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Titolo:
Mean frequency and signal amplitude of the surface EMG of the quadriceps muscles increase with increasing torque - a study using the continuous wavelet transform
Autore:
Karlsson, S; Gerdle, B;
Indirizzi:
Fac Hlth Sci, Dept Rehabil Med, S-58185 Linkoping, Sweden Fac Hlth Sci Linkoping Sweden S-58185 bil Med, S-58185 Linkoping, Sweden Univ Hosp, Pain & Rehabil Ctr, Linkoping, Sweden Univ Hosp Linkoping Sweden Hosp, Pain & Rehabil Ctr, Linkoping, Sweden Univ Umea Hosp, Pain & Rehabil Ctr, Umea, Sweden Univ Umea Hosp Umea Sweden Umea Hosp, Pain & Rehabil Ctr, Umea, Sweden
Titolo Testata:
JOURNAL OF ELECTROMYOGRAPHY AND KINESIOLOGY
fascicolo: 2, volume: 11, anno: 2001,
pagine: 131 - 140
SICI:
1050-6411(200104)11:2<131:MFASAO>2.0.ZU;2-F
Fonte:
ISI
Lingua:
ENG
Soggetto:
I FIBER PREDOMINANCE; DYNAMIC CONTRACTIONS; MYOELECTRIC SIGNALS; STATIC CONTRACTIONS; CONDUCTION-VELOCITY; FORCE RELATIONSHIPS; POWER FREQUENCY; FATIGUE; ELECTROMYOGRAM; SPECTRUM;
Keywords:
EMG; knee extensors; morphology; force; short-time mean frequency; continuous wavelet transform;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Clinical Medicine
Citazioni:
39
Recensione:
Indirizzi per estratti:
Indirizzo: Gerdle, B Fac Hlth Sci, Dept Rehabil Med, S-58185 Linkoping, Sweden Fac Hlth Sci Linkoping Sweden S-58185 -58185 Linkoping, Sweden
Citazione:
S. Karlsson e B. Gerdle, "Mean frequency and signal amplitude of the surface EMG of the quadriceps muscles increase with increasing torque - a study using the continuous wavelet transform", J ELECTROMY, 11(2), 2001, pp. 131-140

Abstract

The continuous wavelet transform (CWT), a time-frequency method. was used when calculating mean Frequency of the power spectrum (MNF) and signal amplitude (RMS) of the surface EMG to investigate their relationships to force during a gradually increasing knee extension (ramp). Based upon the CWT, MNF was redefined to include time dependence on the EMG signal frequency contents, the short-time MNF (STMNF). Surface EMG was recorded from vastus lateralis, rectus femoris and vastus medialis in 21 clinically healthy subjectsduring a brief, gradually increasing contraction up to 100% of a maximum voluntary contraction (MVC), with a duration of approximately 10 s. The relationships between the EMG variables and force using linear regression were determined for each subject. For vastus lateralis, we also investigated if certain aspects of the muscle morphology (i.e., proportions and areas of different fibre types) influenced the EMG-force relationship. For the majority of subjects (17-18 out of 21 subjects) there were significant positive correlations between STMNF and force in the three muscles. Nosex differences were found in intercepts or regression coefficients of STMNF. The muscle morphology had a significant influence on the STMNF-force intercept and the regression coefficient. Positive and highly significant linear correlations between RMS and force were found for all subjects and all three muscles. In conclusion, time frequency methods can be applied when investigating EMG during brief contractions associated with non-stationarity. In a great majority of the subjects, and in the three muscles, significant linear force dependencies were found for STMNF, Thus, when evaluating muscle fatigue, e.g., in ergonomic situations, it is important to consider the force level asone factor that can influence the results. Morphological variables (fibre proportions and fibre areas) influenced the STMNF-force relationship in vastus lateralis. (C) 2001 Elsevier Science Ltd, All rights reserved.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 02/04/20 alle ore 11:08:38