Impact of subclinical neck pain on eye and hand movements in goal-directed upper limb aiming movements.

Individuals with untreated, mild-to-moderate recurrent neck pain or stiffness (subclinical neck pain (SCNP)) have been shown to have impairments in upper limb proprioception, and altered cerebellar processing. It is probable that aiming trajectories will be impacted since individuals with SCNP cannot rely on accurate proprioceptive feedback or feedforward processing (body schema) for movement planning and execution, due to altered afferent input from the neck. SCNP participants may thus rely more on visual feedback, to accommodate for impaired cerebellar processing. This quasi-experimental study sought to determine whether upper limb kinematics and oculomotor processes were impacted in those with SCNP. 25 SCNP and 25 control participants who were right-hand dominant performed bidirectional aiming movements using two different weighted styli (light or heavy) while wearing an eye-tracking device. Those with SCNP had a greater time to and time after peak velocity, which corresponded with a longer upper limb movement and reaction time, seen as greater constant error, less undershoot in the upwards direction and greater undershoot in the downwards direction compared to controls. SCNP participants also showed a trend towards a quicker ocular reaction and movement time compared to controls, while the movement distance was fairly similar between groups. This study indicates that SCNP alters aiming performances, with greater reliance on visual feedback, likely due to altered proprioceptive input leading to altered cerebellar processing.

Biomarkers of Immersion in Virtual Reality Based on Features Extracted from the EEG Signals: A Machine Learning Approach.

Virtual reality (VR) enables the development of virtual training frameworks suitable for various domains, especially when real-world conditions may be hazardous or impossible to replicate because of unique additional resources (e.g., equipment, infrastructure, people, locations). Although VR technology has significantly advanced in recent years, methods for evaluating immersion (i.e., the extent to which the user is engaged with the sensory information from the virtual environment or is invested in the intended task) continue to rely on self-reported questionnaires, which are often administered after using the virtual scenario. Having an objective method to measure immersion is particularly important when using VR for training, education, and applications that promote the development, fine-tuning, or maintenance of skills. The level of immersion may impact performance and the translation of knowledge and skills to the real-world. This is particularly important in tasks where motor skills are combined with complex decision making, such as surgical procedures. Efforts to better measure immersion have included the use of physiological measurements including heart rate and skin response, but so far they do not offer robust metrics that provide the sensitivity to discriminate different states (idle, easy, and hard), which is critical when using VR for training to determine how successful the training is in engaging the user's senses and challenging their cognitive capabilities. In this study, electroencephalography (EEG) data were collected from 14 participants who completed VR jigsaw puzzles with two different levels of task difficulty. Machine learning was able to accurately classify the EEG data collected during three different states, obtaining accuracy rates of 86% and 97% for differentiating easy versus hard difficulty states and baseline vs. VR states. Building on these results may enable the identification of robust biomarkers of immersion in VR, enabling real-time recognition of the level of immersion that can be used to design more effective and translative VR-based training. This method has the potential to adjust aspects of VR related to task difficulty to ensure that participants are immersed in VR.

Subclinical Neck Pain Leads to Differential Changes in Early Somatosensory Evoked Potentials in Response to a Novel Force Matching Tracking Task.

BACKGROUND: Neural adaptions in response to sensorimotor tasks are impaired in those with untreated, recurrent mild-to-moderate neck pain (subclinical neck pain (SCNP)), due to disordered central processing of afferent information (e.g., proprioception). Neural adaption to force modulation, a sensorimotor skill reliant on accurate proprioception, is likely to be impaired in those with SCNP. This study examined changes in somatosensory evoked potential (SEP) peak amplitudes following the acquisition of a novel force matching tracking task (FMTT) in those with SCNP compared to non-SCNP. METHODS: 40 (20 female (F) & 20 male (M); average age (standard deviation, SD): 21.6 (3.01)) right-handed participants received controlled electrical stimulation at 2.47 Hz and 4.98 Hz (averaged 1000 sweeps/frequency) over the right-median nerve, to elicit SEPs before and after FMTT acquisition. Participants used their right thumb to match a series of force profiles that were calibrated to their right thumb (abductor pollicis brevis muscle) strength. To determine if motor learning was impacted, retention was assessed 24 to 48 hours later. Outliers were removed before running independent t-tests on normalized SEP peak amplitudes, and repeated measures analysis of variance (ANOVA) with planned contrasts on absolute and normalized motor performance accuracy. Benjamini-hochberg test was used to correct for multiple independent SEP comparisons. RESULTS: SEP peaks: N18 (t(29.058) = 2.031, p = 0.026), N20 (t(35) = -5.460, p < 0.001), and P25 (t(33) = -2.857, p = 0.004) had group differences. Motor performance: Absolute error (n = 38) had a main effect of time, and significant pre-and post-acquisition contrast for time (both p < 0.001). CONCLUSIONS: Group differences in the olivary-cerebellar pathway (N18), and cortical processing at the somatosensory cortex (N20 and P25), suggests that SCNP alters cortical and cerebellar processing compared to non-SCNP in response to FMTT acquisition. The sensory-motor integration differences in the SCNP group suggests that those with SCNP may rely more on feedback loops for discrete sensorimotor tasks dependent on proprioception. Early SEP changes may be used as a marker for altered neuroplasticity in the context of motor skill acquisition of a novel discrete FMTT in those with SCNP.

Cervico-Ocular and Vestibulo-Ocular Reflexes in Subclinical Neck Pain and Healthy Individuals: A Cross-Sectional Study.

Alterations in neck sensory input from recurrent neck pain (known as subclinical neck pain (SCNP)) result in disordered sensorimotor integration (SMI). The cervico-ocular (COR) and vestibulo-ocular (VOR) reflexes involve various neural substrates but are coordinated by the cerebellum and reliant upon proprioceptive feedback. Given that proprioception and cerebellar processing are impaired in SCNP, we sought to determine if COR or VOR gain is also altered. COR and VOR were assessed using an eye-tracking device in 20 SCNP (9 M and 11 F; 21.8 (SD = 2.35) years) and 17 control (7 M and 10 F; 22.40 (SD = 3.66) years) participants. COR gain (10 trials): A motorized chair rotated the trunk at a frequency of 0.04 Hz and an amplitude of 5° while participants gazed at a circular target that disappeared after three seconds. VOR gain (30 trials): Rapid bilateral head movements away from a disappearing circular target while eyes fixated on the last observed target. Independent t-tests on COR and VOR gain were performed. SCNP had a significantly larger COR gain (p = 0.006) and smaller VOR gain (p = 0.487) compared to healthy controls. The COR group differences suggest an association between proprioceptive feedback and SMI, indicating COR may be a sensitive marker of altered cerebellar processing.

Neck Muscle Vibration Alters Cerebellar Processing Associated with Motor Skill Acquisition of a Proprioceptive-Based Task.

Experimentally induced neck fatigue and neck pain have been shown to impact cortico-cerebellar processing and sensorimotor integration, assessed using a motor learning paradigm. Vibration specifically impacts muscle spindle feedback, yet it is unknown whether transient alterations in neck sensory input from vibration impact these neural processing changes following the acquisition of a proprioceptive-based task. Twenty-five right-handed participants had electrical stimulation over the right median nerve to elicit short- and middle-latency somatosensory evoked potentials (SEPs) pre- and post-acquisition of a force matching tracking task. Following the pre-acquisition phase, controls (CONT, n = 13, 6 F) received 10 min of rest and the vibration group (VIB, n = 12, 6 F) received 10 min of 60 Hz vibration on the right sternocleidomastoid and left cervical extensors. Task performance was measured 24 h later to assess retention. Significant time by group interactions occurred for the N18 SEP peak, 21.77% decrease in VIB compared to 58.74% increase in CONT (F(1,23) = 6.475, p = 0.018, np2 = 0.220), and the N24 SEP peak, 16.31% increase in VIB compared to 14.05% decrease in CONT (F(1,23) = 5.787, p = 0.025, np2 = 0.201). Both groups demonstrated improvements in motor performance post-acquisition (F(1,23) = 52.812, p < 0.001, np2 = 0.697) and at retention (F(1,23) = 35.546, p < 0.001, np2 = 0.607). Group-dependent changes in the SEP peaks associated with cerebellar input (N18) and cerebellar processing (N24) suggests that an altered proprioceptive input from neck vibration impacts cerebellar pathways.

Source Localization of Somatosensory Neural Generators in Adults with Attention-Deficit/Hyperactivity Disorder.

Attention-Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder, where differences are often present relating to the performance of motor skills. Our previous work elucidated unique event-related potential patterns of neural activity in those with ADHD when performing visuomotor and force-matching motor paradigms. The purpose of the current study was to identify whether there were unique neural sources related to somatosensory function and motor performance in those with ADHD. Source localization (sLORETA) software identified areas where neural activity differed between those with ADHD and neurotypical controls when performing a visuomotor tracing task and force-matching task. Median nerve somatosensory evoked potentials (SEPs) were elicited, while whole-head electroencephalography (EEG) was performed. sLORETA localized greater neural activity post-FMT in those with ADHD, when compared with their baseline activity (p < 0.05). Specifically, greater activity was exhibited in BA 31, precuneus, parietal lobe (MNI coordinates: X = -5, Y = -75, and Z = 20) at 156 ms post stimulation. No significant differences were found for any other comparisons. Increased activity within BA 31 in those with ADHD at post-FMT measures may reflect increased activation within the default mode network (DMN) or attentional changes, suggesting a unique neural response to the sensory processing of force and proprioceptive afferent input in those with ADHD when performing motor skills. This may have important functional implications for motor tasks dependent on similar proprioceptive afferent input.

Sensorimotor integration and motor learning during a novel visuomotor tracing task in young adults with attention-deficit/hyperactivity disorder.

Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder that has noted alterations to motor performance and coordination, potentially affecting learning processes and the acquisition of motor skills. This work will provide insight into the role of altered neural processing and sensorimotor integration (SMI) while learning a novel visuomotor task in young adults with ADHD. This work compared adults with ADHD (n = 12) to neurotypical controls (n = 16), using a novel visuomotor tracing task, where participants used their right-thumb to trace a sinusoidal waveform that varied in both frequency and amplitude. This learning paradigm was completed in pre, acquisition, and post blocks, where participants additionally returned and completed a retention and transfer test 24 h later. Right median nerve short latency somatosensory-evoked potentials (SEPs) were collected pre and post motor acquisition. Performance accuracy and variability improved at post and retention measures for both groups for both normalized (P < 0.001) and absolute (P < 0.001) performance scores. N18 SEP: increased in the ADHD group post motor learning and decreased in controls (P < 0.05). N20 SEP: increased in both groups post motor learning (P < 0.01). P25: increased in both groups post motor learning (P < 0.001). N24: increased for both groups at post measures (P < 0.05). N30: decreased in the ADHD group and increased in controls (P < 0.05). These findings suggest that there may be differences in cortico-cerebellar and prefrontal processing in response to novel visuomotor tasks in those with ADHD.NEW & NOTEWORTHY Alterations to somatosensory-evoked potentials (SEPs) were present in young adults with attention-deficit/hyperactivity disorder (ADHD), when compared with neurotypical controls. The N18 and N30 SEP peak had differential changes between groups, suggesting alterations to olivary-cerebellar-M1 processing and SMI in those with ADHD when acquiring a novel visuomotor tracing task. This suggests that short-latency SEPs may be a useful biomarker in the assessment of differential responses to motor acquisition in those with ADHD.

Effect Sizes for Changes in Health and Well-Being Following Treatment With the One-To-Zero Technique in Individuals With Occipito-Atlantal Joint Dysfunction: A Repeated Measures Study.

Objectives: The purpose of this study was to determine effect sizes (ES) for changes in self-reported measures of musculoskeletal pain and dysfunction resulting from the one-to-zero method using a repeated measures study design. Methods: Twenty participants presenting with articular dysfunction of the occipito-atlantal (C0-C1) complex were treated using the one-to-zero method, a high-velocity low-amplitude thrust administered between the C0-C1 complex before treating other restrictive segments in a cephalocaudal direction. The participants completed online questionnaires using Google Forms that assessed aspects of the biopsychosocial model of pain at baseline and within a week after treatment. The questionnaires included the following: (1) Demographic and Health Behavior Survey; (2) Neck Bournemouth Questionnaire (NBQ) or Neck Disability Index (NDI); (3) Beck Anxiety Index (BAI); (4) Insomnia Severity Index (ISI); and (5) 36-Item Short Form Health Survey (SF-36). Paired t test or Wilcoxon signed ranks test was performed, dependent on normality. Cohen's d values were calculated for each questionnaire score (0.20 indicative of small; ≥0.50 medium; and ≥0.80 large ES). Results: The NDI, NBQ, BAI, and ISI had a large ES (all d ≥ 0.80). In the SF-36, 4 subscales had a small to near-medium ES, 1 subscale had a medium to near-large ES, and the remaining 2 had a large ES (d ≥ 0.80). The physical and mental component summary had a large (d = 0.88) and small ES (d = 0.35), respectively. Conclusion: The effect sizes suggest the one-to-zero treatment induces change in various aspects of the biopsychosocial model.

Differential changes in somatosensory evoked potentials and motor performance: pursuit movement task versus force matching tracking task.

Force modulation relies on accurate proprioception, and force-matching tasks alter corticocerebellar connectivity. Corticocerebellar (N24) and corticomotor pathways are impacted following the acquisition of a motor tracing task (MTT), measured using both somatosensory evoked potentials (SEPs) and transcranial magnetic stimulation. This study compared changes in early SEP peak amplitudes and motor performance following a force-matching tracking task (FMTT) to an MTT. Thirty (18 females) right-handed participants, aged 21.4 ± 2.76, were electrically stimulated over the right-median nerve at 2.47 Hz and 4.98 Hz (averaged 1,000 sweeps/rate) to elicit SEPs, recorded via a 64-channel electroencephalography cap, before, and after task acquisition using the right abductor pollicis brevis muscle. Retention was measured 24 h later. Significant time-by-group interactions occurred for the N20 SEP: 6.3% decrease post-FMTT versus 5.5% increase post-MTT (P = 0.013); P25 SEP: 4.0% decrease post-FMTT versus 10.3% increase post-MTT (P = 0.006); and N18 SEP: 113.4% increase post-FMTT versus 4.4% decrease post-MTT (P = 0.006). N18 and N30 showed significant effect of time (both P < 0.001). Motor performance: significant time-by-group interactions-postacquisition: FMTT improved 15.3% versus 24.3% for MTT (P = 0.025), retention: FMTT improved 17.4% and MTT by 30.1% (P = 0.004). Task-dependent differences occurred in SEP peaks associated with cortical somatosensory processing (N20 and P25), and cerebellar input (N18), with similar changes in sensorimotor integration (N30), with differential improvements in motor performance, indicating important differences in cerebellar and sensory processing for tasks reliant on proprioception.NEW & NOTEWORTHY This study demonstrates neurophysiological differences in cerebellar and somatosensory cortex pathways when learning a motor task requiring visuomotor tracking versus a task that requires force-matching modulation, in healthy individuals. The clear neurophysiological differences in early somatosensory evoked potentials associated with cortical somatosensory processing, cerebellar input, and sensorimotor integration between these two tasks demonstrate some of the neural correlates of force modulation and validate the force-matching task for use in future work.

Neck Muscle Vibration Alters Upper Limb Proprioception as Demonstrated by Changes in Accuracy and Precision during an Elbow Repositioning Task.

Upper limb control depends on accurate internal models of limb position relative to the head and neck, accurate sensory inputs, and accurate cortical processing. Transient alterations in neck afferent feedback induced by muscle vibration may impact upper limb proprioception. This research aimed to determine the effects of neck muscle vibration on upper limb proprioception using a novel elbow repositioning task (ERT). 26 right-handed participants aged 22.21 ± 2.64 performed the ERT consisting of three target angles between 80−90° (T1), 90−100° (T2) and 100−110° (T3). Controls (CONT) (n = 13, 6F) received 10 min of rest and the vibration group (VIB) (n = 13, 6F) received 10 min of 60 Hz vibration over the right sternocleidomastoid and left cervical extensor muscles. Task performance was reassessed following experimental manipulation. Significant time by group interactions occurred for T1: (F1,24 = 25.330, p < 0.001, ηp2 = 0.513) where CONT improved by 26.08% and VIB worsened by 134.27%, T2: (F1,24 = 16.157, p < 0.001, ηp2 = 0.402) where CONT improved by 20.39% and VIB worsened by 109.54%, and T3: (F1,24 = 21.923, p < 0.001, ηp2 = 0.447) where CONT improved by 37.11% and VIB worsened by 54.39%. Improvements in repositioning accuracy indicates improved proprioceptive ability with practice in controls. Decreased accuracy following vibration suggests that vibration altered proprioceptive inputs used to construct body schema, leading to inaccurate joint position sense and the observed changes in elbow repositioning accuracy.

Source Localization of Audiovisual Multisensory Neural Generators in Young Adults with Attention-Deficit/Hyperactivity Disorder.

Attention-Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder that exhibits unique neurological and behavioural characteristics. Our previous work using event-related potentials demonstrated that adults with ADHD process audiovisual multisensory stimuli somewhat differently than neurotypical controls. This study utilised an audiovisual multisensory two-alternative forced-choice discrimination task. Continuous whole-head electroencephalography (EEG) was recorded. Source localization (sLORETA) software was utilised to determine differences in the contribution made by sources of neural generators pertinent to audiovisual multisensory processing in those with ADHD versus neurotypical controls. Source localization techniques elucidated that the controls had greater neural activity 164 ms post-stimulus onset when compared to the ADHD group, but only when responding to audiovisual stimuli. The source of the increased activity was found to be Brodmann Area 2, postcentral gyrus, right-hemispheric parietal lobe referenced to Montreal Neurological Institute (MNI) coordinates of X = 35, Y = −40, and Z = 70 (p < 0.05). No group differences were present during either of the unisensory conditions. Differences in the integration areas, particularly in the right-hemispheric parietal brain regions, were found in those with ADHD. These alterations may correspond to impaired attentional capabilities when presented with multiple simultaneous sensory inputs, as is the case during a multisensory condition.

The impact of subclinical neck pain on goal-directed upper limb movement in the horizontal plane.

Subclinical neck pain (SCNP) refers to recurrent neck pain and/or stiffness for which individuals have not yet sought treatment. Prior studies have shown that individuals with SCNP have altered cerebellar processing that exhibits an altered body schema. The cerebellum also plays a vital role in upper limb reaching movements through refining internal models and integrating sensorimotor information. However, the impact of SCNP on these processes has yet to be examined in the context of a rapid goal-directed aiming response that relies on feedforward and feedback processes to guide the limb to the target. To address this, SCNP and control participants performed goal-directed upper limb movements with the dominant and non-dominant hands using light and heavy styli in the horizontal plane. The results show greater peak accelerations in SCNP participants using the heavy stylus. However, there were no other group differences seen, possibly due to the fact that reaching behavior predominantly relies on vision such that any proprioceptive deficits seen in those with SCNP can be compensated. This study illustrates the robust compensatory nature of the CNS when performing end-effector reaching tasks, suggesting studies altering visual feedback may be needed to see the full impact of SCNP on upper limb aiming.

Sensorimotor integration and motor learning during a novel force-matching task in young adults with attention-deficit/hyperactivity disorder.

Introduction: Attention-Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder that exhibits unique neurological and behavioral characteristics. Those with ADHD often have noted impairments in motor performance and coordination, including during tasks that require force modulation. The present study provides insight into the role of altered neural processing and SMI in response to a motor learning paradigm requiring force modulation and proprioception, that previous literature has suggested to be altered in those with ADHD, which can also inform our understanding of the neurophysiology underlying sensorimotor integration (SMI) in the general population. Methods: Adults with ADHD (n = 15) and neurotypical controls (n = 15) performed a novel force-matching task, where participants used their right-thumb to match a trace template that varied from 2-12% of their Abductor Pollicis Brevis maximum voluntary contraction. This motor task was completed in pre, acquisition, and post blocks. Participants also completed a retention test 24 h later. Median nerve somatosensory-evoked potentials (SEPs) were collected pre and post motor acquisition. SEPs were stimulated at two frequencies, 2.47 Hz and 4.98 Hz, and 1,000 sweeps were recorded using 64-electrode electroencephalography (EEG) at 2,048 Hz. SEP amplitude changes were normalized to each participant's baseline values for that peak. Results: Both groups improved at post measures (ADHD: 0.85 ± 0.09; Controls: 0.85 ± 0.10), with improvements maintained at retention (ADHD: 0.82 ± 0.11; Controls: 0.82 ± 0.11). The ADHD group had a decreased N18 post-acquisition (0.87 ± 0.48), while the control N18 increased (1.91 ± 1.43). The N30 increased in both groups, with a small increase in the ADHD group (1.03 ± 0.21) and a more pronounced increase in controls (1.15 ± 0.27). Discussion: Unique neural differences between groups were found after the acquisition of a novel force-matching motor paradigm, particularly relating to the N18 peak. The N18 differences suggest that those with ADHD have reduced olivary-cerebellar-M1 inhibition when learning a novel motor task dependent on force-modulation, potentially due to difficulties integrating the afferent feedback necessary to perform the task. The results of this work provide evidence that young adults with ADHD have altered proprioceptive processing when learning a novel motor task when compared to neurotypical controls.

Design and Development of a Rotating Chair to Measure the Cervico-Ocular Reflex.

Eye reflexes that stabilize gaze are essential in navigating daily life. One such reflex is the cervico-ocular reflex (COR). An important neural structure involved in the COR is the cerebellum, which facilitates proper gaze stability through sensorimotor integration to adjust eye movements accordingly. This reflex is tested by fixating the head in space and rotating the body around the neck. Thus, a rotating chair is needed to elicit proper cervical rotation while keeping the head fixed. The chair that was developed for this project was able to rotate to the specified amplitude (±0.5º of accuracy) and frequency. The parameters of the rotation amount, frequency, and amplitude can be adjusted as desired by the project guidelines. Our project aimed to improve upon existing chair models and develop a chair that can be used to assess the COR in neck pain populations.

Effect of Neck Muscle Fatigue on Hand Muscle Motor Performance and Early Somatosensory Evoked Potentials.

Even on pain free days, recurrent neck pain alters sensorimotor integration (SMI) measured via somatosensory evoked potentials (SEPs). Neck muscle fatigue decreases upper limb proprioception, and thus may interfere with upper limb motor task acquisition and SMI. This study aimed to determine the effect of cervical extensor muscle (CEM) fatigue on upper limb motor acquisition and retention; and SMI, measured via early SEPs. Twenty-four healthy right-handed individuals were randomly assigned to control or CEM fatigue. Baseline SEPs were elicited via median nerve stimulation at the wrist. Participants then lay prone on a padded table. The fatigue group supported a 2 kg weight until they could no longer maintain the position. The control group rested their neck in neutral for 5 min. Participants completed pre- and post-motor skill acquisition while seated, SEPs were again collected. Task retention was measured 24 h later. Accuracy improved post acquisition and at retention for both groups (p < 0.001), with controls outperforming the fatigue group (p < 0.05). The fatigue group had significantly greater increases in the N24 (p = 0.017) and N30 (p = 0.007) SEP peaks. CEM fatigue impaired upper limb motor learning outcomes in conjunction with differential changes in SEP peak amplitudes related to SMI.

The contemporary model of vertebral column joint dysfunction and impact of high-velocity, low-amplitude controlled vertebral thrusts on neuromuscular function.

PURPOSE: There is growing evidence that vertebral column function and dysfunction play a vital role in neuromuscular control. This invited review summarises the evidence about how vertebral column dysfunction, known as a central segmental motor control (CSMC) problem, alters neuromuscular function and how spinal adjustments (high-velocity, low-amplitude or HVLA thrusts directed at a CSMC problem) and spinal manipulation (HVLA thrusts directed at segments of the vertebral column that may not have clinical indicators of a CSMC problem) alters neuromuscular function. METHODS: The current review elucidates the peripheral mechanisms by which CSMC problems, the spinal adjustment or spinal manipulation alter the afferent input from the paravertebral tissues. It summarises the contemporary model that provides a biologically plausible explanation for CSMC problems, the manipulable spinal lesion. This review also summarises the contemporary, biologically plausible understanding about how spinal adjustments enable more efficient production of muscular force. The evidence showing how spinal dysfunction, spinal manipulation and spinal adjustments alter central multimodal integration and motor control centres will be covered in a second invited review. RESULTS: Many studies have shown spinal adjustments increase voluntary force and prevent fatigue, which mainly occurs due to altered supraspinal excitability and multimodal integration. The literature suggests physical injury, pain, inflammation, and acute or chronic physiological or psychological stress can alter the vertebral column's central neural motor control, leading to a CSMC problem. The many gaps in the literature have been identified, along with suggestions for future studies. CONCLUSION: Spinal adjustments of CSMC problems impact motor control in a variety of ways. These include increasing muscle force and preventing fatigue. These changes in neuromuscular function most likely occur due to changes in supraspinal excitability. The current contemporary model of the CSMC problem, and our understanding of the mechanisms of spinal adjustments, provide a biologically plausible explanation for how the vertebral column's central neural motor control can dysfunction, can lead to a self-perpetuating central segmental motor control problem, and how HVLA spinal adjustments can improve neuromuscular function.

The effect of neck muscle fatigue on shoulder humeral rotation joint position sense.

INTRODUCTION: Cervical extensor muscle (CEM) fatigue causes decrements in upper limb proprioceptive accuracy during constrained single-joint tasks. This study used a novel humeral rotation joint position sense (JPS) measurement device to compare JPS accuracy in participants who received acute CEM fatigue vs. non-fatigued controls. METHODS: Participants had vision occluded and were passively guided into postures of internal humeral rotation from a baseline posture before and after a CEM fatigue or control protocol. Mixed model repeated measures ANOVAs were used to verify fatigue and compared absolute, constant, and variable JPS error between groups. RESULTS: CEM fatigue was verified via pre-post reduction in CEM strength, and myoelectric indicators of fatigue. However, between-group comparisons of absolute, constant, and variable JPS error were not statistically significant, despite having large effect sizes. DISCUSSION: Contrary to prevailing literature, unconstrained humeral rotation JPS did not appear to be affected by CEM fatigue in this study. However, between-group differences in JPS error were dwarfed by inter-trial variability, which likely arose due to the unconstrained nature of this task, conflating chances for a Type II error. Future research should perform a kinematic analysis of task constraints to highlight potential compensatory mechanisms obscuring significant findings in this otherwise robust effect.

Extrapolating Beyond the Data in a Systematic Review of Spinal Manipulation for Nonmusculoskeletal Disorders: A Fall From the Summit.

OBJECTIVE: The purpose of this article is to discuss a literature review-a recent systematic review of nonmusculoskeletal disorders-that demonstrates the potential for faulty conclusions and misguided policy implications, and to offer an alternate interpretation of the data using present models and criteria. METHODS: We participated in a chiropractic meeting (Global Summit) that aimed to perform a systematic review of the literature on the efficacy and effectiveness of mobilization or spinal manipulative therapy (SMT) for the primary, secondary, and tertiary prevention and treatment of nonmusculoskeletal disorders. After considering an early draft of the resulting manuscript, we identified points of concern and therefore declined authorship. The present article was developed to describe those concerns about the review and its conclusions. RESULTS: Three main concerns were identified: the inherent limitations of a systematic review of 6 articles on the topic of SMT for nonmusculoskeletal disorders, the lack of biological plausibility of collapsing 5 different disorders into a single category, and considerations for best practices when using evidence in policy-making. We propose that the following conclusion is more consistent with a review of the 6 articles. The small cadre of high- or moderate-quality randomized controlled trials reviewed in this study found either no or equivocal effects from SMT as a stand-alone treatment for infantile colic, childhood asthma, hypertension, primary dysmenorrhea, or migraine, and found no or low-quality evidence available to support other nonmusculoskeletal conditions. Therefore, further research is needed to determine if SMT may have an effect in these and other nonmusculoskeletal conditions. Until the results of such research are available, the benefits of SMT for specific or general nonmusculoskeletal disorders should not be promoted as having strong supportive evidence. Further, a lack of evidence cannot be interpreted as counterevidence, nor used as evidence of falsification or verification. CONCLUSION: Based on the available evidence, some statements generated from the Summit were extrapolated beyond the data, have the potential to misrepresent the literature, and should be used with caution. Given that none of the trials included in the literature review were definitively negative, the current evidence suggests that more research on nonmusculoskeletal conditions is warranted before any definitive conclusions can be made. Governments, insurers, payers, regulators, educators, and clinicians should avoid using systematic reviews in decisions where the research is insufficient to determine the clinical appropriateness of specific care.