Changes in motor unit recruitment thresholds of the human anconeus muscle during torque development preceding shortening elbow extensions.
J Neurophysiol
; 107(10): 2876-84, 2012 May.
Article
en En
| MEDLINE
| ID: mdl-22378176
ABSTRACT
Rate of torque development and the subsequent movement velocity are modulated by motor unit (MU) properties, primarily MU discharge rate and MU recruitment threshold (MURT). In isometric conditions, MURTs have been shown to decrease with increased rates of torque development. It is unclear whether this relationship is similar in the production of dynamic shortening contractions. Using fast joint velocities to drive the system, we aimed to determine how anconeus MURTs recorded during the torque production phase preceding movement were affected in relation to the resultant peak elbow extension velocity. Recruitment thresholds of 17 MUs from 9 young men were tracked throughout non-isokinetic dynamic elbow extensions with velocities ranging from 64°/s to 500°/s at a constant resistance of 25% of maximal voluntary isometric contraction and during isometric elbow extensions (0°/s). Relative MURTs decreased â¼50% from the slowest (<25% of maximal velocity) to the fastest (>75% of maximal velocity) resultant velocity ranges (P < 0.05). Although a significant (P < 0.001) but weak (r = -0.27, R(2) = 0.08) relationship was observed between MURT and resultant peak elbow extension velocity for the group, only 7 of the 17 MUs displayed significant moderate (r = -0.40, R(2) = 0.17) to strong (r = -0.85, R(2) = 0.73) negative MURT-velocity relationships. These data indicate variable responses of MURTs with increasing resultant peak velocity, which may be related to the intrinsic properties of individual MUs.
Texto completo:
1
Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Reclutamiento Neurofisiológico
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Músculo Esquelético
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Codo
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Contracción Isométrica
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Movimiento
Límite:
Adult
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Humans
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Male
Idioma:
En
Revista:
J Neurophysiol
Año:
2012
Tipo del documento:
Article
País de afiliación:
Canadá