Faculty Opinions recommendation of Studies with a reconstituted muscle glycolytic system. The anaerobic glycolytic response to simulated tetanic contraction.

Fatigue and potentiation are two forms of force modulation. A general definition of fatigue is "a circumstance where less than the anticipated contractile response is obtained." Fatigue is associated with depressed Ca2+ release and possibly decreased Ca2+ sensitivity. Potentiation results from increased Ca2+ sensitivity due to regulatory light chain phosphorylation. Muscle fatigue and potentiation can coexist, making it difficult to quantify these processes. With repetitive 10 Hz stimulation, the developed tension first increases, then decreases. Is fatigue present when developed tension first begins to decrease or when it falls below the developed tension of the first response? Intermittent incompletely fused tetanic contractions for which peak developed tension first decreases, then increases, is another unusual example of fatigue. A third example is when twitch contractions following a tetanic contraction decrease to a level below the pretetanic twitch amplitude, indicating that fatigue may have been coexistent with posttetanic potentiation. These observations illustrate the complexity of detecting fatigue, based on the simple, but commonly accepted definition presented above. Care must be taken in interpreting "before vs. after" contractile responses. Even when the contraction amplitude is greater than the initial response, there is no guarantee that mechanisms associated with fatigue are not present. Key words: calcium sensitivity, staircase, posttetanic potentiation, myosin light chains, skeletal muscle

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Effects of the infrared lamp illumination during the process of muscle fatigue in rats

Brazilian Archives of Biology and Technology ◽

10.1590/s1516-89132007000300006 ◽

2007 ◽

Vol 50 (3) ◽

pp. 403-407 ◽

Cited By ~ 2

Author(s):

Andréia Zarzour Abou-Hala ◽

Daniella Galvão Barbosa ◽

Rodrigo Labat Marcos ◽

Cristina Pacheco-Soares ◽

Newton Soares da Silva

Keyword(s):

Energy Density ◽

Muscle Fatigue ◽

Treated Group ◽

Control Group ◽

Force Of Contraction ◽

Tetanic Contraction ◽

Fatigue Process ◽

Infrared Lamp ◽

Tibialis Muscle ◽

Lamp Illumination

In this study the effects of infrared lamp illumination during the muscle fatigue process was studied. Three different groups (n=5) were used: one control group and two treated (Infrared Lamp 780-1400nm), with the energy densities of 0.5 and 1.0 J/cm² and time of illumination of 300 seconds. The treated animals were illuminated in one point directly in the tibialis muscle, after the first tetanic contraction out of six, with an interval between each tetany. The results were registered in an electrophysiograph and the intensity of the force of contraction in grams was analysed. It was observed that the control group presented a reduction in the intensity of the force of contraction, while the treated group managed to maintain it, which was clearly evident in the energy density of 0.5 J/cm². It was concluded that the use of the infrared lamp illumination was efficient concerning resistance to muscle fatigue.

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A bladder contractility constant

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1983.245.5.r673 ◽

1983 ◽

Vol 245 (5) ◽

pp. R673-R677

Author(s):

J. C. Byrne ◽

A. Tozeren

Keyword(s):

Initial Velocity ◽

Active Component ◽

Isometric Force ◽

Muscle Length ◽

Rate Of Change ◽

Contractile Element ◽

Tetanic Contraction ◽

Muscle Contractility ◽

Maximum Isometric Force ◽

The Moment

Muscle contractility can be characterized by two related properties: force and velocity. The initial velocity of a tetanic contraction is inversely related to preload. This was demonstrated experimentally by Hill and quantified in his well-known empiric equation. Subsequent investigators argued that a theoretical maximum contractile element velocity (V max) could be predicted from the rate of change of isometric force. V max has been applied clinically in heart studies, prompting others to use similar methods to evaluate bladder contractility. These attempts have so far been unsuccessful. The present study shows for whole canine bladders that the time to reach maximum isometric force from the moment of onset of active contraction is a constant independent of muscle length, preload, and maximum force. This can be expressed as a frequency constant (omega) whose calculation appears similar to that for V max. In contrast to V max, omega is obtained only from the active component of pressure.

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Lactic and Pyruvic Acid Relations in Contracting Mammalian Muscle

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1956.186.2.221 ◽

1956 ◽

Vol 186 (2) ◽

pp. 221-223 ◽

Cited By ~ 15

Author(s):

Jacob Sacks ◽

Jo H. Morton

Keyword(s):

Lactic Acid ◽

Steady State ◽

Pyruvic Acid ◽

Acid Content ◽

Marked Decrease ◽

Blood Stream ◽

Anaerobic Conditions ◽

Tetanic Contraction ◽

Mammalian Muscle ◽

Lactic Acid Content

Tetanic contraction of mammalian muscle under essentially anaerobic conditions was found to result in marked increase in the pyruvic acid content as well as in the lactic acid content. The increase in lactic acid content was proportionately greater than in the pyruvic acid content. Repeated single twitches at a rate of 1/sec., continued long enough to produce a steady state, resulted in only a slight increase in pyruvic acid content, with a marked decrease in the ratio of pyruvic to lactic acid. The pyruvic acid formed during the steady state of activity appears not to pass into the blood stream.

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