Electromyographic activity pattern of upper limb muscles during different proprioceptive neuromuscular facilitation maneuvers

Abstract

Introduction: The concept of Proprioceptive Neuromuscular Facilitation (PNF) has been used to treat neuromusculoskeletal disorders. Motor irradiation (or simply irradiation) is one of the basic procedures of PNF and consists of generating a force in one body segment in order to generate muscle activation in another. However, there is a significant gap in the literature when it comes to investigating the effectiveness of irradiation in inducing an increase in activity in the target muscles in healthy individuals and those with neuromusculoskeletal disorders (such as plexus injury). Added to this is the imprecision of the nomenclature. In addition, few studies have analyzed motor irradiation directed at the muscles of the upper limb, which are essential in various daily activities.
Objective: The objectives of this study were (i) to identify and analyze the results of experimental and observational studies that applied motor irradiation in healthy adults and those with brachial plexus injuries, focusing on the evaluation of muscle recruitment through surface electromyography (EMG) and (ii) to analyze the muscle activation patterns of the biceps brachii during different irradiation maneuvers. Methods: This thesis included two studies: (i) a scoping review on motor irradiation and the electromyographic pattern of the target muscles and (ii) a cross-sectional study in which the biceps muscle activity pattern of 33 healthy individuals was analyzed during the application of motor irradiation maneuvers. In the cross-sectional study, the participants underwent 4 irradiation maneuvers involving movement patterns with (i) the contralateral upper limb, (ii) the ipsilateral lower limb, (iii) the lower trunk, (iv) the pelvis, with force applied in the opposite direction to the non-preferential limb (performed by an advanced PNF instructor), while the EMG of the biceps brachii, triceps brachii, flexor carpi radialis and brachioradialis was recorded. Results: In the review, only 8 articles met the eligibility criteria. These analyzed the EMG activity of upper limb, trunk and lower
limb muscles during upper and lower limb movement patterns, with inconsistent EMG activation patterns. In the second study, only the EMG profile of the biceps brachii was analyzed, and significant differences were observed in the activity of the biceps brachii during irradiation maneuvers, with less activation during the upper limb extensor pattern when compared to the other three patterns. Conclusion: According to the review, few studies have analyzed the effects of motor irradiation on muscle activation patterns, indicating a significant gap in relevant knowledge. In particular, few studies were identified that investigated upper limb muscle activity, and there are no reports on the profile of the biceps brachii during motor irradiation maneuvers. In the cross-sectional study, it was observed that irradiation maneuvers involving the application of resistance to the upper limb generated less biceps activation on EMG than irradiation maneuvers involving the lower limbs and trunk.