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Wavelet analysis of quadriceps power spectra and amplitude under varying levels of contraction intensity and velocity.
Muscle & Nerve 2014 November
INTRODUCTION: We investigated the effect of contraction intensity [100%, 75%, 50%, and 25% maximum voluntary contraction (MVC)] and movement velocity (50°, 100°, 200°, and 400°/s) on surface electromyography root mean square amplitude (SEMGRMS ) and median frequency (SEMGMDF ) of rectus femoris (RF), vastus lateralis (VL), and vastus medialis (VM).
METHODS: SEMGs during knee extension were resolved into their respective frequencies using wavelet transformations.
RESULTS: RF, VL, and VM muscles displayed increased SEMGMDF as contraction intensity increased from 25% to 50% MVC and from 75% to 100% MVC, and each muscle displayed its own unique frequency shifting patterns. The SEMGMDF was not influenced by movement velocity. SEMGRMS increased in all 3 muscles as contraction intensity increased and was influenced by movement velocity, with the highest values observed at 400° and 200°/s.
CONCLUSIONS: We infer that increasing contraction intensity facilitates greater recruitment of fast-twitch muscle fibers, but there are differing responses in RF, VL, and VM muscles.
METHODS: SEMGs during knee extension were resolved into their respective frequencies using wavelet transformations.
RESULTS: RF, VL, and VM muscles displayed increased SEMGMDF as contraction intensity increased from 25% to 50% MVC and from 75% to 100% MVC, and each muscle displayed its own unique frequency shifting patterns. The SEMGMDF was not influenced by movement velocity. SEMGRMS increased in all 3 muscles as contraction intensity increased and was influenced by movement velocity, with the highest values observed at 400° and 200°/s.
CONCLUSIONS: We infer that increasing contraction intensity facilitates greater recruitment of fast-twitch muscle fibers, but there are differing responses in RF, VL, and VM muscles.
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