Effects of attention on the control of locomotion in individuals with chronic low back pain

The Effect of Total Knee Replacement on Dual-Task Gait Performance in Older Adults

OBJECTIVE

Total knee replacement (TKR) is a common solution for patients with advanced knee osteoarthritis (OA). Still, fall rates remain relatively high after surgery. TKR may alter pain and knee function, balance control, and proprioception. However, given the role of complex (dual-task) walking in fall prediction for older adults, it is unknown how TKR alters the attentional demand of walking in older adults. The goal of this study was to examine the effect of TKR on dual-task walking among older adults.

METHODS

Participants were evaluated 1 month before surgery and 4.5 months after surgery. Participants walked along an instrumented 7-meter path for 1 minute with and without a cognitive task (serial-3 subtraction). Pain and knee function, knee proprioception, dynamic balance, and balance confidence, as well as dual-task costs (DTC) were compared before and after the surgery and factors associated with change in gait DTCs were assessed.

RESULTS

Thirty-eight participants completed the study (age 72.6 years, SD = 4.9; 11 men). A significant decrease in pain was found following TKR, with no change in balance, balance confidence, or proprioception. There were no differences in gait DTCs before and after the surgery. However, change in dynamic balance, specifically reactive postural control and dynamic gait, predicted changes in gait speed and stride time DTCs.

CONCLUSION

The absence of an effect of TKR on gait DTCs can potentially underlie increased fall risk after TKR. Results from this study emphasize the significance of balance as a measure and focal point for rehabilitation after TKR.

IMPACT

This study contributes to our understanding of the attentional cost of walking in people before and after TKR, as well as to factors associated with it. Results from this work can assist formulation of rehabilitation programs for people with knee OA.

The impact of neck pain on gait health: a systematic review and meta-analysis

BACKGROUND

Evidence exists demonstrating the negative impacts of chronic musculoskeletal pain on key measures of gait. Despite neck pain being the second most common musculoskeletal pain condition, there is a paucity of evidence exploring the impacts of neck pain specifically on these outcomes. The aims of this work were to systematically review the current evidence of the associations between chronic neck pain and measures of gait health and to conduct meta-analysis for quantitative assessment of the effect sizes under different walking conditions.

METHODS

Systematic review was conducted following PRISMA guidelines. Databases searched included MEDLINE, Embase, Web of Science, CINAHL, and PEDro. Eligible study designs included observational studies consisting of an exposure group with chronic neck pain and control group without chronic neck pain and primary outcomes relating to gait health. For outcomes amenable to meta-analysis, a random-effects model was used to derive summary estimates of Hedge's g depicted graphically with forest plots. Other gait outcomes were narratively summarized. Risk of bias was also assessed.

RESULTS

The original search yielded 1918 articles; 12 met final eligibility criteria including 10 cross-sectional studies. Outcomes were grouped first by the five domains of gait: pace, rhythm, asymmetry, variability, and postural control; and second by the tested walking conditions. Meta-analyses for gait speed revealed large effect-sizes indicating that individuals with chronic neck pain had slower measures of gait and lower measures of cadence. Gait outcomes that were narratively summarized supported these findings.

CONCLUSION

The quantitative and qualitative findings of this systematic review and meta-analysis suggest a negative impact of CNNP on measures of gait health, particularly gait speed, under various walking conditions. However, broad interpretation of these results should be cautious. Testing gait under dual task conditions may be particularly sensitive to the impact of CNNP, and future work is needed to better understand how pain disrupts this important functionality of the locomotor system. Additionally, consideration should be made to assess measures of variability and investigate these relationships in the older adult population.

Neurocognitive Functioning in Patients with Painful Temporomandibular Disorders

Aim

To investigate psychosocial factors in painful TMD (pTMD) which could have consequences for mastering chronic pain.

Methods

Our study included 22 patients (20 women, 2 men) with pTMD, refractory to conservative treatment, and 19 healthy controls. The control group was matched for gender, age, and educational level, and IQ tested on the Wechsler Abbreviated Scale of Intelligence. Neurocognitive function was tested with the Color-Word Interference Test (CWIT). Pain intensity was reported according to the General Pain Intensity Questionnaire (GPI), using the Numeric Rating Scale (NRS). Self-perceived cognitive difficulties were reported by the Perceived Deficits Questionnaire-Depression 5-item (PDQ-5). Two measures of rumination were included: the Rumination-Reflection Questionnaire (RRQ) and the Ruminative Response Scale (RRS). The Montgomery Åsberg Depression Rating Scale Self-report (MADRS-S) was used to measure depressive symptoms, and the Oral Health Impact Profile-TMD (OHIP-TMD) to measure QoL related to oral health.

Results

There were no statistical differences in age (median pTMD: 55 years, median control: 53 years), educational level, and IQ between pTMD and controls. Median pain intensity in pTMD was NRS 8 at maximum and the median pain duration was 18 years. There were no significant differences in CWIT between pTMD and controls. Self-perceived cognitive function (PDQ) was significantly poorer in pTMD. Rumination scores from both measures, and the depression score from MADRS, were significantly higher in pTMD. The OHIP-TMD score revealed a significantly poorer QoL in pTMD.

Conclusion

The group of pTMD patients have self-perceived cognitive difficulties that may make it more difficult to master chronic pain and common everyday tasks. They reported significantly more self-perceived cognitive difficulties, higher rumination, more depressive symptoms, and lower QoL compared to healthy controls, suggesting that these psychosocial factors could be targeted in treatment and interventions. However, the tested neurocognitive performance was equivalent to the control group.

Associations between gait performance and pain intensity, psychosocial factors, executive functions as well as prefrontal cortex activity in chronic low back pain patients: A cross-sectional fNIRS study

Introduction

Activities of daily living, such as walking, are impaired in chronic low back pain (CLBP) patients compared to healthy individuals. Thereby, pain intensity, psychosocial factors, cognitive functioning and prefrontal cortex (PFC) activity during walking might be related to gait performance during single and dual task walking (STW, DTW). However, to the best of our knowledge, these associations have not yet been explored in a large sample of CLBP patients.

Method

Gait kinematics (inertial measurement units) and PFC activity (functional near-infrared spectroscopy) during STW and DTW were measured in 108 CLBP patients (79 females, 29 males). Additionally, pain intensity, kinesiophobia, pain coping strategies, depression and executive functioning were quantified and correlation coefficients were calculated to determine the associations between parameters.

Results

The gait parameters showed small correlations with acute pain intensity, pain coping strategies and depression. Stride length and velocity during STW and DTW were (slightly to moderately) positively correlated with executive function test performance. Specific small to moderate correlations were found between the gait parameters and dorsolateral PFC activity during STW and DTW.

Conclusion

Patients with higher acute pain intensity and better coping skills demonstrated slower and less variable gait, which might reflect a pain minimization strategy. Psychosocial factors seem to play no or only a minor role, while good executive functions might be a prerequisite for a better gait performance in CLBP patients. The specific associations between gait parameters and PFC activity during walking indicate that the availability and utilization of brain resources are crucial for a good gait performance.

Limited evidence of altered gait parameters in people with chronic nonspecific low back pain

BACKGROUND

Differences in gait parameters have been shown between people with and without low back pain (LBP). However, previous studies did not well control factors such as sex, age, height and walking speed known to influence gait parameters.

RESEARCH QUESTION

Is gait altered in people with LBP when sex, age, height and walking speed are controlled?

METHODS

A series of gait parameters were measured in 16 participants with LBP and 16 age, sex and height matched healthy controls while walking on an instrumented treadmill. LBP group walked at a comfortable speed whilst control group walked at their own comfortable speed and at the comfortable speed of their matched participants with LBP. Pain and disability were measured for the LBP group. The between-group differences in mean, standard deviation (SD) and coefficient of variation (CV) of gait parameters were tested using paired samples t-test, Wilcoxon signed-rank test or two-factor repeated measures analyses of variance.

RESULTS

The median (interquartile range) of pain intensity was 2 (1, 3.5). From 102 tests of between-group difference in mean, SD and CV of 17 gait parameters at both comfortable speed and matched speed walking, only the mean of stride length (p = 0.037) during matched speed walking and SD of single support phase (p = 0.040) during comfortable speed walking showed significant between-group differences. There was no significant between-group difference in the rest means (comfortable walking: p ≥ 0.116; matched speed walking: p ≥ 0.069), SDs (comfortable walking: p ≥ 0.066; matched speed walking: p ≥ 0.098) and CVs of gait parameters (comfortable walking: p ≥ 0.110; matched speed walking: p ≥ 0.121).

SIGNIFICANCE

The lack of significant between-group difference in gait parameters may suggest that the gait of people with low level of LBP were not altered when sex, age and height were controlled.

Biomechanical factors associated with non-specific low back pain in adults: A systematic review

Low back pain (LBP) can result in increased direct medical and non-medical costs to patients, employers, and health care providers. This systematic review aimed to provide a better understanding of the biomechanical factors associated with chronic non-specific LBP in adults. SCOPUS, ScienceDirect, MEDLINE, and Web of Science databases were searched. In total, 26 studies were included and significant differences were noted between healthy controls and LBP patients in various motion. Biomechanical factors among adults with non-specific LBP were altered and differed as compared to healthy controls in various motion might be to compensate the pain during those motions. This review highlighted the biomechanical differences across those with non-specific LBP and healthy adults. Both groups showed a similar level of pain during functional tasks but LBP patients suffered from a moderate level of disability. Future studies should not rely on questionnaire-based pain scale only. The biomechanical factors summarized in this review can be used to diagnose non-specific LBP accurately, and as modifiable targets for exercise-based intervention.

A Case Report on Core Muscles Training for Knee Osteoarthritis Through Core Muscles Activations and Gait Analysis

Knee osteoarthritis (OA) is a chronic joint disease that can affect all ages, but it is more common in the elderly. Pharmacological and non-pharmacological treatments have been invented evolutionarily over the years to halt this disease. Exercise is one of the first-line treatments for knee OA as well as for prevention. This case study features a 47-year-old man who has grade IV bilateral knee OA and has never had any surgery and takes fish oil daily as a supplement. His walking pattern was significantly impacted by the chronic knee discomfort he had in both legs. Thus, the walking gait of this patient was analyzed together with core muscle activation before and after two weeks of core resistance exercise intervention. The knee pain score was assessed using the Western Ontario and McMaster Universities Index (WOMAC). The outcomes of this research depict that core resistance training has the potential to be used as an alternative, non-surgical and non-pharmacological treatment for a patient with knee OA.

Do people with low back pain walk differently? A systematic review and meta-analysis

BACKGROUND

The biomechanics of the trunk and lower limbs during walking and running gait are frequently assessed in individuals with low back pain (LBP). Despite substantial research, it is still unclear whether consistent and generalizable changes in walking or running gait occur in association with LBP. The purpose of this systematic review was to identify whether there are differences in biomechanics during walking and running gait in individuals with acute and persistent LBP compared with back-healthy controls.

METHODS

A search was conducted in PubMed, CINAHL, SPORTDiscus, and PsycINFO in June 2019 and was repeated in December 2020. Studies were included if they reported biomechanical characteristics of individuals with and without LBP during steady-state or perturbed walking and running. Biomechanical data included spatiotemporal, kinematic, kinetic, and electromyography variables. The reporting quality and potential for bias of each study was assessed. Data were pooled where possible to compare the standardized mean differences (SMD) between back pain and back-healthy control groups.

RESULTS

Ninety-seven studies were included and reviewed. Two studies investigated acute pain and the rest investigated persistent pain. Nine studies investigated running gait. Of the studies, 20% had high reporting quality/low risk of bias. In comparison with back-healthy controls, individuals with persistent LBP walked slower (SMD = -0.59, 95% confidence interval (95%CI): -0.77 to -0.42)) and with shorter stride length (SMD = -0.38, 95%CI: -0.60 to -0.16). There were no differences in the amplitude of motion in the thoracic or lumbar spine, pelvis, or hips in individuals with LBP. During walking, coordination of motion between the thorax and the lumbar spine/pelvis was significantly more in-phase in the persistent LBP groups (SMD = -0.60, 95%CI: -0.90 to -0.30), and individuals with persistent LBP exhibited greater amplitude of activation in the paraspinal muscles (SMD = 0.52, 95%CI: 0.23-0.80). There were no consistent differences in running biomechanics between groups.

CONCLUSION

There is moderate-to-strong evidence that individuals with persistent LBP demonstrate differences in walking gait compared to back-healthy controls.

Analysing gait patterns in degenerative lumbar spine diseases: a literature review

OBJECTIVES

To collate the current state of knowledge and explore differences in the spatiotemporal gait patterns of degenerative lumbar spine diseases: lumbar spinal stenosis (LSS), lumbar disc herniation (LDH) and low back pain (LBP).

BACKGROUND

LBP is common presenting complaint with degenerative lumbar spine disease being a common cause. In particular, the gait patterns of LSS, LDH and mechanical-type (facetogenic and discogenic) LBP is not established.

METHODS

A search of the literature was conducted to determine the changes in spatial and temporal gait metrics involved with each type of degenerative lumbar spine disease. A search of databases including Medline, Embase and PubMed from their date of inception to April 18th, 2021 was performed to screen, review and identify relevant studies for qualitative synthesis. Seventeen relevant studies were identified for inclusion in the present review. Of these, 5 studies investigated gait patterns in LSS, 10 studies investigated LBP and 2 studies investigated LDH. Of these, 4 studies employed wearable accelerometry in LSS (2 studies) and LBP (2 studies).

CONCLUSIONS

Previous studies suggest degenerative diseases of the lumbar spine have unique patterns of gait deterioration. LSS is characterised by asymmetry and variability. Spatiotemporal gait deterioration in gait velocity, cadence with increased double-support duration and gait variability are distinguishing features in LDH. LBP involves marginal abnormalities in temporal and spatial gait metrics. Previous studies suggest degenerative diseases of the lumbar spine have unique patterns of gait deterioration. Gait asymmetry and variability, may be relevant metrics for distinguishing between the gait profiles of lumbar spine diseases.

Altered effective connectivity within the cingulo-frontal-parietal cognitive attention networks in chronic low back pain: a dynamic causal modeling study

Dysfunction of the cingulo-frontal-parietal (CFP) cognitive attention network has been associated with the pathophysiology of chronic low back pain (cLBP). However, the direction of information processing within this network remains largely unknown. We aimed to study the effective connectivity among the CFP regions in 36 cLBP patients and 36 healthy controls by dynamic causal modeling (DCM). Both the resting-state and task-related (Multi-Source Interference Task, MSIT) functional magnetic resonance imaging (fMRI) data were collected and analyzed. The relationship between the effective connectivity of the CFP regions and clinical measures was also examined. Our results suggested that cLBP had significantly altered resting-state effective connectivity of the prefrontal cortex (PFC)-to-mid-cingulate cortex (MCC) (increased) and MCC-to-left superior parietal cortex (LPC) (decreased) pathways as compared with healthy controls. MSIT-related DCM suggested that the interference task could significantly increase the effective connectivity of the right superior parietal cortex (RPC)-to-PFC and RPC-to-MCC pathways in cLBP than that in healthy controls. The control task could significantly decrease the effective connectivity of the MCC-to-LPC and MCC-to-RPC pathways in cLBP than that in healthy controls. The endogenous connectivity of the PFC-to-RPC pathway in cLBP was significantly lower than that in healthy controls. No significant correlations were found between the effective connectivity within CFP networks and pain/depression scores in patients with cLBP. In summary, our findings suggested altered effective connectivity in multiple pathways within the CFP network in both resting-state and performing attention-demanding tasks in patients with cLBP, which extends our understanding of attention dysfunction in patients with cLBP.

Low Risk for Persistent Back Pain Disability Is Characterized by Lower Pain Sensitivity and Higher Physical Performance

OBJECTIVE

The STarT Back Tool (SBT) predicts risk for persistent low back pain (LBP)-related disability based on psychological distress levels. Other non-psychological factors associated with LBP, such as pain sensitivity and physical performance, may further characterize SBT-risk subgroups. The purpose of this study was to determine whether a low-risk SBT subgroup demonstrated lower pain sensitivity and/or higher physical performance compared with a medium-/high-risk SBT subgroup.

METHODS

In this cross-sectional, secondary analysis, adults with LBP (N = 76) completed SBT and demographics (age, sex, race, chronicity) questionnaires. Participants underwent pain sensitivity (local and remote pressure pain thresholds, temporal summation, conditioned pain modulation) and physical performance (Back Performance Scale, walking speed, obstacle negotiation, Timed "Up & Go" [TUG], TUG Cognitive) testing. Independent samples t tests determined low- versus medium-/high-risk SBT subgroup differences. A follow-up discriminant function analysis was also conducted.

RESULTS

The medium-/high-risk subgroup demonstrated a lower proportion of participants with acute pain. The low-risk subgroup demonstrated lower pain sensitivity (higher local pressure pain thresholds and higher conditioned pain modulation) and higher physical performance (superior Back Performance Scale scores, faster walking speeds, faster obstacle approach and crossing speeds, and faster TUG completion). Discriminant function analysis results supported the 2-subgroup classification and indicated strong to moderate relationships with obstacle crossing speed, chronicity, and conditioned pain modulation.

CONCLUSION

Lower pain sensitivity and higher physical performance characterized the low-risk SBT subgroup and may represent additional LBP prognostic factors associated with persistent disability. Longitudinal studies are needed to confirm whether these factors can enhance SBT prediction accuracy and further direct treatment priorities.

IMPACT

Sensory and physical factors contribute to SBT risk classification, suggesting additional, non-psychological factors are indicative of favorable LBP outcomes. Findings highlight the need for assessment of multiple factors to improve LBP clinical prediction.

LAY SUMMARY

People at low risk for back pain disability have less sensitivity to pain and better physical performance. By measuring these factors, physical therapists could guide treatment and improve outcomes for people with back pain.

Relationship between gait complexity and pain attention in chronic low back pain

ABSTRACT

Clinical models of chronic low back pain (cLBP) highlight the role of excessive attention to pain and kinesiophobia on the origin of disability. At the motor control level, various mechanisms are involved in the impairments observed in patients with cLBP. We aimed to assess the role of maladaptative attentional behaviors by using a complex systems approach and a visual display as a distraction during walking. Sixteen patients with cLBP with no previous surgery or significant leg pain and 16 healthy matched controls were included. Patients walked on a treadmill at preferred walking speed with and without distraction. Stride time (ST) fractal complexity was assessed using detrended fluctuation analysis. A two-way analysis of variance with repeated measures on distraction was performed on fractal exponents. We found a significant group × distraction interaction effect on fractal complexity of ST series (F(1,30) = 9.972, P = 0.004). Post hoc analysis showed that, without distraction, patients with cLBP had significantly lower ST complexity than controls, but when distracted, they regained gait complexity, recovering the level of controls. Our results suggest that excessive attention to pain causes loss of complexity and adaptability in cLBP and explain alterations of motor control with pain. Fractal analysis seems to be a promising method to explore movement variability and individual adaptability in musculoskeletal disorders.

Dual goals of trunk restriction and stability are prioritized by individuals with chronic low back pain during a volitional movement

BACKGROUND

Individuals with chronic low back pain demonstrate impaired responses to volitional and externally-generated postural perturbations that may impact stability whilst performing activities of daily living. Understanding how balance may be impaired by strategy selection is an important consideration during rehabilitation from low back pain to prevent future injurious balance loss.

RESEARCH QUESTION

This cross-sectional study explored the influence of an active pain episode on volitional movement patterns and stability during a sit-to-stand task in individuals with chronic low back pain compared to those with no low back pain history.

METHODS

Thirteen participants with low back pain who were in an active flare-up and 13 without pain sat on a height-adjusted chair and performed 5 sit-to-stand movements. Sagittal plane kinematics, kinetics, and surface electromyography were used to compute neuromuscular variables across Acceleration, Transition and Deceleration phases. Stability was assessed using times to contact of body centers of mass and pressure to base of support boundaries. Independent samples t-tests were used to examine group effects, and repeated measures analyses of variance assessed within-subjects effects across movement phases.

RESULTS

Individuals with low back pain tended to restrict proximal joint motions through heightened muscle activity while increasing distal joint movement and distal muscle contributions. Individuals with low back pain used a greater driving force, indicated by a longer time to contact of the center of pressure, to achieve comparable center of mass stability. Individuals with low back pain may prioritize trunk restriction and stability through the sit-to-stand movement, possibly related to fear of pain or movement.

SIGNIFICANCE

The tendency for individuals with active low back pain to restrict trunk movements may require additional effort to maintain stability. Further research should examine whether trunk restriction is related to pain-related fear of movement and whether additional cognitive resources are required to maintain movement stability.

Individuals with recurrent low back pain exhibit further altered frontal plane trunk control in remission than when in pain

BACKGROUND

Movement alterations due to low back pain (LBP) could lead to long-term adverse consequences if they do not resolve after symptoms subside. This study aims to determine if altered trunk control associated with recurrent low back pain persists beyond symptom duration.

METHODS

Twenty young adults with recurrent LBP were tested once during an LBP episode and once in symptom remission, and twenty matched back-healthy participants served as controls. Participants walked on a treadmill with five prescribed step widths (0.33, 0.67, 1, 1.33, 1.67 × preferred step width). Motion capture and surface electromyography were used to record trunk kinematics and muscle activation. Thorax-pelvis coordination was calculated using vector coding, and longissimus activation and co-activation were analyzed.

FINDINGS

Young adults with recurrent LBP exhibited a "looser" trunk control strategy in the frontal plane during gait that was persistent regardless of pain status across multiple step widths compared to controls. The looser trunk control was demonstrated by a greater pelvis-only, less thorax-only coordination pattern, and decreased bilateral longissimus co-activation in individuals with recurrent LBP compared to controls. The looser trunk control strategy was further amplified when individuals were in symptom remission and exhibited greater trunk excursion and reduced in-phase coordination in the frontal plane.

INTERPRETATION

The amplification of aberrant movement during symptom remission may suggest that movement patterns or anatomical factors existing prior to the tested painful episode underlie altered trunk control in individuals with recurrent LBP. The symptom remission period of recurrent LBP may be a critical window into clinical evaluation and treatment.

Empirically derived back pain subgroups differentiated walking performance, pain, and disability

ABSTRACT

Low back pain (LBP) is a leading cause of disability. However, the processes contributing to disability are not well understood. Therefore, this study (1) empirically derived LBP subgroups and (2) validated these subgroups using walking performance, pain, and disability measures. Seventy adults with LBP underwent testing for a priori determined sensory (temporal summation; conditioned pain modulation), psychological (positive affect/coping; negative coping), and motor (trunk extensor muscle activation during forward bending and walking) measures. A hierarchical cluster analysis determined subgroups that were then validated using walking (walking speed; Timed Up and Go [TUG]; TUG-Cognitive [TUG-Cog]; obstacle negotiation) and clinical (Brief Pain Inventory; Oswestry Disability Index; low back pressure pain threshold) measures. Two subgroups were derived: (1) a "Maladaptive" subgroup (n = 21) characterized by low positive affect/coping, high negative coping, low pain modulation, and atypical trunk extensor activation and (2) an "Adaptive" subgroup (n = 49) characterized by high positive affect/coping, low negative coping, high pain modulation, and typical trunk extensor activation. There were subgroup differences on 7 of 12 validation measures. The Maladaptive subgroup had reduced walking performance (slower self-selected walking speed, TUG completion, and obstacle approach and crossing speed) and worse clinical presentation (higher pain intensity, pain interference, and disability) (moderate to large effect sizes; P's < 0.05). Findings support the construct validity of this multidimensional subgrouping approach. Longitudinal studies are needed to determine whether the Maladaptive subgroup is predictive of poor outcomes, such as pain chronicity or persistent disability.

The Effects of Perceived Pain in the Past Month on Prefrontal Cortex Activation Patterns Assessed During Cognitive and Motor Performances in Older Adults

OBJECTIVE

Pain is prevalent and functionally impactful in older adults. The prefrontal cortex is involved in pain perception, attentional control, and cortical control of locomotion. Although pain is a known moderator of attentional capacity, its moderating effect on cortical control of locomotion has not been assessed. This study aimed to examine the effects of subjective pain on changes in functional near-infrared spectroscopy-derived measurements of oxygenated hemoglobin (HbO2), gait velocity, and cognitive accuracy from single- to dual-task walking conditions among older adults.

SUBJECTS

The sample consisted of 383 healthy older adults (55% female).

METHODS

Participants completed two single tasks (Single-Task-Walk [STW] and Cognitive Interference [Alpha]) and the Dual-Task-Walk (DTW), during which participants performed the two single tasks simultaneously. The Medical Outcomes Study Pain Severity Scale and Pain Effects Scale were used to assess pain severity and interference. ProtoKinetics Movement Analysis Software was used to assess gait velocity and rate of correct letter generation to assess cognitive accuracy. Functional Near-Infrared Spectroscopy (fNIRS) was used to assess HbO2 during active walking.

RESULTS

Linear mixed-effects models revealed that HbO2 increased from single- to dual-task conditions. Perceived pain presence was associated with an attenuated increase in HbO2 from Alpha to DTW. Among those with pain, worse pain severity was associated with an attenuated increase in HbO2 from STW to DTW. Pain interference did not moderate the increase in HbO2 from single to dual tasks. Pain did not have a moderating effect on behavioral outcomes.

CONCLUSIONS

Task-related changes in the hemodynamic response in the prefrontal cortex during walking may be a sensitive marker of the effects of subjective pain on brain function in healthy older adults.

Young adults with recurrent low back pain demonstrate altered trunk coordination during gait independent of pain status and attentional demands

Pain influences both attention and motor behavior. We used a dual-task interference paradigm to investigate (1) alterations in attentional performance, (2) the ability to switch task prioritization, and (3) the effect of attentional demand on trunk coordination during narrow-based walking in and out of a painful episode in individuals with recurrent low back pain (LBP). We tested twenty young adults with LBP both in and out of a painful episode and compared them to twenty matched back-healthy individuals. Participants simultaneously performed a narrow step width matching task and an arithmetic task, with and without instructions to prioritize either task. A motion capture system was used to record kinematic data, and frontal plane trunk coordination was analyzed using vector coding on the thorax and pelvis angles. Single-task performance, dual-task effect, dual-task performance variability, task prioritization switch, and trunk coordination were analyzed using paired t tests or repeated measures two-way ANOVAs. Results indicated that active pain has a detrimental effect on attentional processes, indicated by poorer single-task performance and increased dual-task performance variability for individuals with recurrent LBP. Individuals with LBP, regardless of pain status, were able to switch task prioritization to a similar degree as their back-healthy counterparts. Compared to the control group, individuals with recurrent LBP exhibited a less in-phase, more pelvis-dominated trunk coordination during narrow-based walking, independent of pain status and regardless of attentional manipulations. Thus, altered trunk coordination in persons with LBP appears to be habitual, automatic, and persists beyond symptom duration.

Compromised balance control in older people with bilateral medial knee osteoarthritis during level walking

About half of the elderly population has knee osteoarthritis (OA), showing altered gait patterns with increased fall risk. The current study aimed to identify the effects of severe bilateral medial knee osteoarthritis on gait balance control, in terms of the inclination angle (IA) of the center of pressure to center of mass vector, and the rate of change of IA (RCIA). Fifteen older adults with severe bilateral medial knee OA and 15 healthy controls walked at their preferred walking speed while the kinematic and forceplate data were measured to calculate IA, RCIA and temporal-spatial parameters. The OA group showed compromised gait balance control, due to a decreased average and range of sagittal RCIA over double-limb support (DLS, p < 0.002) and single-limb support (SLS, p < 0.002), as well as an increased sagittal IA (DLS, p < 0.005). Significantly decreased frontal RCIA averages during DLS, heel-strike and toe-off, and decreased RCIA ranges during SLS and swing (p < 0.027) were also observed. Reducing RCIA during DLS appeared to help reduce the loading rate and pain at the knees, and reduced RCIA at the subsequent SLS. The results indicated an increased risk of loss of balance in the OA group, and may warrant regular monitoring for reduced RCIA during gait to determine fall risk.

Fear of movement is not associated with trunk movement variability during gait in patients with low back pain

BACKGROUND

Literature describing differences in motor control between low back pain (LBP) patients and healthy controls is very inconsistent, which may be an indication for the existence of subgroups. Pain-related psychological factors might play a role causing these differences.

PURPOSE

To examine the relation between fear of movement and variability of kinematics and muscle activation during gait in LBP patients.

STUDY DESIGN

Cross-sectional experimental design.

PATIENT SAMPLE

Thirty-one Chinese LBP patients.

OUTCOME MEASURES

Self-report measures: Visual Analog Score for pain; TAMPA-score; Physiologic measures: electromyography, range of motion.

FUNCTIONAL MEASURES

LBP history; the physical load of profession, physical activity.

METHODS

Patients were divided in high and low fear of movement groups. Participants walked on a treadmill at four speeds: very slow, slow, preferred and fast. Kinematics of the thorax and the pelvis were recorded, together with the electromyography of five bilateral trunk muscle pairs. Kinematic and electromyography data were analysed in terms of stride-to-stride pattern variability. Factor analysis was applied to assess interdependence of 11 variability measures. To test for differences between groups, a mixed-design multivariate analysis of variance was conducted.

RESULTS

Kinematic variability and variability of muscle activation consistently loaded on different factors and thus represented different underlying variables. No significant Group effects on variability of kinematics and muscle activation were found (Hotelling's Trace F=0.237; 0.396, p=.959; .846, respectively). Speed significantly decreased kinematic variability and increased variability in muscle activation (Hotelling's Trace F=8.363; 4.595, p<.0001; <.0001, respectively). No significant interactions between Group and Speed were found (Hotelling's Trace F=0.204; 0.100, p=.762; .963, respectively).

CONCLUSIONS

The results of this study do not support the hypothesis that variability in trunk kinematics and trunk muscle activation during gait in LBP patients are associated with fear of movement.

Low back pain in patients with multiple sclerosis: A systematic review and the prevalence in a French multiple sclerosis population

PURPOSE

The prevalence and management of back pain in MS patients was assessed by a systematic review, and the results of a survey on the characteristics of low back pain in a sample of French MS patients are reported.

METHODS

A systematic search was conducted according to the PRISMA guidelines. The outcomes of interest included the prevalence of back pain, severity of pain and impact on daily activities. Moreover, the prevalence of low back pain and its consequences on daily living in a large French MS population were assessed.

RESULTS

Fourteen studies were included in the systematic review. The prevalence of back pain in MS patients ranged from 8.6 to 50%, but that of low back pain in particular ranged from 41.6 to 52.4%. Concerning the survey, 237 patients participated in the online questionnaire. The prevalence of low back pain in the French MS patients was 76.4%. The patients with chronic low back pain had more limitations in their daily life activities than those without chronic low back pain.

CONCLUSION

Patients with MS commonly suffer from low back pain, but it is still an underdiagnosed cause of pain that reduces one's ability to perform activities in daily life.

Effect of Platform Swing Walkway on Locomotor Behavior in Children With Diplegic Cerebral Palsy: Randomized Controlled Trial

Background

Limited attention has been given to the effectiveness of the platform swing walkway, which is a common way to improve gait pattern through activation of sensory stimuli (visual, auditory, vestibular, and somatosensory).

Objective

The objective of this study was to determine the effect of a platform swing walkway on gait parameters in children with diplegic cerebral palsy (CP).

Methods

A total of 30 children of both sexes (aged 6-8 years) with diplegic CP were enrolled in this study. They were randomly assigned into two groups of equal number: the control group (n=15) and the study group (n=15). The control group received the conventional physical therapy plan, whereas the study group received the same conventional physical therapy program in addition to gait training on a platform swing walkway. Temporal parameters during the gait cycle were collected using gait tracker video analysis, and the Growth Motor Function Measure Scale (GMFM-88) was used to assess standing and walking (Dimensions D and E) before and after the treatment program.

Results

A statistically significant improvement in both groups was noted when comparing the mean values of all measured variables before and after treatment (P≤.05). There were significant differences between the control and study groups with respect to all measured variables, which favored the study group when comparing the posttreatment outcomes (P≤.05).

Conclusions

Results suggest that gait training on platform swing walkways can be included as an alternative therapeutic modality to enhance gait parameters and gross motor function in children with diplegic CP.

Trial Registration

ClinicalTrials.gov NTC04246658; https://clinicaltrials.gov/ct2/show/NTC04246658

The Effects of Cognitive Loading on Motor Behavior in Injured Individuals: A Systematic Review

BACKGROUND

Research suggests that individuals with musculoskeletal injury may have difficulty negotiating physical tasks when they are combined with cognitive loads.

OBJECTIVE

Our objective was to conduct a systematic review to understand the effects of increased cognitive demand on movement patterns among individuals with musculoskeletal injuries.

METHODS

A comprehensive search of PubMed, MEDLINE, the Cumulative Index for Nursing and Allied Health Literature (CINAHL), and SPORTDiscus was conducted to find research reports that included a population that had previously experienced an ankle, knee, or low back injury, included an uninjured control group, and assessed a dual-task paradigm.

RESULTS

Forty-five full-text research reports were assessed, of which 28 studies (six ankle injury, nine knee injury, and 13 low back pain studies) were included in the review. Included studies were assessed for methodological quality and the study design extracted for analysis including the participants, cognitive and physical tasks performed, as well as outcome measures (e.g., three-dimensional kinematics, center of pressure, etc.). All studies included were cross-sectional or case-control with methodological quality scores of 17.8 ± 2.2 out of a possible 22. Twenty-five of the 28 studies found changes in motor performance with dual-task conditions compared with single tasks. Furthermore, 54% of studies reported a significant group by task interaction effect, reporting at least one alteration in injured groups' motor performance under dual-task conditions when compared with an uninjured group.

CONCLUSION

The results of this systematic review indicate that motor performance is further impaired by placing a cognitive load on individuals in populations with musculoskeletal injury. More demanding tasks such as gait appear to be more affected in injured individuals than simple balance tasks. Future investigators may want to consider the difficulty of the tasks included as well as the impact of dual-task paradigms on rehabilitation programs.

Persons in remission from recurrent low back pain alter trunk coupling under dual-task interference during a dynamic balance task

This study investigated effects of cognitive dual-task interference and task prioritization instructions on task performance and trunk control during a dynamic balance task in persons with and without recurrent low back pain (rLBP). First, we tested the hypothesis that those with rLBP rely more on cognitive resources than back-healthy controls, and therefore trunk kinematics would be altered under dual-task interference conditions. Then, we tested participants' ability to modulate task performance in accord with prioritization instructions. Persons with and without rLBP (n = 19/group) performed the Balance-Dexterity Task, which involved single-limb balance while compressing an unstable spring with the other limb, with and without a cognitive task engaging verbal working memory. Trunk coupling was quantified with the coefficient of determination (R²) of an angle-angle plot of thorax-pelvis frontal plane motion. Task performance was quantified using variability of spring compression force and of cognitive task errors. Trunk coupling in the rLBP group was lower than that of the back-healthy control group in the single-task condition (p = 0.024) and increased in the dual-task condition (p = 0.006), abolishing the difference between groups. Significant main effects of task prioritization instruction on performance were observed with no differences between groups, indicating similar performance modulation. Cognitive task error variability decreased with a switch from a single- to dual-task condition, exposing an unexpected facilitation effect. We interpret these findings in the context of movement-specific reinvestment and action-specific perception theories as they pertain to cognitive contributions to posture and how the dual-task interference paradigm may influence those contributions.

Effects of tandem walk and cognitive and motor dual- tasks on gait speed in individuals with chronic idiopathic neck pain: a preliminary study

Introduction: Gait impairment has been associated with neck pain. It is relevant to understand the possible influence of narrow-based walk and an attention-demanding secondary task on gait performance in neck pain.Purpose: To investigate the effects of tandem walk and cognitive and motor dual-tasks on gait speed in persons with chronic idiopathic neck pain (CINP) compared with controls.Methods: A cross-sectional study. Thirty participants with CINP and 30 asymptomatic controls participated in the study. Gait speed was assessed using a timed 10-m walk test at a comfortable pace under four conditions: (1) comfortable walk (as reference); (2) tandem walk (single task); (3) cognitive dual-task walking; and (4) motor dual-task walking. Dual-task interference was calculated.Results: There was no difference in comfortable gait speed between groups (p= 0.40). The CINP group had slower gait speed during the tandem walk than controls (p= 0.02). The dual-task interference on gait speed was not different between groups (p = 0.67 for cognitive, p = 0.93 for motor).Conclusion: Participants with CINP had impaired gait stability during tandem walk. An attention-demanding secondary task did not influence gait speed in individuals with CINP compared to controls. The study suggests that tandem walk could be considered as an assessment tool and part of rehabilitation for neck pain.

Executive Functions and Pain

Abstract. A growing body of literature suggests that chronic-pain patients suffer from problems in various neuropsychological domains, including executive functioning. In order to better understand which components of executive functioning (inhibition, shifting and/or updating) might be especially affected by pain and which mechanisms might underlie this association, we conducted a systematic review, including both chronic-pain studies as well as experimental-pain studies. The chronic-pain studies (N = 57) show that pain is associated with poorer executive functioning. The findings of experimental-pain studies (N = 28) suggest that this might be a bidirectional relationship: Pain can disrupt executive functioning, but poorer executive functioning might also be a risk factor for higher vulnerability to pain.

Motor Control Changes in Low Back Pain: Divergence in Presentations and Mechanisms

Compared to healthy individuals, patients with low back pain demonstrate differences in all aspects of trunk motor control that are most often studied as differences in muscle activity and kinematics. However, differences in these aspects of motor control are largely inconsistent. We propose that this may reflect the existence of 2 phenotypes or possibly the ends of a spectrum, with "tight control" over trunk movement at one end and "loose control" at the other. Both may have beneficial effects, with tight control protecting against large tissue strains from uncontrolled movement and loose control protecting against high muscle forces and resulting spinal compression. Both may also have long-term negative consequences. For example, whereas tight control may cause high compressive loading on the spine and sustained muscle activity, loose control may cause excessive tensile strains of tissues. Moreover, both phenotypes could be the result of either an adaptation process aimed at protecting the low back or direct interference of low back pain and related changes with trunk motor control. The existence of such phenotypes would suggest different motor control exercise interventions. Although some promising data supporting these phenotypes have been reported, it remains to be shown whether these phenotypes are valid, how treatment can be targeted to these phenotypes, and whether this targeting yields superior clinical outcomes. J Orthop Sports Phys Ther 2019;49(6):370-379. Epub 12 Jun 2018. doi:10.2519/jospt.2019.7917.

Effect of dual tasking on anticipatory and compensatory postural adjustments in response to external perturbations in individuals with nonspecific chronic low back pain: Electromyographic analysis

BACKGROUND

In patients with chronic low back pain (CLBP), postural control is a demanding task in terms of attention. Although the attentional demands of postural control have been investigated in these patients, the attentional demands of postural recovery during dual task performance have not been evaluated in patients with nonspecific CLBP.

OBJECTIVE

To investigate the effect of dual tasking on anticipatory and compensatory postural adjustments in response to an external perturbation in patients with nonspecific CLBP.

METHODS

Twenty-five patients with nonspecific CLBP of at least 3 months' duration and 25 healthy persons were exposed to predictable and unpredictable external perturbations. The attentional demands of postural adjustments were evaluated while participants simultaneously performed a cognitive task. Onset latency and integrated electromyographic activity of the trunk and leg muscles were compared between dual task (postural recovery and backward digit span memory) and single task conditions (postural recovery only).

RESULTS

The results showed delayed activation of the tibialis anterior (agonist) and early activation of the gastrocnemius (antagonist) muscles during the dual task in patients with nonspecific CLBP compared to healthy participants. Integrated electromyographic activity was significantly greater in the dual task than the single task condition in the gastrocnemius (antagonist) muscle in patients with nonspecific CLBP compared to healthy persons during unpredictable perturbations.

CONCLUSION

The impaired ankle muscle activities during a cognitive task suggest that postural control recovery following external perturbation requires attentional resources in patients with nonspecific CLBP. This may increase the risk of re-injury in people with nonspecific CLBP while they perform an attentionally demanding task in more difficult circumstances.

The influence of divided attention on walking turns: Effects on gait control in young adults with and without a history of low back pain

The cognitive control of gait is altered in individuals with low back pain, but it is unclear if this alteration persists between painful episodes. Locomotor perturbations such as walking turns may provide a sensitive measure of gait adaptation during divided attention in young adults. The purpose of this study was to investigate changes in gait during turns performed with divided attention, and to compare healthy young adults with asymptomatic individuals who have a history of recurrent low back pain (rLBP). Twenty-eight participants performed 90° ipsilateral walking turns at a controlled speed of 1.5m/s. During the divided attention condition they concurrently performed a verbal 2-back task. Step length and width, trunk-pelvis and hip excursion, inter-segmental coordination and stride-to-stride variability were quantified using motion capture. Mixed-model ANOVA were used to examine the effect of divided attention and group, and interaction effects on the selected variables. Step length variability decreased significantly with divided attention in the healthy group but not in the rLBP group (post-hoc p=0.024). Inter-segmental coordination variability was significantly decreased during divided attention (main effect of condition p <0.000). There were small but significant reductions in hip axial and sagittal motion across groups (main effect of condition p=0.044 and p=0.040 respectively), and a trend toward increased frontal motion in the rLBP group only (post-hoc p=0.048). These findings suggest that the ability to switch attentional resources during gait is altered in young adults with a history of rLBP, even between symptomatic episodes.

Evaluation of Static and Dynamic Balance Tests in Single and Dual Task Conditions in Participants With Nonspecific Chronic Low Back Pain

Objective

The purpose of this study was to investigate static and dynamic balance tests in single, dual cognitive, and dual manual task conditions in participants with and without nonspecific chronic low back pain.

Methods

In this case control study, 40 patients (age range 18-50 years) with nonspecific chronic low back pain for at least 3 months and 40 healthy participants matched for age, weight, height, and sex participated in this study. Balance performance was evaluated using static (One Leg Stance) and dynamic (Modified Star Excursion Balance Test, 10-m walk test, and Timed Up and Go) balance tests. All tests were performed in three conditions: single task (balance only), dual cognitive task (balance and counting numbers backward), and dual manual task (balance and carrying a cup of water).

Results

The results indicated that different balance tests were impaired in dual task conditions compared with single task in each group. Cognitive and balance performances were not significantly different between nonspecific chronic low back pain and healthy participants in all clinical balance tests.

Conclusion

It seems that the static and dynamic balance performance under dual task conditions (excluding the Modified Star Excursion Balance Test) was impaired in each group. Dual tasking did not differ between nonspecific chronic low back pain participants with low level of pain and disability compared with healthy participants.

Effects of narrow-base walking and dual tasking on gait spatiotemporal characteristics in anterior cruciate ligament-injured adults compared to healthy adults

PURPOSE

The present experiment was conducted to examine the hypothesis that challenging control through narrow-base walking and/or dual tasking affects ACL-injured adults more than healthy control adults.

METHODS

Twenty male ACL-injured adults and twenty healthy male adults walked on a treadmill at a comfortable speed under two base-of-support conditions, normal-base versus narrow-base, with and without a cognitive task. Gait patterns were assessed using mean and variability of step length and mean and variability of step velocity. Cognitive performance was assessed using the number of correct counts in a backward counting task.

RESULTS

Narrow-base walking resulted in a larger decrease in step length and a more pronounced increase in variability of step length and of step velocity in ACL-injured adults than in healthy adults. For most of the gait parameters and for backward counting performance, the dual-tasking effect was similar between the two groups.

CONCLUSIONS

ACL-injured adults adopt a more conservative and more unstable gait pattern during narrow-base walking. This can be largely explained by deficits of postural control in ACL-injured adults, which impairs gait under more balance-demanding conditions. The observation that the dual-tasking effect did not differ between the groups may be explained by the fact that walking is an automatic process that involves minimal use of attentional resources, even after ACL injury. Clinicians should consider the need to include aspects of terrain complexity, such as walking on a narrow walkway, in gait assessment and training of patients with ACL injury.

LEVEL OF EVIDENCE

III.

Response inhibition, set shifting, and complex executive function in patients with chronic lower back pain

OBJECTIVE

The aim of our study was to evaluate how response inhibition, set shifting, and complex executive function (represented by risky decision-making) are altered in chronic lower back pain patients.

MATERIALS AND METHODS

A total of 29 patients with chronic lower back pain (CLBP >6 months) aged 49-69 years and 30 healthy volunteers matched for age, gender, and education were enrolled in a case-control study. The study was conducted in the Departments of Neurology and Neurosurgery of Panevėžys Regional Hospital, Lithuania. Pain was evaluated by the visual analog scale, Pakula Pain Questionnaire (Lithuanian analog of McGill Pain Questionnaire), and Fibromyalgia Tender Points Examination. A battery of neuropsychological tests used included Stroop Test Victoria version, Trail Making Test parts A and B, and Game of Dice Task (GDT).

RESULTS

CLBP patients did not score significantly worse in any examined neuropsychological tests. Response Inhibition correlated inversely with number of tender points in CLBP patients. GDT performance showed no significant difference in net score (number of safe minus risky decisions). Unexpectedly, both groups favored risky decisions.

CONCLUSIONS

We found no statistically significant difference in response inhibition, set shifting, or complex executive function between CLBP patients and healthy older adults. Moreover, a risky decision-making pattern found in the Lithuanian population may underscore the importance of cultural context when examining complex executive function. However, further studies are needed to prove this point.

Extrinsic visual feedback and additional cognitive/physical demands affect single-limb balance control in individuals with ankle instability

AIM

To investigate the impact of extrinsic visual feedback and additional cognitive/physical demands on single-limb balance in individuals with ankle instability.

METHODS

Sixteen subjects with ankle instability participated in the study. Ankle instability was identified using the Cumberland Ankle Instability Tool (CAIT). The subject’s unstable ankle was examined using the Athletic Single Leg Stability Test of the Biodex Balance System with 4 different protocols: (1) default setting with extrinsic visual feedback from the monitor; (2) no extrinsic visual feedback; (3) no extrinsic visual feedback with cognitive demands; and (4) no extrinsic visual feedback with physical demands. For the protocol with added cognitive demands, subjects were asked to continue subtracting 7 from a given number while performing the same test without extrinsic visual feedback. For the protocol with added physical demands, subjects were asked to pass and catch a basketball to and from the examiner while performing the same modified test.

RESULTS

The subject’s single-limb postural control varied significantly among different testing protocols (F = 103; P = 0.000). Subjects’ postural control was the worst with added physical demands and the best with the default condition with extrinsic visual feedback. Pairwise comparison shows subjects performed significantly worse in all modified protocols (P < 0.01 in all comparisons) compared to the default protocol. Results from all 4 protocols are significantly different from each other (P < 0.01) except for the comparison between the “no extrinsic visual feedback” and “no extrinsic visual feedback with cognitive demands” protocols. Comparing conditions without extrinsic visual feedback, adding a cognitive demand did not significantly compromise single-limb balance control but adding a physical demand did. Scores from the default protocol are significantly correlated with the results from all 3 modified protocols: No extrinsic visual feedback (r = 0.782; P = 0.000); no extrinsic visual feedback with cognitive demands (r = 0.569; P = 0.022); no extrinsic visual feedback with physical demands (r = 0.683; P = 0.004). However, the CAIT score is not significantly correlated with the single-limb balance control from any of the 4 protocols: Default with extrinsic visual feedback (r = -0.210; P = 0.434); no extrinsic visual feedback (r = -0.450; P = 0.081); no extrinsic visual feedback with cognitive demands (r = -0.406; P = 0.118); no extrinsic visual feedback with physical demands (r = -0.351; P = 0.182).

CONCLUSION

Single-limb balance control is worse without extrinsic visual feedback and/or with cognitive/physical demands. The balance test may not be a valid tool to examine ankle instability.

Mechanical Perturbations of the Walking Surface Reveal Unaltered Axial Trunk Stiffness in Chronic Low Back Pain Patients

INTRODUCTION

Patients with chronic low back pain (CLBP) often demonstrate altered timing of thorax rotations in the transverse plane during gait. Increased axial trunk stiffness has been claimed to cause this movement pattern.

OBJECTIVES

The objective of this study was to assess whether axial trunk stiffness is increased in gait in CLBP patients.

METHODS

15 CLBP patients and 15 healthy controls walked on a treadmill that imposed rotational perturbations in the transverse plane. The effect of these perturbations on transverse pelvis, thorax and trunk (thorax relative to pelvis) rotations was evaluated in terms of residual rotations, i.e., the deviation of these movements from the unperturbed patterns. In view of the heterogeneity of the CLBP group, we additionally performed a subgroup comparison between seven patients and seven controls with maximal between-group contrast for timing of thorax rotations.

RESULTS

Rotations of the walking surface had a clear effect on transverse pelvis, thorax and trunk rotations in all groups. No significant between-group differences on residual transverse pelvis, thorax and trunk rotations were observed.

CONCLUSION

Axial trunk stiffness in gait does not appear to be increased in CLBP. Altered timing of thorax rotations in CLBP does not seem to be a result of increased axial trunk stiffness.

Balance recovery reactions in individuals with recurrent nonspecific low back pain: Effect of attention

People who suffer from Low Back Pain (LBP) demonstrate impaired postural control. Deficits in sensory-motor systems have been proposed to be related to these changes. Considering higher cognitive process contribution to postural control, the aim of this study was to investigate the effects of cognitive load on balance control of patients with LBP. Twenty subjects with recurrent non-specific LBP and 20 healthy controls participated. They stood on a moveable platform with each foot placed on a separate force plate. They were asked to maintain their balance (a) while expecting translations of the support surface at two sizes of perturbation (b) with and without performing a cognitive (auditory Stroop) task. The outcomes included reaction time (RT), latency, initial velocity and amplitude of center of pressure response for balance, and RT for cognitive performance. Compared to the healthy group, LBP group demonstrated delayed RT and latency, and reduced initial velocity (P<0.05). Moreover, they had slower Stroop RT (F=70.88, P<0.001). Concurrent performance of tasks resulted in increased Stroop RT (F=3.42, P=0.03) and adaptation in initial velocity (F=6.70, P=0.01). At the smaller size of perturbation, cognitive load increased velocity in LBP group but decreased this variable in the healthy group. When the cognitive load was added at the larger size of perturbation, velocity of response decreased in LBP group (P<0.05). These findings imply altered cognitive regulation of dynamic balance in patients with LBP and suggest that the adopted strategy might alter depending upon the characteristics of the postural challenge.

Lumbar spine kinematics during walking in people with and people without low back pain

Low back pain (LBP) is a problem that can contribute to functional limitations and disability. Understanding kinematics during walking can provide a basis for examination and treatment in people with LBP. Prior research related to kinematics during walking is conflicting. However, investigators have not considered regional differences in lumbar spine kinematics or movement-based LBP subgroups. In the current study, three-dimensional kinematics of the upper and lower lumbar regions were examined in people with and without LBP. A clinical examination then was conducted to assign people with LBP to a movement-based subgroup and differences in kinematics among subgroups were examined. All subjects displayed significantly more upper than lower lumbar movement in the axial and coronal planes (P<.01). People with LBP displayed significantly less overall lumbar rotation than controls (P<.05). There were no significant group differences in sagittal plane kinematics (P>.05). Walking was limited by or provocative of pain in <25% of subjects with LBP. There were predictable differences in kinematics among some movement-based LBP subgroups that approached statistical significance (P=.09-.11). Walking was provocative of LBP in few subjects, and differences between people with and without LBP and among LBP subgroups were minimal. Limitations include that attempts to standardize gait speed may have minimized observed effects, and there was limited power to detect movement-based LBP subgroup differences.

Energetics and mechanics of walking in patients with chronic low back pain and healthy matched controls

PURPOSE

Walking in patients with chronic low back pain (cLBP) is characterized by motor control adaptations as a protective strategy against further injury or pain. The purpose of this study was to compare the preferred walking speed, the biomechanical and the energetic parameters of walking at different speeds between patients with cLBP and healthy men individually matched for age, body mass and height.

METHODS

Energy cost of walking was assessed with a breath-by-breath gas analyser; mechanical and spatiotemporal parameters of walking were computed using two inertial sensors equipped with a triaxial accelerometer and gyroscope and compared in 13 men with cLBP and 13 control men (CTR) during treadmill walking at standard (0.83, 1.11, 1.38, 1.67 m s(-1)) and preferred (PWS) speeds. Low back pain intensity (visual analogue scale, cLBP only) and perceived exertion (Borg scale) were assessed at each walking speed.

RESULTS

PWS was slower in cLBP [1.17 (SD = 0.13) m s(-1)] than in CTR group [1.33 (SD = 0.11) m s(-1); P = 0.002]. No significant difference was observed between groups in mechanical work (P ≥ 0.44), spatiotemporal parameters (P ≥ 0.16) and energy cost of walking (P ≥ 0.36). At the end of the treadmill protocol, perceived exertion was significantly higher in cLBP [11.7 (SD = 2.4)] than in CTR group [9.9 (SD = 1.1); P = 0.01]. Pain intensity did not significantly increase over time (P = 0.21).

CONCLUSIONS

These results do not support the hypothesis of a less efficient walking pattern in patients with cLBP and imply that high walking speeds are well tolerated by patients with moderately disabling cLBP.

Biomechanics of Lower Limbs during Walking among Candidates for Total Knee Arthroplasty with and without Low Back Pain

The effect of joint pathologies, such as unilateral knee osteoarthritis (UKOA) or low back pain (LBP), on bilateral gait symmetry has gained increased attention during the past decade. This study is the first to compare gait patterns between patients with UKOA and LBP in combination and with UKOA only. Temporal, kinematic, and kinetic variables were measured bilaterally during gait stance phase in 31 subjects with UKOA and LBP (Group I) and 11 subjects with only UKOA (Group II). Group I patients exhibited less hip rotation in the affected limb (A) than in the nonaffected (NA) limb during walking in contrast to Group II patients. Group I patients had minimal bilateral differences in hip abduction and flexion, but Group II patients displayed significantly larger values in the NA limb compared to the A limb for both parameters. Hip flexion patterns were significantly different between Groups I and II. Subjects in both groups adapted gait patterns that minimized vertical ground reaction force, knee flexion motion, and stance time on the UKOA affected limb. The distinct kinematic gait patterns that were revealed in this study may provide clinical value for assessment of patients with UKOA in conjunction with LBP.

Automaticity of walking: functional significance, mechanisms, measurement and rehabilitation strategies

Automaticity is a hallmark feature of walking in adults who are healthy and well-functioning. In the context of walking, “automaticity” refers to the ability of the nervous system to successfully control typical steady state walking with minimal use of attention-demanding executive control resources. Converging lines of evidence indicate that walking deficits and disorders are characterized in part by a shift in the locomotor control strategy from healthy automaticity to compensatory executive control. This is potentially detrimental to walking performance, as an executive control strategy is not optimized for locomotor control. Furthermore, it places excessive demands on a limited pool of executive reserves. The result is compromised ability to perform basic and complex walking tasks and heightened risk for adverse mobility outcomes including falls. Strategies for rehabilitation of automaticity are not well defined, which is due to both a lack of systematic research into the causes of impaired automaticity and to a lack of robust neurophysiological assessments by which to gauge automaticity. These gaps in knowledge are concerning given the serious functional implications of compromised automaticity. Therefore, the objective of this article is to advance the science of automaticity of walking by consolidating evidence and identifying gaps in knowledge regarding: (a) functional significance of automaticity; (b) neurophysiology of automaticity; (c) measurement of automaticity; (d) mechanistic factors that compromise automaticity; and (e) strategies for rehabilitation of automaticity.

Lumbar kinematic variability during gait in chronic low back pain and associations with pain, disability and isolated lumbar extension strength

BACKGROUND

Chronic low back pain is a multifactorial condition with many dysfunctions including gait variability. The lumbar spine and its musculature are involved during gait and in chronic low back pain the lumbar extensors are often deconditioned. It was therefore of interest to examine relationships between lumbar kinematic variability during gait, with pain, disability and isolated lumbar extension strength in participants with chronic low back pain.

METHODS

Twenty four participants with chronic low back pain were assessed for lumbar kinematics during gait, isolated lumbar extension strength, pain, and disability. Angular displacement and kinematic waveform pattern and offset variability were examined.

FINDINGS

Angular displacement and kinematic waveform pattern and offset variability differed across movement planes; displacement was highest and similar in frontal and transverse planes, and pattern variability and offset variability higher in the sagittal plane compared to frontal and transverse planes which were similar. Spearman's correlations showed significant correlations between transverse plane pattern variability and isolated lumbar extension strength (r=-.411) and disability (r=.401). However, pain was not correlated with pattern variability in any plane. The r(2) values suggested 80.5% to 86.3% of variance was accounted for by other variables.

INTERPRETATION

Considering the lumbar extensors role in gait, the relationship between both isolated lumbar extension strength and disability with transverse plane pattern variability suggests that gait variability may result in consequence of lumbar extensor deconditioning or disability accompanying chronic low back pain. However, further study should examine the temporality of these relationships and other variables might account for the unexplained variance.

[Possible changes in energy-minimizer mechanisms of locomotion due to chronic low back pain - a literature review]

One goal of the locomotion is to move the body in the space at the most economical way possible. However, little is known about the mechanical and energetic aspects of locomotion that are affected by low back pain. And in case of occurring some damage, little is known about how the mechanical and energetic characteristics of the locomotion are manifested in functional activities, especially with respect to the energy-minimizer mechanisms during locomotion. This study aimed: a) to describe the main energy-minimizer mechanisms of locomotion; b) to check if there are signs of damage on the mechanical and energetic characteristics of the locomotion due to chronic low back pain (CLBP) which may endanger the energy-minimizer mechanisms. This study is characterized as a narrative literature review. The main theory that explains the minimization of energy expenditure during the locomotion is the inverted pendulum mechanism, by which the energy-minimizer mechanism converts kinetic energy into potential energy of the center of mass and vice-versa during the step. This mechanism is strongly influenced by spatio-temporal gait (locomotion) parameters such as step length and preferred walking speed, which, in turn, may be severely altered in patients with chronic low back pain. However, much remains to be understood about the effects of chronic low back pain on the individual's ability to practice an economic locomotion, because functional impairment may compromise the mechanical and energetic characteristics of this type of gait, making it more costly. Thus, there are indications that such changes may compromise the functional energy-minimizer mechanisms.

High prevalence of falls, fear of falling, and impaired balance in older adults with pain in the United States: findings from the 2011 National Health and Aging Trends Study

OBJECTIVES

To determine the prevalence of clinically relevant falls-related outcomes according to pain status in older adults in the United States.

DESIGN

Cross-sectional analysis of the 2011 National Health and Aging Trends Study, a sample of Medicare enrollees aged 65 and older (response rate 71.0%).

SETTING

In-person assessments were conducted in the home or residential care facility of the sampled study participant.

PARTICIPANTS

Individuals aged 65 and older (n = 7,601, representing 35.3 million Medicare beneficiaries).

MEASUREMENTS

Participants were asked whether they had been "bothered by pain" and the location of pain, as well as questions about balance and coordination, fear of falling, and falls.

RESULTS

Fifty-three percent of the participants reported bothersome pain. The prevalence of recurrent falls in the past year (≥ 2 falls) was 19.5% in participants with pain and 7.4% in those without (age- and sex-adjusted prevalence ratio (PR) = 2.63, 95% confidence interval (CI) = 2.28-3.05). The prevalence of fear of falling that limits activity was 18.0% in those with pain and 4.4% in those without (adjusted PR = 3.98, 95% CI = 3.24-4.87). Prevalence of balance and falls outcomes increased with number of pain sites. For example, prevalence of problems with balance and coordination that limited activity was 6.6% in participants with no pain, 11.6% in those with one site of pain, 17.7% in those with two sites, 25.0% in those with three sites, and 41.4% in those with four or more sites (P < .001 for trend). Associations were robust to adjustment for several potential confounders, including cognitive and physical performance.

CONCLUSION

Falls-related outcomes were substantially more common in older adults with pain than in those without. Accordingly, pain management strategies should be developed and evaluated for falls prevention.