MOTOR UNIT MECHANOMYOGRAPHIC SIGNAL AND SYNCHRONIZED ACTIVITY IN MOTOR UNITS DURING VOLUNTARY MUSCLE CONTRACTIONS
- VernacularTitle:持続的筋力発揮時の運動単位筋振動信号と運動単位の同期化活動
- Author:
SHIGERU MORIMOTO
;
CHIGUSA ISHIWATA
;
NAOMI MIYAMOTO
;
MIFUYU KAMO
- Publication Type:Journal Article
- Keywords:
motor unit;
MUAP;
MMG;
synchronized activity;
prolonged activity.
- From:Japanese Journal of Physical Fitness and Sports Medicine
2009;58(3):365-378
- CountryJapan
- Language:Japanese
-
Abstract:
The aim of the present study was to investigate, by analysis of motor unit action potential (MUAP) and motor unit mechanomyogram (MUMS) wave-forms, whether the synchronized activity of motor units (MUs) is a factor in increasing the integrated value of a mechanomyogram during muscle contraction at relatively low tension levels. MUAP and MUMS of m. vastus medialis were recorded by Ag/AgCl disc electrode ( 5mmφ) and condenser microphone ( 10mmφ), respectively, during muscle contractions, brief isometric constant contractions (BICC) and prolonged isometric constant contraction (PICC) at the target torques from just above the decruitment threshold torque of the objective MU to 20% of maximal voluntary contraction (MVC). The degree of synchronization of MUs, defined from the amplitude of late positive deflection (VLPD), could be seen in MUAP wave-forms.The amplitude of the positive phase in MUMS (MS-Vpositive) had no relationship with the increase of VLPD in BICC condition. During PICC, MS-Vpositive and VLPD increased with time. Applying linear regression analysis on the relation between VLPD and MS-Vpositive, except for data at 20%MVC, there was significant correlation. However, the scale of the time increments, between VLPD and MS-Vpositive, were different comparing exponential and logarithmic figures, respectively. Therefore, in the present experiment, the meaningful relationship between the two parameters could not be introduced. It is necessary to further investigate the relationship between the two parameters including the firing frequency of MU, intramuscular pressure and extent of recording area of both sensors.
