EMG-Assessed Paratonia: A New Approach to Response Inhibition

Overview

Paratonia is the inability to relax muscles during the assessment of muscle tone in the absence of spasticity and parkinsonian rigidity. It can be evaluated qualitatively using clinical scales and objectively through surface electromyography (EMG-assessed paratonia). It is widely accepted that paratonia represents a manifestation of impaired motor response inhibition due to frontal lobe dysfunction. Traditionally, motor response inhibition has been assessed using experimental protocols such as go/no-go and stop-signal tasks. Research has shown that athletes, particularly those engaged in open-skill sports, demonstrate superior motor response inhibition compared to sedentary individuals. Even amateur athletes exhibit better motor response inhibition than sedentary individuals, though to a lesser extent than professional athletes. Given that the etiology of paratonia involves a defect in motor response inhibition, it is hypothesized that EMG-assessed paratonia could become a novel approach for evaluating motor response inhibition. The present study was designed to validate this hypothesis. Specifically, we first tested whether EMG-assessed paratonia in healthy subjects can reveal a well-known aspect of motor response inhibition, namely its correlation with the level of physical activity.

EMG-assessed paratonia was analyzed and compared to assess motor response efficiency in three groups of healthy young adults with different levels of physical activity: professional athletes engaged in closed and open skills sports, amateurs, and sedentary individuals. To analyze EMG-assessed paratonia, two surface electrodes were attached to the biceps and triceps brachii muscles during passive flexion-extension movements of the elbow while the participant remained in a state of maximum relaxation. Any EMG activity detected during these movements was attributed to an inability to relax, thereby reflecting their degree of paratonia.