Combining Motor Imagery With Action Observation Does Not Lead to a Greater Autonomic Response Than Motor Imagery Alone During Simple and Functional Movements: a Randomized Controlled Trial.

Motor Imagery (MI) is defined as a dynamic mental process that involves the representation of an action, in an internal way, without its actual motor execution. The Action Observation (AO) evokes an internal, real-time motor simulation of the movements that the observer is perceiving visually. Both mental processes trigger the activation of the neurocognitive mechanisms that underlie the planning and execution of voluntary movements in a manner that resembles how the action is performed in a real manner.

Both observation and imagination share a great number of common mental processes based primarily on sensory perception, and the information stored by memory systems. The activation of the motor command during a mental practice does not induce an active movement probably due to an inhibitory mechanism in the primary motor cortex on the descending corticospinal tract pathways. However, this inhibition is not complete, for it is well known that the training of mental practice involves a component of the autonomic nervous system (ANS).

It has been shown that both MI and AO lead to changes in the ANS that cause excitatory sympathetic responses, although the neurophysiological bases remain uncertain and are still based on hypotheses. The functional relations between both neurocognitive processes and the sympathetic-excitatory nervous system (SNS) could be based on a preparation phase in which, the activation of the SNS, happens to a near effort and, therefore, to a close energy expenditure in physiological processes (i.e., cardiorespiratory adaptationse) which will take place in order to face said metabolic changes produced by the voluntary movement itself. In addition, several hypotheses have been described regarding the notion that the SNS not only has the quantitative objective of providing energy to the muscle effectors, but that it also qualitatively and specifically designs and adapts the parameters on demand in an attempt to save the energy provided for each precise motor execution.

Taking into account that both MI and AO cause sympathetic-excitatory changes that induce an increase in heart rate, blood pressure, respiratory rate, electrodermal activity , our hypothesis is that the combination of MI and AO induces an autonomic sympathetic-excitatory shift greater than MI does in isolation. Therefore, the main objective of this study was to compare the results obtained from intervention groups on the subject of the activation of the SNS in a program that combined MI with AO, in contrast to an isolated MI program on the one hand in asymptomatic subjects and in the other hand in patients with chronic low back pain.. The secondary objective of the present study was to explore whether there is any relationship between the sympathetic-excitatory response and the ability to generate motor imagery, the mental chronometry, and the level of physical activity.