Kinematic and Electromyographic Study of the Nociceptive Withdrawal Reflex in the Upper Limbs during Rest and Movement

Abstract

This study set out to evaluate nociceptive withdrawal reflex (NWR) excitability and the corresponding mechanical response in the upper limbs during rest and movement. We used a three-dimensional motion analysis system and a surface EMG system to record, in 10 healthy subjects, the NWR in eight upper limb muscles and the corresponding mechanical response in two experimental conditions: rest and movement (reaching for, picking up, and moving a cylinder). The NWR was elicited through stimulation of the index finger with trains of pulses delivered at multiples of the pain threshold (PT). We correlated movement types (reach-to-grasp, grasp-and-lift), movement phases (acceleration, deceleration), and muscle activity types (shortening, lengthening, isometric) with the presence/absence of the NWR (reflex-muscle pattern), with NWR size values, and with the mechanical responses.At rest, when the stimulus was delivered at 4ϫ PT, the NWR was present, in all muscles, in Ͼ90% of trials, and the mechanical response consisted of wrist adduction, elbow flexion, and shoulder anteflexion. At this stimulus intensity, during movement, the reflex-muscle pattern, reflex size, and mechanical responses were closely modulated by movement type and phase and by muscle activity type. We did not find, during movement, significant correlations with the level of EMG background activity.Our findings suggest that a complex functional adaptation of the spinal cord plays a role in modulating the NWR in the transition from rest to movement and during voluntary arm movement freely performed in three-dimensional space. Study of the upper limb NWR may provide a window onto the spinal neural control mechanisms operating during movement.

Botulinum toxin A modifies nociceptive withdrawal reflex in subacute stroke patients

“…We used the same electrical stimulation technique reported elsewhere (Don et al., 2008; Serrao et al., 2006). In brief, using ring electrodes, we stimulated the digital branch of the median nerve supplying the index finger.…”

“…The mean of the EMG area plus 2  SD , calculated in the prestimulus interval, was used as a threshold to determine the presence (denoted by a value above the threshold) or absence (a value below the threshold) of the NWR in the poststimulus interval in each trial. The NWR‐related EMG responses were measured as the difference between the EMG areas in the post‐ versus the prestimulus intervals for each examined muscle (Don et al., 2008; Serrao et al., 2006). …”

Muscle activation patterns in acceleration-based phases during reach-to-grasp movement

“…Phases divided on the basis of the velocity trajectory, which is bell-shaped5 ) , might be related to the phasic drives of the muscles’ activities. The peak of the velocity profile was reported to divide the reaching movement into a hand acceleration phase (positive values of tangential acceleration) and a hand deceleration phase (negative values of acceleration)9, 17 ) . The present study showed that this hand acceleration phase is composed of Phases IA and DA.…”

Modulation of spinal inhibitory reflex responses to cutaneous nociceptive stimuli during upper limb movement

“…With regard to the upper limb, we recently reported that, during reaching and grasping movements, the excitatory component of the WR undergoes state‐ and phase‐dependent modulation according to the mechanical function exerted by each muscle in the course of the motor sequence. In particular, we observed that the amount and direction of the motion occurring at each joint in the course of the motor task were the main factors determining the presence of either a reflex reversal or a co‐presence pattern (Serrao et al. , 2006).…”