Correlation Between Muscle Fatigue And Ultrasound Attenuation

There are for two drawbacks when evaluating muscle fatigue with SEMG signals:First.The SEMG signal is a weak signal.The amplitude and frequency of the signal are mainly defined by the physiological characteristics of the muscle.They exhibit "passive" characteristics and are easily incorporated into the noise.Second.Firstly,the time-domain and frequency-domain analysis of the SEMG signal is needed to obtain helpful information and the real-time performance is poor.The ultrasonic signal has strong directionality,more concentrated energy,and strong penetration.The transmit signal is controllable and has "active" characteristics.Using ultrasound to measure muscle fatigue can improve the signal-to-noise ratio and improve the real-time performance of the system.the theoretical analysis phase,the feasibility of ultrasound evaluation of muscle fatigue was first analyzed:Focusing on the analysis of ultrasonic characteristics in muscle tissue,combined with changes in morphological parameters and physiological parameters during muscle fatigue,the amplitude attenuation model of ultrasound in gradually fatigued muscles was simplified;Secondly,the standard SSA analysis is improved when dealing with a longer time series,and the selection of window length and the number of reconstructed singular values are reviewed.Experimental analysis stage:Firstly,the effects of the improved SSA,wavelet threshold,and empirical formula in suppressing Gaussian noise and random impulse noise are compared and discussed.Se condly,electromyographic signals and ultrasound signals of 10 subjects during the isom etric exercises were collected simultaneously.The collected signals were utilized to analyze the relationship between attenuation of ultrasound amplitude and muscle development and muscle fatigue,and the attenuation of ultrasound in gradually fatigued muscle tissue was analyzed.The attenuation model of ultrasound in gradually fatigued muscle tissue can be lowered to a function only related to attenuation coefficient and propagation distance.For slightly fatigued muscle tissue,its physiological characteristics change(PH value decreases,temperature rises,and muscle thickness increases).These changes result in increased attenuation coefficient and longer propagation distance,which cause attenuatio n of the ultrasound amplitude and exponential attenuation.The attenuation rate of theultrasonic response signal can be used to estimate the degree of muscle development.The more developed the muscles of the subjects,the larger the amplitude of the ultrasound changes with the changes of the muscle tissue status.When the amplitude of the ultrasound changes slowly,the subject's muscles are not sufficiently developed.When dealing with non-stationary sequences and longer time series,the overlapping SVD algorithm has better denoting effect than the standard SSA algorithm.