Upper Limb Neuromuscular Strategies are Altered in Patients with Mechanical Neck Disorders Compared with Asymptomatic Volunteers

The objective of this study was to investigate the neuromuscular strategy used during a cyclical reach and grasp test (CRGT) in patients with mechanical neck disorder. The CRGT is a paced and timed, repetitive reach and grasp task that was designed to monitor both kinematics and electromyography of the upper limb. Patients (n = 9) with moderate to severe neck pain were compared with healthy controls (n = 7). Activities from 10 muscles of the upper limb were acquired during performance of the CRGT and processed to render both temporal/spatial and amplitude indices. Cross- and Pearson correlations of selected muscle pairs were calculated. Comparisons were conducted using nonparametric statistics. All participants completed the CRGT but only patients self-reported pain after performance (visual analog scale rating of 3.9 ± 2.7 on the affected side). Modulation of activity was observed for posture (sitting vs. standing, P = 0.034) and side (affected/nondominant vs. unaffected) for controls (P = 0.005). The patient group did not demonstrate significant differences between these dependent variables. Neuromuscular strategies exhibited by patients during reaching did not alter significantly with variation in side and posture, as they did with controls, indicating the lack of a capacity to modulate muscle activity appropriate to the task. This is a significant consequence of the chronic pain experienced by patients with mechanical neck disorder and may underlie the upper limb disability reported in this patient population.