The Effects of Chiropractic Spinal Adjustment on EEG in Adults with Alzheimer's and Parkinson's Disease: A Pilot Randomised Cross-over Trial.

OBJECTIVES: In this study, we explored the effects of chiropractic spinal adjustments on resting-state electroencephalography (EEG) recordings and early somatosensory evoked potentials (SEPs) in Alzheimer's and Parkinson's disease. METHODS: In this randomized cross-over study, 14 adults with Alzheimer's disease (average age 67 ± 6 years, 2 females:12 males) and 14 adults with Parkinson's disease (average age 62 ± 11 years, 1 female:13 males) participated. The participants underwent chiropractic spinal adjustments and a control (sham) intervention in a randomized order, with a minimum of one week between each intervention. EEG was recorded before and after each intervention, both during rest and stimulation of the right median nerve. The power-spectra was calculated for resting-state EEG, and the amplitude of the N30 peak was assessed for the SEPs. The source localization was performed on the power-spectra of resting-state EEG and the N30 SEP peak. RESULTS: Chiropractic spinal adjustment significantly reduced the N30 peak in individuals with Alzheimer's by 15% (p = 0.027). While other outcomes did not reach significance, resting-state EEG showed an increase in absolute power in all frequency bands after chiropractic spinal adjustments in individuals with Alzheimer's and Parkinson's disease. The findings revealed a notable enhancement in connectivity within the Default Mode Network (DMN) at the alpha, beta, and theta frequency bands among individuals undergoing chiropractic adjustments. CONCLUSIONS: We found that it is feasible to record EEG/SEP in individuals with Alzheimer's and Parkinson's disease. Additionally, a single session of chiropractic spinal adjustment reduced the somatosensory evoked N30 potential and enhancement in connectivity within the DMN at the alpha, beta, and theta frequency bands in individuals with Alzheimer's disease. Future studies may require a larger sample size to estimate the effects of chiropractic spinal adjustment on brain activity. Given the preliminary nature of our findings, caution is warranted when considering the clinical implications. CLINICAL TRIAL REGISTRATION: The study was registered by the Australian New Zealand Clinical Trials Registry (registration number ACTRN12618001217291 and 12618001218280).

A Cross-Day Analysis of EMG Features, Classifiers, and Regressors for Swallowing Events Detection and Fluid Intake Volume Estimation.

Dehydration is a common problem among older adults. It can seriously affect their health and wellbeing and sometimes leads to death, given the diminution of thirst sensation as we age. It is, therefore, essential to keep older adults properly hydrated by monitoring their fluid intake and estimating how much they drink. This paper aims to investigate the effect of surface electromyography (sEMG) features on the detection of drinking events and estimation of the amount of water swallowed per sip. Eleven individuals took part in the study, with data collected over two days. We investigated the best combination of a pool of twenty-six time and frequency domain sEMG features using five classifiers and seven regressors. Results revealed an average F-score over two days of 77.5±1.35% in distinguishing the drinking events from non-drinking events using three global features and 85.5±1.00% using three subject-specific features. The average volume estimation RMSE was 6.83±0.14 mL using one single global feature and 6.34±0.12 mL using a single subject-specific feature. These promising results validate and encourage the potential use of sEMG as an essential factor for monitoring and estimating the amount of fluid intake.

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 Potential Mechanisms of High-Velocity, Low-Amplitude, Controlled Vertebral Thrusts on Neuroimmune Function: A Narrative Review.

The current COVID-19 pandemic has necessitated the need to find healthcare solutions that boost or support immunity. There is some evidence that high-velocity, low-amplitude (HVLA) controlled vertebral thrusts have the potential to modulate immune mediators. However, the mechanisms of the link between HVLA controlled vertebral thrusts and neuroimmune function and the associated potential clinical implications are less clear. This review aims to elucidate the underlying mechanisms that can explain the HVLA controlled vertebral thrust--neuroimmune link and discuss what this link implies for clinical practice and future research needs. A search for relevant articles published up until April 2021 was undertaken. Twenty-three published papers were found that explored the impact of HVLA controlled vertebral thrusts on neuroimmune markers, of which eighteen found a significant effect. These basic science studies show that HVLA controlled vertebral thrust influence the levels of immune mediators in the body, including neuropeptides, inflammatory markers, and endocrine markers. This narravtive review discusses the most likely mechanisms for how HVLA controlled vertebral thrusts could impact these immune markers. The mechanisms are most likely due to the known changes in proprioceptive processing that occur within the central nervous system (CNS), in particular within the prefrontal cortex, following HVLA spinal thrusts. The prefrontal cortex is involved in the regulation of the autonomic nervous system, the hypothalamic-pituitary-adrenal axis and the immune system. Bi-directional neuro-immune interactions are affected by emotional or pain-related stress. Stress-induced sympathetic nervous system activity also alters vertebral motor control. Therefore, there are biologically plausible direct and indirect mechanisms that link HVLA controlled vertebral thrusts to the immune system, suggesting HVLA controlled vertebral thrusts have the potential to modulate immune function. However, it is not yet known whether HVLA controlled vertebral thrusts have a clinically relevant impact on immunity. Further research is needed to explore the clinical impact of HVLA controlled vertebral thrusts on immune function.

A Multiday Evaluation of Real-Time Intramuscular EMG Usability with ANN.

Recent developments in implantable technology, such as high-density recordings, wireless transmission of signals to a prosthetic hand, may pave the way for intramuscular electromyography (iEMG)-based myoelectric control in the future. This study aimed to investigate the real-time control performance of iEMG over time. A novel protocol was developed to quantify the robustness of the real-time performance parameters. Intramuscular wires were used to record EMG signals, which were kept inside the muscles for five consecutive days. Tests were performed on multiple days using Fitts' law. Throughput, completion rate, path efficiency and overshoot were evaluated as performance metrics using three train/test strategies. Each train/test scheme was categorized on the basis of data quantity and the time difference between training and testing data. An artificial neural network (ANN) classifier was trained and tested on (i) data from the same day (WDT), (ii) data collected from the previous day and tested on present-day (BDT) and (iii) trained on all previous days including the present day and tested on present-day (CDT). It was found that the completion rate (91.6 ± 3.6%) of CDT was significantly better (p < 0.01) than BDT (74.02 ± 5.8%) and WDT (88.16 ± 3.6%). For BDT, on average, the first session of each day was significantly better (p < 0.01) than the second and third sessions for completion rate (77.9 ± 14.0%) and path efficiency (88.9 ± 16.9%). Subjects demonstrated the ability to achieve targets successfully with wire electrodes. Results also suggest that time variations in the iEMG signal can be catered by concatenating the data over several days. This scheme can be helpful in attaining stable and robust performance.

Therapeutic effects of aerobic exercise on EEG parameters and higher cognitive functions in mild cognitive impairment patients.

BACKGROUND: Mild cognitive impairment (MCI) is becoming an emerging problem for developing countries where there is an increase in expected age. There is no specific curative therapeutic treatment available for these patients. OBJECTIVE: The objective of this study was to evaluate short and long-term changes in the electroencephalogram (EEG) parameters and cognition of MCI patients with aerobic exercises. METHODS: A randomized controlled trial was conducted on 40 patients which were randomly divided into two groups, 'aerobic exercise treatment group (n = 21)' and 'no-aerobic control group (n = 19)'. Short-term effects of exercise were measured after single session of exercise and long-term effects were measured after an 18 sessions (6 weeks) treatment. The outcomes which were measured were, electroenphelogram paramaters (slowness and complexity of the EEG) and cognitive functions (using mini-mental state examination (MMSE), Montreal cognitive assessment (MoCA), and trail making test (TMT) A and B). RESULTS: After one session of aerobic exercise there were significant improvements in slowness (delta waves; 0.678 ± 0.035 vs 0.791 ± 0.033; p = .015) and complexity (0.601 ± 0.051 vs 0.470 ± 0.042; p = .027) of the EEG in aerobic exercise treated group as compared to no-aerobic exercise group. After six weeks there were significant improvements in slowness (delta waves; 0.581 ± 0.036 vs 0.815 ± 0.025; p = .005) and complexity (0.751 ± 0.045 vs 0.533 ± 0.046; p = .001) of the EEG in the aerobic group as compared to no-aerobic group. Moreover, significant improvements were observed in the MMSE (p = .032), MoCA (p = .036), TMT-A (p = .005), and TMT-B (p = .007) in aerobic exercise group as compared to no-aerobic group. CONCLUSION: Aerobic exercise showed improvement in cognition after short and long-term treatment in MCI subjects and can be used as potential therapeutic candidate.

The Effects of Filter's Class, Cutoff Frequencies, and Independent Component Analysis on the Amplitude of Somatosensory Evoked Potentials Recorded from Healthy Volunteers.

OBJECTIVE: The aim of this study was to investigate the effects of different preprocessing parameters on the amplitude of median nerve somatosensory evoked potentials (SEPs). METHODS: Different combinations of two classes of filters (Finite Impulse Response (FIR) and Infinite Impulse Response (IIR)), three cutoff frequency bands (0.5-1000 Hz, 3-1000 Hz, and 30-1000 Hz), and independent component analysis (ICA) were used to preprocess SEPs recorded from 17 healthy volunteers who participated in two sessions of 1000 stimulations of the right median nerve. N30 amplitude was calculated from frontally placed electrode (F3). RESULTS: The epochs classified as artifacts from SEPs filtered with FIR compared to those filtered with IIR were 1% more using automatic and 140% more using semi-automatic methods (both p < 0.001). There were no differences in N30 amplitudes between FIR and IIR filtered SEPs. The N30 amplitude was significantly lower for SEPs filtered with 30-1000 Hz compared to the bandpass frequencies 0.5-1000 Hz and 3-1000 Hz. The N30 amplitude was significantly reduced when SEPs were cleaned with ICA compared to the SEPs from which non-brain components were not removed using ICA. CONCLUSION: This study suggests that the preprocessing of SEPs should be done carefully and the neuroscience community should come to a consensus regarding SEP preprocessing guidelines, as the preprocessing parameters can affect the outcomes that may influence the interpretations of results, replicability, and comparison of different studies.

The effects of subclinical neck pain on sensorimotor integration following a complex motor pursuit task.

Recurrent subclinical neck pain (SCNP) may be associated with neural plastic changes in sensory processing and sensorimotor integration (SMI); however, its impact on motor learning has not been investigated. The aim of this study was to investigate whether SCNP alters neural markers of SMI during a complex motor acquisition task as compared to a healthy control group. Peripheral N9, spinal N13, brainstem N18, and cortical N20, P25, N24 and N30 early somatosensory evoked potentials (SEPs) were recorded following median nerve stimulation for 24 participants (12 control and 12 SCNP) before and after a 10-min tracing motor task intervention. Retention was assessed 24-48 h later. Significant amplitude differences were observed for both N18 and N24 SEP waveforms between groups, indicating there may be a difference in SMI due to altered afferent input as a result of SCNP. Accuracy increased significantly for both groups post-motor training; however, at retention only the control group showed an additional increase in accuracy. Both N18 and N24 SEP peaks are linked with cerebellar pathways, suggesting that SCNP impacts these connections. Significant correlations between these peaks and performance data were also seen. The differential changes in neurophysiological markers of SMI seen in SCNP suggest that SEPs have the potential to be used as an early screening tool for those at risk of having maladaptive neural plastic changes in response to motor training as a result of SCNP.

Posture modulates the sensitivity of the H-reflex.

The effect of body posture on the human soleus H-reflex via electrical stimulation of the tibial nerve at the popliteal fossa was studied. All parameters that may influence the reflex were controlled stringently. H-reflexes were elicited in three different body postures while keeping the level of background muscle activation to a minimum. The H-reflex curve relative to the M-wave curve did not change significantly in any of the body postures. However, the maximal H-reflex amplitude significantly increased in the prone position compared with the sitting (p = 0.02) and standing positions (p = 0.01). The background level of electrical activity of the soleus muscle did not significantly change during varying body postures. Together, these findings indicate that the effectiveness of the spindle primary afferent synapse on the soleus motor neuron pool changes significantly in prone position as compared to sitting and standing positions. Given that we have controlled the confounding factors excluding the head position relative to the gravity and the receptors that may be differentially activated at varying body postures such as the proprioceptors, it is concluded that the tonic activity from these receptors may presynaptically interfere with the effectiveness of the spindle primary afferent synapses on the soleus motor neurons.

The effects of a single session of spinal manipulation on strength and cortical drive in athletes.

PURPOSE: The primary purpose of this study was to investigate whether a single session of spinal manipulation (SM) increases strength and cortical drive in the lower limb (soleus muscle) of elite Taekwondo athletes. METHODS: Soleus-evoked V-waves, H-reflex and maximum voluntary contraction (MVC) of the plantar flexors were recorded from 11 elite Taekwondo athletes using a randomized controlled crossover design. Interventions were either SM or passive movement control. Outcomes were assessed at pre-intervention and at three post-intervention time periods (immediate post, post 30 min and post 60 min). A multifactorial repeated measures ANOVA was conducted to assess within and between group differences. Time and session were used as factors. A post hoc analysis was carried out, when an interactive effect was present. Significance was set at p ≤ 0.05. RESULTS: SM increased MVC force [F(3,30) = 5.95, p < 0.01], and V-waves [F(3,30) = 4.25, p = 0.01] over time compared to the control intervention. Between group differences were significant for all time periods (p < 0.05) except for the post60 force measurements (p = 0.07). CONCLUSION: A single session of SM increased muscle strength and corticospinal excitability to ankle plantar flexor muscles in elite Taekwondo athletes. The increased MVC force lasted for 30 min and the corticospinal excitability increase persisted for at least 60 min.

Investigation of Optimal Afferent Feedback Modality for Inducing Neural Plasticity with A Self-Paced Brain-Computer Interface.

Brain-computer interfaces (BCIs) can be used to induce neural plasticity in the human nervous system by pairing motor cortical activity with relevant afferent feedback, which can be used in neurorehabilitation. The aim of this study was to identify the optimal type or combination of afferent feedback modalities to increase cortical excitability in a BCI training intervention. In three experimental sessions, 12 healthy participants imagined a dorsiflexion that was decoded by a BCI which activated relevant afferent feedback: (1) electrical nerve stimulation (ES) (peroneal nerve-innervating tibialis anterior), (2) passive movement (PM) of the ankle joint, or (3) combined electrical stimulation and passive movement (Comb). The cortical excitability was assessed with transcranial magnetic stimulation determining motor evoked potentials (MEPs) in tibialis anterior before, immediately after and 30 min after the BCI training. Linear mixed regression models were used to assess the changes in MEPs. The three interventions led to a significant (p < 0.05) increase in MEP amplitudes immediately and 30 min after the training. The effect sizes of Comb paradigm were larger than ES and PM, although, these differences were not statistically significant (p > 0.05). These results indicate that the timing of movement imagery and afferent feedback is the main determinant of induced cortical plasticity whereas the specific type of feedback has a moderate impact. These findings can be important for the translation of such a BCI protocol to the clinical practice where by combining the BCI with the already available equipment cortical plasticity can be effectively induced. The findings in the current study need to be validated in stroke populations.

Association of Subclinical Neck Pain With Altered Multisensory Integration at Baseline and 4-Week Follow-up Relative to Asymptomatic Controls.

OBJECTIVE: The purpose of this study was to test whether people with subclinical neck pain (SCNP) had altered visual, auditory, and multisensory response times, and whether these findings were consistent over time. METHODS: Twenty-five volunteers (12 SCNP and 13 asymptomatic controls) were recruited from a Canadian university student population. A 2-alternative forced-choice discrimination task with multisensory redundancy was used to measure response times to the presentation of visual (color filled circles), auditory (verbalization of the color words, eg, red or blue), and multisensory (simultaneous audiovisual) stimuli at baseline and 4 weeks later. RESULTS: The SCNP group was slower at both visual and multisensory tasks (P = .046, P = .020, respectively), with no change over 4 weeks. Auditory response times improved slightly but significantly after 4 weeks (P = .050) with no group difference. CONCLUSIONS: This is the first study to report that people with SCNP have slower visual and multisensory response times than asymptomatic individuals. These differences persist over 4 weeks, suggesting that the multisensory technique is reliable and that these differences in the SCNP group do not improve on their own in the absence of treatment.

Interexaminer Reliability of Seated Motion Palpation for the Stiffest Spinal Site.

OBJECTIVES: The purpose of this study was to assess the interexaminer reliability of palpation for stiffness in the cervical, thoracic, and lumbar spinal regions. METHODS: In this secondary data analysis, data from 70 patients from a chiropractic college outpatient clinic were analyzed. Two doctors of chiropractic palpated for the stiffest site within each spinal region. Each were asked to select the stiffest segment and to rate their confidence in their palpation findings. Reliability between examiners was calculated as Median Absolute Examiner Differences (MedianAED) and data dispersion as Median Absolute Deviation (MAD). Interquartile analysis of the paired examiner differences was performed. RESULTS: In total, 210 paired observations were analyzed. Nonparametric data precluded reliability determination using intraclass correlation. Findings included lumbar MedianAED = 0.5 vertebral equivalents (VE), thoracic = 1.7 VE, and cervical = 1.4 VE. For the combined dataset, the findings were MedianAED = 1.1 VE; MAD was lowest in the lumbar spine (0.3 VE) and highest in thoracic spine (1.4 VE), and for the combined dataset, MAD = 1.1 VE. Examiners agreed on the segment or the motion segment containing the stiffest site in 54% of the observations. CONCLUSIONS: Interexaminer reliability for palpation was good between 2 clinicians for the stiffest site in each region of the spine and in the combined dataset. This is consistent with previous studies of motion palpation using continuous analysis.

Effects of 12 Weeks of Chiropractic Care on Central Integration of Dual Somatosensory Input in Chronic Pain Patients: A Preliminary Study.

OBJECTIVE: The purpose of this preliminary study was to assess whether the dual somatosensory evoked potential (SEP) technique is sensitive enough to measure changes in cortical intrinsic inhibitory interactions in patients with chronic neck or upper extremity pain and, if so, whether changes are associated with changes in pain scores. METHODS: The dual peripheral nerve stimulation SEP ratio technique was used for 6 subjects with a history of chronic neck or upper limb pain. SEPs were recorded after left or right median and ulnar nerve stimulation at the wrist. SEP ratios were calculated for the N9, N13, P14-18, N20-P25, and P22-N30 peak complexes from SEP amplitudes obtained from simultaneous median and ulnar stimulation divided by the arithmetic sum of SEPs obtained from individual stimulation of the median and ulnar nerves. Outcome measures of SEP ratios and subjects' visual analog scale rating of pains were recorded at baseline, after a 2-week usual care control period, and after 12 weeks of multimodal chiropractic care (chiropractic spinal manipulation and 1 or more of the following: exercises, peripheral joint adjustments/manipulation, soft tissue therapy, and pain education). RESULTS: A significant decrease in the median and ulnar to median plus ulnar ratio and the median and ulnar amplitude for the cortical P22-N30 SEP component was observed after 12 weeks of chiropractic care, with no changes after the control period. There was a significant decrease in visual analog scale scores (both for current pain and for pain last week). CONCLUSION: The dual SEP ratio technique appears to be sensitive enough to measure changes in cortical intrinsic inhibitory interactions in patients with chronic neck pain. The observations in 6 subjects revealed that 12 weeks of chiropractic care improved suppression of SEPs evoked by dual upper limb nerve stimulation at the level of the motor cortex, premotor areas, and/or subcortical areas such as basal ganglia and/or thalamus. It is possible that these findings explain one of the mechanisms by which chiropractic care improves function and reduces pain for chronic pain patients.

Manipulation of Dysfunctional Spinal Joints Affects Sensorimotor Integration in the Prefrontal Cortex: A Brain Source Localization Study.

Objectives. Studies have shown decreases in N30 somatosensory evoked potential (SEP) peak amplitudes following spinal manipulation (SM) of dysfunctional segments in subclinical pain (SCP) populations. This study sought to verify these findings and to investigate underlying brain sources that may be responsible for such changes. Methods. Nineteen SCP volunteers attended two experimental sessions, SM and control in random order. SEPs from 62-channel EEG cap were recorded following median nerve stimulation (1000 stimuli at 2.3 Hz) before and after either intervention. Peak-to-peak amplitude and latency analysis was completed for different SEPs peak. Dipolar models of underlying brain sources were built by using the brain electrical source analysis. Two-way repeated measures ANOVA was used to assessed differences in N30 amplitudes, dipole locations, and dipole strengths. Results. SM decreased the N30 amplitude by 16.9 ± 31.3% (P = 0.02), while no differences were seen following the control intervention (P = 0.4). Brain source modeling revealed a 4-source model but only the prefrontal source showed reduced activity by 20.2 ± 12.2% (P = 0.03) following SM. Conclusion. A single session of spinal manipulation of dysfunctional segments in subclinical pain patients alters somatosensory processing at the cortical level, particularly within the prefrontal cortex.

Effect of Spinal Manipulation on Pelvic Floor Functional Changes in Pregnant and Nonpregnant Women: A Preliminary Study.

OBJECTIVE: The aim of this study was to investigate whether a single session of spinal manipulation of pregnant women can alter pelvic floor muscle function as measured using ultrasonographic imaging. METHODS: In this preliminary, prospective, comparative study, transperineal ultrasonographic imaging was used to assess pelvic floor anatomy and function in 11 primigravid women in their second trimester recruited via notice boards at obstetric caregivers, pregnancy keep-fit classes, and word of mouth and 15 nulliparous women recruited from a convenience sample of female students at the New Zealand College of Chiropractic. Following bladder voiding, 3-/4-dimensional transperineal ultrasonography was performed on all participants in the supine position. Levator hiatal area measurements at rest, on maximal pelvic floor contraction, and during maximum Valsalva maneuver were collected before and after either spinal manipulation or a control intervention. RESULTS: Levator hiatal area at rest increased significantly (P < .05) after spinal manipulation in the pregnant women, with no change postmanipulation in the nonpregnant women at rest or in any of the other measured parameters. CONCLUSION: Spinal manipulation of pregnant women in their second trimester increased the levator hiatal area at rest and thus appears to relax the pelvic floor muscles. This did not occur in the nonpregnant control participants, suggesting that it may be pregnancy related.

Effectiveness of Chiropractic Care to Improve Sensorimotor Function Associated With Falls Risk in Older People: A Randomized Controlled Trial.

OBJECTIVE: This study assessed whether 12 weeks of chiropractic care was effective in improving sensorimotor function associated with fall risk, compared with no intervention, in community-dwelling older adults living in Auckland, New Zealand. METHODS: Sixty community-dwelling adults older than 65 years were enrolled in the study. Outcome measures were assessed at baseline, 4 weeks, and 12 weeks and included proprioception (ankle joint position sense), postural stability (static posturography), sensorimotor function (choice stepping reaction time), multisensory integration (sound-induced flash illusion), and health-related quality of life (SF-36). RESULTS: Over 12 weeks, the chiropractic group improved compared with the control group in choice stepping reaction time (119 milliseconds; 95% confidence interval [CI], 26-212 milliseconds; P = .01) and sound-induced flash illusion (13.5%; 95% CI, 2.9%-24.0%; P = .01). Ankle joint position sense improved across the 4- and 12-week assessments (0.20°; 95% CI, 0.01°-0.39°; P = .049). Improvements were also seen between weeks 4 and 12 in the SF-36 physical component of quality of life (2.4; 95% CI, 0.04-4.8; P = .04) compared with control. CONCLUSION: Sensorimotor function and multisensory integration associated with fall risk and the physical component of quality of life improved in older adults receiving chiropractic care compared with control. Future research is needed to investigate the mechanisms of action that contributed to the observed changes in this study and whether chiropractic care has an impact on actual falls risk in older adults.

Influence of Subclinical Neck Pain on the Ability to Perform a Mental Rotation Task: A 4-Week Longitudinal Study With a Healthy Control Group Comparison.

OBJECTIVE: Mental rotation of objects and the frame of reference of those objects are critical for executing correct and skillful movements and are important for object recognition, spatial navigation, and movement planning. The purpose of this longitudinal study was to compare the mental rotation ability of those with subclinical neck pain (SCNP) to healthy controls at baseline and after 4 weeks. METHODS: Twenty-six volunteers (13 SCNP and 12 healthy controls) were recruited from a university student population. Subclinical neck pain participants had scores of mild to moderate on the Chronic Pain Grade Scale, and controls had minimal or no pain. For the mental rotation task, participants were presented with an object (letter "R") on a computer screen presented randomly in either normal or backwards parity at various orientations (0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°). Participants indicated the object's parity by pressing "N" for normal or "B" for backwards. Each orientation for normal and backward parities was presented 5 times, and the average response time for all letter presentations was calculated for each participant, at baseline and 4 weeks later. RESULTS: Both groups had overall improved response times from baseline to 4 weeks. Healthy participants had significantly improved response times compared to SCNP, both at baseline (P < .05) and 4 weeks (P < .05). CONCLUSIONS: Healthy participants performed better than the SCNP group at both time points. Subclinical neck pain may impair the ability to perform a complex mental rotation task involving cerebellar connections, possibly due to altered body schema.

Changes in H-reflex and V-waves following spinal manipulation.

This study investigates whether spinal manipulation leads to neural plastic changes involving cortical drive and the H-reflex pathway. Soleus evoked V-wave, H-reflex, and M-wave recruitment curves and maximum voluntary contraction (MVC) in surface electromyography (SEMG) signals of the plantar flexors were recorded from ten subjects before and after manipulation or control intervention. Dependent measures were compared with 2-way ANOVA and Tukey's HSD as post hoc test, p was set at 0.05. Spinal manipulation resulted in increased MVC (measured with SEMG) by 59.5 ± 103.4 % (p = 0.03) and force by 16.05 ± 6.16 4 % (p = 0.0002), increased V/M max ratio by 44.97 ± 36.02 % (p = 0.006), and reduced H-reflex threshold (p = 0.018). Following the control intervention, there was a decrease in MVC (measured with SEMG) by 13.31 ± 7.27 % (p = 0.001) and force by 11.35 ± 9.99 % (p = 0.030), decreased V/M max ratio (23.45 ± 17.65 %; p = 0.03) and a decrease in the median frequency of the power spectrum (p = 0.04) of the SEMG during MVC. The H-reflex pathway is involved in the neural plastic changes that occur following spinal manipulation. The improvements in MVC following spinal manipulation are likely attributed to increased descending drive and/or modulation in afferents. Spinal manipulation appears to prevent fatigue developed during maximal contractions. Spinal manipulation appears to alter the net excitability of the low-threshold motor units, increase cortical drive, and prevent fatigue.