| 1. |
- Dent, Jessica R., et al.
(författare)
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Sex differences in acute translational repressor 4E-BP1 activity and sprint performance in response to repeated-sprint exercise in team sport athletes
- 2015
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Ingår i: Journal of Science and Medicine in Sport. - : Elsevier BV. - 1440-2440 .- 1878-1861. ; 18:6, s. 730-736
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: The physiological requirements underlying soccer-specific exercise are incomplete and sex-based comparisons are sparse. The aim of this study was to determine the effects of a repeated-sprint protocol on the translational repressor 4E-BP1 and sprint performance in male and female soccer players.Design: Cross-over design involving eight female and seven male university soccer players.Methods: Participants performed four bouts of 6x 30-m maximal sprints spread equally over 40 min. Heart rate, sprint time and sprint decrement were measured for each sprint and during the course of each bout. Venous blood samples and muscle biopsies from the vastus lateralis were taken at rest, at 15 min and 2 h post-exercise. Results: While males maintained a faster mean sprint time for each bout (P < 0.05) females exhibited a greater decrement in sprint performance for each bout (P < 0.05), indicating a superior maintenance of sprint performance in males, with no sex differences for heart rate or lactate. Muscle analyses revealed sex differences in resting total (P< 0.05) and phosphorylated (P< 0.05) 4E-BP1 Thr37/46, and 15 min post-exercise the 4E-BP1 Thr37/46 ratio decreased below resting levels in males only (P < 0.05), indicative of a decreased translation initiation following repeated sprints.Conclusions: We show that females have a larger sprint decrement indicating that males have a superior ability to recover sprint performance. Sex differences in resting 4E-BP1 Thr37/46 suggest diversity in the training-induced phenotype of the muscle of males and females competing in equivalent levels of team-sport competition.
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| 2. |
- Edge, J, et al.
(författare)
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Ammonium chloride ingestion increases resting mRNA content but attenuates exercise-induced mRNA levels in human skeletal muscle
- 2015
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 10:12
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Tidskriftsartikel (refereegranskat)abstract
- Minimizing the decrease in intracellular pH during high-intensity exercise training promotes greater improvements in mitochondrial respiration. This raises the intriguing hypothesis that pH may affect the exercise-induced transcription of genes that regulate mitochondrial biogenesis. Eight males performed 10x2-min cycle intervals at 80% intensity on two occasions separated by ~2 weeks. Participants ingested either ammonium chloride (ACID) or calcium carbonate (PLA) the day before and on the day of the exercise trial in a randomized, counterbalanced order, using a crossover design. Biopsies were taken from the vastus lateralis muscle before and after exercise. The mRNA level of peroxisome proliferator-activated receptor co-activator 1α (PGC-1α), citrate synthase, cytochome c and FOXO1 was elevated at rest following ACID (P<0.05). During the PLA condition, the mRNA content of mitochondrial- and glucose-regulating proteins was elevated immediately following exercise (P<0.05). In the early phase (0–2 h) of post-exercise recovery during ACID, PGC-1α, citrate synthase, cytochome C, FOXO1, GLUT4, and HKII mRNA levels were not different from resting levels (P>0.05); the difference in PGC-1α mRNA content 2 h post-exercise between ACID and PLA was not significant (P = 0.08). Thus, metabolic acidosis abolished the early post-exercise increase of PGC-1α mRNA and the mRNA of downstream mitochondrial and glucose-regulating proteins. These findings indicate that metabolic acidosis may affect mitochondrial biogenesis, with divergent responses in resting and post-exercise skeletal muscle.
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| 3. |
- Hawke, Emma, et al.
(författare)
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Acidosis and cell signalling
- 2009
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Ingår i: Proceedings of 14th International Biochemistry of Exercise Conference, Muscles as Molecular and Metabolic Machines. Guelph, Canada. Appl Physiol Nutr Metab 2009 Jun 34(3):307-492. - Canadian Science Publishing (NRC Research Press) : Canadian Science Publishing. ; , s. 307-492-
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Konferensbidrag (refereegranskat)
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| 4. |
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| 5. |
- Hawke, Emma, et al.
(författare)
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Effects of induced changes in acid-base balance on mitochondrial adaptations to training
- 2014
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Ingår i: Book of Abstracts of the 19th annual congress of the European College of Sport Science – ECSS Amsterdam 2014. - European College of Sport Science.
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Konferensbidrag (refereegranskat)abstract
- IntroductionEndurance training leads to an improved ability of muscle to utilize oxygen. This is related to an increased density and function of mitochondria. The biogenesis and adaptation of mitochondria is a complex process mediated by various signalling pathways and seems to be highly sensitive to the type of exercise and the local environment in the muscle. Changes in the muslce environment in terms of altered metabolism and substrate accumulation are affected by changes in acid/base balance in response to exercise. Recent studies have shown that changes in acid/base balance may affect the regulation of mitochondrial adaptation to acute exercise; however, how this responds to training and relates to performance adaptations in humans is unclear. Similarly, the effect of acid/base balance on mechanisms underlying mitochondrial biogenesis is unclear. The objectives of this study were to examine the relationship between acid/base balance, mitochondrial biogenesis and adaptation.MethodsNineteen recreationally active men undertook a six-week periodised high-intensity interval training programme, a protocol known to produce increases in mitochondrial biogenesis. Participants were matched for aerobic fitness and randomly assigned to one of two different training groups. One group ingested sodium bicarbonate (alkaline) and the other group ingested a placebo prior to each training session. Performance test results, blood samples and muscle biopsies were collected before and after the six week training period and assessed for changes in aerobic fitness, blood metabolites and muscle markers of mitochondrial function and biogenesis. Changes in gene expression associated with mitochondrial biogenesis were also examined. ResultsAfter the training period, there were significant (P < 0.05) improvements in TTF, Wmax and LT in both groups, citrate synthase activity in the alkaline group and VO2peak in the placebo group. Improvements were also seen in citrate synthase activity in the placebo group and VO2peak in the alkaline group, however these did not reach significance (P = 0.089 and 0.066 respectively).Despite these significant changes within groups in response to training, there were no significant differences between groups.DiscussionBoth training groups showed substantial changes in performance and physiological measures following the training period, however, suppressing exercise-induced acidosis during training did not significantly improve mitochondrial adaptations or performance in comparison to the placebo condition. However, there was a large degree of individual variation in the response and there were trends towards greater adaptations when exercise-induced acidosis was attenuated.
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| 6. |
- Hawke, Emma, et al.
(författare)
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The effects of sex and repeated-sprints on muscle protein signalling
- 2009
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Ingår i: Book of Abstracts of the 14th Annual Congress of the European College of Sport Science, Oslo, Norway, June 2009. Sport Sciences: Nature, Nuture and Culture. - European College of Sport Science. ; , s. 351-352
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Konferensbidrag (refereegranskat)
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| 7. |
- Hawke, Emma, 1975-
(författare)
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Training-induced increase in mitochondrial biogenesis
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Endurance training leads to an improved ability of muscle to utilize oxygen. This is related to an increased density and function of mitochondria. The biogenesis and adaptation of mitochondria is a complex process mediated by various signalling pathways and seems to be highly sensitive to the type of exercise and the local environment in the muscle. Changes in the muslce environment in terms of altered metabolism and substrate accumulation are affected by changes in acid/base balance in response to exercise. Recent studies have shown that changes in acid/base balance may affect the regulation of mitochondrial adaptation to acute exercise; however, how this responds to training and relates to performance adaptations in humans is unclear. Similarly, the effect of acid/base balance on molecular mechanisms underlying mitochondrial biogenesis is unclear. The objectives of this thesis were to examine the relationship between acid/base balance, mitochondrial biogenesis and adaptation and explore the mechanisms which regulate mitochondrial adaptation. To realize these aims a series of related investigations were undertaken. Initially, cultured L6 myotubes were used to assess perturbations of the signaling pathways involved in mitochondrial biogenesis, as a result of alterations in acid/base balance, alone and in combination with lactate. The combined effects of elevated lactate and lowered pH resulted in greater activation of signaling pathways than the effects of altering either lactate or pH alone. These results support previous findings that propose lactate as an important initiator of signaling cascades for the transcription of genes involved in mitochondrial biogenesis. Further, they also indicate that exercise-induced production of lactate and lowering of pH may be important activators of cell signaling involved in muscle adaptation. In a second study, the effects of artificially lowered pH on pre- and post-exercise expression of regulators and downstream target genes involved in mitochondrial biogenesis were assessed. Participants performed high-intensity interval exercise on two separate occasions, following the ingestion of either ammonium chloride or placebo the day before and on the day of the exercise trial in a randomised, counterbalanced order. The mRNA content of PGC-1α, citrate synthase (CS), cytochrome c (CYT-C), hexokinase II (HKII)and glucose transporter 4 (GLUT4) were determined in biopsies taken from the vastus lateralis muscle before, immediately after exercise and during recovery. Results indicated that acidosis increases the expression of PGC-1α and downstream target genes involved in mitochondrial biogenesis at rest, but suppresses the normal increased gene response following high-intensity exercise. These findings indicate that lowered pH may interfere with exercise-induced mitochondrial biogenesis. Finally an intensive training study was conducted to determine whether impeding exercise-induced acidosis during training alters adaptations in mitochondrial function and performance. Another group of participants undertook a six-week periodised high-intensity interval training programme, a protocol known to produce increases in mitochondrial biogenesis. Participants were matched for aerobic fitness and randomly assigned to one of two different training groups. One group ingested sodium bicarbonate and the other group ingested a placebo prior to each training session. Performance tests, blood and muscle biopsies were collected before and after the six week training period and assessed for changes in aerobic fitness, blood metabolites and muscle markers of mitochondrial function and biogenesis. Both training groups showed substantial changes in performance and physiological measures following the training period, however, suppressing exercise-induced acidosis during training did not significantly improve mitochondrial adaptations or performance in comparison to the placebo condition. However, there was a large degree of individual variation in the response and there were trends towards greater adaptations when exercise-induced acidosis was attenuated. The findings from these series of studies show that signaling cascades are influenced by alterations in acid/base balance, alone and in combination with lactate. Skeletal muscle cell-signalling and gene expression networks are extremely complex with multiple points of regulation and signal divergence. Although at this stage the exact mechanism by which acid/base balance plays a role in altering the signaling mechanisms which regulate mitochondrial function, biogenesis and muscle adaptation are unclear, these studies show that the interaction of altered hydrogen ion concentration and substrate accumulation and utilisation plays an important role in mitochondrial adaptation to training.
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| 8. |
- Patten, Christopher, 1968-, et al.
(författare)
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How close is close? : an experimental study of cycling safety related to cycling on rural roads
- 2018
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Konferensbidrag (refereegranskat)abstract
- In Sweden, as well as in many countries in Scandinavia and in northern Europe, there is a growing trend towards daily sport and exercise cycling and cycle commuting. Cycling on rural roads is, whether for health, exercise, sports, leisure or commuting, is hampered by feelings of insecurity and risk caused by motorised traffic passing too close to the cyclist sharing the rural road. A cyclist is often overtaken by cars and other motorised vehicles and does not have control over the distance between them and the other vehicles. However, if the cyclist had control over the distance between themselves and the motor vehicle/object, how much space would they give themselves?The aim of this study was to investigate a scenario where the cyclists had control over the distance between themselves and a fictive motor vehicle or road side object and assess how much space they would give themselves.
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| 9. |
- Stannard, S, et al.
(författare)
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The effect of galactose supplementation on endurance cycling performance
- 2009
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Ingår i: European Journal of Clinical Nutrition. - : Nature Publishing Group. - 0954-3007 .- 1476-5640. ; 63:2, s. 209-214
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES:This study tested the hypothesis that supplementation with galactose before and during endurance exercise would spare carbohydrate (CHO), optimize fat utilization and improve performance compared with a typical sports drink formulation.SUBJECTS:Nine well-trained cyclists undertook three trials, each consisting of 120 min at 65 VO(2max) followed immediately by a set work, self-paced time trial (TT). Three treatments, allocated as a randomized balanced design, consisted of the following: (a) 8% (w/w) solution of galactose (Gal); (b) 8% solution of 50% galactose/50% glucose (Gluc/Gal); and (c) 8% solution of 80% glucose/20% fructose (Gluc/Fru). These were consumed as 0.67 g CHO per kg body wt 45-min pre-exercise; 1.0 g CHO per kg body wt per h for the first 120 min of exercise; 0.33 g CHO per kg body wt during the TT. Blood samples were collected before and during exercise; respiratory gas samples were collected only during fixed workload exercise.RESULTS:Mean TT power output was significantly less in Gal compared with Gluc/Gal (P=0.030). Blood glucose and insulin concentrations were lower, and free fatty acids higher in Gal compared with Gluc/Gal and Gluc/Fru. Respiratory exchange ratio was not significantly different between trials.CONCLUSIONS:Ingestion of an 8% galactose-only solution (12.5 ml per kg body wt per h) is detrimental to endurance performance compared with equivalent volumes of iso-osmotic solutions containing 50% galactose/50% glucose or 80% glucose/20% fructose. This may reflect the inability of the liver to convert galactose into glucose at a rate required to support strenuous exercise intensity.
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| 10. |
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