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  • 1
    ISSN: 1432-1106
    Keywords: Motor unit types ; Twitch and tetanic tensions ; Potentiation ; Peroneus tertius muscle ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Motor units of the cat peroneus tertius muscle were systematically analyzed using the criteria established by Burke et al. (1973). On the basis of their speed of contraction and resistance to fatigue, 121 (97%) of 125 motor units examined in ten adult cats could be classified as belonging to one of four types: fast-fatiguable (FF), fast-resistant (FR), fast-intermediate (FI), and slow-resistant (S). Peroneus tertius was found to contain 30% FF motor units, 9% FI units, 39% FR units, and 22% S units. Contraction times of fast motor units (FF, FR, and FI) ranged from 15 to 27 ms and those of S units from 26 to 42 ms. The mean tetanic tensions were 37 g for FF units, 29 g for FI units, 7.5 g for FR units, and 1.1 g for S units. Fast motor units displayed considerable post-tetanic potentiation of twitch tension. Under similar conditions of stimulation, FF units appeared able to potentiate more and faster than FR units.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1106
    Keywords: Muscle spindle ; Fusimotor ; Afferent ; Intrafusal contraction ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Responses of secondary endings of muscle spindles of the peroneus tertius muscle of the anaesthetized cat have been recorded during repetitive stimulation of functionally single fusimotor fibres that produced slowing of the discharge. In a sample of 125 pairs of single fusimotor fibres and secondary spindle afferents 5 examples of slowing were seen. The amount of slowing became less at longer muscle lengths. Conditioning the spindle by stimulating the muscle nerve at fusimotor strength, at a length 2.5 mm longer than the test length, and then returning to the test length 3 seconds later led to a greater degree of slowing of the discharge than after conditioning stimulation at the test length. With one exception, responses to muscle stretch were reduced during stimulation of a fusimotor fibre that produced slowing. On two occasions stimulating a fusimotor fibre that produced slowing of the response of one secondary ending, led to excitation of two other endings. Two possible explanations for the generation of slowing responses have been considered. The first is that the slowing is the result of contraction of the region of intrafusal fibre directly underlying the secondary sensory ending. The second, which we favour since it accounts for the facts more adequately, is that slowing is the result of shortening of the region of nuclear chain fibres on which the sensory ending lies, produced by movement in an adjacent nuclear bag fibre.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1439-6327
    Keywords: Physical fitness ; $$\dot V_{{\text{O}}_{\text{2}} } $$ max ; $$\dot V_{{\text{O}}_{\text{2}} } $$ 170 ; Maximum steady state ; Aptitude physique ; $$\dot V_{{\text{O}}_{\text{2}} } $$ max ; $$\dot V_{{\text{O}}_{\text{2}} } $$ 170 ; Eégime stable limite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé L'aptitude physique de trois groupes de sujets différents est estimée par la consommation d'O2 pourFC = 170/min. La validité de ce critère est vérifiée en mesurant simultanément la consommation maximum d'O2 et le régime stable limite selon Sadoul et coll. ou Petit et coll. La dépense énergétique atteinte avecFC = 170/min représente une proportion variable de la $$\dot V_{{\text{O}}_{\text{2}} } $$ maximum. Dans chaque groupe on observe une importante dispersion des résultats. La rapport diffère d'un groupe à l'autre: il est en moyenne de 60,1% pour 39 étudiants en médecine, 78,9% pour 57 sauveteurs et 66,1% pour 20 étudiantes. La fréquence de 170/min ne correspond pas toujours à la limite de tolérance d'un effort prolongé; 16% des étudiants maintiennent un exercice musculaire prolongé sans signe d'intolérance avecFC = 180/min. La $$\dot V_{{\text{O}}_{\text{2}} } $$ 170 sous-estime donc leur capacité physique. Cette sous-estimation est accentuée chez les jeunes filles qui atteignent le régime stable limite avecFC moyenne = 178,1/min. Au contraire, les sauveteurs montrent des signes d'intolérance lorsqueFC moyenne dépasse 159,3/min. Cette réduction est attribuée à l'âge plus élevé de ce dernier groupe. La $$\dot V_{{\text{O}}_{\text{2}} } $$ 170 ne précise pas non plus la limite de tolérance chez les malades pulmonaires ou coronariens. Ce critère n'est pas applicable lorsqueFC est influencée en dehors de l'exercice musculaire. La $$\dot V_{{\text{O}}_{\text{2}} } $$ 170 ne représente donc pas dans tous les cas la limite réelle de tolérance à l'effort, c'est pourquoi nous lui préférons une méthode moins simplifiée où des critères objectifs d'intolérance sont recherchés.
    Notes: Summary The physical fitness of three differents groups of subjects is assessed by the O2 uptake corresponding to a 170 beats/min heart rate. The results of this test are compared to the values of $$\dot V_{{\text{O}}_{\text{2}} } $$ maximum and to the “régime stable limite” according to Sadoul et al. resp. Petit et al. The percentage of the maximal O2 uptake reached with a 170/min heart rate is highly variable. An important dispersion is observed in the results of each group of subjects. The percentage also differs from a group to another; its mean value is 60.1% for the 39 students in medecine, 78.9 for 57 rescuers and 66.1% for 20 female students. The 170/min heart rate does not always correspond to the tolerance of a work of long duration; 16% of the students are able to sustain a prolonged muscular work in steady state with a heart rate of 180 beats/min. Using the $$\dot V_{{\text{O}}_{\text{2}} } $$ 170, their physical capacity is underevaluated. This underevaluation is greater in the third group in which the female students reach the maximum steady state with a mean heart rate of 178.1 beats/min. On the contrary, rescuers present intolerance signs when their mean heart rate exceeds 159.3/min. This reduction is probably due of the older age of this group. UsingV o 2 170, we are also unable to define the tolerance limit in pulmonary or coronary disease. This criterion cannot be used when the heart rate is influenced by something else than muscular exercise. So, the $$\dot V_{{\text{O}}_{\text{2}} } $$ 170 does not represent in all the cases, the right tolerance limit to work and we prefer a more complete method using objective criteria for intolerance.
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