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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.
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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.
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  • 3
    ISSN: 1439-6327
    Keywords: Heart Rate ; Body Temperature ; Exercise ; Fréquence cardiaque ; Température corporelle ; Exercice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé L'évolution comparée de la fréquence cardiaque et de la tempërature corporelle est mesurée chez 23 sujets effectuant des exercices musculaires d'une durée d' 1/2 H, avec un métabolisme d'environ 1 L O2/min, à température très élevée (ts 46 °C; th 35 °C). La relation qui unit ces deux paramètres est linéaire tout au moins pour la partie moyenne du diagramme. Pour les valeurs plus faibles, en-dessous de 100 pulsations/min, la fréquence cardiaque est influencée de façon variable par la température corporelle. Au-delà de 170 pulsations/min, la fréquence cardiaque, approchant de sa valeur maximum, n'est plus fonction de l'hyperthermie. L'amplitude de la réaction cardiaque présente de grandes variations individuelles. En moyenne, une élévation de température interne de 1 °C entraîne une accélération cardiaque de 32,3 pulsations/min, cependant, les extrêmes s'étendent de 21 à 46 pulsations/min. La linéarité de la relation justifie l'emploi de la fréquence cardiaque comme témoin d'une surcharge thermique pendant le travail musculaire à haute température. Le comportement individuel est un reflet de l'aptittide de chaque sujet à supporter les températures élevées.
    Notes: Summary Heart rate and body temperature were measured in 23 men walking on a treadmill during 1/2 an hour in a very hot environment (ta 46 °C; twb 35 °C), with an energy expenditure of about 11 O2/min. A linear relationship was found between the two parameters, at least for the middle part of the diagram. For lower values, below 100 beats/min, heart rate is influenced in a variable manner by the body temperature. Above 170 beats/min, heart rate approaches its highest value, and is hence no more influenced by hyperthermy. From one subject to another, the extent of cardiac reaction varies considerabily. On the average, when body temperature increases by 1 °C, heart rate increases by 32,3 beats/min, but extreme values are 21 and 46 beats/min. The linearity of the diagram justifies the use of heart rate as a reference of a thermal overloading during muscular exercise in hot environment. The individual comportment truly reflects each subject's capacity in bearing hot climates.
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  • 4
    ISSN: 1439-6327
    Keywords: Beta-Adrenergic Blockade ; Heart Rate ; Submaximum and Maximum Exercice ; Bêta-bloqueur ; Fréquence cardiaque ; Exercice submaximum et maximum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Resume L'effet d'un bêta-bloqueur sur la réponse cardiaque d'exercice a été vérifié chez 7 jeunes adultes sains. L'ingestion de 80 mg de propranolol entraîne une diminution significative de la fréquence cardiaque à tous les niveaux métaboliques avec d'importantes variations individuelles. Cette modification circulatoire réduit la tolérance à l'exercice musculaire et fait baisser la consommation maximum d'O2, en moyenne de 15,5%.
    Notes: Summary The effect of Beta-adrenergic blockade on the circulatory response has been verified during muscular exercise on 7 healthy young men. The administration of 80 mg propranolol induced a significant decrease in cardiac frequency to each metabolic level, however, with an important individual variation. This modification of the circulation reduces the tolerance to muscular exercise and the maximum oxygen consumption (mean: 15.5%).
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