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1.
  • Calbet, J, et al. (författare)
  • Maximal vascular conductances during whole body upright exercise in humans
  • 2004
  • Ingår i: Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 558:1, s. 319-331
  • Tidskriftsartikel (refereegranskat)abstract
    • That muscular blood flow may reach 2.5 l kg�1 min�1 in the quadriceps muscle has led to the suggestion that muscular vascular conductance must be restrained during whole body exercise to avoid hypotension. The main aim of this study was to determine the maximal arm and leg muscle vascular conductances (VC) during leg and arm exercise, to find out if the maximal muscular vasodilatory response is restrained during maximal combined arm and leg exercise. If during maximal exercise arms and legs had been vasodilated to the observed maximal levels then mean arterial pressure would have dropped at least to 75�77 mmHg in our experimental conditions. It is concluded that skeletal muscle vascular conductance is restrained during whole body exercise in the upright position to avoid hypotension. AVKORTAT ABSTRACT
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2.
  • Calbet, J, et al. (författare)
  • Why do the arms extract less oxygen than the legs during exercise?
  • 2005
  • Ingår i: American Journal of Physiology. Regulatory Integrative and Comparative Physiology. - : American Physiological Society. - 0363-6119 .- 1522-1490. ; 289, s. 1448-1458
  • Tidskriftsartikel (refereegranskat)abstract
    • To determine whether conditions for O2 utilization and O2 off-loading from the hemoglobin are different in exercising arms and legs, six cross-country skiers participated in this study. Femoral and subclavian vein blood flow and gases were determined during skiing on a treadmill at 76% maximal O2 uptake (O2 max) and at O2 max with different techniques: diagonal stride (combined arm and leg exercise), double poling (predominantly arm exercise), and leg skiing (predominantly leg exercise). The percentage of O2 extraction was always higher for the legs than for the arms. At maximal exercise (diagonal stride), the corresponding mean values were 93 and 85% (n = 3; P < 0.05). During exercise, mean arm O2 extraction correlated with the PO2 value that causes hemoglobin to be 50% saturated (P50: r = 0.93, P < 0.05), but for a given value of P50, O2 extraction was always higher in the legs than in the arms. Mean capillary muscle O2 conductance of the arm during double poling was 14.5 (SD 2.6) ml·min–1·mmHg–1, and mean capillary PO2 was 47.7 (SD 2.6) mmHg. Corresponding values for the legs during maximal exercise were 48.3 (SD 13.0) ml·min–1·mmHg–1 and 33.8 (SD 2.6) mmHg, respectively. Because conditions for O2 off-loading from the hemoglobin are similar in leg and arm muscles, the observed differences in maximal arm and leg O2 extraction should be attributed to other factors, such as a higher heterogeneity in blood flow distribution, shorter mean transit time, smaller diffusing area, and larger diffusing distance, in arms than in legs. diffusing capacity; fatigue; oxygen extraction; performance; training
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3.
  • Sahlin, Kent, et al. (författare)
  • No evidence of an intracellular lactate shuttle in rat skeletal muscle.
  • 2002
  • Ingår i: Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 541:Pt 2, s. 569-74
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
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4.
  • Sahlin, Kent, et al. (författare)
  • Ultra-endurance exercise increases the production of reactive oxygen species in isolated mitochondria from human skeletal muscle.
  • 2010
  • Ingår i: Journal of applied physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 108:4, s. 780-787
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
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5.
  • Van Hall, G, et al. (författare)
  • Leg and arm lactate and substrate kinetics during exercise
  • 2003
  • Ingår i: American Journal of Physiology. Endocrinology and Metabolism. - : American Physiological Society. - 0193-1849 .- 1522-1555. ; 284:1, s. E193-E205
  • Tidskriftsartikel (refereegranskat)abstract
    • To study the role of muscle mass and muscle activity on lactate and energy kinetics during exercise, whole body and limb lactate, glucose, and fatty acid fluxes were determined in six elite cross-country skiers during roller-skiing for 40 min with the diagonal stride (Continuous Arm + Leg) followed by 10 min of double poling and diagonal stride at 72-76% maximal O(2) uptake. A high lactate appearance rate (R(a), 184 +/- 17 micromol x kg(-1) x min(-1)) but a low arterial lactate concentration ( approximately 2.5 mmol/l) were observed during Continuous Arm + Leg despite a substantial net lactate release by the arm of approximately 2.1 mmol/min, which was balanced by a similar net lactate uptake by the leg. Whole body and limb lactate oxidation during Continuous Arm + Leg was approximately 45% at rest and approximately 95% of disappearance rate and limb lactate uptake, respectively. Limb lactate kinetics changed multiple times when exercise mode was changed. Whole body glucose and glycerol turnover was unchanged during the different skiing modes; however, limb net glucose uptake changed severalfold. In conclusion, the arterial lactate concentration can be maintained at a relatively low level despite high lactate R(a) during exercise with a large muscle mass because of the large capacity of active skeletal muscle to take up lactate, which is tightly correlated with lactate delivery. The limb lactate uptake during exercise is oxidized at rates far above resting oxygen consumption, implying that lactate uptake and subsequent oxidation are also dependent on an elevated metabolic rate. The relative contribution of whole body and limb lactate oxidation is between 20 and 30% of total carbohydrate oxidation at rest and during exercise under the various conditions. Skeletal muscle can change its limb net glucose uptake severalfold within minutes, causing a redistribution of the available glucose because whole body glucose turnover was unchanged.
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6.
  • Wallén, Eva Flygare, et al. (författare)
  • High prevalence of cardio-metabolic risk factors among adolescents with intellectual disability.
  • 2009
  • Ingår i: Acta Paediatrica. - : Wiley. - 0803-5253 .- 1651-2227. ; 98:5, s. 853-859
  • Tidskriftsartikel (refereegranskat)abstract
    • Abstract Adults with intellectual disabilities (IDs) have poor lifestyle-related health compared with the general population. Our aim was to study whether such differences are present already in adolescents. AIM: To compare the prevalence and severity of cardio-metabolic risk factors and cardio-vascular fitness in adolescents with and without IDs. METHODS: Intellectual disability (ID) students (n = 66) and non-intellectual disability (non-ID) students from practical (non-ID-p) (n = 34) and theoretical (non-ID-t) (n = 56) programmes were recruited from three upper secondary schools. Anthropometric data, blood pressure, body composition, fasting-insulin, fasting-glucose, fasting-lipids and cardio-vascular fitness were measured. RESULTS: Participants with and without ID differed significantly in the prevalence of cardio-metabolic risk factors with participants with ID having a higher percentage of total fat mass, wider waist circumferences (WCs), lower levels of fat-free mass (FFM), lower bone mineral density (BMD) and higher insulin and homeostasis model assessment of insulin resistance (HOMA) levels and poorer cardio-vascular fitness. The healthiest levels were found in the non-ID-t group compared to the group with ID and the group with non-ID-p in between. CONCLUSION: The prevalence of cardio-metabolic risk factors and poor cardio-vascular fitness was found to be high in this young population with intellectual disabilities. Measures should be taken to improve the health messages directed towards children and adolescents with intellectual disabilities.
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7.
  • Rickenlund, Anette, et al. (författare)
  • Effects of oral contraceptives on body composition and physical performance in female athletes.
  • 2004
  • Ingår i: Journal of Clinical Endocrinology and Metabolism. - : The Endocrine Society. - 0021-972X .- 1945-7197. ; 36:5, s. S34-S34
  • Tidskriftsartikel (refereegranskat)abstract
    • Menstrual disturbances are common among female athletes, and oral contraceptives (OCs) are often recommended as estrogen substitution. However, there is little information about the effects of OC use in athletes, and there is great concern that OCs might impair physical performance. The aim of this study was to investigate the effects of OC use on body composition and physical performance in female athletes. Twenty-six endurance athletes (13 with oligo-/amenorrhea and 13 regularly menstruating athletes) and 12 sedentary controls were examined before and after 10 months of treatment with a low dose, monophasic, combined OC. Significant changes in body composition were recorded in the athletes, but not in the controls. There was an increase in weight and fat mass only in athletes with oligo-/amenorrhea. These changes were associated with a decrease in ovarian androgens. OC treatment also increased bone mineral density, with the largest increase in athletes with a low bone mineral density at baseline. Despite significant changes in body composition, little impact on physical performance was recorded. We have demonstrated that OC treatment in female athletes has predominantly beneficial effects on body composition without adverse effects on physical performance and could be used for the prevention of osteoporosis in athletic amenorrhea. However, it cannot be excluded that a marked increase in fat mass might have unfavorable effects for athletic performance in individual women.
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8.
  • Åberg, Anna Cristina, et al. (författare)
  • Calculations of mechanisms for balance control during narrow and single-leg standing in fit older adults: A reliability study.
  • 2011
  • Ingår i: Gait & Posture. - : Elsevier BV. - 0966-6362 .- 1879-2219. ; 34:3, s. 352-7
  • Tidskriftsartikel (refereegranskat)abstract
    • For older people balance control in standing is critical for performance of activities of daily living without falling. The aims were to investigate reliability of quantification of the usage of the two balance mechanisms M1 ‘moving the centre of pressure’ and M2 ‘segment acceleration’ and also to compare calculation methods based on a combination of kinetic (K) and kinematic (Km) data, (K–Km), or Km data only concerning M2. For this purpose nine physically fit persons aged 70–78 years were tested in narrow and single-leg standing. Data were collected by a 7-camera motion capture system and two force plates. Repeated measure ANOVA and Tukey's post hoc tests were used to detect differences between the standing tasks. Reliability was estimated by ICCs, standard error of measurement including its 95% CI, and minimal detectable change, whereas Pearson's correlation coefficient was used to investigate agreement between the two calculation methods. The results indicated that for the tasks investigated, M1 and M2 can be measured with acceptable inter- and intrasession reliability, and that both Km and K–Km based calculations may be useful for M2, although Km data may give slightly lower values. The proportional M1:M2 usage was approximately 9:1, in both anterio-posterior (AP) and medio-lateral (ML) directions for narrow standing, and about 2:1 in the AP and of 1:2 in the ML direction in single-leg standing, respectively. In conclusion, the tested measurements and calculations appear to constitute a reliable way of quantifying one important aspect of balance capacity in fit older people.
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9.
  • Åkesson, Joakim (författare)
  • Idrottens akademisering : kunskapsproduktion och kunskapsförmedling inom idrottsforskning och högre idrottsutbildning [Poster]
  • 2010
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Titel: Idrottens akademisering: Kunskapsproduktion och kunskapsförmedling inom idrottsforskning och högre idrottsutbildning Inledning: Samhällsvetenskapligt orienterad idrottsforskning och idrottsutbildningar på akademisk nivå är relativt nya företeelser i Sverige. Forskningen kom igång på allvar först under 1970-talet och innan 2000-talet fanns det endast ett fåtal idrottsutbildningar i landet. Idag är såväl forskning som utbildning omfattande och differentierad. Frågan är dock hur forskning och utbildning utvecklats, ser ut idag, och förehåller sig till varandra? Vilken kunskap är det som produceras inom idrottsforskningen och vilken kunskap är det som förmedlas inom utbildningarna? Skiljer sig den producerade och förmedlade kunskapen åt? I så fall hur och varför? Syfte: Studien behandlar idrottens akademisering. Med akademisering avses den process genom vilken ett kunskapsområde, i detta fall idrottens, transformeras till ett vetenskapligt kunskapsområde. Syftet med studien är att nå fördjupad förståelse för idrottsutbildningarna och dess relation till idrottsforskningen ur ett kunskapsperspektiv. Teori: Fyra begrepp är särskilt centrala i studien: kunskap, makt, diskurs och institution. Merparten av den teoretiska inspirationen hämtas från fem teoretiker. I centrum står Peter Berger och Thomas Luckmanns kunskapssociologi, Michel Foucaults tankar om diskurs, makt och institution, samt Pierre Bourdieus fältanalys. Därutöver används teorier som handlar om specifika samhällsprocesser och diskurser av olika tidsepoker. Här hämtas stöd i främst Zygmunt Baumans samhällsteori. Metod: Källmaterialet utgörs till största del av olika dokument. Exempel på analyserade dokument är: avhandlingar, forskningsrapporter, tidskriftsartiklar, utredningar, hemsidor, utbildningsplaner och kursplaner. Dokumenten och dess innehåll har i vissa fall hanterats kvalitativt och i andra fall kvantitativt. Den kvalitativa dokumentanalysen har exempelvis genomförts enligt diskursanalytisk modell. Resultat: Studien har visat att det råder en viss diskrepans mellan den kunskap som produceras inom idrottsforskningen och den kunskaps som förmedlas genom akademiska idrottsutbildningar. Den största andelen samhällsvetenskapligt orienterad idrottsforskning har producerats av pedagoger (36%), psykologer (21%), historiker (18%) och sociologer (5%). Samtidigt var 9 av 22 idrottsutbildningar 2008 att beteckna som management¬utbildningar. Skillnaden mellan den typ av kunskap som producerats inom idrottsforskningen och den typ av kunskap som förmedlas inom idrottsutbildningar är således anmärkningsvärd. Diskussion: Sett ur ett diskursivt perspektiv kan forskningen och utbildningen förstås genom dess relation till olika logiker som haft olika framträdande positioner i den allmänna samhällsdiskursen. Tre relevanta logiker som haft olika kan urskiljas: (1) Det moderna produktions- och välfärdssamhällets logik (1900-tal); De problematiserande samhällsperspektivens logik (ca 1960-); Det postmoderna konsumtionssamhällets logik (ca 1990-). Den första dominerade samhällsdiskursen under stora delar av 1900-talet. Idrottsforskning som bygger på denna logik bedrivs utifrån medicinska, fysiologiska, pedagogiska, psykologiska och historiska perspektiv. Idrottsutbildningar som kan ses som byggande på denna logik är tränar-, hälso-, medicin- och fysiologi-, samt psykologiutbildningar. Den andra tillkom under 1960- och 1970-talen och fick genomslag inom idrottsforskningen under 1980- och 1990-talen. Forskning som bygger på denna logik bedrivs exempelvis utifrån sociologiska, etnologiska, genusvetenskapliga och filosofiska perspektiv. Utbildningar som kan ses som byggande på denna logik är kultur- och samhällsutbildningar, samt i viss mån medieutbildningar. Den tredje fick genomslag i samhällsdiskursen under 1990- och 2000-talen och inom idrottsforskning och idrottsutbildning under 2000-talet. Forskning som bygger på denna logik bedrivs exempelvis utifrån management-, ekonomiska-, juridiska-, ledarskaps-, och organisations- perspektiv. Utbildningar som kan ses som byggande på denna logik är Sport Management utbildningar, samt i viss mån medieutbildningar. Man kan allstå tala om forskning och utbildning som bygger på tre olika logiker som varit olika framträdande i den allmänna samhällsdiskursen under olika tidsepoker. Forskningen som etablerades tidigare än utbildningarna bygger i större utsträckning på logiker som tidigare i historien varit mer framträdande.
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10.
  • Andersson, Eva A, 1958-, et al. (författare)
  • Maximal Aerobic Power versus Performance in Two Aerobic Endurance Tests among Young and Old Adults
  • 2011
  • Ingår i: Gerontology. - : S. Karger AG. - 0304-324X .- 1423-0003. ; :Aug, s. 1-11
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Aerobic fitness is of great value for reducing risk of mortality and cardiovascular diseases. Objective: This study evaluated the performance in and correlations between a new test (five-minute pyramid test, 5MPT), the six-minute walk-test (6MWT) and maximal oxygen uptake (VO(2max)) among old and young adults. Methods: Forty-four habitually active adults (females and males), 23 old (64-79 years) and 21 young (20-32 years) participated. In the 5MPT, the participants moved back and forth along a short walkway (5.5 m) over boxes (height: 'old people' 0.42 m, 'young people' 0.62 m) arranged like an elongated step pyramid for 5 min. Power in the pyramid test (5MPT(power)) was calculated as the product of numbers of laps, body weight, gravity and highest box level divided by time. A 6MWT and a maximal cycle ergometer test for direct measurements of VO(2max) were also performed. In all tests heart rate, with on-line electrocardiography, and perceived exertion were recorded. Results: There was a strong correlation between the 5MPT(power) and VO(2max) for the entire group studied (r = 0.98), and each of the four subgroups old and young females and males separately (r = 0.78-0.98). Contrary to several earlier studies, especially involving people with various diseases, the present data showed that 6MWT cannot be used to predict VO(2max) among old females and young adults. The correlation with VO(2max) was weaker for the 6MWT than for the 5MPT(power). The relative performance values for the old compared to the young (ratio old/young × 100) were considerably lower in 5MPT(power) and VO(2max) (47-55%) than in distance and 'work' in the 6MWT (82-86%). Conclusions: The results, with age and gender variations, can be valuable information in health-fitness contexts, since measuring physical aerobic capacity is very significant in connection with risk evaluations of mortality and various diseases. The 5MPT is a rapid, functional, easy and inexpensive tool for predicting assessed maximal aerobic power.
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