilizers of disrupted myofibrillar structures. Later, mRNA and total HSP protein levels, especially HSP70, increased, indicating that HSPs play a role in skeletal muscle recovery and remodeling/adaptation processes to high-force exercise
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| 5. |
- Perez-Valera, Mario, et al.
(författare)
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Angiotensin-Converting Enzyme 2 (SARS-CoV-2 receptor) expression in human skeletal muscle
- 2021
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Ingår i: Scandinavian Journal of Medicine and Science in Sports. - : John Wiley & Sons. - 0905-7188 .- 1600-0838. ; 31:12, s. 2249-2258
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Tidskriftsartikel (refereegranskat)abstract
- The study aimed to determine the levels of skeletal muscle Angiotensin-Converting Enzyme 2 (ACE2, the SARS-CoV-2 receptor) protein expression in men and women and assess whether ACE2 expression in skeletal muscle is associated with cardiorespiratory fitness and adiposity. The level of ACE2 in vastus lateralis muscle biopsies collected in previous studies from 170 men (age:19-65 yrs, weight:56-137 kg, BMI:23-44) and 69 women (age:18-55 yrs, weight:41-126 kg, BMI:22-39) was analysed in duplicate by western blot. VO2max was determined by ergospirometry and body composition by DXA. ACE2 protein expression was 1.8-fold higher in women than men (p=0.001, n=239). This sex difference disappeared after accounting for the percentage of body fat (fat %), VO2max per kg of legs lean mass (VO2max-LLM) and age (p=0.47). Multiple regression analysis showed that the fat % (β=0.47) is the main predictor of the variability in ACE2 protein expression in skeletal muscle, explaining 5.2 % of the variance. VO2max-LLM had also predictive value (β=0.09). There was a significant fat % by VO2max-LLM interaction, such that for subjects with low fat %, VO2max-LLM was positively associated with ACE2 expression while as fat % increased the slope of the positive association between VO2max-LLM and ACE2 was reduced. In conclusion, women express higher amounts of ACE2 in their skeletal muscles than men. This sexual dimorphism is mainly explained by sex differences in fat % and cardiorespiratory fitness. The percentage of body fat is the main predictor of the variability in ACE2 protein expression in human skeletal muscle.
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| 6. |
- Psilander, Niklas
(författare)
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The effect of different exercise regimens on mitochondrial biogenesis and performance
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Endurance training is a powerful tool to improve both health and performance. Physical activity is now recognized as an effective treatment and prevention therapy for a wide range of diseases. One of the most profound adaptations to endurance training is increased mitochondrial function and content within the exercising muscles. Mitochondrial quality and quantity are closely related to several of the positive health effects reported after training. High mitochondrial content strongly correlates with muscle oxidative capacity and endurance performance. Even though it is well known that endurance training increases mitochondrial content, it is unclear which type of training is the most efficient to promote mitochondrial biogenesis. Therefore, the basis for current exercise recommendations relative to mitochondrial biogenesis is poor or absent. Thus, the main objective of this thesis was to evaluate the effect of different training strategies on mitochondrial biogenesis.Recent developments in molecular methods have made it possible to study the initial adaptations to training through measurement of mRNA gene expression of exercise induced genes. One such gene is transcriptional coactivator peroxisome proliferator–activated receptor-γ coactivator-1α (PGC-1α). PGC-1α is a key regulator of mitochondrial biogenesis and the expression of PGC-1α can therefore be used as a marker of this process.The first four studies presented in this thesis are acute exercise studies where two different exercise models were compared using a cross-over design. Muscle biopsies were obtained pre and post exercise and analysed for gene expression and glycogen, apart from study II. The final study was a long-term training study where muscle biopsies were obtained before and after the training period and analysed for mitochondrial enzyme activities and protein content.Study I: The expression of PGC-1α and related genes were examined after 90 min of continuous and interval exercise in untrained subjects. The exercise protocols influenced the expression of genes involved in mitochondrial biogenesis and oxidative metabolism in a similar manner. Both interval and continuous exercise were potent training strategies for relatively sedentary individuals.Study II: The expression of PGC-1α and related genes were examined after low-volume sprint interval (SIT) and high-volume interval (IE) exercise in highly trained cyclists. SIT induced a similar increase in PGC-1α expression as IE despite a much lower time commitment and work completed. Sprint interval exercise might, therefore, be a time efficient training strategy for highly trained individuals.Study III: The expression of PGC-1α and related genes, as well as the activity of upstream proteins, were examined after concurrent (ER: cycling + leg press) and single-mode (E: cycling only) exercise in untrained subjects. PGC-1α expression doubled after ER compared with E. It was concluded that concurrent training might be beneficial for mitochondrial biogenesis in untrained individuals.Study IV: The expression of PGC-1α and related genes were examined after exercise performed with low (LG) and normal (NG) muscle glycogen in well-trained cyclists. PGC-1α expression increased approximately three times more after LG compared with NG. This finding suggested that low glycogen exercise is a potent inducer of mitochondrial biogenesis in well-trained individuals.Study V: Mitochondrial enzyme activity, protein content and endurance performance were examined after eight weeks of concurrent (ES: cycling + leg press) or single-mode (E: cycling only) training in cyclists. ES did not affect enzyme activity, protein content or endurance performance differently than E. The beneficial effect previously observed in untrained subjects did not translate to higher numbers of mitochondria in trained individuals.In three of the studies, I, III, and IV, both glycogen and PGC-1α expression were measured after exercise. These data were then pooled and examined. The highest PGC-1α mRNA expression levels were identified when glycogen levels were low, and vice versa. This suggests that low glycogen might play an important role in the regulation of mitochondrial biogenesis also during interval and concurrent strength and endurance exercise.In conclusion, key markers of mitochondrial biogenesis can be effectively up-regulated by interval, concurrent and low glycogen exercise. A possible explanation for this might be that though the exercise protocols are quite divergent in nature, they all have a pronounced effect on muscle glycogen and/or perturbation in energetic stress.
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| 7. |
- Salier Eriksson, Jane
(författare)
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The heart rate method for estimating oxygen uptake in walking and cycle commuting : Evaluations based on reproducibility and validity studies of the heart rate method and a portable metabolic system
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Walking and cycling to work can contribute to population health, but more objective knowledge concerning exercise intensities, oxygen uptake and the metabolic demands of this physical activity is needed for this and other evaluations. To attain this, valid and reliable instruments are a requirement. The focus of this thesis was to evaluate whether the heart rate method can be used for this purpose. It involves establishing the relation between heart rate and oxygen uptake during ergometer cycling in laboratory conditions, and thereafter checking if the same relation exists during cycle or walking commuting in a metropolitan area.To accomplish this, a portable metabolic system was tested for validity and reliability in laboratory and field conditions and the reproducibility of the heart rate and oxygen uptake relation in the laboratory was evaluated. Furthermore, the heart rate and oxygen uptake relations during cycle and walking commuting was compared with those attained in the laboratory.The first two studies showed that a portable metabolic system is valid during laboratory and sustained field conditions. Studies 3 and 4 showed that the heart rate method with respect to the heart rate-oxygen uptake relationship is reliable on the group level for both walking and cycling commuters during repeated measures in the laboratory. The last two studies showed that applying the heart rate method during cycle commuting leads to valid levels of oxygen uptake on the group level for both males and females. Contrary to that, the measured levels of oxygen uptake in the field during walking commuting were on average 17% higher for males, and 13% higher for females than the values obtained with the heart rate method. For both walking and cycling commuters, the individual spread around the mean values was rather high, creating somewhat wide confidence intervals for the mean values.In summary, the heart rate method can be used for cycle commuters during their normal commuting conditions, while for pedestrians it is necessary to take into account that oxygen uptake per heart rate is higher while walking than that estimated from ergometer cycling in the laboratory.
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