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- Ainegren, Mats, 1963-, et al.
(författare)
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Work economy of amateur and elite cross-country skiers during treadmill roller skiing
- 2009
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Ingår i: 4th Asia Pacific Congress on Sports Technology, APCST2009. - 9781921426384
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Konferensbidrag (refereegranskat)abstract
- This study focused on the work economy of cross-country skiers during treadmill roller skiing in the perspectives; skill, age and gender. The study was investigating the external power output from elevating the transported mass against gravity and overcoming the roller skis rolling resistance, and the internal power from measured oxygen uptake and energy consumption. The roller skis rolling resistance was measured with a fixture on the ski-treadmill and the results showed a significant correlation between normal force and rolling resistance. The results also showed that it was only the amateur skiers who significantly differed in work economy among the five studied groups.
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| 2. |
- Hannukainen, J, et al.
(författare)
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In Vivo Measurements of Glucose Uptake in Human Achilles Tendon During Different Exercise Intensities
- 2005
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Ingår i: International Journal of Sports Medicine. - : Georg Thieme Verlag KG. - 0172-4622 .- 1439-3964. ; 26, s. 727-731
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Tidskriftsartikel (refereegranskat)abstract
- Muscular contraction and loading of adjacent tendons has been demonstrated to cause increased blood flow and metabolic activity in the peritendinous region. However, it is poorly known to what extent the human tendon itself takes up glucose during exercise. Thus, the purpose of this study was to measure tendon glucose uptake with increasing exercise intensity and to compare it to muscle glucose uptake at the same intensities. Eight young men were examined on three separate days during which they performed 35 min of cycling at 30, 55 and 75 % of VO2max, respectively. Glucose uptake was measured directly by positron emission tomography (PET) with 2-[ (18)F]fluoro-2-deoxyglucose ([18F]FDG). [18F]FDG was injected after 10 min of exercise that was continued for a further 25 min after the injection. PET scanning of the thigh and Achilles region was performed after the exercise. Glucose uptake of the Achilles tendon (AT) remained unchanged (7.1 +/- 1.5, 6.6 +/- 1.1, and 6.0 +/- 1.1 micromol.kg(-1).min(-1)) with the increasing workload, although the glucose uptake in m. quadriceps femoris simultaneously clearly increased (48 +/- 35, 120 +/- 35, and 152 +/- 74 micromol.kg(-1).min(-1), p < 0.05). In conclusion, the AT takes up glucose during exercise but in significantly smaller amounts than the skeletal muscle does. Furthermore, glucose uptake in the AT is not increased with the increasing exercise intensity. This may be partly explained by the cycle ergometry exercise used in the present study, which probably causes only a little increase in strain to the AT with increasing exercise intensity.
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| 4. |
- Laaksonen, Marko, et al.
(författare)
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Effects of exhaustive stretch-shortening cycle exercise on muscle blood flow during exercise
- 2006
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Ingår i: Acta Physiologica. - : Wiley. - 1748-1708 .- 1748-1716. ; 186:4, s. 261-270
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Aim: The influence of exhaustive stretch-shortening cycle exercise (SSC) on skeletal muscle blood flow (BF) during exercise is currently unknown. Methods: Quadriceps femoris (QF) BF was measured in eight healthy men using positron emission tomography before and 3 days after exhaustive SSC exercise. The SSC protocol consisted of maximal and submaximal drop jumps with one leg. Needle biopsies of the vastus lateralis muscles were taken immediately and 2 days after SSC for muscle endothelial nitric oxide synthase (eNOS) and interleukin-1-beta (IL-1beta) mRNA level determinations. Results: All subjects reported subjective muscle soreness after SSC (P < 0.001), which was well in line with a decrease in maximal isometric contraction force (MVC) and increase in serum creatine kinase activity (CK) (P = 0.018). After SSC muscle BF was 25% higher in entire QF (P = 0.043) and in its deep and superficial muscle regions, whereas oxygen uptake remained unchanged (P = 0.893). Muscle biopsies revealed increased IL-1beta (30 min: 152 +/- 75%, P = 0.012 and 2 days: 108 +/- 203%, P = 0.036) but decreased or unchanged eNOS (30 min; -21 +/- 57%, P = 0.050 and 2 days: +101 +/- 204%, P = 0.779) mRNA levels after SSC. Conclusion: It was concluded that fatiguing SSC exercise induces increased muscle BF during exercise, which is likely to be associated with pro-inflammatory processes in the exercised muscle.
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| 5. |
- Laaksonen, Marko, 1975-, et al.
(författare)
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Left-ventricular hypertrophy associates to impaired maximal myocardial perfusion in endurance-trained men
- 2009
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Konferensbidrag (refereegranskat)abstract
- Long-term endurance training induces morphological adaptations in heart, such as left-ventricular (LV) hypertrophy caused by wall thickening and cavity enlargement. Interestingly, these anatomical changes in the heart are strikingly similar to certain pathophysiological changes (Pellicia 2000). Previous studies have shown that the perfusion response in myocardium during dipyridamole- or adenosine infusion is decreased in several pathophysiological states with LV hypertrophy (e.g. Stolen et al. 2004). However, studies in endurance athletes with LV hypertrophy have shown contradictory results on myocardial perfusion response ranging from reduced to increased myocardial perfusion during dipyridamole- or adenosine-induced vasodilation compared to untrained men (Kjaer et al. 2005; Kalliokoski et al. 2002). The degree of hypertrophy could explain the discrepant findings in studies in athletes, but it has not been thoroughly investigated. Thus, we examined totally 31 endurance athletes (ET) and 25 untrained (UT) men in order to study the association between myocardial functional and anatomical parameters measured with echocardiography, and myocardial perfusion (at rest and during maximal vasodilation induced by iv adenosine) measured with Positron Emission Tomography. Both VO2max (60+-5 vs 42+-8 ml/kg/min, p<0.001) and LVmass index (169+-27 vs 102+-15 g/m2, p<0.001) were markedly higher in ET. Resting myocardial perfusion was similar between the groups (ET 0.7+-0.2 vs UT 0.8+-0.2 ml/g/min, p=0.22) whereas adenosine-stimulated perfusion was lower in ET (2.9+-1.0 vs 3.7+-1.0 ml/g/min, p<0.01). VO2max correlated inversely with adenosine-stimulated perfusion in ET (r=-0.39, p=0.03) and with resting perfusion in UT (-0.49, p=0.01). Forward LV work correlated linearly with resting perfusion in both groups (ET r=0.54, p<0.01; UT r=0.50, p=0.01). ET group was further divided into three subgroups according to LVmass index (ET1: LVmass index <150g/m2, n=9; ET2 LVmass index 150-180 g/m2, n=12; ET3 LVmass index >180 gm2, n=10). Adenosine-induced myocardial perfusion decreased gradually when LVmass increased (UT 3.7+-1.+0 vs ET1 3.3+-0.9 vs ET2 2.7+-1.4 vs ET3 2.6+-0.5 mL g-1 min-1, p=0.008). LVmass index was also inversely related to adenosine-induced perfusion in entire study population (r=-0.46, p<0.01). Therefore, these results suggest that endurance training-induced severe cardiac hypertrophy impairs myocardial perfusion capacity. Kalliokoski K et al. (2002) Med Sci Sports Exerc 34:948-53 Kjaer A et al. (2005) Am J Cardiol 96:1692-98 Pellicia A (2000) Curr Cardiol Rep 2(2):166-71 Stolen KQ et al (2004) 10(2):132-40
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| 10. |
- Laaksonen, Marko, et al.
(författare)
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The association between muscle EMG and perfusion in knee extensor muscles
- 2006
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Ingår i: Clinical Physiology and Functional Imaging. - 1475-0961 .- 1475-097X. ; 26:2, s. 99-105
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Tidskriftsartikel (refereegranskat)abstract
- The relationships between electromyographic (EMG) activity and force as well as muscle blood flow and work have been well established. However, the association between muscle blood flow and EMG activity remains unsolved. Thus, to test the hypothesis that muscle EMG activity relates to muscle perfusion in different compartments of the quadriceps femoris (QF) muscle, 12 healthy male subjects were studied. During two very submaximal exercise bouts, at different exercise intensities, oxygen labelled radiowater and positron emission tomography were used to measure muscle perfusion. In addition, produced force of knee extensors and muscle EMG activity in the vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) muscles were recorded during both exercise bouts. Although the exercise intensity and average force production was higher during the second exercise bout (3815 vs. 5117 N; p=0.007), the mean EMG activity was lower (RF; p<0.001) or unchanged (VL; p=0.722 and VM; p=0.640). During the second exercise period, perfusion also remained unchanged in the entire QF muscle (p=0.223) and in its separate muscles (VL, p=0.703; VM, p=0.141; RF, p=0.113) in a group level. However, the individual changes in muscle perfusion were tightly related to changes in muscle EMG activity in VL (r=0.84; p=0.002) and in VM (r=0.68; p=0.015) but poorly in the RF muscle (r=0.40; p=0.257). In conclusion, the different associations between muscle perfusion and EMG activity in different QF muscles suggests specific functional role of the vasti muscles and the RF muscle.
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