Identification of Fiber Type Proportions in Gastrocnemius Lateralis and Soleus Muscles Using Surface EMG Signals and Concentration Measure Derived From Rihaczek Distribution

Fiber type proportion influences the fatigue characteristics and force production in skeletal muscles. In this study, surface electromyography signals and concentration measure derived from Rihaczek distribution are used to identify the fiber type proportions in gastrocnemius lateralis (GL) and soleus (SOL) muscles. Signals are acquired using standard protocols until the subjects experience muscle fatigue and are processed using Rihaczek distribution. Further, a comparative study is performed to analyze the advantages of energy-based features over complexity, statistical, and spectral frequency-based features in analyzing the fiber type proportions. Features such as renyi information, spectral skewness, spectral flatness, and peak frequency are also extracted from the distributions of non-fatigue (NF) and fatigue (F) segments. Results indicate that the extracted features showed a decrease during fatigue in the signals of GL and an increase in the case of SOL, reflecting their distinct fiber composition. The highest statistical significance of p equal to 4.26E-05 and 6.47E-05 respectively is obtained using concentration measure for differentiating the signals of GL and SOL during NF and F states. The lowest significance is observed for renyi information in discriminating the signals. The energy-based features like concentration measure and spectral flatness are found highly sensitive to fiber-type variations compared to other features considered in this study. Thus, the proposed method using Rihaczek distribution is found suitable for identifying the fiber type differences among GL and SOL. This approach may be utilized for identifying the fiber typology in different skeletal muscles which finds application in sports science.