Nonlinear Characteristics Of Local Muscle Fatigue. Exercise-induced Muscle Tone Signals

Vibromyography is usually called as muscle sound, which is caused by muscle contraction as a result of the voice of muscle fiber sliding friction, in a word, It's an acoustic wave caused by muscle movement. Muscle sound value of the potential important applications can be non-invasive measurement of muscle motor unit, for our athletes, in training through real-time monitoring of muscular sound as much as possible, properly stimulate muscle movement, muscle contraction to increase the speed and explosive force, to improve the performance will go a long way. In this paper, non-linear chaotic dynamic analysis method was used to analysis of muscle tone of the chaotic signal characteristics; observed changes and characteristics of non-linear analysis of indicators such as signals complexity, orderly and so on, during gastrocnemius and soleus muscle fatigue in the process of dynamic load, then compared the differences between the two, given the neuromuscular system activities mechanism of exercise-induced muscle fatigue. This study included two experiments, 10 subjects participated in the experiment, a total of 20 tests. Experiments were given a password in accordance with the experiment requirements to finish action, applying the first generation of dual-channel acoustic analyzer to gather the real-time signal, then, use matlab calculation of non-linear analysis indicators such as correlation dimension, largest Lyapunov index. The results showed that muscle tone is a signal feature of the nonlinear dynamics of chaotic signals through analysis of phase space reconstruction, correlation dimension, as its non-linear characteristics between periodic signal and random signal; Experimental results show that with the deepening of fatigue, changes in phase-space map has become more soft, tend to be more rules, that is to say from a state of disorder tend to be more orderly, the time delay become larger and more stable, by comparing the phase-space reconstruction before and after fatigue, calculating the time delay and the correlation dimension, lyapunov index of gastrocnemius and soleus muscle. The correlation dimension lyapunov index reduced shows that with the deepening of fatigue, the regularity of muscle tone signals increased , the complexity reduced, the complexity from a higher value developed to a lower value. As the subject's physique, skinfold thickness, skin surface temperature, the degree of action is different, the calculation results was impact, so the general trend of the correlation dimension and lyapunov index of gastrocnemius, soleus muscle was decreased ,did not show very good linear trend.I think the reduction of system complexity is the result of reducing in the central nervous system frequency of payment, as a large number of impulse spread to the nerve center of the cerebral cortex, so excited about the long-term, leading to increased consumption, with the deepening of fatigue, in order to reduce consumption, the release of the central nervous system will reduce the frequency. At the same time, the central nervous system of the motor neurons control the level of the fine reduced, leading the degree of motor unit activities synchronization to strengthen. Muscle tone developed to the form of simple and orderly, that is, muscle tone decreased the complexity of the signal is the result of central nervous system protective function.Soleus muscle mainly composed by I-type fiber or red slow muscle fibers, so it is slow-twitch fibers, slow reduction of red muscle with a high aerobic capacity and fatigue resistance. Gastrocnemius is type II, that is shrinking fast white muscle fibers, in the aspects of aerobic capacity, contraction speed and fatigue resistance is poor, Belonging to high-intensity, short-term movement of the muscle type. Due to the difference muscle type and the function of the movement, calculated results showed that the average and the slope of the absolute value of correlation dimension of soleus muscle is small than gastrocnemius, meanwhile the average and the slope of the absolute value of lyapunov index of soleus muscle is small than gastrocnemius. Relative small for the complexity, which is considered as a strong anti-fatigue. Accordingly, I believe that the correlation dimension and lyapunov index can be used to determine the type of muscle. This still need more theory and experiment to prove.The results seemed to suggest the synchronization activities of motor units may be one of the important mechanisms that controlling muscle work during exercise and muscle can be classified by calculating chaotic characteristics index.