Why It is preferable to use increased efforts to prepare adult swimmers (EN,RO)

Why It is preferable to use increased efforts to prepare adult swimmers

Moto: Tony MacGuinness, Yesterday at 10:53
Professor Victor Selouyanov of the former Soviet Union has discovered how to make fast and intermediate aerobic fibers, and this principle forms the basis for the Impact of Swimming ...
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by MIHAI URSTA / INMS Buc.
(cut from the mastery posted on the INMS blog, Buc.RO.#)

Muscle fiber - a bidirectional approach,

#Estimating the emptying of glycogen stores in muscle during exercise showed that more intense efforts were closely correlated with greater glycogen consumption predominantly in Type II muscle fibers (9, 36).
ATP production based on the immediate phosphate system, i.e., dephosphorylation of creatine phosphate (Fc), was found to be higher in type II fibers during intense exercise (30, 33).
This is explainable because these metabolites (Fc and glycogen) have been found to be continued in larger amounts in muscle fiber type II.
It is known that the release of lactate from the muscle cell increases in parallel with the intensity of the effort. An interesting fact is that two of the major lactococcal monocarboxylic (TML) carriers that are in the cell membrane, but have different properties in terms of reaction rate.
The TML4 isomer that is predominantly found in the Type II muscle fiber membrane has a large dissociation constant (easily catches the substrate, the lactate molecule, but it dissociates it more heavily) with Km (Michaelis constant) of 20-35mM over time which for the TML1 isomer is more present in the type I, Km Km fiber membrane is 3-5mM (11, 20).
This also shows the ability and the predisposition of Type II muscle fibers to produce and use anaerobic energy, and as mentioned before, this facilitates faster muscle contraction.
By using muscle biopsies it is possible to appreciate the changes in the percentage of expression in muscles, each type of muscle fiber, the size of its cross-section, and the level of capillary, which were influenced by the nature of the protocol followed in the experiment.
All of these together indicate the existence of a certain way of recruiting muscle fibers during exercise, according to which type I fibers having a lower threshold of triggering action potentials are recruited at low intensities, whereas in type II, the fiber contraction is determined by higher stress intensities (13, 17) (Fig. 4).
Interestingly, the idea of ​​making a parallel between discoveries made from laboratory studies and analyzes and eye-to-eye assessments of the correspondence between speed and / or intensity of contraction and oxygen consumption or heart rate, when measuring oxygen consumption is possible, knowing that there is a close relationship between the level of oxygen consumption and that of the heart rate (8).
Surely completing them with measurements of blood and muscle metabolites in the blood and muscles, it comes in and improves the accuracy of measuring the degree of involvement in the recruitment and activation level of the three main muscle fiber groups during exercise.

#the theme of the paper: "The way in which the recruitment of type II muscle fibers affects the kinetics of oxygen absorption during dynamic physical exercise"
scientific candidate
at the Institute of Physiology of the August Krogh - Copenhagen exercise

Initiator Section Sports Physiology - prof./mast. - MIHAI URSTA

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Dece este de preferat folosirea eforturilor marite in pregatirea inotatorilor adulti

Moto: Tony MacGuinness, Ieri la 10:53

Profesorul Victor Selouyanov al fostei Uniuni Sovietice, a descoperit cum sa faca fibre rapide si intermediare aerobe, iar acest principiu formeaza baza Impactului de inot ...

by MIHAI URSTA / INMS Buc. 

(decupaj din materialul postat pe blogul INMS, Buc.RO.#)

Fibra musculara - o abordare bidirectionala,

#Estimarea golirii rezervelor de glicogen din muschi in timpul exercitiului a aratat ca efectuarea eforturilor mai intense au fost strans corelata cu un consum mai marit de glicogen predominant in fibrele musculare de tip II (9, 36). 

  Productia de ATP pe baza sistemului fosfagen imediat, adica, defosforilarea fosfatului de creatina (Fc), s-a stabilit a fi mai mare in fibrele de tipul II,  in timpul exercitiilor intense (30, 33).

Acest lucru este explicabil, pentru ca acesti metaboliti ( Fc si glicogenul) au fost descoperiti a fi continuti in cantitati mai mari in tipul II de fibra musculara. 

  Se stie ca eliberarea lactatului din celula musculara creste in paralel cu intensitatea efortului. Un fapt interesant constatat, este acela ca, doi dintre principalii transportatorii monocarboxilici de lactat (TML) care se afla in membrana celulara, dar au proprietati diferite in ceea ce priveste viteza de reactie.

Izomerul TML4 care se gaseste predominant in membrana fibrelor musculare de tip II are o mare constanta de disociere (prinde usor substratul, molecula de lactat, dar se disociaza mai greu de ea), avand Km (constanta Michaelis) de 20-35mM, in timp ce pentru izomerul TML1 prezent mai mult in membrana fibrelor de tipul I, Km este de 3-5mM (11, 20).

 Aceasta arata de asemenea abilitatea dar si predispozitia fibrelor musculare de tipul II de a produce si folosi energia in mod anaerob, si asa cum a fost mentionat mai inainte, acest lucru faciliteaza viteza mai mare de contractie a muschiului. 

  Prin folosirea biopsiilor musculare este posibil aprecierea schimbarilor survenite in procentul de exprimare in muschi, al fiecarui tip de fibra musculara, al marimii sectiunii transversale a acestuia, precum si al nivelului de capilarizare, care au fost influentate de natura protocolului urmat in cadrul experimentului. 

Acestea toate, impreuna, indica existenta unui anume mod de recrutare al fibrelor musculare in timpul efortului, in concordanta cu care, tipul I de fibre care au un prag mai scazut al declansarii potentialelor de actiune sunt recrutate la intensitati reduse, in timp ce in tipul II, contractia fibrelor este determinata de intensitati mai mari ale efortului (13, 17) (Fig 4).
  Devine interesanta ideea de a face o paralela intre descoperirile facute in urma studiilor si analizelor facute in laborator si aprecierile facute cu ochiul liber,in privinta corespondentei dintre viteza si/sau intensitatea contractiei si consumul de oxigen sau frecventa cardiaca,cand masurarea consumului de oxigen nu este posibila, stiut fiind ca exista o stransa relatie intre nivelul consumului de oxigen si cel al frecventei cardiace (8).

Cu siguranta completarea acestora cu masuratori ale variatilor de metaboliti in sange si muschi, vine si imbunatateste acuratetea masurarii gradului de implicare in ceea ce priveste recrutarea si nivelul de activare al celor trei grupe principale de fibre musculare in timpul efortului.

tema lucrarii: "Modul prin care recrutarea fibrelor musculare de tipul II afecteaza cinetica absorbtiei oxigenului in timpul exercititului fizic dinamic"
candidat stiintific
la Institutul de Fiziologie a exercitiului fizic August Krogh - Copenhaga
Initiator Sectiune Fiziologie sportiva

Mihai Ursta,     mihai71ursta@yahoo.dk,

Bibliografie:

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9. Gollnick P.D., Piehl K. and Saltin B. (1974). Selective glycogen depletion pattern in human skeletal muscle fibres after exercise of varying intensity and at varying pedaling rate. J Physiol (Lond) 241:45-57

11. Hallestrap A.P. and Meredith D. (2004) The SLC16 gene family-from monocarboxylate transporters (MCTs) to aromatic amino acid transporters and beyond. Pflűgers Arch 447: 619-628.

13. Henneman E., Somjen G. and Carpenter D.O. (1965). Functional significance of the cell size in spinal motorneurons.J Neurophysiol 28:560-580

20. Juel C and Halestrap A.P. (1999) Lactate transport in skeletal muscle: role and regulation of the monocarboxylate transporter. J Physiol 517: 633-642.

17. Houtman C.J., Stegeman D.F., Van Dijk J.P. Zwarts M.J. (2003) Changes in muscle fibers conduction velocity indicates recruitment of distinct motor unit populations J Appl Physiol 95: 1045-1054.

30. Sahlin K., Sönderlund K., Tonkonogi M. and Hirakoba K. (1997). Phosphocreatine content in single fibres of human muscle after sustained submaximal exercise. Am J Physiol 273:C172-C178

33. Sönderlund K. and Hultman E. (1991). ATP and phosphocreatine changes in single human muscle fibres following intense electrical stimulation. Am J Physiol 261:E737-E741.

36. Vøllestad N.K. and Blom P.C. (1985). Effect of varying exercise intensity on glycogen depletion in human muscle fibers. Acta Physiol Scand 125 (3):395-405.