Machine Learning Based Linking of Patient Reported Outcome Measures to WHO International Classification of Functioning, Disability, and Health Activity/Participation Categories.

BACKGROUND: In the primary and secondary medical health sector, patient reported outcome measures (PROMs) are widely used to assess a patient's disease-related functional health state. However, the World Health Organization (WHO), in its recently adopted resolution on "strengthening rehabilitation in all health systems", encourages that all health sectors, not only the rehabilitation sector, classify a patient's functioning and health state according to the International Classification of Functioning, Disability and Health (ICF). AIM: This research sought to optimize machine learning (ML) methods that fully and automatically link information collected from PROMs in persons with unspecific chronic low back pain (cLBP) to limitations in activities and restrictions in participation that are listed in the WHO core set categories for LBP. The study also aimed to identify the minimal set of PROMs necessary for linking without compromising performance. METHODS: A total of 806 patients with cLBP completed a comprehensive set of validated PROMs and were interviewed by clinical psychologists who assessed patients' performance in activity limitations and restrictions in participation according to the ICF brief core set for low back pain (LBP). The information collected was then utilized to further develop random forest (RF) methods that classified the presence or absence of a problem within each of the activity participation ICF categories of the ICF core set for LBP. Further analyses identified those PROM items relevant to the linking process and validated the respective linking performance that utilized a minimal subset of items. RESULTS: Compared to a recently developed ML linking method, receiver operating characteristic curve (ROC-AUC) values for the novel RF methods showed overall improved performance, with AUC values ranging from 0.73 for the ICF category d850 to 0.81 for the ICF category d540. Variable importance measurements revealed that minimal subsets of either 24 or 15 important PROM variables (out of 80 items included in full set of PROMs) would show similar linking performance. CONCLUSIONS: Findings suggest that our optimized ML based methods more accurately predict the presence or absence of limitations and restrictions listed in ICF core categories for cLBP. In addition, this accurate performance would not suffer if the list of PROM items was reduced to a minimum of 15 out of 80 items assessed.

The Back Muscle Surface Electromyography-Based Fatigue Index: A Digital Biomarker of Human Neuromuscular Aging?

As part of our quest for digital biomarkers of neuromuscular aging, and encouraged by recent findings in healthy volunteers, this study investigated if the instantaneous median frequency (IMDF) derived from back muscle surface electromyographic (SEMG) data monitored during cyclic back extensions could reliably differentiate between younger and older individuals with cLBP. A total of 243 persons with cLBP participated in three experimental sessions: at baseline, one to two days after the first session, and then again approximately six weeks later. During each session, the study participants performed a series of three isometric maximal voluntary contractions (MVC) of back extensors using a dynamometer. These were followed by an isometric back extension at 80% MVC, and-after a break-25 slow cyclic back extensions at 50% MVC. SEMG data were recorded bilaterally at L5 (multifidus), L2 (longissimus dorsi), and L1 (iliocostalis lumborum). Linear mixed-effects models found the IMDF-SEMG time-course changes more rapidly in younger than in older individuals, and more prominently in male participants. The absolute and relative reliabilities of the SEMG time-frequency representations were well compared between older and younger participants. The results indicated an overall good relative reliability, but variable absolute reliability levels. IMDF-SEMG estimates derived from cyclic back extensions proved to be successful in reliably detecting differences in back muscle function in younger vs. older persons with cLBP. These findings encourage further research, with a focus on assessing whether an IMDF-SEMG-based index could be utilized as a tool to achieve the preclinical detection of back muscle aging, and possibly predict the development of back muscle sarcopenia.

Do the WHO-ICF personal factors "age" and "sex" impact limited activity and restricted participation category profiles differently between younger and older women and men in multimodal chronic back pain rehabilitation?

PURPOSE: To investigate if the International Classification of Functioning and Health (ICF) context factors "age" and "sex" would impact the disablement and respective improvement with rehabilitation defined with the ICF core set for chronic low back pain (cLBP). Furthermore, associations between limitations/restrictions and measures of body function or quality of life were of interest. MATERIALS AND METHODS: One thousand five hundred and twelve employed cLBP patients who completed 6 months of outpatient rehabilitation and for whom complete assessments were available before and after rehabilitation. Rehabilitation comprised of progressive resistance training, psychological counseling, and educational sessions. Main outcome measures were the ICF-activity/participation core categories automatically predicted from random forests and utilizing information from the Roland Morris Disability Questionnaire and Pain Disability Index. RESULTS: Generalized linear-mixed models revealed that upon completion of rehabilitation the presence of a limitation within the ICF activity "walking" significantly decreased with significant between-group differences. The category "doing housework" demonstrated gender-specific differences, and both gender- and age-specific differences were observed for work-related participation categories. There were no meaningful associations between ICF limitation/restriction categories and body function measures (point-biserial/Spearman's correlations). CONCLUSIONS: The personal factors "age" and "sex" impact some ICF limitation/restriction categories in cLBP; appropriately addressing these personal features could further improve phase III rehabilitation outcome.Implications for rehabilitationConsistent with calls to explore the age and sex/gender influence on health and disease, little is known how these factors affect the disablement of individuals with chronic back pain.The factors "age" and "sex" drive differences in some categories within the ICF activity/restriction categories.If age- and gender-specific features in activities and participation are not appropriately addressed through interventions, rehabilitation outcome may remain suboptimal in cLBP.

Reproducibility of the 6-minute walk test in lung transplant recipients.

PURPOSE: There is reason to believe that the favorable measurement properties of the 6­minute walk test (6MWT) reported for retest reliability and its capability to detect a true change in healthy individuals or persons with chronic respiratory disease may not apply to lung transplant recipients (LuTXr). We therefore investigated retest reliability of the 6MWT and, in addition, made an attempt to explore whether the 6MWT was sensitive enough to detect important changes that occur with postacute rehabilitation in LuTXr after first time LuTX. METHODS: Immediately before postacute rehabilitation, 50 LuTXr completed 6MWT testing twice, separated by 1-2 workdays (retest reliability), and were reassessed after completion of rehabilitation 2 months later (sensitivity to changes). Body function measures and health-related quality of life (HRQoL) assessments were collected at baseline. RESULTS: Baseline retest 6­minute walk distance (6MWD) and the age-related predicted walking distance (6MWD%pred) scores significantly increased before postacute rehabilitation. The intraclass coefficient of correlation ICC of the 6MWD was 0.93 (95% confidence interval, CI: 0.88-0.96) and its smallest real difference (SRD) 79 m (95% CI: 52;107). Receiver operating curve analyses revealed the rehabilitation associated changes in 6MWD/6MWD%pred to exceed the SRD/SRD% values in a highly accurate way. CONCLUSION: The 6MWT overall represents a reliable functional performance tool in LuTXr that is sensitive to detect changes in physical performance as a result of medical postacute rehabilitation.

Perceived psychosocial stressors and coping resources in chronic low back pain patients as classified by the avoidance-endurance model.

Objectives: The Avoidance-Endurance Model distinguishes between subgroups of low back pain (LBP) patients with three maladaptive styles of coping with pain: fear-avoidance (FAR), distress-endurance (DER), eustress-endurance (EER), and one adaptive coping style (AR). This study aimed to compare the quantity of patients' perceived psychosocial stressors and coping resources across these subgroups. Materials and methods: This cross-sectional study was conducted at an outpatient rehabilitation center for patients with chronic musculoskeletal pain. One hundred and thirty-seven patients (69 women/68 men) with chronic LBP were assessed using the following: a demographic checklist, the visual analogue scale, Avoidance-Endurance Questionnaire, Roland-Morris Disability Questionnaire, Pain Disability Index, and 36-Item Short Form. Subsequently, patients participated in semi-structured interviews led by clinical psychologists, which were intended to identify their perception of stressors and coping resources. The quantity of psychosocial stressors and coping resources were analyzed using deductive and inductive content analyses and then compared between subgroups using chi-square-tests. Results: FARs experienced significantly higher levels of "mental suffering" (p = <0.001) and "other workplace problems" compared to ARs and EERs (p = <0.001). DERs reported significantly higher levels of "mental suffering" (p = <0.001), "job stress" (p = 0.022), and "familial losses" (p = 0.029) compared to ARs, whereas the AR group demonstrated significantly more "coping resources" (p = 0.001) compared to FARs. Conclusion: AEM-subgroups differed in the quantity of perceived psychosocial stressors and coping resources with AR, who demonstrated a lower risk for pain chronicity and reported the highest quantity of resources. The variability across subgroups may imply differences in patients needs regarding therapeutic interventions and suggests that a resource-centered approach to cope with stress and pain may be beneficial.

Changes in the International Classification of Functioning, Disability, and Health Components "Activity/Participation" as Predicted Through Patient-Reported Outcomes Along With Comprehensive Back Pain Rehabilitation.

OBJECTIVES: The World Health Organization (WHO) recommended the International Classification of Functioning, Disability and Health (ICF) but its use in clinical practice is sparse. This study investigated the limitations and restrictions in the most relevant brief ICF core set categories for chronic low back pain (cLBP) as automatically predicted from routinely measured outcomes using a novel, validated mapping algorithm. MATERIALS AND METHODS: Of 2718 cLBP patients recruited, data from 1541 (64% females) were available from before and at the end of 6 months comprehensive outpatient rehabilitation. Assessments included the Roland Morris Disability Questionnaire (RMDQ) and Pain Disability Index (PDI) questionnaires, the percentage of patients with predicted limitations and restrictions in important activity and participation ICF categories, bodily functional measurements, pain intensity, and anxiety/depression (EQ-5D). RESULTS: At baseline, both the RMDQ and the PDI measures were within the third of the lowest disability scores whilst 80% of the patients had limitations with "maintaining a body position" and 30% with "walking" ICF categories. Intervention-associated gains in the maximum isometric lumbar extension and flexion strength and the lumbar range of motion were significant overall, but improvements in patients' ICF limitations/restrictions varied. Anxiety/depression, lumbar range of motion, and extension strength all had a significant impact on the majority of the ICF categories, whereas flexion strength had none. DISCUSSION: The rate of patients with predicted limitations/restrictions in activity/participation ICF core categories for cLBP partly mirrored disability levels and the impact of the body function scores on these limitations/restrictions in ICF categories was varied. Thus, assessing problems in the ICF activity/participation core categories is of relevance to clinical practice for both treatment goal setting and intervention planning. This may be achieved by computer-generated mapping without additional time burden.

In-depth analysis of life values and their corresponding inhibitors and facilitators in chronic low back pain patients: A mixed-method approach.

BACKGROUND: The struggle with pain often interferes with the ability of chronic low back pain (CLBP) patients to pursue important life values due to psychological inflexibility. OBJECTIVE: This research examined life values, related inhibitors and facilitators relevant to personalized therapy planning. METHODS: Two hundred and forty-four CLBP patients completed the Chronic Pain Values Inventory (CPVI). Of these, 68 patients were interviewed to assess inhibitors and facilitators related to life values. Mixed-effects models quantitatively examined differences in the values, structuring content analysis served to qualitatively analyze the interviews. RESULTS: Participants rated the value "family" as being of highest importance and success. The largest discrepancy between importance and success was found for "health". Content analyses revealed a broad range of inhibitors and facilitators related to the examined life values with the highest number of inhibitors related to "work". Facilitators were also found to be of relevance to all life values, but to a lower extent than inhibitors. CONCLUSIONS: The perceived importance and success of life values and their related inhibitors and facilitators may differentially affect CLBP patients. Considering such individual aspects is therefore of utmost importance to improve patient care, as they enable treatment goals and the therapeutic strategies to be adapted accordingly.

Mapping patient reported outcome measures for low back pain to the International Classification of Functioning, Disability and Health using random forests.

BACKGROUND: There is need for feasible and efficient concepts to document patients functioning impairment according to the International Classification of Functioning, Disability and Health (ICF) without imposing additional burden to clinical practice. AIM: The aim of this study was to develop and validate an automatic linking approach that translates information derived from patient reported outcome measures (PROMs) into the ICF. DESIGN: Proof-of-concept study. SETTING: Participants completed both the Roland-Morris disability questionnaire and the Pain Disability Index and were interviewed using the activity and participation component of the ICF brief core set for low back pain. POPULATION: A total of 244 patients with light to moderate chronic low back pain (cLBP); additionally, 19 patients with higher levels of pain were recruited and assessed for validation purposes. METHODS: Based on information extracted from the PROMs and considering the factors age and gender, random forest models that predicted the presence or absence of an impairment at the specific ICF category were computed and validated. RESULTS: Accuracy of the models was found to be acceptable for the most relevant ICF brief core set categories for low back pain if applied at the population level. CONCLUSIONS: The presented approach can be assumed valid if applied at large on population level. The results are of relevance for the further development of automatic linking programs that would allow the ICF-based classification of functioning properties within the International Classification of Diseases (ICD-11) for any health condition. CLINICAL REHABILITATION IMPACT: The presented approach eases the documentation of patients' functioning impairment according to the standardized ICF.

Correction to: Age- and sex-specific effects in paravertebral surface electromyographic back extensor muscle fatigue in chronic low back pain.

Unfortunately, the author names in the author group section were incorrectly captured in the published online paper.

Psychological Subgrouping to Assess the Risk for the Development or Maintenance of Chronic Musculoskeletal Pain: Is This the Way Forward?

BACKGROUND: Because musculoskeletal pain problems are so prevalent, new methods of evaluating and treating patients are needed to increase effectiveness. Subgrouping is a method wherein patients are classified into defined groups on the basis of psychosocial factors with the expectation of more specific and tailored treatments can be prescribed for them. For those seeking care for a new episode, the risk of developing chronic pain-related disability is assessed, whereas, for those with existing pain, the risk for the maintenance of the chronic pain problem is evaluated. AIM: The purpose of this narrative review is to examine how patients are classified into subgroups with regard to methods of evaluation and to ascertain whether subgrouping actually facilitates treatment. RESULTS: For the development of disability, screening tools, for example, the Örebro Musculoskeletal Pain Screening Questionnaire, accurately stratify patients into groups (eg, high, medium, low risk) that predict future pain-related work disability. In addition, several studies show that treatments that directly key in on risk groups enjoy enhanced outcomes compared with treatment as usual. For the maintenance of chronic musculoskeletal pain problems, there are several instruments that classify patients into specific groups or profiles, for example, on the basis of the avoidance and endurance model or the International Classification of Functioning, Disability and Health (ICF) assessment. Although some evidence shows that these classifications are related to treatment outcome, we found no study that directly tested a system for providing treatment matched to the subgrouping for maintenance. CONCLUSIONS: We conclude that it is possible to reliably subgroup patients with musculoskeletal problems. Likewise, treatments that address the risk factors in the screening procedure may enhance outcomes compared with treatment as usual. More work is needed, however, to better understand the mechanism, so that assessment methods can be improved, and treatment specific to subgroups can be developed and evaluated.

Age- and sex-specific effects in paravertebral surface electromyographic back extensor muscle fatigue in chronic low back pain.

The impact of aging on the back muscles is not well understood, yet may hold clues to both normal aging and chronic low back pain (cLBP). This study sought to investigate whether the median frequency (MF) surface electromyographic (SEMG) back muscle fatigue method-a proxy for glycolytic muscle metabolism-would be able to detect age- and sex-specific differences in neuromuscular and muscle metabolic functions in individuals with cLBP in a reliable way, and whether it would be as sensitive as when used on healthy individuals. With participants seated on a dynamometer (20° trunk anteflexion), paraspinal SEMG activity was recorded bilaterally from the multifidus (L5), longissimus (L2), and iliolumbalis (L1) muscles during isometric, sustained back extensions loaded at 80% of maximum from 117 younger (58 females) and 112 older (56 female) cLBP individuals. Tests were repeated after 1-2 days and 6 weeks. Median frequency, the SEMG variable indicating neuromuscular fatigue, was analyzed. Maximum back extensor strength was comparable between younger and older participants. Significantly less MF-SEMG back muscle fatigue was observed in older as compared to younger, and in older female as compared to older male cLBP individuals. Relative reliability was excellent, but absolute reliability appeared large for this SEMG-fatigue measure. Findings suggest that cLBP likely does not mask the age-specific diagnostic potential of the MF-SEMG back extensor fatigue method. Thus, this method possesses a great potential to be further developed into a valuable biomarker capable of detecting back muscle function at risk of sarcopenia at very early stages.

The impact of age and gender on the ICF-based assessment of chronic low back pain.

PURPOSE: To evaluate the impact of age and gender on the international classification of functioning, disability and health (ICF)-based assessment for chronic low back pain. METHODS: Two hundred forty-four chronic low back pain patients (52% female) with a mean age of 49 years (SD =17.64) were interviewed with the comprehensive ICF core set for activities and participation, and environmental factors. After conducting explorative factor analysis, the impact of age and gender on the different factors was analyzed using analyzes of variances. RESULTS: Results revealed that older patients experienced more limitations within "self-care and mobility" and "walking" but less problems with "transportation" compared to younger patients. Older or middle-aged low back pain patients further perceived more facilitation through "architecture and products for communication", "health services", and "social services and products for mobility" than younger patients. Regarding gender differences, women reported more restriction in "housework" than men. An interaction effect between age and gender was found for "social activities and recreation" with young male patients reporting the highest impairment. CONCLUSIONS: The study demonstrated that the comprehensive ICF core set classification for chronic low back pain is influenced by age and gender. This impact is relevant for ICF-based assessments in clinical practice, and should be considered in intervention planning for rehabilitative programs. Implications for rehabilitation It is important to consider age and gender differences when classifying with the ICF. The intervention planning based on the ICF should focus on improvement of bodily functioning and mobility in older patients, facilitation of household activities in women, consideration of work-life balance and recreation (e.g., through mindfulness based stress reduction), and reduction of dissatisfaction with rehabilitation in younger patients. It is important to offer patients the opportunity to participate in intervention planning based on the ICF. For intervention planning professionals should bear in mind the resource-oriented approach of the ICF (e.g., facilitation through environmental factors), and a collaboration with other professionals.

Impairments in Postural Control and Retest Reliability of Dynamic Posturographic Measures After Lung Transplantation.

OBJECTIVES: The aims of the study were to classify impairments in postural control using computerized posturography in lung transplant recipients undergoing subacute rehabilitation and to examine the retest reliability of these measures. METHODS: In a prospective repeated-measures study, 50 lung transplant recipients underwent clinical and quantitative posturographic testing (SMART EquiTest), which included the sensory organization test, motor control test, and limits of stability test. Testing was repeated after 1 to 2 days and upon completion of rehabilitation, 2 mos later. Main outcome measures were the following: sensory organization test-composite score, motor control test-latency and amplitude scaling, limits of stability test-movement velocity, and endpoint excursion/maximum excursion. RESULTS: At the beginning of rehabilitation, the mean sensory organization test-composite score and limits of stability test, but not the motor control test scores, were below normative reference values and and did not return to normal after rehabilitation. Intraclass correlation coefficients(2,1) yielded excellent relative reliability for all posturographic tests. The smallest detectable differences observed for the sensory organization test and limits of stability test exceeded the mean changes observed upon completion of rehabilitation. CONCLUSIONS: Impairments in sensory and anticipatory postural control were insufficiently restored after subacute lung transplantation rehabilitation. The little sensitivity of the sensory organization test-composite score or limits of stability test scores to detect a minimal change in performance due to rehabilitation limits the clinical applicability of these tests as objective outcome measures in lung transplantation rehabilitation.

Feasibility and Reliability of Functional Muscle Tests in Lung Transplant Recipients.

OBJECTIVE: This study investigates the feasibility, reliability, and correlations of recommended functional tests in lung transplant recipients shortly after surgery. DESIGN: This is an observational study. METHODS: Fifty patients (28 females) performed well-standardized maximum isometric back extension in a sitting position, handgrip strength, and Biering-Sørensen endurance tests shortly before discharge from the acute hospital, shortly thereafter, and 2 mos later after subacute rehabilitation. RESULTS: Back extension testing was well feasible, but only two thirds of the patients could perform the Biering-Sørensen test at baseline and they experienced a greater number of minor but no major adverse events. Absolute reliability measures and the intraclass correlation coefficients were excellent for the strength (0.97-0.98 [0.95-0.99]) and good for the endurance tests (0.69 [0.26-0.87]). Handgrip revealed high correlation with back strength (≥0.75) but not with Biering-Sørensen scores. CONCLUSIONS: Well-controlled maximum back strength testing is feasible and reliable, and the scores are highly correlated with grip strength in lung transplant recipients shortly before hospital discharge. The Biering-Sørensen test should be limited to patients without dominant weakness and/or fear. Future research should investigate whether grip instead of back extension strength can safely be used for proper exercise prescription.

Estimating Neural Control from Concentric vs. Eccentric Surface Electromyographic Representations during Fatiguing, Cyclic Submaximal Back Extension Exercises.

Purpose: To investigate the differences in neural control of back muscles activated during the eccentric vs. the concentric portions of a cyclic, submaximal, fatiguing trunk extension exercise via the analysis of amplitude and time-frequency parameters derived from surface electromyographic (SEMG) data. Methods: Using back dynamometers, 87 healthy volunteers performed three maximum voluntary isometric trunk extensions (MVC's), an isometric trunk extension at 80% MVC, and 25 cyclic, dynamic trunk extensions at 50% MVC. Dynamic testing was performed with the trunk angular displacement ranging from 0° to 40° and the trunk angular velocity set at 20°/s. SEMG data was recorded bilaterally from the iliocostalis lumborum at L1, the longissimus dorsi at L2, and the multifidus muscles at L5. The initial value and slope of the root mean square (RMS-SEMG) and the instantaneous median frequency (IMDF-SEMG) estimates derived from the SEMG recorded during each exercise cycle were used to investigate the differences in MU control marking the eccentric vs. the concentric portions of the exercise. Results: During the concentric portions of the exercise, the initial RMS-SEMG values were almost twice those observed during the eccentric portions of the exercise. The RMS-SEMG values generally increased during the concentric portions of the exercise while they mostly remained unchanged during the eccentric portions of the exercise with significant differences between contraction types. Neither the initial IMDF-SEMG values nor the time-course of the IMDF-SEMG values significantly differed between the eccentric and the concentric portions of the exercise. Conclusions: The comparison of the investigated SEMG parameters revealed distinct neural control strategies during the eccentric vs. the concentric portions of the cyclic exercise. We explain these differences by relying upon the principles of orderly recruitment and common drive governing motor unit behavior.

Comparisons in Muscle Function and Training Rehabilitation Outcomes Between Avoidance-Endurance Model Subgroups.

OBJECTIVES: Evidence suggests that chronic low back pain patients with fear-avoidance (FAR) or endurance behavior are at risk of treatment failure and pain maintenance, with bodily overuse or underuse being assumed as mediating mechanisms for pain chronification. This study sought to examine whether or not the avoidance-endurance model subgroups, FAR, distress-endurers (DER), eustress-endurers (EER), and adaptive responders (AR), differed in physical measures and outcomes after training therapy. MATERIALS AND METHODS: A total of 137 chronic low back pain patients were assessed before, at the end of, and 6 months after a 6-month rehabilitation training. Patients performed maximum back extension strength and trunk range-of-motion measures, flexion-relaxation tests, and completed the following questionnaires: Avoidance-Endurance Questionnaire, Roland-Morris Disability Questionnaire, Pain Disability Index, 36-Item Short-Form Health Survey, International Physical Activity Questionnaire, and visual analog scale. Statistical analysis included cluster analysis, analysis of covariances, and mixed-effects models. RESULTS: At baseline, avoidance-endurance model subgroups did not differ in physical measures and activity levels. At the end of training, patients' back-related health was significantly improved in all subgroups. However, the DER and the FAR were found to be more impaired before and after the intervention compared with EER and AR, as indicated by a higher pain intensity, higher disability levels, lower quality of life, and inferior working capacity. DISCUSSION: Although FAR and DER did not differ in physical measures or activity levels from EER and AR, they demonstrated poor lower back-related health at baseline and after intervention. Thus, future research should elucidate as to which additional interventions could optimize their health.

Diagnostic value of trunk flexion-extension testing in old chronic low back pain patients.

PURPOSE: Dynamic trunk flexion-extension testing has been proven to objectively diagnose low back pain in persons under the age of 60 years but older persons have difficulty complying with standardized movement velocity. METHODS: 190 patients and 71 matched healthy volunteers (18-90 years of age) performed modified testing by holding static positions at standing, half, and full trunk flexion. RESULTS: Lumbar extensor muscle activity in isometric positions was significantly higher in patients with higher activity in the oldest (60-90 years) and the middle-aged (40-59 years) but not in the youngest (18-39 years) subgroups compared to normal. There were no differences in gross trunk range of motion, half flexion relaxation ratio, proprioception, muscle activity differences between positions, and fear-avoidance behavior. The diagnostic accuracy as expressed by the area under the curve was fair (0.74). CONCLUSIONS: Lumbar extensor muscle activity demonstrated moderate to good diagnostic value in old patients.

Age-related test-retest reliability of isometric trunk torque measurements in patiens with chronic low back pain.

OBJECTIVE: To investigate the short- and long-term reliability of isometric trunk strength measurements in patients with chronic low back pain in different age groups. DESIGN: Test-retest reliability study. PATIENTS: A total of 210 patients (age groups 18-39, 40-59 and 60-90 years). METHODS: Patients performed testing at baseline, 1-2 days (day 2) and 6 weeks. RESULTS: Only the oldest age group showed similar extension strength on all three test days All age groups showed significant changes in rotation and flexion scores from baseline to 6 weeks. Younger age groups (18-39 and 40-59 years) showed significant increases in extension, flexion, and rotation strength at both short-term (baseline to day 2) and long-term (baseline to 6 weeks) retests, but not from day 2 to 6 weeks. In patients over 60 years of age the smallest real differences normalized to baseline (%) were smaller from day 2 to 6 weeks than from baseline to 6 weeks. Long-term intraclass correlation coefficients were lowest between baseline and 6 weeks. No relevant impacts of feelings, motivation, or pain on reliability were detected. CONCLUSION: Reliability of isometric trunk strength measurements in patients with chronic low back pain is similar in older and younger patients. Short-term test repetition a few days after baseline is recommended, if clinically feasible, and especially in research evaluating the effects of exercise on strength.

Age and gender related neuromuscular pattern during trunk flexion-extension in chronic low back pain patients.

BACKGROUND: The root mean square surface electromyographic activity of lumbar extensor muscles during dynamic trunk flexion and extension from standing has repeatedly been recommended to objectively assess muscle function in chronic low back pain patients. However, literature addressing older patients is sparse. This cross sectional study sought to examine differences in neuromuscular activation between age groups (>60 versus 40-60 versus <40 years) and sexes during a standardized trunk flexion-extension task. METHODS: A total of 216 patients (62 older, 84 middle-aged, 70 younger) performed maximum trunk extensions followed by trunk flexion extension testing thereby holding static positions at standing, half, and full trunk flexion. The lumbar extensor muscle activity and 3d-accelerometric signals intended to monitor hip and trunk position angles were recorded from the L5 (multifidus) and T4 (semispinalis thoracis) levels. Permutation ANOVA with bootstrapped confidence intervals were performed to examine for age and gender related differences. Ridge-regressions investigated the impact of physical-functional and psychological variables to the half flexion relaxation ratio (i.e. muscle activity at the half divided by that in maximum flexion position). RESULTS: Maximum back extension torque was slightly but significantly higher in youngest compared to oldest patients if male and females were pooled. Normalized RMS-SEMG revealed highest lumbar extensor muscle activity at standing in the oldest and the female groups. Patients over 60 years showed lowest activity changes from standing to half (increments) and from half to the maximum flexion position (decrements) leading to a significantly lower half flexion relaxation ratio compared to the youngest patients. These oldest patients demonstrated the highest hip and lowest lumbothoracic changes of position angles. Females had higher regional hip and gross trunk ranges of movement compared to males. Lumbothoracic flexion and the muscle activity at standing had a significant impact on the half flexion relaxation ratio. CONCLUSIONS: The neuromuscular activation pattern and the kinematics in this trunk flexion-extension task involving static half flexion position changed according to age and sex. The test has a good potential to discriminate between impaired and unimpaired neuromuscular regulation of back extensors in cLBP patients, thereby allowing the design of more individualized exercise programs.