Does movement preparation enhance attending to bodily sensations in the back in people with persistent low back pain?

Attention has been proposed to play an important role in persisting pain, with excessive attentional processes towards pain information leading to worse pain outcomes and maladaptive behaviors. Nevertheless, research on somatosensory attending during the anticipation of pain-related movements is still scarce. This study investigated if individuals with chronic and recurrent lower back pain compared to pain-free controls, show enhanced attending to somatosensory information in the back while anticipating back-recruiting movements. 43 healthy control, 33 recurrent (RLBP) and 33 chronic low back (CLBP) pain sufferers were asked to perform back-recruiting movements. Before the movement initiation cue, a task-irrelevant tactile stimulus was administered to participants' lower back to elicit somatosensory evoked potentials (SEPs), used as an index of somatosensory attending. In contrast to our hypothesis, most identified SEP components did not differ across groups. The only exception was the P175 amplitude which was larger for the CLBP group compared to individuals with RLBP and healthy controls. The current study did not find robust evidence of enhanced somatosensory attending to the back in people with persisting lower back pain. The finding that CLBP, but not RLBP individuals, had larger amplitudes to the P175 component, is discussed as possibly reflecting a higher state of emotional arousal in these patients when having to prepare the back-recruiting movements.

Physical or Cognitive Exertion Does Not Influence Cortical Movement Preparation for Rapid Arm Movements.

The contribution of central factors to movement preparation (e.g., the contingent negative variation [CNV]) and the influence of fatigue on such factors are still unclear, even though executive cognitive functions are regarded as key elements in motor control. Therefore, this study examined CNV amplitude with electroencephalography in 22 healthy humans during a rapid arm movement task prior to and following three experimental conditions: (a) a no exertion/control condition, (b) a physical exertion, and (c) a cognitive exertion. CNV amplitude was affected neither by a single bout of physical/cognitive exertion nor by the control condition. Furthermore, no time-on-task effects of the rapid arm movement task on the CNV were found. Exertion did not affect cortical movement preparation, which is in contrast to previous findings regarding time-on-task effects of exertion on CNV. Based on the current findings, the rapid arm movement task is deemed suitable to measure cortical movement preparation, without being affected by learning effects and physical/cognitive exertion.

Hypervigilance for Bodily Sensations in the Back During a Movement Task in People With Chronic and Recurrent Low Back Pain.

OBJECTIVES: The current study assessed the role of hypervigilance for bodily sensations in the back in long-term low back pain problems. METHODS: People with chronic low back pain, recurrent low back pain, and no low back pain were compared on the extent to which they attended to somatosensory stimuli on the back during a movement task. To measure hypervigilance, somatosensory event-related potentials (SEPs) to task-irrelevant tactile stimuli on the back were measured when preparing movements in either a threatening or a neutral condition, indicated by a cue signaling possible pain on the back during movement or not. RESULTS: Results showed stronger attending to stimuli on the back in the threat condition than in the neutral condition, as reflected by increased amplitude of the N96 SEP. However, this effect did not differ between groups. Similarly, for all 3 groups the amplitude of the P172 was larger for the threatening condition, suggesting a more general state of arousal resulting in increased somatosensory responsiveness. No significant associations were found between somatosensory attending to the back and theorized antecedents such as pain catastrophizing, pain-related fear, and pain vigilance. DISCUSSION: The current study confirmed that individuals preparing a movement attended more toward somatosensory stimuli at the lower back when anticipating back pain during the movement, as measured by the N96 SEP. However, no differences were found between participants with chronic low back pain or recurrent low back pain, or the pain-free controls.

Does experimentally induced pain-related fear influence central and peripheral movement preparation in healthy people and patients with low back pain?

Nonspecific chronic low back pain (CLBP) is a multifactorial disorder. Pain-related fear and altered movement preparation are considered to be key factors in the chronification process. Interactions between both have been hypothesized, but studies examining the influence of situational fear on movement preparation in low back pain (LBP) are wanting, as well as studies differentiating between recurrent LBP (RLBP) and CLBP. Therefore, this study examined whether experimentally induced pain-related fear influences movement preparation. In healthy controls (n = 32), RLBP (n = 31) and CLBP (n = 30) patients central and peripheral measures of movement preparation were assessed by concurrently measuring trunk muscle anticipatory postural adjustments (APA) with electromyography and contingent negative variation with EEG during performance of rapid arm movements. Two conditions were compared, one without (no fear) and one with (fear) possibility of painful stimulation to the back during rapid arm movements. Visual analogue scales were used to assess pain-related expectations/fear in both conditions. The experimentally induced fear of pain during movement performance led to an increase in contingent negative variation amplitude, which was similar in all 3 groups. Concerning APAs, no effects of fear were found, but group differences with generally delayed APAs in CLBP compared with controls and RLBP patients were evident. These results suggest that with fear, an attentional redirection towards more conscious central movement preparation strategies occurs. Furthermore, differences in movement preparation in patients with RLBP and CLBP exist, which could explain why patients with RLBP have more recovery capabilities than patients with CLBP.

Are Functional Brain Alterations Present in Low Back Pain? A Systematic Review of EEG Studies.

This systematic review analyzed available literature on functional brain alterations in low back pain (LBP) measured with electroencephalography (EEG), as until now evidence thereof was unclear. Four electronic databases were systematically searched the 10th of March 2018, resulting in 12 included studies. Studies showed a risk of bias of 37.5 to 75% using the Newcastle-Ottawa Scale for case-control studies. Limited evidence reported higher amplitudes of balance-related potentials and early components of somatosensory evoked potentials (SEP) to noxious stimuli, and altered feedback-related negativity and P300 potentials during decision-making in chronic LBP (CLBP). These findings suggest postural strategies requiring a higher cortical attention-demand, increased sensory-discriminative processing of noxious input, and altered decision-making in CLBP. However, further research is warranted as these inferences were based on single studies. Moderate evidence for unaltered amplitude of late-phase SEPs to noxious stimuli and auditory evoked potentials in LBP implies that the affective-emotional processing of stimuli might be unaffected in LBP. Furthermore, moderate evidence indicated disturbed habituation of somatosensory stimuli in LBP. Most studies examined nonspecific or mixed CLBP populations, hence EEG-quantified brain activity in (sub)acute or recurrent LBP still needs to be explored. PERSPECTIVE: This review presents an overview of the current understanding of the functional LBP brain measured with EEG. The limited evidence in current research suggests altered cortical function regarding balance control, somatosensory processing, and decision making in LBP, and highlights opportunities for future EEG-research.

Predicting treatment adherence and outcome to outpatient multimodal rehabilitation in chronic low back pain.

BACKGROUND: There is a growing need to identify patient pre-treatment characteristics that could predict adherence and outcome following specific interventions. OBJECTIVE: To identify predictors of adherence and outcome to outpatient multimodal rehabilitation in chronic low back pain (CLBP). METHODS: A total of 273 CLBP patients participated in an exercise-based rehabilitation program. Patients who completed ⩾ 70% of the treatment course were classified as adherent. Patients showing a post-treatment reduction of ⩾ 30% in Oswestry Disability Index (ODI) and Visual Analogue Scale (VAS) back pain intensity scores were assigned to the favorable outcome group. RESULTS: Multivariate logistic regression revealed that higher age, higher ability to perform low-load activities, and higher degrees of kinesiophobia increased the odds to complete the rehabilitation program. By contrast, lower levels of education and back pain unrelated to poor posture increased the odds for non-adherence. Furthermore, a favorable outcome was predicted in case the cause for LBP was known, shorter symptom duration, no pain in the lower legs, no difficulties falling asleep, and short-term work absenteeism. CONCLUSIONS: Assessment and consideration of patient pre-treatment characteristics is of great importance as they may enable therapists to identify patients with a good prognosis or at risk for non-responding to outpatient multimodal rehabilitation.

Physical and cognitive exertion do not influence feedforward activation of the trunk muscles: a randomized crossover trial.

Fatigue arises during everyday activities, diminishes movement performance, and increases injury risk. Physical (PE) and cognitive exertion (CE) can induce similar feelings of fatigue, but it is not clear whether these also similarly affect movement performance. Therefore, this study examined the influence of PE and CE on anticipatory postural adjustments (APAs) of trunk muscles, which are feedforward mechanisms that contribute to motor control and controlled movement. Rapid arm movement tasks (RAM) were used to induce APAs of the trunk muscles prior and following three experimental conditions in 20 healthy adults: seated rest without exertion (NE), a combined isometric modified Biering-Sörensen and static abdominal curl to induce PE, and a modified incongruent Stroop colour-word task to induce CE. Fatigue was assessed using self-reported measures, and APA onset latencies of the trunk muscles with surface electromyography. Statistical analyses revealed that neither PE nor CE influence APAs of the trunk. Therefore, it is hypothesized that the influence of fatigue on movement performance might not be through altered motor control, but rather by reduced motivation. However, the possibility that fatigue might influence other mechanisms which contribute to trunk motor control, such as APA amplitude and variability, cannot be excluded and need further examination.

Somatosensory attending to the lower back is associated with response speed of movements signaling back pain.

The present study investigated if preparing a movement that is expected to evoke pain results in hesitation to initiate the movement (i.e., avoidance) and, especially, if the allocation of attention to the threatened body part mediates such effect. To this end, healthy volunteers (N = 33) performed a postural perturbation task recruiting lower back muscles. In 'threat trials', the movement was sometimes followed by an experimental pain stimulus on the back, whereas in 'no-threat trials', a non-painful control stimulus was applied. Electroencephalography (EEG) was used to assess attending to the lower back. Specifically, somatosensory evoked potentials (SEPs) to task-irrelevant tactile stimuli administered to the lower back were recorded during movement preparation. Reaction times (RTs) were recorded to assess movement initiation. The results revealed faster responses and enhanced somatosensory attending to the lower back on threat trials than on no-threat trials. Importantly, the amplitude of the N95 SEP component predicted RTs and was found to partially mediate the effect of pain anticipation on movement initiation. These findings suggest that somatosensory attending might be a potential mechanism by which pain anticipation can modulate motor execution.

Determining Predictive Outcome Factors for a Multimodal Treatment Program in Low Back Pain Patients: A Retrospective Cohort Study.

OBJECTIVE: The purpose of this study was to determine the factors predictive of outcomes in a multifaceted rehabilitation program for acute and chronic low back pain (LBP) patients. METHODS: A retrospective cohort study was performed on 565 LBP patients (153 acute and 412 chronic) who participated in a multimodal treatment program at an outpatient clinic in Belgium between 2007 and 2010. The predictive value of several factors, including age, sex, body mass index, fat percentage, Oswestry Disability Index score, Beck Depression Index score, Numeric Pain Rating Scale score for back and leg pain intensity, and Tampa Scale for Kinesiophobia score on favorable treatment outcomes was examined using logistic regression analysis. RESULTS: The results from the multivariate regression indicated that a higher score on the Tampa Scale for Kinesiophobia (odds ratio [OR] = 0.92) decreases the odds of a favorable outcome following a multimodal treatment program in acute LBP. Older age (OR = 0.97), low LBP intensity (OR = 1.191), and higher scores on the Beck Depression Index (OR = 0.96) and the Oswestry LBP Disability Index (OR = 0.93) decreased the odds of a favorable treatment outcome in chronic LBP. CONCLUSIONS: The findings of this study indicate that factors predictive of a (un)favorable treatment outcome differ between acute and chronic LBP. Specifically, kinesiophobia is predictive of poor treatment outcome in acute LBP. In chronic LBP, older age, low LBP intensity, and higher degrees of depression and LBP-related disability are predictive of poor treatment outcome. Therapists should consider assessing these predictive factors at intake to tailor the content of the multimodal treatment program to individual patient needs.

Lumbar muscle structure and function in chronic versus recurrent low back pain: a cross-sectional study.

BACKGROUND CONTEXT: Heterogeneity exists within the low back pain (LBP) population. Some patients recover after every pain episode, whereas others suffer daily from LBP complaints. Until now, studies rarely make a distinction between recurrent low back pain (RLBP) and chronic low back pain (CLBP), although both are characterized by a different clinical picture. Clinical experiences also indicate that heterogeneity exists within the CLBP population. Muscle degeneration, like atrophy, fat infiltration, alterations in muscle fiber type, and altered muscle activity, compromises proper biomechanics and motion of the spinal units in LBP patients. The amount of alterations in muscle structure and muscle function of the paraspinal muscles might be related to the recurrence or chronicity of LBP. PURPOSE: The aim of this experimental study is to evaluate differences in muscle structure (cross-sectional area and lean muscle fat index) and muscle activity of the multifidus (MF) and erector spinae (ES) during trunk extension, in patients with RLBP, non-continuous CLBP, and continuous CLBP. STUDY DESIGN AND SETTING: This cross-sectional study took place in the university hospital of Ghent, Belgium. Muscle structure characteristics and muscle activity were assessed by magnetic resonance imaging (MRI). PATIENT SAMPLE: Fifty-five adults with non-specific LBP (24 RLBP in remission, 15 non-continuous CLBP, 16 continuous CLBP) participated in this study. OUTCOME MEASURES: Total cross-sectional area, muscle cross-sectional area, fat cross-sectional area, lean muscle fat index, T2-rest and T2-shift were assessed. METHODS: A T1-weighted Dixon MRI scan was used to evaluate spinal muscle cross-sectional area and fat infiltration in the lumbar MF and ES. Muscle functional MRI was used to evaluate the muscle activity of the lumbar MF and ES during a lumbar extension exercise. Before and after the exercise, a pain assessment was performed. This study was supported by grants from the Special Research Fund of Ghent University (DEF12/AOP/022) without potential conflict of interest-associated biases in the text of the paper. RESULTS: Fat cross-sectional area and lean muscle fat index were significantly higher in MF and ES in continuous CLBP compared with non-continuous CLBP and RLBP (p<.05). No differencesbetween groups were found for total cross-sectional area and muscle cross-sectional area in MF or ES (p>.05). Also, no significant differences between groups for T2-rest were established. T2-shift, however, was significantly lower in MF and ES in RLBP compared with, respectively, non-continuous CLBP and continuous CLBP (p<.05). CONCLUSIONS: These results indicate a higher amount of fat infiltration in the lumbar muscles, in the absence of clear atrophy, in continuous CLBP compared with RLBP. A lower metabolic activity of the lumbar muscles was seen in RLBP replicating a relative lower intensity in contractions performed by the lumbar muscles in RLBP compared with non-continuous and continuous CLBP. In conclusion, RLBP differs from continuous CLBP for both muscle structure and muscle function, whereas non-continuous CLBP seems comparable with RLBP for lumbar muscle structure and with continuous CLBP for lumbar muscle function. These results underline the differences in muscle structure and muscle function between different LBP populations.

Applying an active lumbopelvic control strategy during lumbar extension exercises: Effect on muscle recruitment patterns of the lumbopelvic region.

OBJECTIVE: Examine whether implementing an active lumbopelvic control strategy during high load prone lumbar extension exercises affects posterior extensor chain recruitment and lumbopelvic kinematics. METHODS: Thirteen healthy adults acquired an optimal active lumbopelvic control strategy during guided/home-based training sessions. During the experimental session electromyography was used to evaluate the activity of the posterior extensor chain muscles during high load trunk/bilateral leg extension exercises with/without application of the strategy. Video-analysis was used to evaluate thoracic/lumbar/hip angles. RESULTS: Implementing the active lumbopelvic control strategy decreased the lordotic angle during trunk (p=0.045; -3.2°) and leg extension exercises (p=0.019; -10°). The hip angle was solely affected during trunk extension (p<0.001;+9.2°). The posterior extensor chain (i.e. mean of the relative activity of all muscles (%MVIC) was recruited to a higher extent (p=0.026;+9%) during trunk extension exercises performed with active lumbopelvic control. Applying the strategy during leg extension exercises lead to less activity of longissimus thoracic (p=0.015; -10.2%) and latissimus dorsi (p=0.010; -4.4%), and increased gluteus maximus activity (p≤0.001;+16.8%). CONCLUSIONS: When healthy people are taught/instructed to apply an active lumbopelvic control strategy, this will decrease the degree of lumbar (hyper)lordosis and this influences the recruitment patterns of trunk and hip extensors. Hence, the possible impact on predetermined training goals should be taken into account by trainers.