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  • 151.
    Psilander, Niklas
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Kristoffer, Toldnes Cumming
    NIH, Norwegian School of Sport and Health Sciences, Oslo, Norway.
    Engström, Björn
    Capio Atro Clinic, Sophiahemmet, Stockholm, Sweden.
    Ekblom, Björn
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Raastad, Truls
    2NIH, Norwegian School of Sport and Health Sciences, Oslo, Norway .
    Retention of myonuclei after grave atrophy in human skeletal muscle, a case study2017Inngår i: Acta Physiologica Volume 219, Issue S710 February 2017, 2017, Vol. 219, s. 14-43Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Introduction: the current textbook model suggests that the myonuclear domain size is constant for muscle fibers in both their atrophic and hypertrophic state. However, recent animal studies show that myonuclear content is maintained after atrophy leading to a decreased myonuclear domain size (Gundersen et al. J Physiol. 2008 Jun 1;586(11):2675-81). This remains to be investigated in human skeletal muscle and the aim of the present study was therefore to study the effect of grave atrophy on myonuclear content and domain size in the vastus medialis muscle.

    Materials and Methods: biopsies were obtained from vastus medialis on a 22 year old female patient before and 6 weeks after an anterior cruciate ligament reconstructionand meniscus repair surgery. Histochemical analyses were done to analyze fiber cross sectional area (CSA), fiber type composition and number of myonuclei per fiber.

    Results: the CSA of type II muscle fibers decreased by 35% (from 4297±55 to 2807±64 µm2) whereas the number of myonuclei per fiber remained stable (3.4±0.4 and 3.9±0.5, pre and post respectively). The nuclear domain size was thereby decreased by ~40% (from 1255 to 722 µm2). There were only minor changes in type I muscle fiber CSA, myonuclei content and domain size.

    Conclusion: in line with previous findings from animal studies, the present case study shows that the number of myonuclei per fiber is maintained and the domain size is reduced in human skeletal muscle after immobilization induced atrophy.

  • 152.
    Psilander, Niklas
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Forskningsgruppen Mitokondriell funktion och metabolisk kontroll.
    Wang, Li
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Forskningsgruppen Mitokondriell funktion och metabolisk kontroll.
    Westergren, Jens
    Tonkonogi, Michail
    Sahlin, Kent
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Forskningsgruppen Mitokondriell funktion och metabolisk kontroll.
    Mitochondrial gene expression in elite cyclists: effects of high-intensity interval exercise.2010Inngår i: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 110, nr 3, s. 597-606Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Little is known about the effect of training on genetic markers for mitochondrial biogenesis in elite athletes. We tested the hypothesis that low-volume sprint interval exercise (SIE) would be as effective as high-volume interval exercise (IE). Ten male cyclists competing on national elite level (W (max) 403 ± 13 W, VO(2peak) 68 ± 1 mL kg(-1) min(-1)) performed two interval exercise protocols: 7 × 30-s "all-out" bouts (SIE) and 3 × 20-min bouts at ~87% of VO(2peak) (IE). During IE, the work was eightfold larger (1,095 ± 43 vs. 135 ± 5 kJ) and the exercise duration 17 times longer (60 vs. 3.5 min) than during SIE. Muscle samples were taken before and 3 h after exercise. The mRNA of upstream markers of mitochondrial biogenesis [peroxisome proliferator-activated receptor-γ coactivator-1 (PGC-1α), PGC-1α-related coactivator (PRC) and peroxisome proliferator-activated receptor δ (PPARδ)] increased to the same extent after SIE and IE (6-, 1.5- and 1.5-fold increase, respectively). Of the downstream targets of PGC-1α, mitochondrial transcription factor A (Tfam) increased only after SIE and was significantly different from that after IE (P < 0.05), whereas others increased to the same extent (pyruvate dehydrogenase kinase, PDK4) or was unchanged (nuclear respiratory factor 2, NRF2). We conclude that upstream genetic markers of mitochondrial biogenesis increase in a similar way in elite athletes after one exercise session of SIE and IE. However, since the volume and duration of work was considerably lower during SIE and since Tfam, the downstream target of PGC-1α, increased only after SIE, we conclude that SIE might be a time-efficient training strategy for highly trained individuals.

  • 153.
    Rajamäki, Niklas
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Styrketräning via ocklusion: en metod för effektivisering av styrketräning2007Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Syfte och frågeställningar

    Syftet med undersökningen har varit att jämföra två olika styrketräningsmetoder med olika grader av ocklusion för träning av musculus (m.) biceps brachii med avseende på styrka och hypertrofi.

    - Vilken av de två träningsmetoderna påverkar mest effektivt biceps brachiis styrkeutveckling?

    - Vilken av de två träningsmetoderna påverkar mest effektivt biceps brachiis storlek?

    Metod

    Sju manliga försökspersoner fördelade på två grupper (tre i relaxationsgruppen, fyra i kontraktionsgruppen) fick genomgå två tester för att mäta maximal styrka i m. biceps brachii samt ett test för att mäta överarmens omkrets. Därefter fick de träna specifik bicepsträning tre gånger i veckan under fem veckor för att åter testas. Skillnaden i träning för de båda grupperna bestod av en tydlig relaxation (avslappning) en gång under varje rörelsecykel för relaxationsgruppen (relaxationen varade i ca en sekund och utfördes då hanteln var längst ner i rörelsen) medan kontraktionsgruppen ombeddes att kontrahera (spänna) muskeln under hela rörelseförloppet. För- och eftertest jämfördes mot varandra i ett beroende T-test även ökningen i träningsbelastning jämfördes mellan det andra och fjortonde passet. Därefter jämfördes förändringen mellan grupperna.

    Resultat

    Den enda signifikanta förändringen i båda träningsgrupperna för sig noterades i det funktionella testet, med en ökning av den maximala styrkan (p=0,03 för kontraktionsgruppen; p=0,03 för relaxationsgruppen). En ökning av totalbelastningen i antal kg per träningspass noterades, men ökningarna var inte signifikanta. Vid en jämförelse av träningseffekterna av relaxations- och kontraktionsträning av biceps brachii tillsammans uppnåddes statistisk signifikans såväl avseende ökning av omkrets (p=0,0136), för maximal styrka (p=0,0002) som för den totala belastningen mellan det andra och fjortonde träningspasset (p= 0,0293).

    Slutsats

    Sammanfattningsvis kan det konstateras att inga tydliga skillnader mellan träningsgrupperna kunnat urskiljas. Om resultaten för de båda träningsgrupperna sammanvägs uppnås en signifikant ökning av såväl omkrets som maximal styrka.

  • 154. Reilly, Thomas
    et al.
    Ekblom, Björn
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Björn Ekbloms forskningsgrupp.
    The use of recovery methods post-exercise.2005Inngår i: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 23, nr 6, s. 619-27Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Competitive soccer engages many of the body's systems to a major extent. The musculoskeletal, nervous, immune and metabolic systems are stressed to a point where recovery strategies post-exercise become influential in preparing for the next match. Intense activity at a 7-day training camp causes participants to experience lowered concentrations of non-killer cells and T-helper cells. Two consecutive games in 24 h produce disturbances in the testosterone-cortisol ratio. When competitive schedules are congested, the recovery process should be optimized for performance capabilities to be restored to normal as soon as possible. There is evidence that glycogen stores are reduced near to depletion at the end of a soccer game and that a diet high in carbohydrates can aid recovery. Water alone is not the best means of restoring body fluids, since carbohydrate-electrolyte drinks display better intestinal absorption and reduce urine output. Some relief from muscle soreness may be achieved by means of a warm-down. Deep-water running regimens can replace conventional physical training in the days after competition. Massage, cryotherapy and alternative therapies have not been shown to be consistently effective. It is concluded that optimizing recovery post-exercise depends on a combination of factors that incorporate a consideration of individual differences and lifestyle factors. The procedures to facilitate recovery processes should start immediately the game or training finishes. Match administrators and tournament planners should consider the stressful consequences for players in periods of congested fixtures and alleviate the physiological strain as far as possible by allowing 72 h between competitive games. This frequency of competition is unlikely to be sustainable in the long term.

  • 155. Rosenbloom, Christine A
    et al.
    Loucks, Anne B
    Ekblom, Björn
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Björn Ekbloms forskningsgrupp.
    Special populations: the female player and the youth player.2006Inngår i: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 24, nr 7, s. 783-93Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Females and youth are frequently described as "special" populations in football literature, but together these two populations outnumber male players. What makes females "special" is that they tend to eat less when training and competing than their male counterparts, leading to lower intakes of energy, carbohydrate, and some nutrients. Youth football players are special in regard to energy and nutrient requirements to promote growth and development, as well as to fuel sport. There is limited research on the dietary habits of these two populations, but the available literature suggests that many female and youth players need to increase carbohydrate intake, increase fluid intake, and develop dietary habits to sustain the demands of training and competition.

  • 156.
    Rundqvist, Håkan Claes
    et al.
    Karolinska Institutet .
    Esbjörnsson, Mona
    Karolinska Institutet .
    Rooyackers, Olav
    Huddinge University Hospital .
    Osterlund, Ted
    Karolinska Institutet.
    Moberg, Marcus
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Åstrandlaboratoriet, Eva Blomstrands forskningsgrupp.
    Apró, William
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Åstrandlaboratoriet, Eva Blomstrands forskningsgrupp.
    Blomstrand, Eva
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Åstrandlaboratoriet, Eva Blomstrands forskningsgrupp.
    Jansson, Eva
    Karolinska Institutet .
    Influence of nutrient ingestion on amino acid transporters and protein synthesis in human skeletal muscle after sprint exercise2017Inngår i: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 123, nr 6, s. 1501-1515Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 157. Râdegran, Göran
    et al.
    Blomstrand, Eva
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Eva Blomstrands forskningsgrupp.
    Saltin, Bengt
    Peak muscle perfusion and oxygen uptake in humans: importance of precise estimates of muscle mass.1999Inngår i: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 87, nr 6, s. 2375-80Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The knee extensor exercise model was specifically developed to enable in vivo estimates of peak muscle blood flow and O(2) uptake in humans. The original finding, using thermodilution measurements to measure blood flow in relation to muscle mass [P. Andersen and B. Saltin. J. Physiol. (Lond.) 366: 233-249, 1985], was questioned, however, as the measurements were two- to threefold higher than those previously obtained with the (133)Xe clearance and the plethysmography technique. As thermodilution measurements have now been confirmed by other methods and independent research groups, we aimed to address the impact of muscle mass estimates on the peak values of muscle perfusion and O(2) uptake. In the present study, knee extensor volume was determined from multiple measurements with computer tomography along the full length of the muscle. In nine healthy humans, quadriceps muscle volume was 2.36 +/- 0.17 (range 1. 31-3.27) liters, corresponding to 2.48 +/- 0.18 (range 1.37-3.43) kg. Anthropometry overestimated the muscle volume by approximately 21-46%, depending on whether quadriceps muscle length was estimated from the patella to either the pubic bone, inguinal ligament, or spina iliaca anterior superior. One-legged, dynamic knee extensor exercise up to peak effort of 67 +/- 7 (range 55-100) W rendered peak values for leg blood flow (thermodilution) of 5.99 +/- 0.66 (range 4.15-9.52) l/min and leg O(2) uptake of 856 +/- 109 (range 590-1,521) ml/min. Muscle perfusion and O(2) uptake reached peak values of 246 +/- 24 (range 149-373) and 35.2 +/- 3.7 (range 22.6-59. 6) ml. min(-1). 100 g muscle(-1), respectively. These peak values are approximately 19-33% larger than those attained by applying anthropometric muscle mass estimates. In conclusion, the present findings emphasize that peak perfusion and O(2) uptake in human skeletal muscle may be up to approximately 30% higher than previous anthropometric-based estimates that use equivalent techniques for blood flow measurements.

  • 158.
    Sahlin, Kent
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Forskningsgruppen Mitokondriell funktion och metabolisk kontroll.
    Control of lipid oxidation at the mitochondrial level.2009Inngår i: Applied physiology, nutrition, and metabolism = Physiologie appliquée, nutrition et métabolisme, ISSN 1715-5312, Vol. 34, nr 3, s. 382-8Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The rate of lipid oxidation during exercise is controlled at several sites, and there is a reciprocal dependency between oxidation of lipids and carbohydrates (CHO). It is well known that the proportion of the 2 fuels oxidized is influenced by substrate availability and exercise intensity, but the mechanisms regulating fuel preferences remain unclear. During intense exercise, oxidation of long-chain fatty acids (LCFAs) decreases, and the major control is likely to be at the mitochondrial level. Potential mitochondrial sites for control of lipid oxidation include transport of LCFAs into mitochondrial matrix, beta-oxidation, the tricarboxylic acid cycle, and the electron transport chain (ETC). CHO catabolism may impair lipid oxidation by interfering with the transfer of LCFAs into mitochondria and by competing for mutual cofactors (i.e., nicotinamide adenine dinucleotide and (or) coenzyme A (CoA)). The different effect of energy state on the catabolism of CHO and lipids is likely to be of major importance in explaining the shift in fuel utilization during intensive exercise. Formation of acetyl-CoA from CHO is activated by a low energy state, and will lead to accumulation of products that are inhibitory to lipid oxidation. In contrast, beta-oxidation of LCFAs to acetyl-CoA is not stimulated by a low energy state. Further interaction between CHO and LCFAs may occur by substrate competition for electron carriers at ETC, due to provisions of electrons through different complexes. Feedback inhibition of beta-oxidation by redox state is thought to be an important mechanism for the slowing of lipid oxidation during intensive exercise.

  • 159.
    Sahlin, Kent
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Åstrandlaboratoriet, Forskningsgruppen Mitokondriell funktion och metabolisk kontroll. Karolinska institutet.
    Fernström, Maria
    Karolinska institutet.
    Svensson, Michael
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap. Karolinska institutet.
    Tonkonogi, Michail
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap. Karolinska institutet.
    No evidence of an intracellular lactate shuttle in rat skeletal muscle.2002Inngår i: Journal of Physiology, ISSN 0022-3751, E-ISSN 1469-7793, Vol. 541, nr Pt 2, s. 569-74Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The concerted view is that cytosolic pyruvate is transferred into mitochondria and after oxidative decarboxylation further metabolized in the tricarboxylic acid cycle. Recently this view has been challenged. Based on experimental evidence from rat skeletal muscle it has been concluded that mitochondria predominantly oxidize lactate in vivo and that this constitutes part of an 'intracellular lactate shuttle'. This view appears to be gaining acceptance in the scientific community and due to its conceptual importance, confirmation by independent experiments is required. We have repeated the experiments in mitochondria isolated from rat soleus muscle. Contrary to the previously published findings we cannot find any mitochondrial respiration with lactate. Analysis of lactate dehydrogenase (LDH) by spectrophotometry demonstrated that the activity in the mitochondrial fraction was only 0.7 % of total activity. However, even when external LDH was added to mitochondria, there were no signs of respiration with lactate. In the presence of conditions where lactate is converted to pyruvate (external additions of both LDH and NAD(+)), mitochondrial oxygen consumption increased. Furthermore, we provide theoretical evidence that direct mitochondrial lactate oxidation is energetically unlikely. Based on the present data we conclude that direct mitochondrial lactate oxidation does not occur in skeletal muscle. The presence of an 'intracellular lactate shuttle' can therefore be questioned.

  • 160.
    Sahlin, Kent
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Forskningsgruppen Mitokondriell funktion och metabolisk kontroll.
    Harris, R C
    Control of lipid oxidation during exercise: role of energy state and mitochondrial factors.2008Inngår i: Acta physiologica (Oxford, England), ISSN 1748-1716, Vol. 194, nr 4, s. 283-91Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Despite considerable progress during recent years our understanding of how lipid oxidation (LOx) is controlled during exercise remains incomplete. This review focuses on the role of mitochondria and energy state in the control of LOx. LOx increases in parallel with increased energy demand up to an exercise intensity of about 50-60% of VO(2max) after which the contribution of lipid decreases. The switch from lipid to carbohydrate (CHO) is of energetic advantage due to the increased ATP/O(2) yield. In the low-intensity domain (<50%VO(2max)) a moderate reduction in energy state will stimulate both LOx and CHO oxidation and relative fuel utilization is mainly controlled by substrate availability and the capacity of the metabolic pathways. In the high-intensity domain (>60%VO(2max)) there is a pronounced decrease in energy state, which will stimulate glycolysis in excess of the substrate requirements of the oxidative processes. This will lead to acidosis, reduced levels of free Coenzyme A (CoASH) and reduced levels of free carnitine. Acidosis and reduced carnitine may limit the carnitine-mediated transfer of long-chain fatty acids (LCFA) into mitochondria and may thus explain the observed reduction in LOx during high-intensity exercise. Another potential mechanism, suggested in this review, is that Acyl-CoA synthetase (ACS), an initial step in LCFA catabolism, functions as a regulator of LOx. ACS activity is suggested to be under control of CoASH and energy state. Furthermore, evidence exists that additional control points exist beyond mitochondrial FA influx. The nature and site of this control remain to be investigated.

  • 161.
    Sahlin, Kent
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Forskningsgruppen Mitokondriell funktion och metabolisk kontroll.
    Sallstedt, E-K
    Bishop, D
    Tonkonogi, Michail
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Turning down lipid oxidation during heavy exercise--what is the mechanism?2008Inngår i: Journal of physiology and pharmacology : an official journal of the Polish Physiological Society, ISSN 1899-1505, Vol. 59 Suppl 7, s. 19-30Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A high potential for lipid oxidation is a sign of metabolic fitness and is important not only for exercise performance but also for health promotion. Despite considerable progress during recent years, our understanding of how lipid oxidation is controlled remains unclear. The rate of lipid oxidation reaches a peak at 50-60% of V(O2 max) after which the contribution of lipids decreases both in relative and absolute terms. In the high-intensity domain (>60% V(O2 max)), there is a pronounced decrease in energy state, which will stimulate the glycolytic rate in excess of the substrate requirements of mitochondrial oxidative processes. Accumulation of glycolytic products will impair lipid oxidation through an interaction with the carnitine-mediated transfer of FA into mitochondria. Another potential site of control is Acyl-CoA synthetase (ACS), which is the initial step in FA catabolism. The activity of ACS may be under control of CoASH and energy state. There is evidence that additional control points exist beyond mitochondrial influx of fatty acids. The electron transport chain (ETC) with associated feed-back control by redox state is one suggested candidate. In this review it is suggested that the control of FA oxidation during heavy exercise is distributed between ACS, CPT1, and ETC.

  • 162.
    Sahlin, Kent
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Forskningsgruppen Mitokondriell funktion och metabolisk kontroll.
    Seger, Jan
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Effects of prolonged exercise on the contractile properties of human quadriceps muscle.1995Inngår i: European Journal of Applied Physiology and Occupational Physiology, ISSN 0301-5548, E-ISSN 1432-1025, Vol. 71, s. 180-186Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The contractile properties of the quadriceps muscle were measured in seven healthy male subjects before, during and after prolonged cycling to exhaustion. Special efforts were made to obtain measurements immediately after exercise. The exercise intensity corresponded to about 75% of estimated maximal O2 uptake and time to exhaustion was mean 85 (SEM 9) min. At the end of the cycling heart rate and perceived exertion for the legs were 94% and 97% of maximal values, respectively. Maximal voluntary isometric force (MVC) had decreased after 5 min of exercise to a mean 91 (SEM 4)% of the pre-exercise value (P < 0.05) and decreased further to a mean 82 (SEM 6) and mean 66 (SEM 5)% after 40-min cycling and at exhaustion, respectively. A new finding was that during recovery reversal of MVC occurred in different phases where the half recovery time of the initial rapid phase was about 2 min. The MVC was a mean 80 (SEM 2)% of the pre-exercise value after 30 min and was not affected by superimposed electrical stimulation. Maximal voluntary concentric and eccentric forces decreased to 74% and 80% of initial values at exhaustion (P < 0.05). The kinetics of isometric contraction expressed as the time between 5% and 50% of tension (rise time) and the time between 95% and 50% of tension (relaxation time) were not significantly affected by the prolonged cycling. The electromechanical delay measured as the time between the first electrical stimulus and 5% of tension decreased from a mean 32 (SEM 1) ms at rest to a mean 26.6 (SEM 0.6) ms at fatigue (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

  • 163.
    Sahlin, Kent
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Åstrandlaboratoriet, Forskningsgruppen Mitokondriell funktion och metabolisk kontroll.
    Shabalina, Irina G
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Åstrandlaboratoriet. Stockholm University.
    Mattsson, C Mikael
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Åstrandlaboratoriet, Björn Ekbloms forskningsgrupp.
    Bakkman, Linda
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Åstrandlaboratoriet. Karolinska Institutet.
    Fernström, Maria
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Åstrandlaboratoriet. Karolinska Institutet.
    Rozhdestvenskaya, Zinaida
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Åstrandlaboratoriet.
    Enqvist, Jonas K
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Åstrandlaboratoriet, Björn Ekbloms forskningsgrupp.
    Nedergaard, Jan
    Stockholm University.
    Ekblom, Björn T
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Åstrandlaboratoriet, Björn Ekbloms forskningsgrupp.
    Tonkonogi, Michail
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Åstrandlaboratoriet. University of Dalarna.
    Ultra-endurance exercise increases the production of reactive oxygen species in isolated mitochondria from human skeletal muscle.2010Inngår i: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 108, nr 4, s. 780-787Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Exercise-induced oxidative stress is important for the muscular adaptation to training but may also cause muscle damage. We hypothesized that prolonged exercise would increase mitochondrial production of reactive oxygen species (ROS) measured in vitro and that this correlates with oxidative damage. Eight male athletes (24-32 years) performed ultra-endurance exercise (kayaking/running/cycling) with an average work intensity of 55% VO2peak for 24 h. Muscle biopsies were taken from vastus lateralis before exercise, immediately after exercise and after 28 h of recovery. The production of H2O2 was measured fluorometrically in isolated mitochondria with the Amplex red and peroxidase system. Succinate-supported mitochondrial H2O2 production was significantly increased after exercise (73% higher, P=0.025) but restored to the initial level at recovery. Plasma level of free fatty acids (FFA) increased 4-fold and exceeded 1.2 mmol l(-1) during the last 6 h of exercise. Plasma FFA at the end of exercise was significantly correlated to mitochondrial ROS production (r=0.74, P<0.05). Mitochondrial content of 4-hydroxy-nonenal-adducts (a marker of oxidative damage) was increased only after recovery and was not correlated with mitochondrial ROS production. Total thiol-group level and glutathione peroxidase activity were elevated after recovery. In conclusion: ultra-endurance exercise increases ROS production in isolated mitochondria but this is reversed after 28 h recovery. Mitochondrial ROS production was not correlated with oxidative damage of mitochondrial proteins, which was increased at recovery but not immediately after exercise. Key words: antioxidative defence, fatty acids, oxidative stress.

  • 164.
    Sahlin, Kent
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Åstrandlaboratoriet, Forskningsgruppen Mitokondriell funktion och metabolisk kontroll.
    Tonkonogi, Michail
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Åstrandlaboratoriet, Forskningsgruppen Mitokondriell funktion och metabolisk kontroll.
    Fernström, Maria
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Åstrandlaboratoriet.
    The leaky mitochondrion.2004Inngår i: Physiology News, Vol. 56, s. 27-28Artikkel i tidsskrift (Annet vitenskapelig)
  • 165.
    Salomonsson Flockhart, Mikael
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Muscle glycogen depletion and resynthesis in highly trained male cyclists2011Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Aim

    The aim of this study was to establish a method to create a difference between groups in muscle glycogen content as well as to investigate the effect of training in low muscle glycogen state on metabolic and physiological parameters.

    Method

    During two trials, a subject group of ten highly trained male road or mountain bike cyclists ((mean±SD) age, hight, body weight, VO2max, and VO2max·kg-1 was 28±5 years, 74.7±6.3 kg, 183±6 cm, 4876±332 mL min-1, 64.4±2.8 mL·kg-1 min-1), performed a glycogen depletion exercise followed by a night’s rest and a second exercise session. In the study, which was a crossover design, the subjects were randomly chosen to perform the first trial on a carbohydrate rich diet or a diet with no of carbohydrates. All the testing was performed on a Monark 839E ergometer bike and muscle biopsy sampling was collected before depletion exercise, before the exercise the following day and three hours post exercise. Plasma FFA and glucose was analyzed from venous blood collected at rest.

    Results

    Muscle glycogen pre depletion exercise was 623±180 and 645±133 mmol·kg dw-1 glycosyl units for non-CHO and CHO trials respectively. The depletion exercise followed by 13 hours of rest resulted in a significant decrease in muscle glycogen in the non-CHO (p<0.0001), and CHO trials (p<0.01) to 166±71 and 478±111 mmol·kg dw-1 respectively. In the non-CHO trial net glycogen depletion correlated positively with pre depletion glycogen storage.  After the completion of exercise 2 and the following three hour rest period, glycogen content in non-CHO and CHO-trial was 130±52 and477±97 mmol·kg dw-1, respectively. In low glycogen state, the non-CHO trial resulted in an increase in FFA measured in blood plasma at rest and in an increase in Borg rating of perceived exertion (RPE) as well as a reduction in blood glucose during exercise. 

    Conclusion

    The protocol used in the present study was successful in creating a difference in muscle glycogen storage and training in low glycogen state was associated with an increase of several physiological parameters indicating a possible impairment of endurance exercise performance.

  • 166.
    Sandberg, Erik
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Är det kul att kunna?: En studie av gymnasieelevers allsidiga rörelsekompetens ur ett motivationsperspektiv.2008Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [en]

    Syfte och frågeställningar

    Studiens syfte har varit att kartlägga gymnasieelevers motivationstyp, allsidiga rörelsekompetens samt grad av fysisk aktivitet i fem klasser på en skola i centrala Stockholm. Frågeställningarna var följande: Finns det skillnader i grad av fysisk aktivitet hos gymnasieeleverna med hög respektive låg allsidig rörelsekompetens? Finns det skillnader i typ av motivationen till idrott och hälsa hos elever med hög respektive låg allsidig rörelsekompetens? Hur ser gymnasieelevernas allsidiga rörelsekompetens ut?

     

    Metod

    Metoderna som använts i studien är observation samt en kvantitativ enkät. Ett bekvämlighetsurval gjordes. Urvalet innehöll fem gymnasieklasser i år två bestående av 138 elever på en kommunal skola i centrala Stockholm. Det externa bortfallet var 54 procent och det interna bortfallet 0 procent. Elevernas allsidiga rörelsekompetens mäts med NyTidstestets version för skolår nio, genom att elevernas utförande av olika rörelsemoment observeras och bedöms av testets funktionärer. Elevernas motivation och grad av fysiska aktivitet mäts med en enkät. De 35 procent lägsta resultaten har jämförts med de 35 procent högsta på NyTidstestet för att undersöka de eventuella skillnaderna hos grupperna. Resultaten har bearbetats statistiskt i SPSS med korstabeller. Den teoretiska utgångspunkt som använts i studien är Robert J Vallerands modell Hierarchical Model of Intrinsic and Extrensic Motivation. Modellen redogör för de olika typerna av motivation, vilka konsekvenser olika typer av motivation får för individen, vilka faktorer som påverkar motivationen samt på vilka nivåer motivationen existerar.

     

    Resultat

    Studien visar att eleverna med högst resultat på NyTidstestet var i större utsträckning måttligt fysiskt aktiva mer än tre timmar i veckan. Studien visar inga signifikanta skillnader i motivationstyp hos eleverna. Enligt NyTidstestet har majoriteten av eleverna en motorik som klassificeras som tillfredställande enligt bedömningskriterierna för NyTidstestet.

     

    Slutsats

    Studien visar ett signifikant samband mellan graden av måttlig fysisk aktivitet och hög respektive låg allsidig rörelsekompetens hos eleverna.

      

    De flesta elever i studien var inre motiverade till idrott och hälsa i första hand och väldigt få var amotiverade i första hand oavsett låg eller hög allsidig rörelsekompetens. De olika typerna av yttre motivation visar att elever med hög allsidig rörelsekompetens i större utsträckning motiveras av identifierad reglering än de med låg samt i lägre utsträckning av introjicerad reglering och yttre reglering. Skillnaderna var inte signifikanta.

     

    Elevernas motorikprofil visar att de som grupp presterar bättre än eleverna i skolår nio i en referensstudie vilket följer den trend som referensstudien fann att elever presterar bättre på NyTidstestet efter hand som de blir äldre, men det höga bortfallet innebär att resultaten istället skulle kunna vara lägre.

  • 167.
    Schantz, Peter
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Capillary supply in hypertrophied human skeletal muscle1982Inngår i: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 114, s. 635-637Artikkel i tidsskrift (Fagfellevurdert)
  • 168.
    Schantz, Peter
    Gymnastik- och idrottshögskolan, GIH.
    Mitokondrierna och träningen1998Inngår i: Svensk Idrottsforskning: Organ för Centrum för Idrottsforskning, ISSN 1103-4629, nr 3, s. 56-60Artikkel i tidsskrift (Annet vitenskapelig)
  • 169.
    Schantz, Peter
    Gymnastik- och idrottshögskolan, GIH.
    Något om de fysiologiska effekterna av styrketräning1984Inngår i: Tidskrift i gymnastik & idrott, ISSN 0281-5338, nr 7, s. 4-7Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
  • 170.
    Schantz, Peter
    Gymnastik- och idrottshögskolan, GIH.
    Om rörelsen i rullstolen2000Inngår i: Svensk Idrottsforskning: Organ för Centrum för Idrottsforskning, ISSN 1103-4629, nr 3, s. 36-39Artikkel i tidsskrift (Annet vitenskapelig)
  • 171.
    Schantz, Peter
    Gymnastik- och idrottshögskolan, GIH.
    Ryggmärgsskadades muskulatur vid träning1997Inngår i: Svensk Idrottsforskning: Organ för Centrum för Idrottsforskning, ISSN 1103-4629, nr 4, s. 17-19Artikkel i tidsskrift (Annet vitenskapelig)
  • 172.
    Schantz, Peter
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Dhoot, Gurtej
    Coexistence of slow and fast isoforms of contractile and regulatory proteins in human skeletal muscle fibres induced by endurance training1987Inngår i: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 131, s. 147-154Artikkel i tidsskrift (Fagfellevurdert)
  • 173.
    Schantz, Peter
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Henriksson, Jan
    Enzyme levels of NADH shuttle systems: measurements in isolated muscle fibres from humans of differing physical activity1987Inngår i: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 129, s. 505-515Artikkel i tidsskrift (Fagfellevurdert)
  • 174.
    Schantz, Peter
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Henriksson, Jan
    Increases in myofibrillar ATPase intermediate human skeletal muscle fibers in response to endurance training.1983Inngår i: Muscle and Nerve, ISSN 0148-639X, E-ISSN 1097-4598, nr 6, s. 553-556Artikkel i tidsskrift (Fagfellevurdert)
  • 175.
    Schantz, Peter
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Randall Fox, Emily
    Norgren, Peter
    Tydén, Anders
    The relationship between the mean muscle fibre area and the muscle cross-sectional area of the thigh in subjects with large differences in thigh girth1981Inngår i: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 113, s. 537-539Artikkel i tidsskrift (Fagfellevurdert)
  • 176.
    Schantz, Peter
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Åstrandlaboratoriet, FoU-gruppen för rörelse, hälsa och miljö.
    Salier Eriksson, Jane
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Åstrandlaboratoriet, FoU-gruppen för rörelse, hälsa och miljö.
    Rosdahl, Hans
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Åstrandlaboratoriet, FoU-gruppen för rörelse, hälsa och miljö.
    The heart rate method for estimating oxygen uptake: analyses of reproducibility using a range of heart rates from commuter walking2019Inngår i: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 119, nr 11-12, s. 2655-2671Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background. The heart rate method, based on the linear relation between heart rate and oxygen uptake, is potentially valuable to monitor intensity levels of physical activities. However, this depends not least on its reproducibility under standard conditions. This study aims therefore to evaluate the reproducibility of the heart rate method in the laboratory using a range of heart rates associated with walking commuting.

     

    Methods. On two different days, heart rate and oxygen uptake measurements were made during three submaximal (model 1) and a maximal exercise intensity (model 2) on a cycle ergometer in the laboratory. 14 habitual walking commuters participated. The reproducibility, based on the regression equations from test and retest and using three levels of heart rate from the walking commuting was analyzed. Differences between the two models were also analyzed. 

     

    Results. For both models, there were no significant differences between test and retest in the constituents of the regression equations (y-intercept, slope and r-value). Neither were there any systematic differences in estimated absolute levels of VO2 between test and retest for either model. However, some rather large individual differences were seen in both models. Furthermore, no significant differences were seen between the two models in slopes, intercepts and r-values of the regression equations or in the estimated VO2.

     

    Conclusion. The heart rate method shows good reproducibility on the group level in estimating oxygen consumption from heart rate – oxygen uptake relations in the laboratory, and based on three levels of heart rate which are representative for walking commuting. However, on the individual level, some large variations were seen.

  • 177.
    Schantz, Peter
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Sjöberg, Berit
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Svedenhag, Jan
    Malate-aspartate and alpha-glycerophophate shuttle enzyme levels in human skeletal muscle: methodological considerations and effect of endurance training1986Inngår i: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 128, s. 397-407Artikkel i tidsskrift (Fagfellevurdert)
  • 178.
    Schantz, Peter
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Sjöberg, Berit
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Widebeck, Ann-Marie
    Ekblom, Björn
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Human skeletal muscle of trained and untrained paraplegics and tetraplegics1997Inngår i: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, nr 161, s. 31-39Artikkel i tidsskrift (Fagfellevurdert)
  • 179. Schiffer, Tomas A
    et al.
    Ekblom, Björn
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Åstrandlaboratoriet, Björn Ekbloms och Mats Börjessons forskningsgrupp.
    Lundberg, Jon O
    Weitzberg, Eddie
    Larsen, Filip J
    Dynamic regulation of metabolic efficiency explains tolerance to acute hypoxia in humans.2014Inngår i: The FASEB Journal, ISSN 0892-6638, E-ISSN 1530-6860, Vol. 28, nr 10, s. 4303-11Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The maximum power principle dictates that open biological systems tend to self-organize to a level of efficiency that allows maximal power production. Applying this principle to cellular energetics and whole-body physiology would suggest that for every metabolic challenge, an optimal efficiency exists that maximizes power production. On exposure to hypoxia, it would be favorable if metabolic efficiency would rapidly adjust so as to better preserve work performance. We tested this idea in humans by measuring metabolic efficiency and exercise tolerance under normoxic (Fio2=20.9%) and hypoxic (Fio2=16%) conditions, where Fio2 is fraction of inhaled oxygen. The results were compared with respirometric analyses of skeletal muscle mitochondria from the same individuals. We found that among healthy trained subjects (n=14) with a wide range of metabolic efficiency (ME), those with a high ME during normoxic exercise were able to better maintain exercise capacity (Wmax) in hypoxia. On hypoxic exposure, these subjects acutely decreased their efficiency from 19.2 to 17.4%, thereby likely shifting it closer to a degree of efficiency where maximal power production is achieved. In addition, mitochondria from these subjects had a lower intrinsic respiration compared to subjects that showed a large drop in Wmax in hypoxia An acute shift in efficiency was also demonstrated in isolated mitochondria exposed to physiological levels of hypoxia as P/O ratio increased from 0.9 to 1.3 with hypoxic exposure. These findings suggest the existence of a physiological adaptive response by which metabolic efficiency is dynamically optimized to maximize power production.-Schiffer, T. A., Ekblom, B., Lundberg, J. O., Weitzberg, E., Larsen, F. J. Dynamic regulation of metabolic efficiency explains tolerance to acute hypoxia in humans.

  • 180. Schiffer, Tomas A
    et al.
    Peleli, Maria
    Sundqvist, Michaela L
    Ekblom, Björn
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Åstrandlaboratoriet, Björn Ekbloms forskningsgrupp.
    Lundberg, Jon O
    Weitzberg, Eddie
    Larsen, Filip J
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Åstrandlaboratoriet, Forskningsgruppen Mitokondriell funktion och metabolisk kontroll.
    Control of Human Energy Expenditure by Cytochrome C Oxidase Subunit IV-2.2016Inngår i: American Journal of Physiology - Cell Physiology, ISSN 0363-6143, E-ISSN 1522-1563, Vol. 311, nr 3, s. C452-C461Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Resting metabolic rate (RMR) in human shows pronounced individual variations, but the underlying molecular mechanism remains elusive. Cytochrome C oxidase (COX) plays a key role in control of metabolic rate and recent studies of the subunit 4 isoform 2 (COX IV-2) indicate involvement in the cellular response to hypoxia and oxidative stress. We evaluated whether the COX subunit IV isoform composition may explain the pronounced individual variations in resting metabolic rate (RMR). RMR was determined in healthy humans by indirect calorimetry and correlated to levels of COX IV-2 and COX IV-1 in Vastus Lateralis. Over expression and knock down of the COX IV isoforms were performed in primary myotubes followed by evaluation of the cell respiration and production of reactive oxygen species. Here we show that COX IV-2 protein is constitutively expressed in human skeletal muscle and strongly correlated to RMR. Primary human myotubes overexpressing COX IV-2 displayed markedly (>60%) lower respiration, reduced (>50%) cellular H2O2 production, higher resistance towards both oxidative stress and severe hypoxia compared to control cells. These results suggest an important role of isoform COX IV-2 in the control of energy expenditure, hypoxic tolerance and mitochondrial ROS homeostasis in humans.

  • 181.
    Seger, Jan
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Laboratoriet för biomekanik och motorisk kontroll (BMC).
    Neuromuscular aspects of eccentric knee extensor actions: effects of electrical stimulation, age, gender and training1998Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The overall aim of this thesis was to study the effects of electrical stimulation, age, gender and training on the torque- and EMG-velocity relationships during eccentric knee extensor muscle actions in man. An isokinetic custom-built dynamometer was evaluated and used throughout the thesis.

    During maximal voluntary efforts eccentric torque output was similar to isometric and did not change with velocity. Superimposing electrical stimulation onto a maximal effort caused a specific increase in eccentric torque output. Submaximal electrical stimulation alone also produced a relatively higher eccentric than concentric torque. These results indicate the presence of a neural tension-regulating mechanism during maximal voluntary eccentric muscle actions in man.

    The hypothesis that such a mechanism would be more pronounced in children than adultswas not corroborated by the results from children, pre- and postpuberty. The adult pattern of interdependence between torque, EMG and muscle action type seemed to be established before puberty in both males and females. Comparisons between genders indicated a higher eccentric to concentric ratio of electromechanical eficiency at high velocity in postpuberty and adult females.

    Training with either pure eccentric or concentric maximal isokinetic muscle actions resulted in mode and velocity specific adaptations, particularly for eccentric training, in peak torque, muscle cross-sectional area, electromechanical efficiency and cross education, that is increase in strength of the contralateral leg. On the other hand, no or only minor training effects were seen on mean torque, muscle fibre morphology, eccentric to concentric EMG ratios and antagonist muscle activity.

    The expression of net eccentric torque output during maximal voluntary eccentric knee extensor actions have shown several distinct features separating it from concentric and isometric actions. Clarification of the underlying neuromuscular mechanisms remains a challenge for future research.

  • 182.
    Seger, Jan
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Arvidsson, Britt
    Thorstensson, Alf
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Laboratoriet för biomekanik och motorisk kontroll (BMC).
    Specific effects of eccentric and concentric training on muscle strength and morphology in humans.1998Inngår i: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 79, s. 49-57Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The purpose of this study was to compare pure eccentric and concentric isokinetic training with respect to their possible specificity in the adaptation of strength and morphology of the knee extensor muscles. Ten moderately trained male physical education students were divided into groups undertaking eccentric (ETG) and concentric (CTG) training. They performed 10 weeks of maximal isokinetic (90 degrees x s(-1)) training of the left leg, 4x10 repetitions - three times a week, followed by a second 10-week period of similar training of the right-leg. Mean eccentric and concentric peak torques increased by 18% and 2% for ETG and by 10% and 14% for CTG, respectively. The highest increase in peak torque occurred in the eccentric 90 degrees x s(-1) test for ETG (35%) whereas in CTG strength gains ranged 8%-15% at velocities equal or lower than the training velocity. Significant increases in strength were observed in the untrained contra-lateral leg only at the velocity and mode used in ipsilateral training. Cross-sectional area of the quadriceps muscle increased 3%-4% with training in both groups, reaching statistical significance only in ETG. No major changes in muscle fibre composition or areas were detected in biopsies from the vastus lateralis muscle for either leg or training group. In conclusion, effects of eccentric training on muscle strength appeared to be more mode and speed specific than corresponding concentric training. Only minor adaptations in gross muscle morphology indicated that other factors, such as changes in neural activation patterns, were causing the specific training-induced gains in muscle strength.

  • 183.
    Seger, Jan
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Thorstensson, Alf
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Laboratoriet för biomekanik och motorisk kontroll (BMC).
    Effects of eccentric versus concentric training on thigh muscle strength and EMG.2005Inngår i: International Journal of Sports Medicine, ISSN 0172-4622, E-ISSN 1439-3964, Vol. 26, s. 45-52Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The purpose of this study was to compare pure eccentric and concentric strength training regarding possible specific effects of muscle action type on neuromuscular parameters, such as a decreased inhibition during maximal voluntary eccentric actions. Two groups of young healthy adult men performed 10 weeks of either eccentric or concentric unilateral isokinetic knee extensor training at 90 degrees.s(-1), 4 sets of 10 maximal efforts, 3 days a week. Knee extensor torque and surface EMG from the quadriceps and hamstring muscle groups were collected and quantified in a window between 30 and 70 degrees knee angle (range of motion 90-5 degrees ) during maximal voluntary eccentric and concentric knee extensor actions at 30, 90, and 270 degrees.s(-1). Changes in strength of the trained legs revealed more signs of specificity related to velocity and contraction type after eccentric than concentric training. No major training effects were present in eccentric to concentric ratios of agonist EMG or in relative antagonist (hamstring) activation. Thus, for the trained leg, the muscle action type and speed specific changes in maximal voluntary eccentric strength could not be related to any effects on neural mechanisms, such as a selective increase in muscle activation during eccentric actions. Interestingly, with both types of training there were specific cross-education effects, that is, action type and velocity specific increases in strength occurred in the contralateral, untrained, leg, accompanied by a specific increase in eccentric to concentric EMG ratio after eccentric training.

  • 184.
    Seger, Jan
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Thorstensson, Alf
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Laboratoriet för biomekanik och motorisk kontroll (BMC).
    Electrically evoked eccentric and concentric torque-velocity relationships in human knee extensor muscles.2000Inngår i: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 169, s. 63-69Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The torque-velocity relationship, obtained during in situ conditions in humans, demonstrates a levelling-off of eccentric torque output at the isometric torque level, at least for knee extensor actions. In contrast, the in vitro force-velocity relationship for animal muscle preparations is characterized by a sharp rise in eccentric force from isometric maximum. A force-regulating 'protective' mechanism has been suggested during maximal voluntary high-tension eccentric muscle actions. To investigate this phenomenon, maximal voluntary and three different levels of submaximal, electrically induced torques were compared during isometric and low velocity (10, 20 and 30 degrees s-1) isokinetic eccentric and concentric knee extensor actions in 10 healthy, moderately trained subjects. Eccentric torque was higher than isometric during electrically evoked, but not during maximal voluntary muscle actions. In contrast, concentric torque was significantly lower than isometric for both maximal voluntary and submaximal, electrically evoked conditions. Comparisons of normalized torques (isometric value under each condition set to 100%) demonstrated that the maximal voluntary eccentric torque had to be increased by 20%, and the isometric by 10% in order for the maximal voluntary torque-velocity curve to coincide with the electrically stimulated submaximal ones. These results support the notion that a tension-regulating mechanism is present primarily during eccentric maximal voluntary knee extensor actions.

  • 185.
    Seger, Jan
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Thorstensson, Alf
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Laboratoriet för biomekanik och motorisk kontroll (BMC).
    Muscle strength and electromyogram in boys and girls followed through puberty.2000Inngår i: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 81, s. 54-61Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The main purpose of this study was to investigate the changes in anthropometric measures and muscle strength that occur during puberty in children from the age of 11 to 16 years. Special attention was paid to possible gender- and muscle action-type-specific alterations in torque/velocity and EMG/velocity characteristics. Sixteen children participated in the study (9 boys and 7 girls). Eccentric and concentric muscle strength was measured on an isokinetic dynamometer at angular velocities of 45, 90 and 180 degrees x s(-1). Simultaneously, a surface electromyogram (EMG) was recorded from the quadriceps muscle. At the age of 11, the boys and girls exhibited equal anthropometric measures and strength performance. In both genders, body measures and muscle strength increased significantly during the 5-year period, with larger increases being recorded for the boys. In addition, the boys increased selectively their eccentric torque per body mass, indicating an action-type-specific change in muscle quality. The general shape of the torque/velocity relationship exhibited an adult-like pattern both before and after puberty, and did not differ between genders. Both pre- and postpuberty, myoelectric activity was generally lower during eccentric than concentric actions, the highest values occurring for both genders in the concentric 180 degrees x s(-1) test. Ratios of eccentric to concentric torque per EMG, which reflect electromechanical efficiency, showed no significant changes with age. A significant velocity- and gender-specific change in electromechanical efficiency was observed at the highest speed at postpuberty, where the ratio for the girls was higher than for the boys.

  • 186.
    Seger, Jan
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Thorstensson, Alf
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Laboratoriet för biomekanik och motorisk kontroll (BMC).
    Muscle strength and myoelectric activity in prepubertal and adult males and females.1994Inngår i: European Journal of Applied Physiology and Occupational Physiology, ISSN 0301-5548, E-ISSN 1432-1025, Vol. 69, s. 81-87Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The compare children and adults of both genders with respect to torque-velocity, electromyogram (EMG)-velocity and torque-EMG relationships during maximal voluntary knee extensor muscle actions. Four groups of purpose of this investigation was to ten subjects each were studied comprising 11-year-old girls and boys and female and male physical education students (22-35 years). Maximal voluntary eccentric (lengthening) and concentric (shortening) actions of the knee extensors were performed at the constant velocities of 45, 90 and 180 degrees.s-1. Average values for torque and EMG activity, recorded by surface electrodes from the quadriceps muscle, were taken for the mid 40 degrees of the 80 degrees range of motion. The overall shapes of the torque- and EMG-velocity relationships were similar for all four groups, showing effects of velocity under concentric (torque decrease and EMG increase) but not under eccentric conditions. Eccentric torques were always greater than velocity-matched concentric ones, whereas the eccentric EMG values were lower than the concentric ones at corresponding velocities. Torque output per unit EMG activity was clearly higher for eccentric than for concentric conditions and the difference was of similar magnitude for all groups. Thus, the torque-EMG-velocity relationships would appear to have been largely independent of gender and to be fully developed at a prepubertal age.

  • 187.
    Seger, Jan
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Björn Ekbloms forskningsgrupp.
    Westing, Stephen
    Hanson, Mats
    Karlson, Eddy
    Ekblom, Björn
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Björn Ekbloms forskningsgrupp.
    A new dynamometer measuring concentric and eccentric muscle strength in accelerated, decelerated, or isokinetic movements1988Inngår i: European Journal of Applied Physiology and Occupational Physiology, ISSN 0301-5548, E-ISSN 1432-1025, Vol. 57, s. 526-530Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new computerized dynamometer (the SPARK System) is described. The system can measure concentric and eccentric muscle strength (torque) during linear or nonlinear acceleration or deceleration, isokinetic movements up to 400 degrees.s-1, and isometric torque. Studies were performed to assess: I. validity and reproducibility of torque measurements; II. control of lever arm position; III. control of different velocity patterns; IV. control of velocity during subject testing; and, V. intra-individual reproducibility. No significant difference was found between torque values computed by the system and known torque values (p greater than 0.05). No difference was present between programmed and external measurement of the lever arm position. Accelerating, decelerating and isokinetic velocity patterns were highly reproducible, with differences in elapsed time among 10 trials being never greater than 0.001 s. Velocity during concentric and eccentric isokinetic quadriceps contractions at 30 degrees.s-1, 120 degrees.s-1 and 270 degrees.s-1 never varied by more than 3 degrees.s-1 among subjects (N = 21). Over three days of testing, the overall error for concentric and eccentric quadriceps contraction peak torque values for 5 angular velocities between 30 degrees.s-1 and 270 degrees.s-1 ranged from 5.8% to 9.0% and 5.8% to 9.6% respectively (N = 25). The results indicate that the SPARK System provides valid and reproducible torque measurements and strict control of velocity. In addition, the intra-individual error is in accordance with those reported for other similar devices.

  • 188.
    Shcherbina, Anna
    et al.
    Stanford University.
    Mattsson, C. Mikael
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Waggott, Daryl
    Stanford University.
    Salisbury, Heidi
    Stanford University.
    Christle, Jeffrey W
    Stanford University.
    Hastie, Trevor J
    Stanford University.
    Wheeler, Matthew
    Stanford University.
    Ashley, Euan A.
    Stanford University.
    Accuracy in wrist-worn, sensor-based measurements of heart rate and energy expenditure in a diverse cohort2016Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Background: The ability to measure activity and physiology through wrist-worn devices provides an opportunity for cardiovascular medicine. However, the accuracy of commercial devices is largely unknown. Objective: To assess the accuracy of seven commercially available wrist-worn devices in estimating heart rate (HR) and energy expenditure (EE) and to propose a wearable sensor evaluation framework. Methods: We evaluated the Apple Watch, Basis Peak, Fitbit Surge, Microsoft Band, Mio Alpha 2, PulseOn, and Samsung Gear S2. Participants wore devices while being simultaneously assessed with continuous telemetry and indirect calorimetry while sitting, walking, running, and cycling. Sixty volunteers (29 male, 31 female, age 38 +/- 11 years) of diverse age, height, weight, skin tone, and fitness level were selected. Error in HR and EE was computed for each subject/device/activity combination. Results: Devices reported the lowest error for cycling and the highest for walking. Device error was higher for males, greater body mass index, darker skin tone, and walking. Six of the devices achieved a median error for HR below 5% during cycling. No device achieved an error in EE below 20 percent. The Apple Watch achieved the lowest overall error in both HR and EE, while the Samsung Gear S2 reported the highest. Conclusions: Most wrist-worn devices adequately measure HR in laboratory-based activities, but poorly estimate EE, suggesting caution in the use of EE measurements as part of health improvement programs. We propose reference standards for the validation of consumer health devices (http://precision.stanford.edu/).

  • 189.
    Sjölund, Jonas
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Johansson, Samuel
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Akuta effekter på uppmärksamhetsförmåga efter ett aerobt medelintensivt träningspass2012Independent thesis Advanced level (degree of Master (One Year)), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Sammanfattning

    Syfte, frågeställningar och hypotes

    Syftet med denna studie var att undersöka om ett aerobt medelintensivt träningspass har någon akut effekt på uppmärksamhetsförmågan.

     

    • Finns det någon akut effekt på uppmärksamhetsförmågan, mätt med Trail Marking Test, 5 minuter efter ett avslutat aerobt medelintensivt cykelträningspass?

     

    Hypotesen var att aerob medelintensiv cykelträning förbättrar testpersonernas uppmärksamhetsförmåga.

     

    Metod

    Studien var av kvantitativ ansats och studiedesignen var crossover. Urvalet bestod utav 14 unga vuxna med en medelålder på 24,4(SD: 2,28). Könsfördelningen var fyra kvinnor och tio män.  En grupp blev först testad efter vila sedan efter fysisk aktivitet. Den andra gruppen blev testad först efter fysisk aktivitet och därefter efter vila. Två deltest användes för att bedöma testpersonernas uppmärksamhetsförmåga med och utan interventionen medelintensiv aerob träning. En ANOVA jämförde uppmärksamhetsförmågan efter aktivitet med uppmärksamhetsförmågan efter vila.

     

    Resultat

    Resultatet i denna studie visade ingen signifikant förbättring i uppmärksamhetsförmåga efter ett medelintensivt aerobt cykelträningspass. En tendens (p = 0,07) till förbättring hittades i en av de två grupperna i det mer krävande deltestet av uppmärksamhetsförmåga. Denna tendens visar på en förbättring i uppmärksamhetsförmåga efter medelintensivt aerobt arbete

     

    Slutsats

    Uppmärksamhetsförmågan förbättras inte signifikant efter medelintensiv aerob cykelträning i denna grupp av fysiskt högaktiva och kognitivt högpresterande studenter. Den tendens som framkom i en delgrupp stödjer tidigare forskning och hypotesen i denna studie. Tendensen kan vara en indikation på att en förbättring av uppmärksamhetsförmågan är möjlig vid mer kognitivt krävande uppgifter. Framtida studier borde använda fler olika kognitiva tester och undersöka om akuta effekter av fysisk aktivitet på uppmärksamhetsförmågan beror på individers fysiska aktivitetsnivå.

  • 190. Svedenhag, Jan
    et al.
    Seger, Jan
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Björn Ekbloms forskningsgrupp.
    Running on land and in water: comparative exercise physiology1992Inngår i: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 24, nr 10, s. 1155-1160Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of water immersion on cardiorespiratory and blood lactate responses during running was investigated. Wearing a buoyant vest, 10 trained runners (mean age 26 yr) ran in water at four different and specified submaximal loads (target heart rates 115, 130, 145, and 155-160 beats.min-1) and at maximal exercise intensity. Oxygen uptakes (VO2), heart rates, perceived exertion, and blood lactate concentrations were measured. Values were compared with levels obtained during treadmill running. For a given VO2, heart rate was 8-11 beats.min-1 lower during water running than during treadmill running, irrespective of exercise intensity. Both the maximal oxygen uptake (4.03 vs 4.60 1 x min-1) and heart rate (172 vs 188 beats.min-1) were lower during water running. Perceived exertion (legs and breathing) and the respiratory exchange ratio (RER) were higher during submaximal water running than during treadmill running, while ventilation (1 x min-1) was similar. The blood lactate concentrations were consistently higher in water than on the treadmill, both when related to VO2 and to %VO2max. Partly in conformity with earlier cycle ergometer studies, these data suggest that immersion induces acute cardiac adjustments that extend up to the maximal exercise level. Furthermore, both the external hydrostatic load and an altered running technique may add to an increased anaerobic metabolism during supported water running.

  • 191. Svensson, M
    et al.
    Malm, C
    Tonkonogi, Michail
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Ekblom, Björn
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Björn Ekbloms forskningsgrupp.
    Sjödin, B
    Sahlin, Kent
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Forskningsgruppen Mitokondriell funktion och metabolisk kontroll.
    Effect of Q10 supplementation on tissue Q10 levels and adenine nucleotide catabolism during high-intensity exercise.1999Inngår i: International Journal of Sport Nutrition, ISSN 1050-1606, Vol. 9, nr 2, s. 166-80Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of the present study was to investigate the concentration of ubiquinone-10 (Q10), at rest, in human skeletal muscle and blood plasma before and after a period of high-intensity training with or without Q10 supplementation. Another aim was to explore whether adenine nucleotide catabolism, lipid peroxidation, and mitochondrial function were affected by Q10 treatment. Seventeen young healthy men were assigned to either a control (placebo) or Q10-supplementation (120 mg/day) group. Q10 supplementation resulted in a significantly higher plasma Q10/total cholesterol level on Days 11 and 20 compared with Day 1. There was no significant change in the concentration of Q10 in skeletal muscle or in isolated skeletal muscle mitochondria in either group. Plasma hypoxanthine and uric acid concentrations increased markedly after each exercise test session in both groups. After the training period, the postexercise increase in plasma hypoxanthine was markedly reduced in both groups, but the response was partially reversed after the recovery period. It was concluded that Q10 supplementation increases the concentration of Q10 in plasma but not in skeletal muscle.

  • 192.
    Södergård, Olof
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Manselin, Tom
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Effekter av intermittent syretillförsel under sex veckors löpträning2014Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Syfte och frågeställningar

    Syftet med denna studie var att undersöka vilka fysiologiska effekter sex veckors högintensiv intervallträning (HIIT) på löpband med hyperoxi (>20,94  % syre) samt med normoxi (normal rumsluft) hade under kontrollerade former. De frågeställningar som hjälpte att besvara syftet var: (1) Hur förändras VO2max efter sex veckors högintensiv träning? (2) Hur förändras prestationen efter sex veckors högintensiv träning? (3) Hur påverkas löpekonomin av sex veckors HIIT? (4) Vilka fysiologiska effekter gav hyperoxiträning?

     

    Metod

    I studien deltog initialt åtta manliga vältränade löpare varav fem stycken fullföljde studien. Karaktäristiken för de fem försökspersonerna (FP) var: ålder (år) 27,6 ± 5,8, längd (cm)180,9 ± 5,0, vikt (kg) 68,6 ± 6,2, årsbästa 10 km (mm:ss) 33:44 ± 01:11 och VO2max (ml/kg/min) 69,0 ± 2,3. FP delades in i test- och kontrollgrupp och studien var utformat som en single-blind. Under en sex veckors träningsperiod tränade FP två gånger per vecka under kontrollerade former i laboratoriemiljö på löpband. Träningen bestod av HIIT i 3-6 st x 6 min arbete med 4 min vila. Hyperoxigruppen fick tillgång till intermittent extra syre genom Oxelerate. Normoxigruppen fick normal rumsluft administrerad genom samma apparatur. Det gjordes tester innan och efter träningsperioden som bestod av ett submaximalt test för att fastställa laktattröskel och löpekonomi, samt ett maximalt syreupptagningstest där även prestationen mättes.

     

    Resultat

    De signifikanta (P <0,05) resultat studien kunde visa på var att prestationen förbättrades för alla FP efter sex veckors HIIT (414,6 ± 85,8 till 460,6 ± 80,4 sekunder). Maxlaktatet blev signifikant högre hos hyperoxigruppen (17,7 %) och signifikant lägre hos normoxigruppen (-19,1 %).

     

    Slutsats

    HIIT gav en signifikant ökad prestation för alla FP. Hyperoxi hade bara effekt på maxlaktat. Löpekonomin och VO2max var oförändrad efter sex veckors HIIT.

  • 193.
    Tais, Senna
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Elektromyografisk aktivitet och power i en knäböj: en explorativ studie2009Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Syfte

    Syftet med föreliggande studie var att studera korrelationen mellan EMG-respons och effektutveckling i samband med genomförande av knäböj.

    Metod

    Fyra manliga testpersoner deltog genom att utföra både knäböj 90° och djupa knäböj i en Smith-maskin som är ansluten till en Linear Encoder som möjliggör beräkning av effektutveckling. Samtidigt registrerades elektromyografisk aktivitet i musklerna Vastus lateralis, Hamstrings och Gluteus maximus. De utförde knäböj på olika relativa belastningsnivåer; 20, 40, 60, 80, 100% av 1RM.

    Resultat

    Resultaten visade inte en stark korrelation mellan medel-EMG och power, inte heller mellan medel-EMG och hastighet, dock indikerade resultaten mellan de sistnämnda en tendens till att en lägre EMG aktivitet uppstod vid de högre hastigheterna. En starkare korrelation kunde antydas mellan medel-EMG och belastning/kraft. Ingen tydlig skillnad mellan musklerna påträffades i förhållande till resultaten ovan. Dock var Hamstrings den muskeln som uppvisade den svagaste korrelationen.

    Slutsats

    EMG-aktiviteten var i stor grad densamma för respektive muskel trots olika belastningar, olika powervärden samt olika utföranden. Nervsystemet tycks därmed arbeta på ett särskilt sätt, oberoende av de andra parametrarna. Däremot kunde man se en svagare tendens för lägre EMG-aktivitet vid de högre hastigheterna. Hamstringsmuskulaturen var den som hade mest avvikande mönster, detta kan bero på det faktum att den har ett mer komplicerat förlopp än de andra två musklerna som testats.

  • 194. Terzis, Gerasimos
    et al.
    Georgiadis, Giorgos
    Stratakos, Grigoris
    Vogiatzis, Ioannis
    Kavouras, Stavros
    Manta, Panagiota
    Mascher, Henrik
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Eva Blomstrands forskningsgrupp.
    Blomstrand, Eva
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Eva Blomstrands forskningsgrupp.
    Resistance exercise-induced increase in muscle mass correlates with p70S6 kinase phosphorylation in human subjects.2008Inngår i: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 102, nr 2, s. 145-52Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The purpose of the present study was to investigate the possible relationship between a change in Thr(389) phosphorylation of p70S6 kinase (p70(S6k)) after a single resistance training session and an increase in skeletal muscle mass following short-term resistance training. Eight male subjects performed an initial resistance training session in leg press, six sets of 6RM with 2 min between sets. Muscle biopsies were obtained from the vastus lateralis before (T1) and 30 min after the initial training session (T2). Six of these subjects completed a 14-week resistance-training programme, three times per week (nine exercises, six sets, 6RM). A third muscle biopsy was obtained at the end of the 14-week training period (T3). One repetition maximum (1RM) squat, bench press and leg press strength as well as fat-free mass (FFM, with dual energy X-ray absorptiometry) were determined at T1 and T3. The results show that the increase in Thr(389) phosphorylation of p70(S6k) after the initial training session was closely correlated with the percentage increase in whole body FFM (r = 0.89, P < 0.01), FFM(leg) (r = 0.81, P < 0.05), 1RM squat (r = 0.84, P < 0.05), and type IIA muscle fibre cross sectional area (r = 0.82, P < 0.05) after 14 weeks of resistance training. These results may suggest that p70(S6k) phosphorylation is involved in the signalling events leading to an increase in protein accretion in human skeletal muscle following resistance training, at least during the initial training period.

  • 195. Terzis, Gerasimos
    et al.
    Spengos, Konstantinos
    Mascher, Henrik
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Eva Blomstrands forskningsgrupp.
    Georgiadis, Giorgos
    Manta, Panagiota
    Blomstrand, Eva
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Eva Blomstrands forskningsgrupp.
    The degree of p70(S6k) and S6 phosphorylation in human skeletal muscle in response to resistance exercise depends on the training volume.2010Inngår i: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 110, nr 4, s. 835-43Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Regular performance of resistance exercise induces an increase in skeletal muscle mass, however, the molecular mechanisms underlying this effect are not yet fully understood. The purpose of the present investigation was to examine acute changes in molecular signalling in response to resistance exercise involving different training volumes. Eight untrained male subjects carried out one, three and five sets of 6 repetition maximum (RM) in leg press exercise in a random order. Muscle biopsies were taken from the vastus lateralis both prior to and 30 min after each training session and the effect on protein signalling was studied. Phosphorylation of Akt was not altered significantly after any of the training protocols, whereas that of the mammalian target of rapamycin was enhanced to a similar extent by training at all three volumes. The phosphorylation of p70S6 kinase (p70(S6k)) was elevated threefold after 3 × 6 RM and sixfold after 5 × 6 RM, while the phosphorylation of S6 was increased 30- and 55-fold following the 3 × 6 RM and 5 × 6 RM exercises, respectively. Moreover, the level of the phosphorylated form of the gamma isoform of p38 MAPK was enhanced three to fourfold following each of the three protocols, whereas phosphorylation of ERK1/2 was unchanged 30 min following exercise. These findings indicate that when exercise is performed in a fasted state, the increase in phosphorylation of signalling molecules such as p70(S6k) and the S6 ribosomal protein in human muscle depends on the exercise volume.

  • 196.
    Thorstensson, Alf
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Laboratoriet för biomekanik och motorisk kontroll (BMC).
    Oddsson, Lars
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Laboratoriet för biomekanik och motorisk kontroll (BMC).
    Andersson, Eva
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Laboratoriet för biomekanik och motorisk kontroll (BMC).
    Arvidsson, Åke
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Laboratoriet för biomekanik och motorisk kontroll (BMC).
    Balance in muscle strength between agonist and antagonist muscles of the trunk.1985Inngår i: Biomechanics IX: proceedings of the ninth International Congress of Biomechanics held in 1983 at Waterloo, Ontario, Canada. B / [ed] David A. Winter, 1985, s. 15-20Konferansepaper (Annet vitenskapelig)
  • 197. Tokuno, Craig D
    et al.
    Cresswell, Andrew G
    Thorstensson, Alf
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Laboratoriet för biomekanik och motorisk kontroll (BMC).
    Carpenter, Mark G
    Age-related changes in postural responses revealed by support-surface translations with a long acceleration-deceleration interval.2010Inngår i: Clinical Neurophysiology, ISSN 1388-2457, E-ISSN 1872-8952, Vol. 121, nr 1, s. 109-17Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Translations with longer acceleration-deceleration intervals reveal more age-related differences in postural control, which are otherwise masked by the deceleration effects inherent to shorter translations.

  • 198.
    Tonkonogi, Michail
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Fernström, Maria
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Walsh, Brandon
    Ji, Li Li
    Rooyackers, Olav
    Hammarqvist, Folke
    Wernerman, Jan
    Sahlin, Kent
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Åstrandlaboratoriet, Forskningsgruppen Mitokondriell funktion och metabolisk kontroll.
    Reduced oxidative power but unchanged antioxidative capacity in skeletal muscle from aged humans.2003Inngår i: Pflügers Archiv: European Journal of Physiology, ISSN 0031-6768, E-ISSN 1432-2013, Vol. 446, nr 2, s. 261-9Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The hypothesis that the aging process is associated with mitochondrial dysfunction and oxidative stress has been investigated in human skeletal muscle. Muscle biopsy samples were taken from seven old male subjects [OS; 75 (range 61-86) years] and eight young male subjects [YS; 25 (22-31) years]. Oxidative function was measured both in permeabilised muscle fibres and isolated mitochondria. Despite matching the degree of physical activity, OS had a lower training status than YS as judged from pulmonary maximal O(2) consumption ( Vdot;O(2)max, -36%) and handgrip strength (-20%). Both maximal respiration and creatine-stimulated respiration were reduced in muscle fibres from OS (-32 and -34%, respectively). In contrast, respiration in isolated mitochondria was similar in OS and YS. The discrepancy might be explained by a biased harvest of "healthy" mitochondria and/or disruption of structural components during the process of isolation. Cytochrome C oxidase was reduced (-40%, P<0.01), whereas UCP3 protein tended to be elevated in OS ( P=0.09). Generation of reactive oxygen species by isolated mitochondria and measures of antioxidative defence (muscle content of glutathione, glutathione redox status, antioxidative enzymes activity) were not significantly different between OS and YS. It is concluded that aging is associated with mitochondrial dysfunction, which appears to be unrelated to reduced physical activity. The hypothesis of increased oxidative stress in aged muscle could not be confirmed in this study.

  • 199.
    Tonkonogi, Michail
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Harris, B
    Sahlin, Kent
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Forskningsgruppen Mitokondriell funktion och metabolisk kontroll.
    Mitochondrial oxidative function in human saponin-skinned muscle fibres: effects of prolonged exercise.1998Inngår i: Journal of Physiology, ISSN 0022-3751, E-ISSN 1469-7793, Vol. 510 ( Pt 1), s. 279-86Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    1. The influence of prolonged exhaustive exercise on mitochondrial oxidative function was investigated in ten men. 2. Muscle biopsies were taken before and after exercise and mitochondrial respiration investigated in fibre bundles made permeable by pretreatment with saponin. 3. After exercise, respiration in the absence of ADP increased by 18 % (P < 0.01), but respiration at suboptimal ADP concentration (0.1 mM) and maximal ADP-stimulated respiration (1 mM ADP) remained unchanged. 4. In the presence of creatine (20 mM), mitochondrial affinity for ADP increased markedly and respiration at suboptimal ADP concentration (0.1 mM) was similar (pre-exercise) or higher (post-exercise; P < 0.05) than with 1 mM ADP alone. The increase in respiratory rate with creatine was correlated to the relative type I fibre area (r = 0.84). Creatine-stimulated respiration increased after prolonged exercise (P < 0.01). 5. The respiratory control index (6.8 +/- 0.4, mean +/- s.e.m.) and the ratio between respiration at 0.1 and 1 mM ADP (ADP sensitivity index, 0.63 +/- 0.03) were not changed after exercise. The sensitivity index was negatively correlated to the relative type I fibre area (r = -0.86). 6. The influence of exercise on muscle oxidative function has for the first time been investigated with the skinned-fibre technique. It is concluded that maximal mitochondrial oxidative power is intact or improved after prolonged exercise, while uncoupled respiration is increased. The latter finding may contribute to the elevated post-exercise oxygen consumption. The finding that the sensitivity of mitochondrial respiration for ADP and creatine are related to fibre-type composition indicates intrinsic differences in the control of mitochondrial respiration between fibres.

  • 200.
    Tonkonogi, Michail
    et al.
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap.
    Sahlin, Kent
    Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, Forskningsgruppen Mitokondriell funktion och metabolisk kontroll.
    Physical exercise and mitochondrial function in human skeletal muscle.2002Inngår i: Exercise and sport sciences reviews, ISSN 0091-6331, E-ISSN 1538-3008, Vol. 30, nr 3, s. 129-37Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Muscle adaptation to endurance training involves qualitative changes in intrinsic properties of mitochondria. After training, the ADP sensitivity of miitochondrion is decreased whereas the effect of creatine on respiration is increased. This results in an improved control of aerobic energy production. Acute exercise does not adversely affect mitochondrial function.

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