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| 2. |
- Esbjörnsson Liljedahl, Mona
(författare)
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Human muscle response to sprint exercise in a gender perspective
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Anaerobic performance, muscle characteristics and acute and chronic response to sprint exercise were studied in physically active healthy women (n=35; age 24) and men (n=38; age 25). The aims of the present study were to: 1) Establish if women possess lower oxidative and glycolytic capacity, higher proportion of type I fibres and smaller type II fibre areas in relation to type I fibre areas in thigh musculature than men. 2) Investigate if the same muscle variables predict anaerobic performance in women and men. 3) Identify muscle variables explaining gender differences in anaerobic performance. 4) Investigate if the effect of anaerobic training on muscle characteristics and maximal power output differ between women and men. 5) Study if there is a gender difference in metabolic activation of type I and type II muscle fibres and in sympathoadrenergic activation, during 30-s cycle sprints. Methods: Sprint exercise or sprint training were performed using a 30-s Wingate-test. Muscle biopsies from vastus lateralis were obtained before and immediately after sprint exercise or before and after 4 weeks of sprint training. Biopsies were analysed for fibre types, fibre areas, enzyme activities, glycogen and total creatine content. Content of glycogen, lactate, creatine phosphate, creatine, ATP, inosine monophosphate (IMP), inosine, hypoxanthine and xanthine were also analysed in pools of type I and type II fibres. Venous blood was sampled and analysed for lactate, ammonia, catecholamines and breakdown products of ATP before, during and after sprint exercise. Results: Cross-sectional fibre areas of type I, IIA and IIB fibres were smaller and type II/I area ratio, relative area of fibre type II, and activities of lactate dehydrogenase (LD) and M-subunit of LD were lower in women than in men, but not citrate synthase activity. Low proportion of type II fibres, phosphofructokinase activity and low relative M-subunit activity, seemed to reduce anaerobic performance in both genders. Lower M-subunit activity may contribute to the lower capacity of women than of men to perform anaerobic exercise. Sprint training decreased gender differences in mean power output, type II fibre cross-sectional area, but did not reduce gender difference in LD activity. Exercise-induced glycogen degradation was smaller in women than in men in type I fibres, but not in type Il fibres. This was also supported by lower lactate content in women's type I fibres after exercise. Reduction in ATP content and accumulation of IMP during bouts of sprint exercise was similar in men and women in both type I and II fibres. After recovery between bouts of sprint exercise, women showed lower muscle IMP and inosine than did men, especially in type II fibres. At systemic level, women as compared to men showed lower accumulation of ammonia, inosine, xanthine, hypoxanthine, uric acid and catecholamines in plasma, and of lactate in blood, following repeated sprint exercise. Conclusion: Knowledge about fibre-type-specific and gender related differences in the metabolic response to sprint exercise may, besides being of basic scientific value, have implications for response to sprint training and therefore also for the planning of gender-specific training programs, including the recovery period between bouts of sprint exercise.
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- Norman, Barbara, et al.
(författare)
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Strength, power, fiber types, and mRNA expression in trained men and women with different ACTN3 R577X genotypes
- 2009
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Ingår i: Journal of applied physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 106, s. 959-965
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Tidskriftsartikel (refereegranskat)abstract
- .-alpha-Actinins are structural proteins of the Z-line. Human skeletal muscle expresses two alpha-actinin isoforms, alpha-actinin-2 and alpha-actinin-3, encoded by their respective genes ACTN2 and ACTN3. ACTN2 is expressed in all muscle fiber types, while only type II fibers, and particularly the type IIb fibers, express ACTN3. ACTN3 (R577X) polymorphism results in loss of alpha-actinin-3 and has been suggested to influence skeletal muscle function. The X allele is less common in elite sprint and power athletes than in the general population and has been suggested to be detrimental for performance requiring high power. The present study investigated the association of ACTN3 genotype with muscle power during 30-s Wingate cycling in 120 moderately to well-trained men and women and with knee extensor strength and fatigability in a subset of 21 men performing isokinetic exercise. Muscle biopsies were obtained from the vastus lateralis muscle to determine fiber-type composition and ACTN2 and ACTN3 mRNA levels. Peak and mean power and the torque-velocity relationship and fatigability output showed no difference across ACTN3 genotypes. Thus this study suggests that R577X polymorphism in ACTN3 is not associated with differences in power output, fatigability, or force-velocity characteristics in moderately trained individuals. However, repeated exercise bouts prompted an increase in peak torque in RR but not in XX genotypes, suggesting that ACTN3 genotype may modulate responsiveness to training. Our data further suggest that alpha-actinins do not play a significant role in determining muscle fiber-type composition. Finally, we show that ACTN2 expression is affected by the content of alpha-actinin-3, which implies that alpha-actinin-2 may compensate for the lack of alpha-actinin-3 and hence counteract the phenotypic consequences of the deficiency.
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- Rundqvist, Håkan C, et al.
(författare)
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Amino Acid Transport after Sprint Exercise and Oral Amino Acids : 90 Board #6 June 1, 9
- 2016
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Ingår i: Medicine & Science in Sports & Exercise: Volume 48(5S) Supplement 1, May 2016, p 5. - : Ovid Technologies (Wolters Kluwer Health). ; , s. 5-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- PURPOSE: To study if oral ingestion of essential amino acids (oral EAA) increases the amino acid transporter SNAT2, Akt/mTOR signaling and muscle protein synthesis (MPS) after sprint exercise.METHODS: 12 healthy subjects performed three 30-s sprints with 20 minutes rest in between. Subjects consumed EAA + maltodextrin solution or flavoured water (placebo) during the sprint exercise up to 15 min after the last sprint in a randomized order with one month interval. In vivo MPS rate was measured using a stable isotope technique. Subject received a stable isotope of phenylalanine (D5-phenylalanine) to label the precursor pool for protein synthesis. Continuous infusion started before the first sprint and was ended 200 min after the last sprint. Two post exercise biopsies (vastus lateralis) were obtained 80 min and 200 min after last sprint. The amount of labelled phenylalanine incorporated into muscle protein over these 2 hours represents the in vivo MPS rate and was expressed as fractional synthesis rate (FSR %) calculated by dividing amount of labelled phenylalanine incorporated during these 2 hours by the amount in the free amino acid (precursor) plasma pool. Biopsies were also analyzed for Akt/mTOR signaling and SNAT2 amino acid transporter by Western blot and for SNAT2 gene expression by real-time PCR. Blood samples were analyzed for amino acids, glucose, lactate, and insulin. Four subjects, involuntary vomiting after exercise during EAA condition, showed a minor increase in plasma leucine and were presented separately.RESULTS: Non-vomiting subjects (n=8): The expression of the amino acid transporter SNAT2 was higher both at the protein (P<0.05) and the mRNA (P<0.001) level after EEA than after placebo. Fold increase for phosphorylated Akt, mTOR and p70 was 1.7-3.6 (P<0.01 - P<0.001) comparing EAA with placebo. FSR % after EEA was increased by 25 % (P=0.02) compared to placebo. None of these variables were significantly increased in the subjects who vomited.CONCLUSION: Oral EAA increased MPS after sprint exercise. Enhanced capacity for amino acid transport and subsequent enhanced Akt/mTOR signaling are suggested to mediate the increased MPS.
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- Rundqvist, Håkan Claes, et al.
(author)
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Influence of nutrient ingestion on amino acid transporters and protein synthesis in human skeletal muscle after sprint exercise
- 2017
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In: Journal of applied physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 123:6, s. 1501-1515
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Journal article (peer-reviewed)abstract
- Nutrient ingestion is known to increase the exercise-induced stimulation of muscle protein synthesis following resistance exercise. Less is known about the effect of nutrients on muscle protein synthesis following sprint exercise. At two occasions separated by one month, twelve healthy subjects performed three 30-s sprints with 20-min rest between bouts. In randomized order, they consumed a drink with essential amino acids and maltodextrin (nutrient) or flavored water (placebo). Muscle biopsies were obtained 80 and 200 min after the last sprint and blood samples were taken repeatedly during the experiment. Fractional synthetic rate (FSR) was measured by continuous infusion of L-[(2)H5]-phenylalanine up to 200 min postexercise. The mRNA and protein expression of SNAT2 were both 1.4-fold higher (P < 0.05) after nutrient intake compared to placebo at 200 min postexercise. Phosphorylated Akt, mTOR and p70S6k was 1.7- to 3.6-fold higher (P<0.01) 80 min after the last sprint with nutrient ingestion as compared to placebo. In addition, FSR was higher (P<0.05) with nutrients when plasma phenylalanine (FSRplasma) was used as a precursor, but not when intracellular phenylalanine (FSRmuscle) was used. Significant correlations were also found between FSRplasma on the one hand and plasma leucine and serum insulin on the other hand in the nutrient condition. The results show that nutrient ingestion induces the expression of the amino acid transporter SNAT2, stimulates Akt/mTOR signaling and most likely the rate of muscle protein synthesis following sprint exercise.
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| 6. |
- Rundqvist, Håkan C., et al.
(author)
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Systemic Effect On Myotube Size After Sprint Exercise Combined With Nutrients
- 2018
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In: Medicine & Science in Sports & Exercise. - : Lippincott Williams & Wilkins. - 0195-9131 .- 1530-0315. ; 50:5S, s. 807-807
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Journal article (other academic/artistic)abstract
- PURPOSE: To study systemic effects of sprint exercise combined with nutrient ingestion on muscle cell hypertrophy. It was hypothesized that the size of human muscle cells increases when they are exposed to post-exercise serum in nutrient but not in placebo condition. Previously studies have shown that oral ingestion of essential amino acids (EAA) and carbohydrate results in higher activation of Akt/mTOR signalling and higher rate of muscle protein synthesis following sprintexercise in humans. Both local and systemic factors may contribute to these effects. Moreover, If the nutrient-induced effects on signalling and muscle protein synthesis result into muscle hypertrophy is not known. In this study we “isolate” the systemic effects by exposing cultured muscle cells for post sprint exercise serum from either nutrient ingestions or placebo.METHODS: This study is based on a previous study, were healthy subjects performed three 30-s sprints with 20 minutes rest in between. Subjects ingested a flavoured drink containing EAA and maltodextrin (nutrient) or only flavoured water (placebo) during the sprint exercise session up to 15 min after the last sprint in a randomized order with one month interval. Blood samples were collected before during and up to 200 minutes after the last sprint and were analyzed for EEA, insulin lactate and glucose. Human myoblasts were isolated from vastus lateralis and differentiated into multinucleated myotubes, which were cultured in serum collected from 5 subjects fromthe sprint exercise study described above. Blood samples, obtained at 80 min after the last sprint, were chosen since the peak values for the accumulation of insulin and EAA occur approximately atthat time point.RESULTS: Both serum insulin (6-fold; P<0.05) and plasma leucine levels (2.6-fold; P<0.01) were higher after nutrient compared to placebo 80 min post-exercise. Plasma lactate and glucose levels did not differ between the conditions. Myotube size was 16% larger after exposure to post sprint exercise serum obtained during nutrient as compared to placebo (P<0.05).CONCLUSIONS: Systemic factors may stimulate muscle hypertrophy after sprint exercise when combined with nutrient ingestion. If such a systemic effect may be counteracted by intracellular metabolic perturbations after sprint exercise is not known.
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| 7. |
- Stenkula, Karin G., et al.
(author)
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Postprandial triglyceride levels rather than fat distribution may reflect early signs of disturbed fat metabolism in Iraqi immigrants
- 2022
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In: Lipids in Health and Disease. - : Springer Science and Business Media LLC. - 1476-511X. ; 21, s. 1-12
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Journal article (peer-reviewed)abstract
- Purpose: Previous studies have shown that at a similar body mass index, Middle Eastern immigrants are more insulin resistant and at higher risk for type 2 diabetes (T2D) than native Europeans. Insulin resistance is strongly associated with disturbed fat metabolism and cardiovascular disease (CVD). However, fat metabolism is poorly investigated comparing Middle Eastern and European ethnicities. Methods: This observational study included 26 Iraqi and 16 Swedish-born men without T2D or clinical risk factors for CVD. An oral fat tolerance test (OFTT) was performed, where plasma triglycerides (p-TG) were measured for 6 h. mRNA expression and adipocyte size were measured in subcutaneous adipose tissue biopsies collected prior to OFTT, and magnetic resonance imaging was conducted to assess body fat distribution. Results: The median p-TG accumulation was higher and the clearance slower among Iraqis than Swedes. None of the groups reached their fasting p-TG (Iraqis 1.55 mmol/l; Swedes 0.95 mmol/l) after 6 h (Iraqis p-TG 3.10 mmol/l; Swedes p-TG 1.50 mmol/l). Adipocyte size, mRNA expression, and fat accumulation in the liver, muscle and abdomen were similar in both groups. Conclusion: Postprandial p-TG levels rather than fat distribution may reflect early signs of disturbed fat metabolism in Iraqi immigrants without CVD risk factors.
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