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Dellagrana RA, Rossato M, Orssatto LBR, Sakugawa RL, Baroni BM, Diefenthaeler F. Effect of Photobiomodulation Therapy in the 1500 m Run: An Analysis of Performance and Individual Responsiveness. Photobiomodul Photomed Laser Surg 2020; 38:734-742. [PMID: 33227224 DOI: 10.1089/photob.2019.4785] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Objective: The aims of this study were to verify the effects of photobiomodulation therapy (PBMT) on time trial run performance over 1500 m, as well as on individual responsiveness of recreative runners. Materials and methods: Nineteen recreationally trained runners participated in a randomized, crossover, double-blind placebo-controlled trial. The study was divided in four sessions: (1) incremental maximal running test; (2) 1500 m run control (without placebo or PBMT); and (3, 4) PBMT or placebo before 1500 m run. PBMT or placebo was applied over 14 sites per lower limb immediately before time trial run using a mixed wavelength device (33 diodes: 5 LASERs of 850 nm, 12 LEDs of 670 nm, 8 LEDs of 880 nm, and 8 LEDs with 950 nm). PBMT delivered 30 J per site, with a total energy dose of 840 J. Physiological variables [maximal oxygen uptake (VO2MAX), velocity associated to VO2MAX (vVO2MAX), peak of velocity, and respiratory compensation point (RCP)] were assessed during incremental maximal test. During 1500 m races we accessed the following: time, heart rate, and lower limb rate perception exertion per lap, total time, and blood lactate concentration ([Lac]). Results: PBMT had no significant difference and likely trivial effect for performance in the total time trial run over 1500 m compared to placebo. In the responsiveness analyses, 10 participants positively responded to PBMT, whereas total time reduced for responders (-10.6 sec; -3.18%) and increased for nonresponders (+6.0 sec; +1.73%). Responders presented higher aerobic parameters (VO2MAX and RCP) than nonresponders. Moreover, responders had lower time per lap and [Lac] (1 and 3 min) when PBMT was applied. Conclusions: PBMT applied immediately before running in noncontrolled environment was not able to improve the 1500 m performance of recreationally trained runners. However, responders to PBMT presented higher aerobic capacity than nonresponders.
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Affiliation(s)
- Rodolfo André Dellagrana
- Laboratório de Biomecânica (BIOMEC), Centro de Desportos, Universidade Federal de Santa Catarina, Florianópolis, Brazil
- Programa de Pós-Graduação em Ciências do Movimento, Universidade Federal de Mato Grosso do Sul, Campo Grande, Brazil
| | - Mateus Rossato
- Laboratório de Biomecânica (BIOMEC), Centro de Desportos, Universidade Federal de Santa Catarina, Florianópolis, Brazil
- Laboratório de Desempenho Humano, Faculdade de Educação Física, Universidade Federal do Amazonas, Manaus, Brazil
| | - Lucas B R Orssatto
- School of Exercise and Nutrition Sciences, Queensland University of Technology, Brisbane, Australia
| | - Raphael Luiz Sakugawa
- Laboratório de Biomecânica (BIOMEC), Centro de Desportos, Universidade Federal de Santa Catarina, Florianópolis, Brazil
| | - Bruno Manfredini Baroni
- Programa de Pós-Graduação em Ciências de Reabilitação, Departamento de Fisioterapia, Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, Brazil
| | - Fernando Diefenthaeler
- Laboratório de Biomecânica (BIOMEC), Centro de Desportos, Universidade Federal de Santa Catarina, Florianópolis, Brazil
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Neels JG, Grimaldi PA. Physiological functions of peroxisome proliferator-activated receptor β. Physiol Rev 2014; 94:795-858. [PMID: 24987006 DOI: 10.1152/physrev.00027.2013] [Citation(s) in RCA: 117] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The peroxisome proliferator-activated receptors, PPARα, PPARβ, and PPARγ, are a family of transcription factors activated by a diversity of molecules including fatty acids and fatty acid metabolites. PPARs regulate the transcription of a large variety of genes implicated in metabolism, inflammation, proliferation, and differentiation in different cell types. These transcriptional regulations involve both direct transactivation and interaction with other transcriptional regulatory pathways. The functions of PPARα and PPARγ have been extensively documented mainly because these isoforms are activated by molecules clinically used as hypolipidemic and antidiabetic compounds. The physiological functions of PPARβ remained for a while less investigated, but the finding that specific synthetic agonists exert beneficial actions in obese subjects uplifted the studies aimed to elucidate the roles of this PPAR isoform. Intensive work based on pharmacological and genetic approaches and on the use of both in vitro and in vivo models has considerably improved our knowledge on the physiological roles of PPARβ in various cell types. This review will summarize the accumulated evidence for the implication of PPARβ in the regulation of development, metabolism, and inflammation in several tissues, including skeletal muscle, heart, skin, and intestine. Some of these findings indicate that pharmacological activation of PPARβ could be envisioned as a therapeutic option for the correction of metabolic disorders and a variety of inflammatory conditions. However, other experimental data suggesting that activation of PPARβ could result in serious adverse effects, such as carcinogenesis and psoriasis, raise concerns about the clinical use of potent PPARβ agonists.
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Affiliation(s)
- Jaap G Neels
- Institut National de la Santé et de la Recherche Médicale U 1065, Mediterranean Center of Molecular Medicine (C3M), Team "Adaptive Responses to Immuno-metabolic Dysregulations," Nice, France; and Faculty of Medicine, University of Nice Sophia-Antipolis, Nice, France
| | - Paul A Grimaldi
- Institut National de la Santé et de la Recherche Médicale U 1065, Mediterranean Center of Molecular Medicine (C3M), Team "Adaptive Responses to Immuno-metabolic Dysregulations," Nice, France; and Faculty of Medicine, University of Nice Sophia-Antipolis, Nice, France
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3
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New molecular findings in congenital myopathies due to selenoprotein N gene mutations. J Neurol Sci 2011; 300:107-13. [DOI: 10.1016/j.jns.2010.09.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2010] [Revised: 09/08/2010] [Accepted: 09/08/2010] [Indexed: 11/21/2022]
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4
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Turpeinen JP, Leppävuori J, Heinonen OJ, Kaila K, Salo J, Lilja M, Kesäniemi YA. Muscle fiber type I influences lipid oxidation during low-intensity exercise in moderately active middle-aged men. Scand J Med Sci Sports 2006; 16:134-40. [PMID: 16533352 DOI: 10.1111/j.1600-0838.2004.00436.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The simultaneous effects of body composition, cardiorespiratory fitness, physical activity, and muscle fiber characteristics on lipid oxidation at basal state and during exercise were studied in a population-based group (n = 70) of middle-aged men. Body composition, oxygen uptake, and lipid oxidation were determined in a volitional maximal exercise test, physical activity with a questionnaire, muscle fiber characteristics with muscle biopsy, and resting metabolic rate and lipid oxidation at basal state with indirect calorimetry. In regression analysis, type I muscle fibers contributed significantly to lipid oxidation at basal state (r = 0.30, r2 = 0.07, P<0.05) and during low-intensity exercise (r = 0.35, r2 = 0.10, P<0.05). ANOVA revealed 7.7% (P = 0.268) lower lipid oxidation at basal state, 14% (P<0.05) lower lipid oxidation in low-intensity exercise, and 10.5% (P = 0.088) lower lipid oxidation in moderate-intensity exercise in muscle fiber tertile I (type I muscle fiber count 28.8%) compared with muscle fiber tertile III (type I muscle fiber count 71.4%). In conclusion, the muscle fiber distribution contributed significantly to lipid oxidation during low-intensity exercise in moderately active middle-aged men.
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Affiliation(s)
- J-P Turpeinen
- Department of Internal Medicine and Biocenter Oulu, University of Oulu, Oulu, Finland.
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5
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Schrauwen-Hinderling VB, Hesselink MKC, Schrauwen P, Kooi ME. Intramyocellular lipid content in human skeletal muscle. Obesity (Silver Spring) 2006; 14:357-67. [PMID: 16648604 DOI: 10.1038/oby.2006.47] [Citation(s) in RCA: 136] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Fat can be stored not only in adipose tissue but also in other tissues such as skeletal muscle. Fat droplets accumulated in skeletal muscle [intramyocellular lipids (IMCLs)] can be quantified by different methods, all with advantages and drawbacks. Here, we briefly review IMCL quantification methods that use biopsy specimens (biochemical quantification, electron microscopy, and histochemistry) and non-invasive alternatives (magnetic resonance spectroscopy, magnetic resonance imaging, and computed tomography). Regarding the physiological role, it has been suggested that IMCL serves as an intracellular source of energy during exercise. Indeed, IMCL content decreases during prolonged submaximal exercise, and analogously to glycogen, IMCL content is increased in the trained state. In addition, IMCL content is highest in oxidative, type 1 muscle fibers. Together, this, indeed, suggests that the IMCL content is increased in the trained state to optimally match fat oxidative capacity and that it serves as readily available fuel. However, elevation of plasma fatty acid levels or dietary fat content also increases IMCL content, suggesting that skeletal muscle also stores fat simply if the availability of fatty acids is high. Under these conditions, the uptake into skeletal muscle may have negative consequences on insulin sensitivity. Besides the evaluation of the various methods to quantify IMCLs, this perspective describes IMCLs as valuable energy stores during prolonged exercise, which, however, in the absence of regular physical activity and with overconsumption of fat, can have detrimental effects on muscular insulin sensitivity.
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Affiliation(s)
- Vera B Schrauwen-Hinderling
- Department of Radiology, University Hospital Maastricht, P.O. Box 5800, 6202 AZ Maastricht, The Netherlands.
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6
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Ferreiro A, Ceuterick-de Groote C, Marks JJ, Goemans N, Schreiber G, Hanefeld F, Fardeau M, Martin JJ, Goebel HH, Richard P, Guicheney P, Bönnemann CG. Desmin-related myopathy with mallory body-like inclusions is caused by mutations of the selenoprotein N gene. Ann Neurol 2004; 55:676-86. [PMID: 15122708 DOI: 10.1002/ana.20077] [Citation(s) in RCA: 157] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Desmin-related myopathies (DRMs) are a heterogeneous group of muscle disorders, morphologically defined by intrasarcoplasmic aggregates of desmin. Mutations in the desmin and the alpha-B crystallin genes account for approximately one third of the DRM cases. The genetic basis of the other forms remain unknown, including the early-onset, recessive form with Mallory body-like inclusions (MB-DRMs), first described in five related German patients. Recently, we identified the selenoprotein N gene (SEPN1) as responsible for SEPN-related myopathy (SEPN-RM), a unique early-onset myopathy formerly divided in two different nosological categories: rigid spine muscular dystrophy and the severe form of classical multiminicore disease. The finding of Mallory body-like inclusions in two cases of genetically documented SEPN-RM led us to suspect a relationship between MB-DRM and SEPN1. In the original MB-DRM German family, we demonstrated a linkage of the disease to the SEPN1 locus (1p36), and subsequently a homozygous SEPN1 deletion (del 92 nucleotide -19/+73) in the affected patients. A comparative reevaluation showed that MB-DRM and SEPN-RM share identical clinical features. Therefore, we propose that MB-DRM should be categorized as SEPN-RM. These findings substantiate the molecular heterogeneity of DRM, expand the morphological spectrum of SEPN-RM, and implicate a necessary reassessment of the nosological boundaries in early-onset myopathies.
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Affiliation(s)
- Ana Ferreiro
- Institut National de la Santé et de la Recherche Médicale U582, Institut de Myologie, Groupe Hospitalier Pitié-Salpêtrière, Paris, France.
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7
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Strohm E, Daniels W. Ultrastructure meets reproductive success: performance of a sphecid wasp is correlated with the fine structure of the flight-muscle mitochondria. Proc Biol Sci 2003; 270:749-54. [PMID: 12713750 PMCID: PMC1691295 DOI: 10.1098/rspb.2002.2282] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Organisms show a remarkable inter-individual variation in reproductive success. The proximate causes of this variation are not well understood. We hypothesized that the ultrastructure of costly or complex tissues or organelles might affect reproductive performance. We tested this hypothesis in females of a sphecid wasp, the European beewolf, Philanthus triangulum (Hymenoptera, Sphecidae), that show considerable variation in reproductive success. The most critical component of reproduction in beewolf females is flying with paralysed honeybees, which more than double their weight. Because of the high energetic requirements for flight, we predicted that the ultrastructure of the flight-muscle mitochondria might influence female success. We determined the density of mitochondria and the density of the inner mitochondrial membranes (DIMM) of the flight muscles as well as age, body size and fat content. Only DIMM had a significant influence on female reproductive success, which might be mediated by an elevated adenosine triphosphate (ATP) supply. The variation in DIMM might result from differences in larval provisions or from an accumulation of mutations in the mitochondrial genome. Our results support the hypothesis that the organization of complex structures contributes to inter-individual variation in reproductive success.
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Affiliation(s)
- Erhard Strohm
- Department of Animal Ecology and Tropical Biology, Theodor-Boveri-Institute, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany.
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8
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Ferreiro A, Estournet B, Chateau D, Romero NB, Laroche C, Odent S, Toutain A, Cabello A, Fontan D, Dos Santos HG, Haenggeli CA, Bertini E, Urtizberea JA, Guicheney P, Fardeau M. Multi-minicore disease-searching for boundaries: Phenotype analysis of 38 cases. Ann Neurol 2001. [DOI: 10.1002/1531-8249(200011)48:5<745::aid-ana8>3.0.co;2-f] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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9
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Meydani M, Fielding RA, Cannon JG, Blumberg JB, Evans WJ. Muscle uptake of vitamin E and its association with muscle fiber type. J Nutr Biochem 1997. [DOI: 10.1016/s0955-2863(96)00176-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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10
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Freyssenet D, Berthon P, Denis C. Mitochondrial biogenesis in skeletal muscle in response to endurance exercises. Arch Physiol Biochem 1996; 104:129-41. [PMID: 8818195 DOI: 10.1076/apab.104.2.129.12878] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Repeated bouts of endurance exercise stimulates mitochondrial biogenesis in skeletal muscle. The synthesis of mitochondrial proteins involves a coordinated expression of both nuclear and mitochondrial genes. During this process, multiples sites of regulation have been identified at the transcriptional and translational levels. After their synthesis, mitochondrial proteins originating from the nuclear genome are imported into newly synthesized preexisting membranes and directed to one of the four mitochondrial subcompartments. The detailed mechanisms of the endurance training-induced mitochondrial biogenesis are still poorly understood. In particular, much work is needed to identify the molecular signals able to stimulate and coordinate the expression of mitochondrial proteins in response to endurance training. This will be a great help in the future to understand clearly the intimate mechanisms of mitochondrial biogenesis in skeletal muscle and the factors involved in endurance exercise performance.
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Affiliation(s)
- D Freyssenet
- Laboratoire de Physiologie-GIP Exercise, Faculté de Médecine, Université Jean Monnet, Saint-Etienne, France.
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11
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Schalin-Jäntti C, Laurila E, Löfman M, Groop LC. Determinants of insulin-stimulated skeletal muscle glycogen metabolism in man. Eur J Clin Invest 1995; 25:693-8. [PMID: 7498245 DOI: 10.1111/j.1365-2362.1995.tb01988.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
To examine factors which influence skeletal muscle glycogen synthesis in man, we related insulin sensitivity measured by euglycaemic insulin clamp in 43 healthy males to muscle glycogen synthase (GS) activity, GS protein content (Western blot), glycogen concentrations and fibre composition. Insulin increased muscle glycogen content (P < 0.05) and the change in glycogen content correlated with the GS protein content (r = 0.90, P = 0.01). GS protein concentration correlated inversely with age (r = -0.69, P = 0.04). Non-oxidative glucose disposal was inversely related to per cent type 2B fibres (r = -0.52, P < 0.05). The influence of age on these relationships was separately studied in young (n = 12, age = 26 +/- 2 years) and elderly (n = 15, age = 56 +/- 2 years) males. Insulin increased GS activity significantly only in young subjects (from 17.8 +/- 3.0 to 25.3 +/- 3.2 nmol mg protein-1 min-1; P = 0.015). GS activity and non-oxidative glucose disposal correlated in young (r = 0.69, P = 0.01) but not in the elderly (r = 0.064, P = 0.82) males, and this relationship was not influenced by the degree of obesity. In conclusion, muscle fibre type and GS activity are both determinants of muscle glycogen metabolism in healthy, normoglycaemic males. The close relationship between non-oxidative glucose metabolism and GS activity in young males is altered in ageing.
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12
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Abstract
Proportions of slow (type 1) muscle fibres of the vastus lateralis and percentage body fat were measured in 11 healthy sedentary men. The proportion of slow muscle fibres was inversely related to fatness; at least 40% of the variability in fatness may be related to variation in muscle fibre type. Metabolic evidence in 50 men, provided by the respiratory exchange ratio (RER) during cycle ergometry, indicated that fatter men (or, in the subset of 11 men, those with a low proportion of slow muscle fibres) combusted less fat during work at 100 W than did lean men (or those with a high proportion of slow fibres). The effects of fitness and of body size were excluded in the analysis. The evidence supports the hypothesis that muscle fibre type is an aetiological factor for obesity.
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Affiliation(s)
- A J Wade
- Department of Physiology, London Hospital Medical College, UK
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13
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Ramsbottom R, Williams C, Boobis L, Freeman W. Aerobic fitness and running performance of male and female recreational runners. J Sports Sci 1989; 7:9-20. [PMID: 2733082 DOI: 10.1080/02640418908729818] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The purpose of the present study was to assess fitness and running performance in a group of recreational runners (men, n = 18; women, n = 13). 'Fitness' was determined on the basis of their physiological and metabolic responses during maximal and submaximal exercise. There were strong correlations between VO2 max and treadmill running speeds equivalent to blood lactate concentrations of 2 mmol l-1 (V-2 mM) or 4 mmol l-1 (V-4 mM), 'relative running economy' and 5 km times (r = -0.84), but modest and non-significant correlations between muscle fibre composition and running performance. The results of the submaximal exercise tests suggested that the female runners were as well trained as the male runners. However, the men still recorded faster 5 km times (19.20 +/- 1.97 min vs 20.97 +/- 1.70 min; P less than 0.05). Therefore the of the present study suggest that the faster performance times recorded by the men were best explained by their higher VO2 max values, rather than their training status per se.
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Affiliation(s)
- R Ramsbottom
- Department of Physical Education and Sports Science, University of Technology, Loughborough, Leicestershire
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Baumann H, Jäggi M, Soland F, Howald H, Schaub MC. Exercise training induces transitions of myosin isoform subunits within histochemically typed human muscle fibres. Pflugers Arch 1987; 409:349-60. [PMID: 3627955 DOI: 10.1007/bf00583788] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Fibre type composition based on histochemical myosin ATPase reaction was studied in cross sections of biopsies from the vastus lateralis muscle of men. In addition, protein composition as well as peptide patterns of isolated myosin heavy chains were examined in batches of individually classified fibres from the same biopsies. High intensity endurance training during 8 weeks induces significant decreases by 31-70% of the type IIB fibre population in 3 of 4 subjects (in one case no change was observed). These decreases were offset by corresponding increases in either type I or type IIA fibres with the type IIC fibres remaining always below 3%. A total of 13 professional cyclists with training periods over several years have a 20 times lower content of type IIB fibres than 4 sedentary controls and a concomitant high content of 80% of type I fibres. The content of type I and type IIB fibres of 8 sprinter athletes did almost not differ from that of controls. Thus the type IIB fibres respond most sensitively with a decrease to aerobic endurance training. Since both type IIA and IIB fibres were identical in protein composition containing the same fast variety of myosin light chains and heavy chains as well as troponin-I, their interconversion could not be seen at the molecular level. However, the slow variety of myosin light chains and of troponin-I started accumulating after 8 weeks of training in type IIA fibres. Furthermore, the myosin heavy chain isoform started shifting by producing new peptide patterns that resemble the digestion pattern of slow myosin heavy chains in fibres which still classified as type IIA. These changes on the molecular level in type IIA fibres mark the beginning of their transition over the intermediate and variable type IIC fibres, towards the slow type I fibre.
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Essén-Gustavsson B, Henriksson J. Enzyme levels in pools of microdissected human muscle fibres of identified type. Adaptive response to exercise. ACTA PHYSIOLOGICA SCANDINAVICA 1984; 120:505-15. [PMID: 6237550 DOI: 10.1111/j.1748-1716.1984.tb07414.x] [Citation(s) in RCA: 113] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Enzyme activities were determined in pools of type I (slow twitch) and II A and II B (fast twitch) fibres of the thigh muscle from individuals engaged to a high degree in physical training of an endurance character and from non-endurance-trained controls. The endurance-trained (ET) group had significantly higher activity levels of the mitochondrial enzymes citrate synthase, malate dehydrogenase, and 3-OH-acylCoA dehydrogenase both in type I (2.1X, 1.7X, 1.4X) and in type II A (2.3X, 1.8X, 1.4X) and II B fibres (2.0X, 1.5X, 1.5X) than the non-endurance-trained (NET) group. Of the glycolytic enzymes, phosphofructokinase (PFK) in type I fibres was significantly higher (1.8X) in the ET than in the NET group whereas glyceraldehydephosphate dehydrogenase (GAPDH) in type I fibres was similar in the two groups. In type II fibres both PFK and GAPDH levels tended to be higher in the ET group. Lactate dehydrogenase (LDH) of both fibre types were not different in the two groups. Type I fibres differed significantly from type II fibres for all the six enzymes measured in both groups. However, no significant difference between fibres of types II A and II B was found. The results indicate that fibres of types I, II A and II B in human skeletal muscle all possess great adaptability with regard to their oxidative capacity. Furthermore, the data suggest that extensive endurance training may enhance the glycolytic capacity in both type I and type II fibres although the glycolytic capacity of the muscle as a whole generally is low in endurance trained subjects owing to a predominance of type I fibres. It is concluded that further studies are needed to determine whether there is a metabolic distinction between fibres of types II A and II B.
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