engleski

Quantitative parameters of muscular activation in response to opposite sequences of radial neurodynamic test performed to maximum tolerable pain

Aim: To investigate non-invasively quantitative parameters of muscular activation in response to elongation stress of the radial nerve with a radial neurodynamic test (RNT) performed until the onset of subjectively maximal tolerable pain in two different sequences: proximal and distal. Methods: The test movements consisted of a common RNT performed until subjectively maximal tolerable painful symptoms in two opposite sequences. The myoelectric components were subsequently compared with those recorded during a 20-s relaxed position (reference), and during a strong biceps brachii muscle stretch. EMG amplitude of relevant muscles and median frequency (MDF) were calculated for each maneuver, while EMG amplitude and mean frequency (MNF) were calculated for each phase of RNT. Amplitude was calculated as mean amplitude value (MAV) and it was normalized to the reference positions. MNF was calculated from the estimated Welch's averaged periodogram. The manoeuvres were performed in a random sequence. Results: The myoelectric mean amplitude values (MAV) increased continuously while the myoelectric mean frequency (MNF) decreased in an opposite continuous trend during the performance of the neural tension manoeuvres, showing synchronization of motor units firing activity and mimicking pure muscular contraction. The results are statistically significant when compared to those of the relaxed reference position [p ≤ 0.03 (MAV), p ≤ 0.004 (MDF)] and those recorded during a strong biceps brachii muscle stretch [p ≤ 0.02 (MAV), p ≤ 0.002 (MDF)]. Conclusion: The continuous increase of MAV and the concomitant continuous decrease of MNF toward the end of each radial nerve tension manoeuvre indicate genuine muscular contraction in response to neural mechanical loading. This activation seems to increase continuously, and motor unit activation seems to synchronize, following the increase in tensile stress in the nerve. These records differ significantly from those collected during the strong stretch of biceps brachii, implicating that muscular stretch itself may not be responsible for the presented phenomenon. The data seem to not support the common theory of reflex mediated muscle activation in response to mechanical loading of nerves, and support the idea that the mechanism is modulated and more complex than originally thought.

muscle, nerve, neurodynamics, nociceptive flexor reflex, tonus

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