Linear and non-linear analysis of surface electromyograms in weightlifters
The present research was aimed at investigating the peculiarities of surface electromyogram (sEMG) signals in 12 weightlifting athletes (WLA) and 9 control subjects (control group, CG) The sEMG signals were recorded from both vastus lateralis muscles during 20 s isometric contractions made at 30% and 60% of the maximal voluntary contraction (MVC). Ground reaction force (vertical component) was recorded using a force plate. The sEMG was analysed in the frequency domain and the median frequency (MDF) was computed over successive 1 s epochs. A non-linear technique, recurrence quantification analysis was also applied to assess the presence and time course of deterministic structures in sEMG. The percentage of determinism (%DET) was used as a synthetic parameter to quantify the amount of regularly repeating sEMG waves within the signal itself (bursts). In 5 WLA the sEMG displayed a clear burst activity centred at 11 Hz. These bursts were correlated with force output oscillations and were evident both at 30% and 60%MVC. The MDF decay with time was more evident in WLA than in CG subjects. The %DET increased in WLA, this increase being more evident during 60%MVC contractions. Our results seemed to suggest a special disposition among WLA for the development of long-term changes in firing probability during sub-maximal isometric exercise. The MDF and %DET data provided indications of a greater involvement of fast twitch muscle fibres in WLA than in CG.
© Copyright 2001 European Journal of Applied Physiology. Springer. Kaikki oikeudet pidätetään.
Aiheet: | lihasfysiologia lihas painonnosto lihassähkökäyrä |
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Aihealueet: | voima ja nopeus urheilu biologiset ja lääketieteelliset tieteet |
DOI: | 10.1007/s004210000364 |
Julkaisussa: | European Journal of Applied Physiology |
Julkaistu: |
2001
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Vuosikerta: | 84 |
Numero: | 4 |
Sivuja: | 337-342 |
Julkaisutyypit: | artikkeli elektroninen julkaisu |
Kieli: | englanti (kieli) |
Taso: | kehittynyt |