The purpose of this study was to investigate whether application of bipolar galvanic vestibular stimulation (GVS) would influence the common modulation of motor unit discharge rate in bilateral soleus muscles during quiet standing. Soleus motor unit activity was recorded with fine wire electrodes in each leg. Subjects stood, with eyes closed, on two adjacent force platforms to record postural sway with the head facing straight ahead, turned to right, or turned left. Subjects also swayed voluntarily without GVS to the same position as evoked during the GVS. There was no difference in the common drive to bilateral soleus motoneurons during quiet standing and voluntary sway tasks. Common drive was significantly lower during right cathode GVS with the head straight or turned to the right. These results demonstrate that manipulation of vestibular afferent input influences the common modulation of bilateral soleus motor unit pairs during quiet standing.
Marc Monsour, Tanya D. Ivanova, Tim D. Wilson and S. Jayne Garland
Yi-Ming Huang, Ya-Ju Chang, Miao-Ju Hsu, Chia-Ling Chen, Chia-Ying Fang and Alice May-Kuen Wong
The purpose of this study was to evaluate whether agonist muscle fatigue changed the coactivation time and the co-contraction magnitude of the agonist and antagonist muscle, and if the agonist muscle fatigue produced bias (constant error: CE) and inconsistency (variable error: VE) of the force. Subjects are 10 healthy people and one person with impaired proprioception. EMG and force for fast (0.19 ± 0.06 s) and slow (1.20 ± 0.44 s) targeted isometric dorsiflexions were recorded before and after fatigue of the dorsiflexors. The results revealed that the coactivation time increased after fatigue only in the slow contractions but the co-contraction magnitude did not change. The postfatigue increment of the CE was greater in the fast contractions than in the slow ones. We conclude that the postfatigue compensatory strategy can reduce the fatigue-induced bias. The change of muscles activation level after fatigue might be under the influence of the common drive. Impaired proprioception is a possible cause of the fatigue-related increase in bias and inconsistency.
Mark Holten Mora-Jensen, Pascal Madeleine and Ernst Albin Hansen
.1007/s00421-008-0878-4 De Luca , C.J. , & Erim , Z. ( 1994 ). Common drive of motor units in regulation of muscle force . Trends in Neurosciences, 17 , 299 – 305 . PubMed 10.1016/0166-2236(94)90064-7 Dennerlein , J.T. , Mote , C.D. , Jr. , & Rempel , D.M. ( 1998 ). Control strategies
Danilo Bondi, Sergio Di Sano, Vittore Verratti, Giampiero Neri, Tiziana Aureli and Tiziana Pietrangelo
tasks to better understand the common drives of neuromotor performances. Specific parameters of tracing task, as well of other graphomotor tasks, should be taken into account in the evaluation of developmental trajectories and dysfunctions. The results of our study could shed a new light into the
Courtney L. Pollock, Michael A. Hunt, Taian M. Vieira, Alessio Gallina, Tanya D. Ivanova and S. Jayne Garland
about the ankle poststroke requires the investigation of the role of each plantarflexor muscle in the control of postural sway. Interestingly, despite the asymmetry of postural control following stroke, during maintenance of standing balance under external loading, a moderate level of common drive to