Complementary roles of central command and muscular reflex in the regulation of heart rate during submaximal isometric contraction.
Electromyogr Clin Neurophysiol
; 32(1-2): 3-10, 1992.
Article
em En
| MEDLINE
| ID: mdl-1541244
ABSTRACT
During submaximal isometric contraction, the heart rate (HR) and the electromyographic activity (EMG) increase continuously. Although activation of the muscle and the cardiovascular center is placed partly under the common control of the central command, the nature of the relationship that may exist between HR and the integrated electromyogram (iEMG) is seldom studied. Seventeen healthy men, 22.4 +/- 0.5 years of age (M +/- SE), performed isometric contractions with the right elbow flexors. Forces of 25, 40, 50 and 65% of the maximum voluntary contraction (MVC) were used, and the contractions were sustained until (isotonic isometric contraction IIC) and beyond exhaustion (anisotonic isometric contraction AIC). During IIC, a linear relationship exists between HR and iEMG; the slope of this relationship is independent of the relative force developed, which is in favor of a predominant role played by the central command in HR increase. The increase in the ratio iEMG/HR at the approach of local muscular exhaustion would indicate that at the end of IIC there is an increase in the relative part furnished by the information of peripheral origin in HR regulation. During AIC, the force (F) decreases in an exponential manner and stabilizes at around 25% MVC from tAIC = 70 s on. The iEMG and HR change independently iEMG decreases like F such that iEMG/F remains constant; HR continues to increase in the first phase corresponding to the rapid decrease in F and iEMG, then in a second phase, it decreases linearly with respect to time. Our results suggest that the action of the central command is dominant during stage 1 of AIC, while during stage 2 the relative part furnished by the muscle reflexes increases. Beyond tAIC = 70 s, there seems to be a certain degree of central fatigue.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Recrutamento Neurofisiológico
/
Reflexo
/
Frequência Cardíaca
/
Contração Isométrica
/
Músculos
Limite:
Adolescent
/
Adult
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Humans
/
Male
Idioma:
En
Revista:
Electromyogr Clin Neurophysiol
Ano de publicação:
1992
Tipo de documento:
Article
País de afiliação:
França