The effect of experimentally induced pain in the cervical, shoulder or orofacial regions on cervical neuromuscular and kinematic features: a systematic review and meta-analysis

In this systematic review, we synthesize the literature investigating the effect of experimentally induced pain in the cervical, shoulder, or orofacial regions on cervical neuromuscular and kinematic features. Databases were searched up to November 1st, 2023. A total of 29 studies using hypertonic saline injection (n = 27) or glutamate injection (n = 2) as experimental pain models were included. Meta-analyses revealed reduced upper trapezius activation during shoulder flexion/abduction when pain was induced in the upper trapezius (standardized mean difference: -0.90, 95% confidence interval: [-1.29; -0.51]), splenius capitis (-1.03 [-1.44; -0.63]), and supraspinatus (-0.63 [-1.25; -0.01]), but not in the subacromial space (0.22 [-0.16; 0.60]). Furthermore, experimentally induced pain caused a caudal redistribution of activation within the upper trapezius (0.96 [0.58; 1.34]) but did not change the medio-lateral distribution (0.11 [-0.22; 0.42]). None of these adaptations persisted after pain resolution. Low-quality evidence supported the absence of an effect of experimental pain on upper trapezius muscle activation during manual dexterity and cervical flexion/extension tasks, as well as on cervical flexor and extensor muscle activation during cervical and jaw tasks. Inconsistent and limited evidence, attributed to the large heterogeneity of task and outcomes, precluded drawing meaningful conclusions about the effects of experimentally induced pain in the cervical region on cervical kinematics. Overall, cervical muscle activation tended to decrease in response to experimentally induced pain, and the decrease of muscle activation depended on the location of the painful stimulus. These adaptations are only partially representative of muscle activation patterns observed in clinical populations. PERSPECTIVE: This systematic review and meta-analysis revealed a reduced or unchanged muscle activation during experimental pain in the cervical, shoulder or orofacial regions, depending on the task and location of nociceptive stimulation. There was inconsistent evidence on cervical kinematics. These findings enhance our understanding of neuromuscular adaptations to acute experimental pain.