Effects of Motor Imagery and Action Observation on Electromyographic Activity and Intramuscular Oxygenation in the Hand Gripping Gesture

Motor imagery is defined as a dynamic mental process of an action, without its real motor execution. Action observation training consists of watching an action performed by someone else. Both motor imagery and action observation have been shown to produce a neurophysiological activation of the brain areas related to the planning and execution of voluntary movement in a manner that resembles how the action is performed in reality.

Several studies have shown that patients can report a significant improvement in strength with motor imagery training. There is also evidence regarding the improvements in motor skills in participants who perform motor imagery training combined with mirror therapy. Motor imagery is recognized as one of the most popular and effective forms of training to improve learning strategies and to increase the capacity to perfect sports movements, as has been observed in rhythmic gymnastics athletes.

In addition to the previously mentioned adaptations, a recent research proved that motor imagery and action observation provoke an activation of the sympathetic-excitatory nervous system. Changes in respiration, heart rate and skin temperature are produced, as well as an increase in electrodermal activity.

Both motor imagery and action observation are interventions that can generate adaptive neuroplastic changes on a cortical level, leading to a decrease in chronic pain. These rehabilitation techniques are used in pain treatment and impaired movement injuries that could be due to a nervous system alteration.

Action observation effectively facilitates motor learning, and is a tool for rehabilitation in neurological and musculoskeletal diseases. Action observation training leads to significant improvements in static balance and helps improve gait in patients with hemiparesis after an ictus.

A recent study showed that the patient's functionality loss is lessened if motor imagery and action observation are applied after an immobilization process, reducing the loss of wrist mobility, strength and muscle mass.

The effectiveness of motor imagery is controversial; several studies have presented unfavorable outcomes from this technique. Some variables, such as the duration of the sessions, the time employed the type of motor task or the number of sessions can influence the outcomes of these studies. Thus, it is necessary to clarify the controversial aspects of motor imagery, which lead us to perform this study.

This study evaluates variables that have not yet shown conclusive results: intramuscular oxygenation and electromyography. Focusing principally on the effectiveness of the treatment and the adaptations that are generated on an intramuscular level leads to a better understanding of what occurs as a result of training with motor imagery and action observation, and also whether these variables influence the effectiveness of the treatment.

Therefore, the primary objective of this study was to evaluate the effects of motor imagery and action observation combined with a hand grip strength program on strength gains in asymptomatic participants. The secondary objective was to assess the influence of motor imagery and action observation training combined with a hand grip strength program on electromyographic activity and intramuscular oxygenation of the forearm muscles.