The ipsilateral corticospinal responses to cross-education are dependent upon the motor-training intervention

Abstract

This study aimed to identify the ipsilateral corticospinal responses of the contralateral limb following different types of unilateral motor-training. Three groups performing unilateral slow-paced strength training (SPST), non-paced strength training (NPST) or visuomotor skill training (VT) were compared to a control group. It was hypothesised that 4 weeks of unilateral SPST and VT, but not NPST, would increase ipsilateral corticospinal excitability (CSE) and reduce short-interval cortical inhibition (SICI), resulting in greater performance gains of the untrained limb. Tracking error of the untrained limb reduced by 29 and 41% following 2 and 4 weeks of VT. Strength of the untrained limb increased by 8 and 16% following 2 and 4 weeks of SPST and by 6 and 13% following NPST. There was no difference in cross-education of strength or tracking error. For the trained limb, SPST and NPST increased strength (28 and 26%), and VT improved by 47 and 58%. SPST and VT increased ipsilateral CSE by 89 and 71% at 2 weeks. Ipsilateral CSE increased 105 and 81% at 4 weeks following SPST and VT. The NPST group and control group showed no changes at 2 and 4 weeks. SPST and VT reduced ipsilateral SICI by 45 and 47% at 2 weeks; at 4 weeks, SPST and VT reduced SICI by 48 and 38%. The ipsilateral corticospinal responses are determined by the type of motor-training. There were no differences in motor performance between SPST, NPST and VT. The data suggests that the corticospinal responses to cross-education are different and determined by the type of motor-training.

Dominant and nondominant leg press training induce similar contralateral and ipsilateral limb training adaptations with children

“…Based on adult research, increases in corticospinal excitability (Kidgell et al 2011;Leung et al 2018) and decreased corticospinal inhibition (i.e. short interval cortical inhibition) of the contralateral limbs (Latella et al 2012;Leung et al 2018) could contribute to enhanced motor unit recruitment and rate coding-induced increases in strength and power (Behm 1995;Behm et al 2008) with the training effects observed with children in this study. However, a meta-analysis by Manca et al (2018) indicated that the magnitude of corticospinal excitability did not correlate with cross-education changes.…”

“…Farthing in his review (Farthing 2009) explains that a mechanism of cross-education would be related to plasticity of the cortical pathways involved in motor planning input as well as plasticity in the motor command of the motor cortex increasing agonist activation (Hortobagyi et al 1997;Farthing et al 2007) and decreasing co-contractions (Carolan and Cafarelli 1992). Based on adult research, increases in corticospinal excitability (Kidgell et al 2011;Leung et al 2018) and decreased corticospinal inhibition (i.e. short interval cortical inhibition) of the contralateral limbs (Latella et al 2012;Leung et al 2018) could contribute to enhanced motor unit recruitment and rate coding-induced increases in strength and power (Behm 1995;Behm et al 2008) with the training effects observed with children in this study.…”

Motor cortical circuits contribute to crossed facilitation of trunk muscles induced by rhythmic arm movement

“…strength training, or motor learning and skill acquisition. Evidence has suggested that the level of contractions and types of motor training can influence the amount of crossed facilitation observed in the untrained muscle 21,55 . To the best of our knowledge, this is the first study reporting that unilateral arm cycling alone for 20 min or less is unlikely to induce acute changes in corticospinal drive to the trunk muscle.…”

A single session of submaximal grip strength training with or without high-definition anodal-TDCS produces no cross-education of maximal force

“…4 Several studies have reported no change in the ipsilateral TMS responses, 12,13,14 whilst others have reported increased ipsilateral M1 excitability and reduced intracortical inhibition. 8,15,16 Irrespective of the above, it has been suggested that changes in excitability of the ipsilateral M1 could be due to neural mechanisms associated with cross-activation. 17,18,19 Cross-activation is based upon the observation that unilateral muscle actions result in a bilateral increase in corticospinal excitability 9,17,20,21,22 and a decrease in intracortical inhibition of the ipsilateral M1.…”