Fatigue effects on motor unit activity during submaximal contractions.
Arch Phys Med Rehabil
; 81(9): 1211-6, 2000 Sep.
Article
em En
| MEDLINE
| ID: mdl-10987164
ABSTRACT
OBJECTIVE:
To examine motor unit changes during the development of fatigue in healthy subjects.DESIGN:
Automated decomposition-enhanced spike-triggered averaging was used to characterize motor unit size and firing rate in the dominant vastus medialis during maintained contractions at 10% and 30% of maxima voluntary contraction (MVC).SETTING:
Academic outpatient neuromuscular clinic.PARTICIPANTS:
Healthy laboratory personnel. MAIN OUTCOMEMEASURES:
Surface electromyogram, surface-detected motor unit action potential amplitude (S-MUAP), mean firing rate, force (MVC), motor unit index.RESULTS:
Surface electromyogram values and S-MUAP amplitudes increased during both 10% and 30% MVC fatiguing contractions, while mean firing rates decreased. A motor unit index, indicating the degree of motor unit pool activation, increased similarly to S-MUAP size, implying that new and larger units were recruited to maintain the contraction. Repeated contractions led to earlier motor unit changes and fatigue.CONCLUSION:
During submaximal fatiguing contractions, additional motor units are activated to maintain strength. These changes begin early, within the first minute, particularly after a previous fatiguing effort.
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Base de dados:
MEDLINE
Assunto principal:
Músculo Esquelético
/
Fadiga
/
Contração Muscular
Limite:
Adult
/
Female
/
Humans
/
Male
/
Middle aged
Idioma:
En
Ano de publicação:
2000
Tipo de documento:
Article