基于肌音信号短时傅里叶变换的桡侧腕屈肌疲劳程度研究

Muscle Fatigue of Flexor Carpi Radialis Based on Short-Time Fourier Transform to Mechanomyography

肌肉疲劳是由运动引起的肌肉最大随意收缩力减小的现象,其研究可应用于生理医学的职业病预防或体育工程的运动员训练等方面。本文采用短时傅里叶变换对肌音信号进行处理,提取频域特征平均功率频率(Mean Power Frequency,MPF)和中值频率(Median Frequency,MDF),研究其与肌肉疲劳程度之间的关系。9名健康的男性志愿者参与了本次试验,采用等值于60%最大随意收缩力(MVC)的力产生恒力肌肉疲劳,同步记录每一位受试者桡侧腕屈肌的肌音信号,对提取的频域参数进行分析。将持续30s的肌肉疲劳过程分为6个时间阶段(每个阶段为5s),并对每个时间阶段内的MPF和MDF计算均值。结果表明,随着肌肉疲劳程度加深,肌音信号的MPF和MDF在每个时间阶段内的均值均呈现近似线性下降的趋势。在30s肌肉疲劳过程中,从第1阶段(1~5s)到第6阶段(26~30s),MPF均值下降了15.8%,MDF均值下降了26.1%。基于短时傅里叶变换提取的MPF和MDF指标能良好地反映疲劳敏感性和稳定性,在评定肌肉静态疲劳方面是较好的参考指标。本文采用的方法和得到的结果为后期更深入地使用肌音信号对肌肉疲劳程度进行量化研究提供了依据。

M u s c l e fatigue,caused b y doing sports,is a p h e n o m e n o n of the decrease of the m a x I m u m voluntary contraction （MVC ） , w h I c h could be used in the fields of the prevention of occupational diseases in physiology or medicine and of the training of athletes in physical engineering. This paper adopted short-time Fourier transform to process the MMG,then gained the features of frequency domain,that is,mean p o w e r frequency （M P F ） a n d me d I a n frequency （MDF ） ,and finally investigated the relationship bet w e e n these features and the degree of muscle fatigue. The subjects of this experiments w e r e 9 healthy male volunteers w h o produced the muscle fatigue with constant force by performing 60% of MVC and simultaneously w e r e recorded separately the m e c h a n o m y o g r a p h y （MMG ） signals of flexor carpi radialis. B y analyzing the parameters of the the frequency-domain gaining f r o m the experiment,the results demonstrated that if the process of muscle fatigue w e r e divide into 6 time segments,with thedegree of muscle fatigue increasing, the average values of MPF and MDF ----the t w o features of frequency-domainrespectively presented the trend of an approximately linear decline at each time s e g m e n t. During the 30 s of musclefatigue,the declining range of the average values of MPF w a s 15. 8 % f r o m the first to the sixth time segment,the declining range of the average values of MDF w a s 26.1% f r o m the first to the sixth stage. T h e index of M P F and MDF based on short-time Fourier transform demonstrated high sensibility and stability to reflect muscle fatigue, suggesting the potential application of MPF a n d MDF as reference indices in evaluating static muscle fatigue. T h e method adopted in this paper and the results of this experiment provided the basis for the quantitative research of the degree of muscle fatigue b y using MMG further in the future.