Corticospinal Modulations during Motor Imagery of Concentric, Eccentric, and Isometric Actions

International audienceIt is not known yet whether the neurophysiological specificity of eccentric, concentric and isometric contractions can also be observed when these are mentally simulated. Therefore our aim was to assess corticospinal excitability during motor imagery (MI) of different contraction types and to test whether a passive movement during MI could have additional effects.METHODS:Twelve young participants imagined contractions of the wrist flexors, firstly with the arm motionless (static mode) and secondly with a congruent passive movement (wrist extension during eccentric MI and wrist flexion during concentric MI). Motor evoked potentials (MEP) and H-reflexes were elicited in Flexor Carpi Radialis (FCR) at rest and during the three types of MI. As a secondary outcome, the MEPs of one antagonist (Extensor Carpi Radialis, ECR), elicited concomitantly with FCR MEP recording, were also analysed.RESULTS:In static mode, FCR MEPs were facilitated during isometric (p=0.046) and concentric (p=0.039) MI, but not during eccentric MI (p=0.902). With passive congruent movements, FCR MEPs were enhanced during all imagined contraction types, including eccentric (p=0.047). FCR H-reflexes increased only during eccentric MI accompanied with wrist extension (p=0.003). ECR MEPs were modulated only when a passive congruent movement was provided (p=0.040).CONCLUSION- Like actual contractions, eccentric MI exhibits specific neural correlates, compared to isometric and concentric MI, which should be considered when using this modality for training. The present results showed that adding passive movements congruent to the eccentric MI task would enhance its impact over corticospinal structures