Ipsilateral corticomotor responses are confined to the homologous muscle following cross-education of muscular strength

Mason, Joel; Frazer, Ashlyn K.; Horvath, Deanna; Pearce, Alan J.; Avela, Janne; Howatson, Glyn; Kidgell, Dawson

doi:10.1139/apnm-2017-0457

Cited by 15 publications

(20 citation statements)

References 68 publications

(127 reference statements)

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“…In the context of cross-education and bilateral transfer, several acute studies that have used TMS have shown increased CSE (Muellbacher et al 2000;Hortobágyi et al 2003;Perez and Cohen 2008;Howatson et al 2011;Frazer et al 2017), decreased SICI (Perez and Cohen 2008;Leung et al 2015), and decreased interhemispheric inhibition (IHI) (Perez and Cohen 2008;Howatson et al 2011) in the iM1. While some structural changes occur within several motor areas (Ruddy et al 2017;Pruitt et al 2016), experimental findings from chronic cross-education studies support a mixture of increased CSE (Hendy et al 2015;Kidgell et al 2011;Kidgell et al 2015) and a decrease in cortical inhibition (SICI, IHI and silent period duration) (Hortobágyi et al 2011;Hendy et al 2012;Kidgell et al 2015;Coombs et al 2016;Mason et al 2017) in the neural structures innervating the untrained limb.…”

Section: The Cortical Adaptations To Cross-education Are Dependent Upmentioning

confidence: 97%

“…Sample size calculations were established on the average effect sizes for changes in the magnitude of strength transfer following a short-term unilateral strength training program and VT. Using previous cross-education data in healthy untrained adults (Mason et al 2017), we estimated that 10 participants in each group would provide at least 80% power (95% confidence interval) to detect a 18% cross-transfer of strength and 16% transfer of VT performance using a repeated measures design (G*Power 3.1.7 software).…”

Section: Participants and Sample Size Calculationsmentioning

confidence: 99%

“…Interestingly, cross-education is commonly used to describe the magnitude of strength transfer following unilateral strength training, whilst bilateral transfer is used to describe the transfer of motor skills. However there has been no study that has compared the magnitude of transfer following both strength and skill training and they have been studied as separate entities (Criscimagna-Hemminger et al 2003;Lee et al 2009;Hinder et al 2013;Coombs et al 2016;Mason et al 2017).…”

Section: Introductionmentioning

confidence: 99%

“…Concurrent activation of both cerebral cortices, a process known as cross-activation or bilateral activation, has been reported during both unilateral skill and strength training (Ruddy and Carson, 2013;Hendy and Kidgell, 2014;Carroll et al 2008;Lee et al 2010;Hinder et al 2011;Hinder et al 2013;Frazer et al 2017). Moreover, transcranial magnetic stimulation (TMS) studies have shown increased excitability of the ipsilateral primary motor cortex (iM1) of a resting limb during unilateral voluntary contractions (increased cross-activation) (Muellbacher et al 2000;Liepert et al 2001;Hortobágyi et al 2003;Hendy and Kidgell, 2014;Zult et al 2016;Frazer et al 2017;Mason et al 2017). The elevated activity in the iM1 appears to be associated with the changes in motor function of the untrained limb following unilateral training (Kidgell et al 2011;Latella et al 2012;Kidgell et al 2015;Coombs et al 2016;Mason et al 2017;Christiansen et al 2017).…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, transcranial magnetic stimulation (TMS) studies have shown increased excitability of the ipsilateral primary motor cortex (iM1) of a resting limb during unilateral voluntary contractions (increased cross-activation) (Muellbacher et al 2000;Liepert et al 2001;Hortobágyi et al 2003;Hendy and Kidgell, 2014;Zult et al 2016;Frazer et al 2017;Mason et al 2017). The elevated activity in the iM1 appears to be associated with the changes in motor function of the untrained limb following unilateral training (Kidgell et al 2011;Latella et al 2012;Kidgell et al 2015;Coombs et al 2016;Mason et al 2017;Christiansen et al 2017). We have recently shown that the improvement in strength of the trained arm following strength training and the improvement in motor-skill performance (e.g., upper limb tracking task) following skill training, are controlled by similar mechanisms that originate within the M1 (Leung et al 2017).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2018

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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.

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Section: The Cortical Adaptations To Cross-education Are Dependent Upmentioning

confidence: 97%

Section: Participants and Sample Size Calculationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2018

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Determining the potential sites of neural adaptation to cross-education: implications for the cross-education of muscle strength

et al. 2018

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Cross-education describes the strength gain in the opposite, untrained limb following a unilateral strength training program. Since its discovery in 1894, several studies now confirm the existence of cross-education in contexts that involve voluntary dynamic contractions, eccentric contraction, electrical stimulation, whole-body vibration and, more recently, following mirror feedback training. Although many aspects of cross-education have been established, the mediating neural mechanisms remain unclear. Overall, the findings of this review show that the neural adaptations to cross-education of muscle strength most likely represent a continuum of change within the central nervous system that involves both structural and functional changes within cortical motor and non-motor regions. Such changes are likely to be the result of more subtle changes along the entire neuroaxis which include, increased corticospinal excitability, reduced cortical inhibition, reduced interhemispheric inhibition, changes in voluntary activation and new regions of cortical activation. However, there is a need to widen the breadth of research by employing several neurophysiological techniques (together) to better understand the potential mechanisms mediating cross-education. This fundamental step is required in order to better prescribe targeted and effective guidelines for the clinical practice of cross-education. There is a need to determine whether similar cortical responses also occur in clinical populations where, perhaps, the benefits of cross-education could be best observed.

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Contralateral Effects of Unilateral Strength and Skill Training: Modified Delphi Consensus to Establish Key Aspects of Cross-Education

et al. 2020

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Background Cross-education refers to increased motor output (i.e., force generation, skill) of the opposite, untrained limb following a period of unilateral exercise training. Despite extensive research, several aspects of the transfer phenomenon remain controversial. Methods A modified two-round Delphi online survey was conducted among international experts to reach consensus on terminology, methodology, mechanisms of action, and translational potential of cross-education, and to provide a framework for future research. Results Through purposive sampling of the literature, we identified 56 noted experts in the field, of whom 32 completed the survey, and reached consensus (75% threshold) on 17 out of 27 items. Conclusion Our consensus-based recommendations for future studies are that (1) the term ‘cross-education’ should be adopted to refer to the transfer phenomenon, also specifying if transfer of strength or skill is meant; (2) functional magnetic resonance imaging, short-interval intracortical inhibition and interhemispheric inhibition appear to be promising tools to study the mechanisms of transfer; (3) strategies which maximize cross-education, such as high-intensity training, eccentric contractions, and mirror illusion, seem worth being included in the intervention plan; (4) study protocols should be designed to include at least 13–18 sessions or 4–6 weeks to produce functionally meaningful transfer of strength, and (5) cross-education could be considered as an adjuvant treatment particularly for unilateral orthopedic conditions and sports injuries. Additionally, a clear gap in views emerged between the research field and the purely clinical field. The present consensus statement clarifies relevant aspects of cross-education including neurophysiological, neuroanatomical, and methodological characteristics of the transfer phenomenon, and provides guidance on how to improve the quality and usability of future cross-education studies.

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Ipsilateral corticomotor responses are confined to the homologous muscle following cross-education of muscular strength

Cited by 15 publications

References 68 publications

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

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

Determining the potential sites of neural adaptation to cross-education: implications for the cross-education of muscle strength

Contralateral Effects of Unilateral Strength and Skill Training: Modified Delphi Consensus to Establish Key Aspects of Cross-Education

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