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WS-33-4 Measurement of muscle fatigue using muscle fiber conduction velocity
Workshop 34. Event-relatedpotentials (ERPs) in psychiatric disorders tients, however, unchanged or even prolonged CMCTs can also be found. In few patients, the size of MEPs seems to increase. Magnetic thresholds appear not to change in both groups. We conclude that TMS is a valuable and practicable method to investigate the corticospinal tract in fatigue. First results point io both an exercise-induced reduction of central drive and a possibly compensatory facilitation.
] WS-33-2 ] Techniques for quantitating central and peripheral fatigue Robert G. Miller 1.2, Jane Kent Braun z, Michael Weiner 2. 1Department of Neurology, California Pacific Medical Center; z University of California at San Francisco, San Francisco, CA In motivated and healthy young subjects, central fatigue is usually not significant, however, in many patients with neuromuscular diseases, central fatigue is an important component of the fatigue process. To assess central fatigue quantitatively, we utilize the measurement of added force in response to a brief tetanic train of stimuli superimposed upon a maximum voluntary contraction. In addition, we examine the relationship between declining maximum voluntary contraction force and declining tetanic tension during fatigue, since they should fall in parallel when there is no central fatigue. To quantitate peripheral fatigue we utilize the compound muscle action potential (CMAP) as an indicator of neuromuscular transmission and muscle membrane function, twitch tension and tetanic tension as an index of muscular force generation, and altered metabolites measured by nuclear magnetic resonance spectroscopy to evaluate bioenergetic changes during fatigue. The difficult task of evaluating excitation contraction coupling impairment is estimated by correlating changes in twitch tension with changes in CMAP, speed of force generation and relaxation in the twitch and the tetanus, and changes in the ratio of surface rectified E M G over force. In patients, upper motor neuron dysfunction is quantitated by analyzing rapid repetitive movements, the speed of voluntary force generation during a rapid submaximal isometric contraction and also the added force measure. Fatigue is a complex phenomenon and simultaneous measurement of both central and peripheral factors is necessary to begin to understand its pathophysiology.
IWS-33-3] Electromyographic manifestations of muscle fatigue
$59
cular fatigue threshold will be described with special reference to 1) muscle fiber types, 2) energy supply and excitation-contraction (E-C) coupling, and 3) excitability of spinal motor neuron pools.
WS-33-4] Measurement of muscle fatigue using muscle fiber conduction velocity Akio Kimura, Kozo Hanayama 1, Naoichi Chino t, Yasutomo Okajima. Keio Univ. Tsukigase Rehabilitation Center;
1Dept. of Rehabilitation Medicine, Keio Univ. School of Medicine It is known that the muscle fiber conduction velocity varies depending on the conditions of muscle use such as in a prolonged activity causing muscle fatigue. To determine the change of the muscle fiber conduction velocity after loading of 50% maximal voluntary contraction, we measured the conduction velocity using a surface electrode array that we originally developed. Biceps brachii muscles of twenty healthy male volunteers aged 20 to 42 years old (mean = 26.3) were examined. E M G signals during minimal isometric contraction were detected by the surface electrode array consisting of fifteen electrodes spaced at 5 mm intervals. This method makes it possible to visualize the propagation of motor unit action potentials, so it is easy to measure the muscle fiber conduction velocity. Mean conduction velocity of all subjects before loading was 3.33 -t- 0.28 m/s. On the other hand, the conduction velocity after contraction maintaining 50% of maximal voluntary contraction torque as long as possible was 2.59 4- 0.33 m/s. This decrease of the conduction velocity was statistically significant. Moreover, from the results of the recovery pattern of the conduction velocity during 6 min minimal contraction after loading, subjects were divided into two groups. One group showing significant recovery have had the endurance time exceeding 50 s during loading of 50% maximal voluntary contraction. The other group showing no apparent recovery have had the endurance time less than 50 s. It is postulated that two patterns of recovery of the muscle fiber conduction velocity reflects the difference of muscle fiber type.
WS-34. EVENT-RELATED POTENTIALS (ERPS) IN PSYCHIATRIC DISORDERS
I WS-34-1 ] Late positive components of ERPs and arousal level in schizophrenia
Toshio Moritani. Laboratory of Applied Physiology, The Graduate
Hiroshi Aikawa, Ryoichi Toyoshima, Toshio Yamauchi.
School of Human and Environmental Studies, Kyoto University
Department of Neuropsychiatry, Saitama Medical School, Japan
Human muscle fatigue studies have been performed under a variety of experimental conditions and the electromyographic (EMG) signal has quite often been used as a means of assessment of muscle fatigue. In many cases, the concept of fatigue is applied to assessing deterioration of muscle performance, i.e. "failure point" at which the muscle is no longer able to sustain the required force output level. The physiological data within the muscle shows timedependent changes during the time course of muscle fatigue development. Such changes have been shown to be related to hydrogen ion and metabolite accumulation and to sodium and potassium ion concentration shifts. These changes would in turn affect the muscle excitation-contraction coupling including the muscle membrane properties, muscle action potential propagation, leading to EMG manifestations of muscle fatigue distinct from mechanical manifestations. In this workshop, different EMG techniques for assessing the extent of muscular fatigue and muscle work capacity at neuromus-
The relationships between late positive components (LPCs) of ERPs and arousal level in schizophrenia was examined. The subjects were 24 schizophrenics and 20 normal controls. EEG data were taken one minute and 10 minutes after the onset of EEG recording. Each recording was analysed into power spectra using a Fourier transformation; first under resting conditions and then under auditory stimulation task conditions. The classification into two groups, relatively low- and high-arousal groups, was based upon the directions of the alpha wave amplitude changes after rest and upon tasks. The alpha wave reactivities were measured by the absolute magnitudes of the alpha wave amplitude changes after rest and upon tasks. ERPs were recorded using the odd-ball paradigm with eyes closed. The responses to each target and nontarget tone were averaged separately, and a total of about 50 trials without artifacts and errors were averaged for target responses. LPCs-amplitudes were defined as the average amplitude of ERPs between 250- and 450-ms after stimulus onset.
] WS-33-2 ] Techniques for quantitating central and peripheral fatigue Robert G. Miller 1.2, Jane Kent Braun z, Michael Weiner 2. 1Department of Neurology, California Pacific Medical Center; z University of California at San Francisco, San Francisco, CA In motivated and healthy young subjects, central fatigue is usually not significant, however, in many patients with neuromuscular diseases, central fatigue is an important component of the fatigue process. To assess central fatigue quantitatively, we utilize the measurement of added force in response to a brief tetanic train of stimuli superimposed upon a maximum voluntary contraction. In addition, we examine the relationship between declining maximum voluntary contraction force and declining tetanic tension during fatigue, since they should fall in parallel when there is no central fatigue. To quantitate peripheral fatigue we utilize the compound muscle action potential (CMAP) as an indicator of neuromuscular transmission and muscle membrane function, twitch tension and tetanic tension as an index of muscular force generation, and altered metabolites measured by nuclear magnetic resonance spectroscopy to evaluate bioenergetic changes during fatigue. The difficult task of evaluating excitation contraction coupling impairment is estimated by correlating changes in twitch tension with changes in CMAP, speed of force generation and relaxation in the twitch and the tetanus, and changes in the ratio of surface rectified E M G over force. In patients, upper motor neuron dysfunction is quantitated by analyzing rapid repetitive movements, the speed of voluntary force generation during a rapid submaximal isometric contraction and also the added force measure. Fatigue is a complex phenomenon and simultaneous measurement of both central and peripheral factors is necessary to begin to understand its pathophysiology.
IWS-33-3] Electromyographic manifestations of muscle fatigue
$59
cular fatigue threshold will be described with special reference to 1) muscle fiber types, 2) energy supply and excitation-contraction (E-C) coupling, and 3) excitability of spinal motor neuron pools.
WS-33-4] Measurement of muscle fatigue using muscle fiber conduction velocity Akio Kimura, Kozo Hanayama 1, Naoichi Chino t, Yasutomo Okajima. Keio Univ. Tsukigase Rehabilitation Center;
1Dept. of Rehabilitation Medicine, Keio Univ. School of Medicine It is known that the muscle fiber conduction velocity varies depending on the conditions of muscle use such as in a prolonged activity causing muscle fatigue. To determine the change of the muscle fiber conduction velocity after loading of 50% maximal voluntary contraction, we measured the conduction velocity using a surface electrode array that we originally developed. Biceps brachii muscles of twenty healthy male volunteers aged 20 to 42 years old (mean = 26.3) were examined. E M G signals during minimal isometric contraction were detected by the surface electrode array consisting of fifteen electrodes spaced at 5 mm intervals. This method makes it possible to visualize the propagation of motor unit action potentials, so it is easy to measure the muscle fiber conduction velocity. Mean conduction velocity of all subjects before loading was 3.33 -t- 0.28 m/s. On the other hand, the conduction velocity after contraction maintaining 50% of maximal voluntary contraction torque as long as possible was 2.59 4- 0.33 m/s. This decrease of the conduction velocity was statistically significant. Moreover, from the results of the recovery pattern of the conduction velocity during 6 min minimal contraction after loading, subjects were divided into two groups. One group showing significant recovery have had the endurance time exceeding 50 s during loading of 50% maximal voluntary contraction. The other group showing no apparent recovery have had the endurance time less than 50 s. It is postulated that two patterns of recovery of the muscle fiber conduction velocity reflects the difference of muscle fiber type.
WS-34. EVENT-RELATED POTENTIALS (ERPS) IN PSYCHIATRIC DISORDERS
I WS-34-1 ] Late positive components of ERPs and arousal level in schizophrenia
Toshio Moritani. Laboratory of Applied Physiology, The Graduate
Hiroshi Aikawa, Ryoichi Toyoshima, Toshio Yamauchi.
School of Human and Environmental Studies, Kyoto University
Department of Neuropsychiatry, Saitama Medical School, Japan
Human muscle fatigue studies have been performed under a variety of experimental conditions and the electromyographic (EMG) signal has quite often been used as a means of assessment of muscle fatigue. In many cases, the concept of fatigue is applied to assessing deterioration of muscle performance, i.e. "failure point" at which the muscle is no longer able to sustain the required force output level. The physiological data within the muscle shows timedependent changes during the time course of muscle fatigue development. Such changes have been shown to be related to hydrogen ion and metabolite accumulation and to sodium and potassium ion concentration shifts. These changes would in turn affect the muscle excitation-contraction coupling including the muscle membrane properties, muscle action potential propagation, leading to EMG manifestations of muscle fatigue distinct from mechanical manifestations. In this workshop, different EMG techniques for assessing the extent of muscular fatigue and muscle work capacity at neuromus-
The relationships between late positive components (LPCs) of ERPs and arousal level in schizophrenia was examined. The subjects were 24 schizophrenics and 20 normal controls. EEG data were taken one minute and 10 minutes after the onset of EEG recording. Each recording was analysed into power spectra using a Fourier transformation; first under resting conditions and then under auditory stimulation task conditions. The classification into two groups, relatively low- and high-arousal groups, was based upon the directions of the alpha wave amplitude changes after rest and upon tasks. The alpha wave reactivities were measured by the absolute magnitudes of the alpha wave amplitude changes after rest and upon tasks. ERPs were recorded using the odd-ball paradigm with eyes closed. The responses to each target and nontarget tone were averaged separately, and a total of about 50 trials without artifacts and errors were averaged for target responses. LPCs-amplitudes were defined as the average amplitude of ERPs between 250- and 450-ms after stimulus onset.