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.

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.

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.

Difference Between Male and Female Ice Hockey Players in Muscle Activity, Timing, and Head Kinematics During Sudden Head Perturbations.

This study examined sex differences in head kinematics and neck muscle activity during sudden head perturbations. Sixteen competitive ice hockey players participated. Three muscles were monitored bilaterally using surface electromyography: sternocleidomastoid, scalene, and splenius capitis. Head and thorax kinematics were measured. Head perturbations were induced by the release of a 1.5-kg weight attached to a wire wrapped around an adjustable pulley secured to the participant's head. Perturbations were delivered in 4 directions (flexion, extension, right lateral bend, and left lateral bend). Muscle onset times, muscle activity, and head kinematics were examined during 3 time periods (2 preperturbation and 1 postperturbation). Females had significantly greater head acceleration during left lateral bend (31.4%, P < .05) and flexion (37.9%, P = .01). Females had faster muscle onset times during flexion (females = 51 ± 11 ms; males = 61 ± 10 ms; P = .001) and slower onset times during left lateral bend and extension. Females had greater left/right sternocleidomastoid and scalene activity during extension (P = .01), with no difference in head acceleration. No consistent neuromuscular strategy could explain all directional sex differences. Females had greater muscle activity postperturbation during extension, suggesting a neuromuscular response to counter sudden acceleration, possibly explaining the lack of head acceleration differences.

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.

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.

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.

A Machine Learning Approach to Classifying EEG Data Collected with or without Haptic Feedback during a Simulated Drilling Task.

Artificial Intelligence (AI), computer simulations, and virtual reality (VR) are increasingly becoming accessible tools that can be leveraged to implement training protocols and educational resources. Typical assessment tools related to sensory and neural processing associated with task performance in virtual environments often rely on self-reported surveys, unlike electroencephalography (EEG), which is often used to compare the effects of different types of sensory feedback (e.g., auditory, visual, and haptic) in simulation environments in an objective manner. However, it can be challenging to know which aspects of the EEG signal represent the impact of different types of sensory feedback on neural processing. Machine learning approaches offer a promising direction for identifying EEG signal features that differentiate the impact of different types of sensory feedback during simulation training. For the current study, machine learning techniques were applied to differentiate neural circuitry associated with haptic and non-haptic feedback in a simulated drilling task. Nine EEG channels were selected and analyzed, extracting different time-domain, frequency-domain, and nonlinear features, where 360 features were tested (40 features per channel). A feature selection stage identified the most relevant features, including the Hurst exponent of 13-21 Hz, kurtosis of 21-30 Hz, power spectral density of 21-30 Hz, variance of 21-30 Hz, and spectral entropy of 13-21 Hz. Using those five features, trials with haptic feedback were correctly identified from those without haptic feedback with an accuracy exceeding 90%, increasing to 99% when using 10 features. These results show promise for the future application of machine learning approaches to predict the impact of haptic feedback on neural processing during VR protocols involving drilling tasks, which can inform future applications of VR and simulation for occupational skill acquisition.

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 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.

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 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.

Sustained Isometric Wrist Flexion and Extension Maximal Voluntary Contractions on Corticospinal Excitability to Forearm Muscles during Low-Intensity Hand-Gripping.

The wrist extensors demonstrate an earlier fatigue onset than the wrist flexors. However, it is currently unclear whether fatigue induces unique changes in muscle activity or corticospinal excitability between these muscle groups. The purpose of this study was to examine how sustained isometric wrist extension/flexion maximal voluntary contractions (MVCs) influence muscle activity and corticospinal excitability of the forearm. Corticospinal excitability to three wrist flexors and three wrist extensors were measured using motor evoked potentials (MEPs) elicited via transcranial magnetic stimulation. Responses were elicited while participants exerted 10% of their maximal handgrip force, before and after a sustained wrist flexion or extension MVC (performed on separate sessions). Post-fatigue measures were collected up to 10-min post-fatigue. Immediately post-fatigue, extensor muscle activity was significantly greater following the wrist flexion fatigue session, although corticospinal excitability (normalized to muscle activity) was greater on the wrist extension day. Responses were largely unchanged in the wrist flexors. However, for the flexor carpi ulnaris, normalized MEP amplitudes were significantly larger following wrist extension fatigue. These findings demonstrate that sustained isometric flexion/extension MVCs result in a complex reorganization of forearm muscle recruitment strategies during hand-gripping. Based on these findings, previously observed corticospinal behaviour following fatigue may not apply when the fatiguing task and measurement task are different.

Audiovisual Multisensory Processing in Young Adults With Attention-Deficit/Hyperactivity Disorder.

Multisensory integration is a fundamental form of sensory processing that is involved in many everyday tasks. Those with Attention-Deficit/Hyperactivity Disorder (ADHD) have characteristic alterations to various brain regions that may influence multisensory processing. The overall aim of this work was to assess how adults with ADHD process audiovisual multisensory stimuli during a complex response time task. The paradigm used was a two-alternative forced-choice discrimination task paired with continuous 64-electrode electroencephalography, allowing for the measurement of response time and accuracy to auditory, visual, and audiovisual multisensory conditions. Analysis revealed that those with ADHD ( n = 10) respond faster than neurotypical controls ( n = 12) when presented with auditory, visual, and audiovisual multisensory conditions, while also having race model violation in early response latency quantiles. Adults with ADHD also had more prominent multisensory processing over parietal-occipital brain regions at early post-stimulus latencies, indicating that altered brain structure may have important outcomes for audiovisual multisensory processing. The present study is the first to assess how those with ADHD respond to multisensory conditions during a complex response time task, and demonstrates that adults with ADHD have unique multisensory processing when assessing both behavioral response time measures and neurological measures.

The Influence of Subclinical Neck Pain on Neurophysiological and Behavioral Measures of Multisensory Integration.

Multisensory integration (MSI) is necessary for the efficient execution of many everyday tasks. Alterations in sensorimotor integration (SMI) have been observed in individuals with subclinical neck pain (SCNP). Altered audiovisual MSI has previously been demonstrated in this population using performance measures, such as reaction time. However, neurophysiological techniques have not been combined with performance measures in the SCNP population to determine differences in neural processing that may contribute to these behavioral characteristics. Electroencephalography (EEG) event-related potentials (ERPs) have been successfully used in recent MSI studies to show differences in neural processing between different clinical populations. This study combined behavioral and ERP measures to characterize MSI differences between healthy and SCNP groups. EEG was recorded as 24 participants performed 8 blocks of a simple reaction time (RT) MSI task, with each block consisting of 34 auditory (A), visual (V), and audiovisual (AV) trials. Participants responded to the stimuli by pressing a response key. Both groups responded fastest to the AV condition. The healthy group demonstrated significantly faster RTs for the AV and V conditions. There were significant group differences in neural activity from 100-140 ms post-stimulus onset, with the control group demonstrating greater MSI. Differences in brain activity and RT between individuals with SCNP and a control group indicate neurophysiological alterations in how individuals with SCNP process audiovisual stimuli. This suggests that SCNP alters MSI. This study presents novel EEG findings that demonstrate MSI differences in a group of individuals with SCNP.

Audiovisual Multisensory Integration and Evoked Potentials in Young Adults With and Without Attention-Deficit/Hyperactivity Disorder.

The purpose of this study was to assess how young adults with attention-deficit/hyperactivity disorder (ADHD) process audiovisual (AV) multisensory stimuli using behavioral and neurological measures. Adults with a clinical diagnosis of ADHD (n = 10) and neurotypical controls (n = 11) completed a simple response time task, consisting of auditory, visual, and AV multisensory conditions. Continuous 64-electrode electroencephalography (EEG) was collected to assess neurological responses to each condition. The AV multisensory condition resulted in the shortest response times for both populations. Analysis using the race model (Miller, 1982) demonstrated that those with ADHD had violation of the race model earlier in the response, which may be a marker for impulsivity. EEG analysis revealed that both groups had early multisensory integration (MSI) occur following multisensory stimulus onset. There were also significant group differences in event-related potentials (ERPs) in frontal, parietal, and occipital brain regions, which are regions reported to be altered in those with ADHD. This study presents results examining multisensory processing in the population of adults with ADHD, and can be used as a foundation for future ADHD research using developmental research designs as well as the development of novel technological supports.

Audiohaptic Feedback Enhances Motor Performance in a Low-Fidelity Simulated Drilling Task.

When used in educational settings, simulations utilizing virtual reality (VR) technologies can reduce training costs while providing a safe and effective learning environment. Tasks can be easily modified to maximize learning objectives of different levels of trainees (e.g., novice, intermediate, expert), and can be repeated for the development of psychomotor skills. VR offers a multisensory experience, providing visual, auditory, and haptic sensations with varying levels of fidelity. While simulating visual and auditory stimuli is relatively easy and cost-effective, similar representations of haptic sensation still require further development. Evidence suggests that mixing high- and low-fidelity realistic sensations (e.g., audition and haptic) can improve the overall perception of realism, however, whether this also leads to improved performance has not been examined. The current study examined whether audiohaptic stimuli presented in a virtual drilling task can lead to improved motor performance and subjective realism, compared to auditory stimuli alone. Right-handed participants (n = 16) completed 100 drilling trials of each stimulus type. Performance measures indicated that participants overshot the target during auditory trials, and undershot the target during audiohaptic trials. Undershooting is thought to be indicative of improved performance, optimizing both time and energy requirements.

Muscle activation changes after exercise rehabilitation for chronic low back pain.

OBJECTIVE: To investigate the changes in 2 electromyographic measures, flexion relaxation (FR) response and feed-forward activation of the deep abdominals, associated with low back pain (LBP) after different rehabilitation interventions. DESIGN: A 2x2 factorial design with subjects' self-selecting treatment with randomization after 4 weeks to either the specific exercise group or exercise advice group for a further 12-week period. SETTING: General community practitioners and university training center. PARTICIPANTS: Subjects with chronic nonspecific LBP were recruited for this study. A total of 112 people were initially screened, and 60 were recruited for the study, with 50 being available for long-term follow-up. INTERVENTION: Four weeks of treatment (manipulative or nonmanipulation) and 12 weeks of subsequent exercise (supervised Swiss ball training or exercise advice). MAIN OUTCOME MEASURES: The Oswestry Disability Index, FR response measured at T12-L1 and L4-5, and feed-forward activation of the deep abdominal muscles. RESULTS: More rapid improvements in disability were identified for subjects who received the supervised exercise program. The FR response at L4-5 also increased more for those who received directly supervised exercise. Long-term follow-up showed that there was still a between-group difference in the FR response, despite no difference in self-rated disability. Long-term changes were observed for the feed-forward activation of the deep abdominals; however, no exercise or treatment effects were identified. CONCLUSIONS: Supervised exercise rehabilitation leads to more rapid improvements in self-rated disability, which were associated with greater improvement in the low back FR response.