University of New Hampshire
Mentor: Dr. Ronald Croce
A Comparison of Short-Time Fourier and Wavelet Transforms on EMG and MMG Frequency Spectrum During Fatiguing Muscular Contractions
At present there is a dearth of research comparing electromyographic (EMG) and mechanomyographic (MMG) frequency responses during dynamic muscle contractions computed by short-time Fourier transformation (STFT), and more computer-intensive time–frequency analyses, such as wavelet transformations (WT), despite the fact that WT analysis has been found to be both decidedly valid, reliable (da Silva, et al., 2008), and superior (Beck et al., 2008). The primary purpose of this investigation was to compare frequency spectra analyzed using traditional STFT and WT of vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF) muscles during fatiguing isokinetic flexion and extension. Secondly, this investigation examined peak and mean knee extensor torque, EMG and MMG amplitude, and median and mean frequency spectra of VL, VM, and RF muscles to determine physiological changes occurring during muscle fatigue. To determine the effect of fatigue on the VM, VL, and RF, twelve healthy adult male university students (age = 22.5 ± 2.0 years) performed two discontinuous rounds of maximum effort, flexion-extension movements to fatigue at a velocity of 1800/s on an Isokinetic dynamometer. Fatigue data were analyzed at the following percentages of total number of repetitions completed (TNR): 1%-, 15%-, 30%-, 45%-, 60%-, 75%-, 90%-, and 100%-, and at the final repetition of a post-2-min-rest bout of flexion-extension (100%-Post). Data were analyzed and by comparing contraction intensity and muscle fatigue spectra using FFT and WT, we were able to determine which method of waveform analysis is most effectual in monitoring fatigue in contracting muscles.