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Twitch Analysis as an Approach to Motor Unit Activation During Electrical Stimulation

 

作者: Marc Heyters,   Alain Carpentier,   Jacques Duchateau,   Karl Hainaut,  

 

期刊: Canadian Journal of Applied Physiology  (NRC Available online 1994)
卷期: Volume 19, issue 4  

页码: 451-461

 

ISSN:1066-7814

 

年代: 1994

 

DOI:10.1139/h94-037

 

出版商: NRC Research Press

 

关键词: muscle contraction;mechanical twitch;motor point;nerve

 

数据来源: NRC

 

摘要:

The mechanical twitch in response to increasing electrical stimulus intensity, delivered both over the motor point and motor nerve, was recorded in the first dorsal interosseous (FDI) and the adductor pollicis (AP), and only over the motor point in the soleus (Sol), lateral (LG), and medial (MG) gastrocnemius muscles of human subjects. The relationship between intensity of electrical stimulation (ES) and twitch torque showed a positive linear regression in all muscles. In the FDI and AP the relationship was not significantly different when ES was applied at the motor point or over the motor nerve. At small intensities of activation, ES induced larger twitch torques in the MG and LG, which contain a roughly equal proportion of slow and fast motor units (MUs) compared to the Sol, which is composed mainly of slow type fibres. Moreover, the relationship between ES intensity and twitch time-to-peak is best fitted in all muscles by a power curve that shows a greater twitch time-to-peak range in its initial part for muscles containing a larger proportion of fast MUs (LG, MG) than for muscles mainly composed of slow MUs (Sol). In conclusion, these results induced by ES at the motor point and/or over the motor nerve confirm the concept of a reversed sequence of MU activation, as compared to voluntary contractions, and document this viewpoint in muscles of different function and composition. The reversed sequence of MU activation is more clearly evident during motor point ES.Key words: muscle contraction, mechanical twitch, motor point, nerve

 

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