ABSTRACT
Motor Imagery (MI) reproduces cognitive operations associated with the actual motor preparation and execution. Postural recordings during MI reflect somatic motor commands targeting peripheral effectors involved in balance control. However, how these relate to the actual motor expertise and may vary along with the MI modality remains debated. In the present experiment, two groups of expert and non-expert gymnasts underwent stabilometric assessments while performing physically and mentally a balance skill. We implemented psychometric measures of MI ability, while stabilometric variables were calculated from the center of pressure (COP) oscillations. Psychometric evaluations revealed greater MI ability in experts, specifically for the visual modality. Experts exhibited reduced surface COP oscillations in the antero-posterior axis compared to non-experts during the balance skill (14.90%, 95% CI 34.48-4.68, p < 0.05). Experts further exhibited reduced length of COP displacement in the antero-posterior axis and as a function of the displacement area during visual and kinesthetic MI compared to the control condition (20.51%, 95% CI 0.99-40.03 and 21.85%, 95% CI 2.33-41.37, respectively, both p < 0.05). Predictive relationships were found between the stabilometric correlates of visual MI and physical practice of the balance skill, as well as between the stabilometric correlates of kinesthetic MI and the training experience in experts. Present results provide original stabilometric insights into the relationships between MI and expertise level. While data support the incomplete inhibition of postural commands during MI, whether postural responses during MI of various modalities mirror the level of motor expertise remains unclear.
ABSTRACT
Action observation (AO) alone or combined with motor imagery (AOâ¯+â¯MI) has been shown to engage the motor system. While recent findings support the potential relevance of both techniques to enhance muscle function, this issue has received limited scientific scrutiny. In the present study, we implemented a counterbalanced conditions design where 21 participants performed 10 maximal isometric contractions (12-s duration) of elbow flexor muscles against a force platform. During the inter-trial rest periods, participants completed i) AO of the same task performed by an expert athlete, ii) AOâ¯+â¯MI, i.e. observation of an expert athlete while concurrently imagining oneself performing the same task, and iii) watching passively a video documentary about basketball shooting (Control). During force trials, we recorded the total force and integrated electromyograms from the biceps brachii and anterior deltoideus. We also measured skin conductance from two finger electrodes as an index of sympathetic nervous system activity. Both AO and AOâ¯+â¯MI outperformed the Control condition in terms of total force (2.79-3.68%, pâ¯<â¯0.001). For all conditions, we recorded a positive relationship between the biceps brachii activation and the total force developed during the task. However, only during AO was a positive relationship observed between the activation of the anterior deltoideus and the total force. We interpreted the results with reference to the statements of the psycho-neuromuscular theory of mental practice. Present findings extend current knowledge regarding the priming effects of AO and AOâ¯+â¯MI on muscle function, and may contribute to the optimization of training programs in sports and rehabilitation.
