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- Komi, P V, et al.
(author)
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Skeletal muscle fibres and muscle enzyme activities in monozygous and dizygous twins of both sexes.
- 1977
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In: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 100:4, s. 385-92
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Journal article (peer-reviewed)abstract
- Significance of the genetic component in determining the interindividual variation observed in skeletal muscle fibre composition and enzyme activities was investigated in 31 pairs of male and female monozygous (MZ) and dizygous (DZ) twins, whose ages ranged in all but one pair (11 years) from 15 to 24 years. Percent distribution of slow twitch muscle fibres and activities of Ca2+ and Ng2+ stimulated ATPases, creatine phosphokinase, myokinase, phosphorylase, lactate dehydrogenase (LDH) and distribution of its isozyme LDH-1 were all analyzed in biopsy samples taken from the vastus lateralis muscle. The data disclosed that in contrast to DZ twins the MZ twins of both sexes had an essentially identical muscle fibre composition. Calculation of the heritability estimate for this parameter gave the values of 99.5% and 92.8%, respectively for males and females. In contrast to the fibre composition presence of a significant genetic component was not observed in any of the enzyme activities studied. It was concluded that there is a predominant genetic influence on the skeletal muscle fibre composition in man, and thus also on the potential capacity of the muscles to perform work.
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- Laaksonen, Marko, et al.
(author)
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Effects of exhaustive stretch-shortening cycle exercise on muscle blood flow during exercise
- 2006
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In: Acta Physiologica. - : Wiley. - 1748-1708 .- 1748-1716. ; 186:4, s. 261-270
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Journal article (peer-reviewed)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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- Thorstensson, Alf, et al.
(author)
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Effect of strength training on EMG of human skeletal muscle.
- 1976
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In: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 98:2, s. 232-6
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Journal article (peer-reviewed)abstract
- The effects of an 8 weeks period of systematic progressive strength training on the EMG activity of the leg extensor muscles (vastus lateralis and rectus femoris) were investigated in 8 healthy male subjects (22-31 yrs). After training there were indications (n.s.) of a decline in integrated EMG (IEMG) during maximal isometric knee extension as well as in the IEMG vs isometric force relationship. The averaged motor unit potential (AMUP) did not demonstrate any significant changes due to the strength training regimen. In conformity with earlier findings no or only minor alterations were observed in anthropometrics, muscle enzyme activities and fibre composition. The fibre area ratio indicated a specific effect of the training stimuli on the fast twitch muscle fibres. Thus, EMG-analyses, as employed in the present study, did not provide any conclusive additional explanation as to the mechanisms behind the well established gains in muscle strength performance induced by the applied strength training program.
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