Sustainability of a Motor Control Exercise Intervention: Analysis of Long-Term Effects in a Low Back Pain Study.

Development of chronic pain after a low back pain episode is associated with increased pain sensitivity, altered pain processing mechanisms and the influence of psychosocial factors. Although there is some evidence that multimodal therapy (such as behavioral or motor control therapy) may be an important therapeutic strategy, its long-term effect on pain reduction and psychosocial load is still unclear. Prospective longitudinal designs providing information about the extent of such possible long-term effects are missing. This study aims to investigate the long-term effects of a homebased uni- and multidisciplinary motor control exercise program on low back pain intensity, disability and psychosocial variables. 14 months after completion of a multicenter study comparing uni- and multidisciplinary exercise interventions, a sample of one study center (n = 154) was assessed once more. Participants filled in questionnaires regarding their low back pain symptoms (characteristic pain intensity and related disability), stress and vital exhaustion (short version of the Maastricht Vital Exhaustion Questionnaire), anxiety and depression experiences (the Hospital and Anxiety Depression Scale), and pain-related cognitions (the Fear Avoidance Beliefs Questionnaire). Repeated measures mixed ANCOVAs were calculated to determine the long-term effects of the interventions on characteristic pain intensity and disability as well as on the psychosocial variables. Fifty four percent of the sub-sample responded to the questionnaires (n = 84). Longitudinal analyses revealed a significant long-term effect of the exercise intervention on pain disability. The multidisciplinary group missed statistical significance yet showed a medium sized long-term effect. The groups did not differ in their changes of the psychosocial variables of interest. There was evidence of long-term effects of the interventions on pain-related disability, but there was no effect on the other variables of interest. This may be partially explained by participant's low comorbidities at baseline. Results are important regarding costless homebased alternatives for back pain patients and prevention tasks. Furthermore, this study closes the gap of missing long-term effect analysis in this field.

Psychosocial Moderators and Mediators of Sensorimotor Exercise in Low Back Pain: A Randomized Multicenter Controlled Trial.

The effects of exercise interventions on unspecific chronic low back pain (CLBP) have been investigated in many studies, but the results are inconclusive regarding exercise types, efficiency, and sustainability. This may be because the influence of psychosocial factors on exercise induced adaptation regarding CLBP is neglected. Therefore, this study assessed psychosocial characteristics, which moderate and mediate the effects of sensorimotor exercise on LBP. A single-blind 3-arm multicenter randomized controlled trial was conducted for 12-weeks. Three exercise groups, sensorimotor exercise (SMT), sensorimotor and behavioral training (SMT-BT), and regular routines (CG) were randomly assigned to 662 volunteers. Primary outcomes (pain intensity and disability) and psychosocial characteristics were assessed at baseline (M1) and follow-up (3/6/12/24 weeks, M2-M5). Multiple regression models were used to analyze whether psychosocial characteristics are moderators of the relationship between exercise and pain, meaning that psychosocial factors and exercise interact. Causal mediation analysis were conducted to analyze, whether psychosocial characteristics mediate the exercise effect on pain. A total of 453 participants with intermittent pain (mean age = 39.5 ± 12.2 years, f = 62%) completed the training. It was shown, that depressive symptomatology (at M4, M5), vital exhaustion (at M4), and perceived social support (at M5) are significant moderators of the relationship between exercise and the reduction of pain intensity. Further depressive mood (at M4), social-satisfaction (at M4), and anxiety (at M5 SMT) significantly moderate the exercise effect on pain disability. The amount of moderation was of clinical relevance. In contrast, there were no psychosocial variables which mediated exercise effects on pain. In conclusion it was shown, that psychosocial variables can be moderators in the relationship between sensorimotor exercise induced adaptation on CLBP which may explain conflicting results in the past regarding the merit of exercise interventions in CLBP. Results suggest further an early identification of psychosocial risk factors by diagnostic tools, which may essential support the planning of personalized exercise therapy. Level of Evidence: Level I. Clinical Trial Registration: DRKS00004977, LOE: I, MiSpEx: grant-number: 080102A/11-14. https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00004977.

Medical exercise and physiotherapy modes and frequency as predictors for a recurrence of chronic non-specific low back pain.

BACKGROUND: A considerable part of patients with non-specific low back pain (LBP) suffer from a recurrence of symptoms after therapy cessation. OBJECTIVE: The aim of this cohort study was to evaluate the predictive value of active and passive treatments and treatment modalities on a recurrence of low back pain after cessation of medically prescribed therapy. METHODS: Patients with non-specific LBP from a health- and therapy-center were included. Treatments were monitored and categorized as active or passive. During one year after therapy cessation, patients were monitored to retrieve information about recurrence of symptoms. Patients were dichotomized (recurrence versus no recurrence). An ROC-Analysis was used to determine optimal cut-offs for relevant treatment characteristics' (passive versus active; frequency) impact on recurrence risk. The relative risk for a recurrence was calculated based on Chi2-test. RESULTS: Data from 96 participants (56 females, 40 males, mean age 49 years, standard deviation 11 years) were analysed. A total of 34 participants had recurring LBP. The frequency of active treatment differed significantly between groups with or without recurrence (p< 0.05). A therapy frequency of 1.45 active treatments/week was a sensitive cut-off (sensitivity: 0.73) to discriminate the recurrence groups. Participants with an active therapy frequency of less than 1.45 treatments per week showed an 82% increased relative recurrence risk (RR: 1.824 (95%-CI: 1.077-3.087)). CONCLUSIONS: The results empathize the importance of active treatments (i.e. exercise) in the therapy and (secondary) prevention of non-specific LBP. Less than 1.45 active treatment sessions/week increases the 1-year-risk of a recurrence by 82%. Performing at least two treatments sessions per week is therefore recommended.

Stress and Self-Efficacy as Long-Term Predictors for Chronic Low Back Pain: A Prospective Longitudinal Study.

PURPOSE: Psychosocial variables are known risk factors for the development and chronification of low back pain (LBP). Psychosocial stress is one of these risk factors. Therefore, this study aims to identify the most important types of stress predicting LBP. Self-efficacy was included as a potential protective factor related to both, stress and pain. PARTICIPANTS AND METHODS: This prospective observational study assessed n = 1071 subjects with low back pain over 2 years. Psychosocial stress was evaluated in a broad manner using instruments assessing perceived stress, stress experiences in work and social contexts, vital exhaustion and life-event stress. Further, self-efficacy and pain (characteristic pain intensity and disability) were assessed. Using least absolute shrinkage selection operator regression, important predictors of characteristic pain intensity and pain-related disability at 1-year and 2-years follow-up were analyzed. RESULTS: The final sample for the statistic procedure consisted of 588 subjects (age: 39.2 (±13.4) years; baseline pain intensity: 27.8 (±18.4); disability: 14.3 (±17.9)). In the 1-year follow-up, the stress types "tendency to worry", "social isolation", "work discontent" as well as vital exhaustion and negative life events were identified as risk factors for both pain intensity and pain-related disability. Within the 2-years follow-up, Lasso models identified the stress types "tendency to worry", "social isolation", "social conflicts", and "perceived long-term stress" as potential risk factors for both pain intensity and disability. Furthermore, "self-efficacy" ("internality", "self-concept") and "social externality" play a role in reducing pain-related disability. CONCLUSION: Stress experiences in social and work-related contexts were identified as important risk factors for LBP 1 or 2 years in the future, even in subjects with low initial pain levels. Self-efficacy turned out to be a protective factor for pain development, especially in the long-term follow-up. Results suggest a differentiation of stress types in addressing psychosocial factors in research, prevention and therapy approaches.

Sudden gait perturbations elicit sex-specific neuromuscular trunk responses in persons with low back pain.

Persons with low back pain (LBP) exhibit delayed trunk muscle onset and increased co-contractions as a response to quasi-static and dynamic sudden trunk loading in comparison to back-healthy controls. Although LBP is more prevalent in females, sex-specific responses have not been well documented. Therefore, the purpose was to explore sex-specific neuromuscular differences, to gait perturbation, in LBP patients. Twenty-nine LBP patients (12m/17f;31 ± 10yrs; 174 ± 12 cm; 71 ± 16 kg) walked on a split-belt treadmill at 1 m/s, while 15 right-sided random perturbations (treadmill-belt decelerating, 40 m/s2, 50 ms duration; 200 ms after heel contact) were applied. Muscle activity was assessed using a 12-lead surface EMG (6 back/6 abdominal muscles; 4000 Hz). EMG-RMS [%] (0-200 ms after perturbation) was calculated and normalized to RMS of unperturbed gait for each muscle. Furthermore, muscle onsets (ms) were determined. Two-way ANOVA (factors: sex/muscle) was applied to account for sex differences in main outcomes. EMG-RMS (amplitudes; mean) ranged from 356% to 901% in males and 349% to 694% in females representing a significant interaction effect (sex * muscle: p = 0.017). Post-hoc analysis revealed significant differences for EMG-RMS analysis of rectus abdominis left (p = 0.043; f > m) as well as obliques externus right/left (p = 0.018/p = 0.005; f < m). In the time domain, females showed overall, shorter (mean: 90 ± 16 ms) response times compared to males (mean: 98 ± 22 ms, sex effect: p < 0.0001). In this LBP population, abdominal muscle activation discriminated females from males. Specifically, females had higher activity of the rectus abdominis muscles and lower activation of the externus oblique muscles. These different activation strategies might be relevant to the development of sex-specific intervention strategies.

Visual and instrumental diagnostics using chromokinegraphics: Reliability and validity for low back pain stratification.

BACKGROUND: Low back pain patients have been suggested to exhibit dysfunctional spinal movement patterns. However, there is a lack of clinically applicable but valid and reliable assessment tools, helping to discriminate normal and pathologically altered movement. OBJECTIVE: We aimed to examine whether kinematic parameters determined with an ultrasound-based motion analysis and thereof derived chromokinegraphical angle-time matrices (CATMAs) are able to discriminate between non-symptomatic and symptomatic movement behaviour in individuals with non-specific chronic (CLBP), specific low back pain (SLBP), and controls. METHODS: Thoracic and lumbar spine range of motion (ROM [∘]); angular velocity (V [∘/sec]) and side-to-side differences [%] during a lateral flexion movement were assessed in 17 healthy participants, 16 individuals with CLBP and 11 SLBP patients. CATMAs ratings of two investigators (6-item Likert scale) were dichotomised, classifying the observed movement as physiological or non-physiological. Intrarater and interrater reliability were estimated using kappa statistics and Cronbach's Alpha. T-tests and a ROC analysis to determine optimal cut-offs for the separation of the collectives as well as contingency tables for selectivity of the cut-offs (motor outcomes) were calculated. RESULTS: CATMA ratings displayed partly moderate to good (rater B; i.e. CLBP vs. controls) and partly insufficient discriminant validity (rater A). Due to this, inter-rater reliability was poor (k= 0.061 to 0.135), while intra-rater-reliability was moderate to good for both raters (k= 0.329 to 0.625) except for SLBP vs. controls (rater A; k=-0.18). Regarding kinematics, group differences occurred neither in ROM nor in V (p> 0.05), but in terms of the relative side comparison between CLBP and controls (p<0.05). ROC analysis (CLBP vs. controls) revealed an optimal cut-off at side asymmetries of 16.9% (ROM) and 28.9% (V). Between SLBP patients and controls, no significant differences were observed neither in terms of the absolute values nor the relative side differences of both kinematic variables. CONCLUSIONS: Side asymmetries of V and ROM may be used to differentiate between controls and individuals with CLBP. CATMAs appear to be of limited diagnostic value for the identification of pathological spine movement.

The Feasibility and Effectiveness of a New Practical Multidisciplinary Treatment for Low-Back Pain: A Randomized Controlled Trial.

Low-back pain is a major health problem exacerbated by the fact that most treatments are not suitable for self-management in everyday life. Particularly, interdisciplinary programs consist of intensive therapy lasting several weeks. Additionally, therapy components are rarely coordinated regarding reinforcing effects, which would improve complaints in persons with higher pain. This study assesses the effectiveness of a self-management program, firstly for persons suffering from higher pain and secondly compared to regular routines. Study objectives were treated in a single-blind multicenter controlled trial. A total of n = 439 volunteers (age 18-65 years) were randomly assigned to a twelve-week multidisciplinary sensorimotor training (3-weeks-center- and 9-weeks-homebased) or control group. The primary outcome pain (Chronic-Pain-Grade) as well as mental health were assessed by questionnaires at baseline and follow-up (3/6/12/24 weeks, M2-M5). For statistical analysis, multiple linear regression models were used. N = 291 (age 39.7 ± 12.7 years, female = 61.1%, 77% CPG = 1) completed training (M1/M4/M5), showing a significantly stronger reduction of mental health complaints (anxiety, vital exhaustion) in people with higher than those with lower pain in multidisciplinary treatment. Compared to regular routines, the self-management-multidisciplinary treatment led to a clinically relevant reduction of pain-disability and significant mental health improvements. Low-cost exercise programs may provide enormous relief for therapeutic processes, rehabilitation aftercare, and thus, cost savings for the health system.

Dose-response relationship of core-specific sensorimotor interventions in healthy, well-trained participants: study protocol for a (MiSpEx) randomized controlled trial.

BACKGROUND: Core-specific sensorimotor exercises are proven to enhance neuromuscular activity of the trunk, improve athletic performance and prevent back pain. However, the dose-response relationship and, therefore, the dose required to improve trunk function is still under debate. The purpose of the present trial will be to compare four different intervention strategies of sensorimotor exercises that will result in improved trunk function. METHODS/DESIGN: A single-blind, four-armed, randomized controlled trial with a 3-week (home-based) intervention phase and two measurement days pre and post intervention (M1/M2) is designed. Experimental procedures on both measurement days will include evaluation of maximum isokinetic and isometric trunk strength (extension/flexion, rotation) including perturbations, as well as neuromuscular trunk activity while performing strength testing. The primary outcome is trunk strength (peak torque). Neuromuscular activity (amplitude, latencies as a response to perturbation) serves as secondary outcome. The control group will perform a standardized exercise program of four sensorimotor exercises (three sets of 10 repetitions) in each of six training sessions (30 min duration) over 3 weeks. The intervention groups' programs differ in the number of exercises, sets per exercise and, therefore, overall training amount (group I: six sessions, three exercises, two sets; group II: six sessions, two exercises, two sets; group III: six sessions, one exercise, three sets). The intervention programs of groups I, II and III include additional perturbations for all exercises to increase both the difficulty and the efficacy of the exercises performed. Statistical analysis will be performed after examining the underlying assumptions for parametric and non-parametric testing. DISCUSSION: The results of the study will be clinically relevant, not only for researchers but also for (sports) therapists, physicians, coaches, athletes and the general population who have the aim of improving trunk function. TRIAL REGISTRATION: German Clinical Trials Register, ID: DRKS00012917 . Registered on 22 August 2017.

Muscle Strength and Neuromuscular Control in Low-Back Pain: Elite Athletes Versus General Population.

The purpose of the study was to investigate the athletic-based specificity of muscle strength and neuromuscular control of spine stability in chronic non-specific low-back pain (LBP). Thirty elite athletes and 29 age-matched non-athletes with (15 athletes and 15 non-athletes) and without LBP (15 athletes and 14 non-athletes) participated in the study. Muscle strength was measured during maximal isometric trunk flexion and trunk extension contractions. The neuromuscular control of spine stability was analyzed by determining trunk stiffness, trunk damping, and onset times of the lumbar and thoracic erector spinae muscles after sudden perturbations (quick release experiments) as well as maximum Lyapunov exponents (local dynamic stability) using non-linear time series analysis of repetitive lifting movements. LBP was assessed using the visual analog scale. We found lower maximal trunk extension moments (p = 0.03), higher trunk damping (p = 0.018) and shorter onset times (p = 0.03) of the investigated trunk muscles in LBP patients in both athletes and non-athletes. Trunk stiffness and the local dynamic stability did not show any differences (p = 0.136 and p = 0.375, respectively) between LBP patients and healthy controls in both groups. It can be concluded that, despite the high-level of training in athletes, both athletes and non-athletes with LBP showed the same deconditioning of the lumbar extensor muscles and developed similar strategies to ensure spine stability after sudden perturbations to protect the spine from pain and damage. The findings highlight that specific training interventions for the trunk muscles are not only crucial for individuals of the general population, but also for well-trained athletes.

Effect of high-intensity perturbations during core-specific sensorimotor exercises on trunk muscle activation.

Core-specific sensorimotor exercises are proven to enhance neuromuscular activity of the trunk. However, the influence of high-intensity perturbations on training efficiency is unclear within this context. Sixteen participants (29±2yrs; 175±8cm; 69±13kg) were prepared with a 12-lead bilateral trunk EMG. Warm-up on a dynamometer was followed by maximum voluntary isometric trunk (flex/ext) contraction (MVC). Next, participants performed four conditions for a one-legged stance with hip abduction on a stable surface (HA) repeated randomly on an unstable surface (HAP), on a stable surface with perturbation (HA+P), and on an unstable surface with perturbation (HAP+P). Afterwards, bird dog (BD) was performed under the same conditions (BD, BDP, BD+P, BDP+P). A foam pad under the foot (HA) or the knee (BD) was used as an unstable surface. Exercises were conducted on a moveable platform. Perturbations (ACC 50m/sec2;100ms duration;10rep.) were randomly applied in the anterior-posterior direction. The root mean square (RMS) normalized to MVC (%) was calculated (whole movement cycle). Muscles were grouped into ventral right and left (VR;VL), and dorsal right and left (DR;DL). Ventral-Dorsal and right-left ratios were calculated (two way repeated-measures ANOVA;α=0.05). Amplitudes of all muscle groups in bird dog were higher compared to hip abduction (p≤0.0001; Range: BD: 14±3% (BD;VR) to 53±4%; HA: 7±2% (HA;VR) to 16±4% (HA;DR)). EMG-RMS showed significant differences (p<0.001) between conditions and muscle groups per exercise. Interaction effects were only significant for HA (p=0.02). No significant differences were present in EMG ratios (p>0.05). Additional high-intensity perturbations during core-specific sensorimotor exercises lead to increased neuromuscular activity and therefore higher exercise intensities. However, the beneficial effects on trunk function remain unclear. Nevertheless, BD is more suitable to address trunk muscles.

How do we stand? Variations during repeated standing phases of asymptomatic subjects and low back pain patients.

An irreproducible standing posture can lead to mis-interpretation of radiological measurements, wrong diagnoses and possibly unnecessary treatment. This study aimed to evaluate the differences in lumbar lordosis and sacrum orientation in six repetitive upright standing postures of 353 asymptomatic subjects (including 332 non-athletes and 21 athletes - soccer players) and 83 low back pain (LBP) patients using a non-invasive back-shape measurement device. In the standing position, all investigated cohorts displayed a large inter-subject variability in sacrum orientation (∼40°) and lumbar lordosis (∼53°). In the asymptomatic cohort (non-athletes), 51% of the subjects showed variations in lumbar lordosis of 10-20% in six repeated standing phases and 29% showed variations of even more than 20%. In the sacrum orientation, 53% of all asymptomatic subjects revealed variations of >20% and 31% of even more than 30%. It can be concluded that standing is highly individual and poorly reproducible. The reproducibility was independent of age, gender, body height and weight. LBP patients and athletes showed a similar variability as the asymptomatic cohort. The number of standing phases performed showed no positive effect on the reproducibility. Therefore, the variability in standing is not predictable but random, and thus does not reflect an individual specific behavioral pattern which can be reduced, for example, by repeated standing phases.

A random-perturbation therapy in chronic non-specific low-back pain patients: a randomised controlled trial.

The purpose of the study was to assess the effectiveness of a specific rehabilitation therapy for chronic non-specific low-back pain patients, based on a random/irregular functional perturbation training induced by force disturbances to the spine. Forty patients (20 controls and 20 in the perturbation-based group) finished the whole experimental design. A random-perturbation exercise, which included variable and unpredictable disturbances, was implemented in the therapy of the perturbation-based group (13 weeks, two times per week and 1.5 h per session). The participants of the control group did not receive any specific training. Low-back pain, muscle strength, and neuromuscular control of spine stability were investigated before and after the therapy using the visual analog scale, maximal isometric and isokinetic contractions, nonlinear time series analysis, and by determining the stiffness and damping of the trunk after sudden perturbations. The perturbation-based therapy reduced patient's low-back pain (35%), increased muscle strength (15-22%), and trunk stiffness (13%), while no significant changes were observed in the control group. It can be concluded that the proposed therapy has the potential to enhance trunk muscle capability as well as sensory information processing within the motor system during sudden loading and, as a consequence, improve the stabilization of the trunk.

Effects of dual-task conditions on cervical spine movement variability.

BACKGROUND: The potential to accurately perform cervical movements during more challenging tasks might be of importance to prevent dysfunctional motion characteristics. Although sensorimotor function during dual-task conditions are of increasing interest in biomedical and rehabilitation research, effects of such conditions on movement consistency of the neck have not yet been investigated. OBJECTIVE: In this crossover MiSpEx(Medicine in Spine Exercise)-diagnostic study, we aimed to explore differences between single and dual-task conditions on cervical movement variability. METHODS: Nineteen healthy participants (9 male; 24.5 ± 3.3 y) performed 10 repetitive maximal cervical movements in (1) flexion/extension and (2) lateral flexion, during one single- and during two dual-task test conditions (cognitive, motor) in a randomised and cross-over sequence. Latter consisted of a working memory n-back task (n= 2) and a repetitive ankle movement task. Range of motion (RoM) was assessed using an external three-dimensional ultrasonic movement analysis system. Coefficient of variation (CV) for repetitive RoM was analysed for differences between conditions and controlled for variances in intra-individual movement characteristics. RESULTS: Friedman and post-hoc Bonferroni-adjusted confidence intervals for differences from single- to dual-task values revealed changes in CV in flexion/extension from single-task to motor dual-task (+0.02 ± 0.02 (97.5%CI: 0.01; 0.03); p< 0.05) but not to cognitive dual-task condition (+0.01 ± 0.02 (97.5%CI: 0.003; 0.02)) nor for lateral flexion (p> 0.05). Pearson regression analyses revealed a linear negative (p< 0.01) influence of CV in flexion/extension on differences from single to both cognitive (R=2 0.47) and motor dual-task (R=2 0.55). Results for lateral flexion are comparable, baseline CV negatively impacts differences to cognitive (R=2 0.2) and motor dual-task performance (R=2 0.76; p< 0.01). CONCLUSIONS: Participants with comparable low cervical CV at single-task display a profound increase during dual-task conditions while participants with a higher variability remained almost stable or showed a decrease. The results point toward a complex interrelationship of motion patterns and adaptation processes during challenging tasks in respect of cervical CV.

Neuromuscular trunk activation patterns in back pain patients during one-handed lifting.

AIM: To analyze neuromuscular activity patterns of the trunk in healthy controls (H) and back pain patients (BPP) during one-handed lifting of light to heavy loads. METHODS: After assessment of back pain (graded chronic pain scale according to von Korff) all subjects (n = 43) performed a warm-up (treadmill walking). Next, subjects were instructed to lift 3 × a 20 kg weight placed in front of them (with both hand) onto a table (height: 0.75 m). Subsequently, all subjects lifted with one hand (left-side, 3 repetitions) a weight of 1 kg (light), 10 kg (middle) and 20 kg (heavy) in random order from the ground up onto the table left of them. Trunk muscle activity was assessed with a 12-lead EMG (6 ventral/6 dorsal muscles; 4000 Hz). EMG-RMS (%) was averaged over the 3 repetitions and analyzed for the whole one-handed lifting cycle, then normalized to RMS of the two-handed lifting. Additionally, the mean (normalized) EMG-RMS of four trunk areas [right/left ventral area (VR/VL); right/left dorsal area (DR/DL)] was calculated. Data were analyzed descriptively (mean ± SD) followed by student's t-test comparing H and BPP (α = 0.05). With respect to the unequal distribution of subjects in H and BPP, a matched-group analysis was conducted. Seven healthy controls were gender- and age-matched (group Hmatched) to the 7 BPP. In addition, task failure was calculated and compared between H/Hmatchedvs BPP using χ2. RESULTS: Seven subjects (3m/4f; 32 ± 7 years; 171 ± 7 cm; 65 ± 11 kg) were assigned to BPP (pain grade ≥ 2) and 36 (13m/23f; 28 ± 8 years; 174 ± 10 cm; 71 ± 12 kg) to H (pain grade ≤ 1). H and BPP did not differ significantly in anthropometrics (P > 0.05). All subjects were able to lift the light and middle loads, but 57% of BPP and 22% of H were not able to lift the heavy load (all women). χ2 analysis revealed statistically significant differences in task failure between H vs BPP (P = 0.03). EMG-RMS ranged from 33% ± 10%/30% ± 9% (DL, 1 kg) to 356% ± 148%/283% ± 80% (VR, 20 kg) in H/BPP with no statistical difference between groups regardless of load (P > 0.05). However, the EMG-RMS of the VR was greatest in all lifting tasks for both groups and increased with heavier loads. CONCLUSION: Heavier loading leads to an increase (2- to 3-fold) in trunk muscle activity with comparable patterns. Heavy loading (20 kg) leads to task failure, especially in women with back pain.

Unexpected walking perturbations: Reliability and validity of a new treadmill protocol to provoke muscular reflex activities at lower extremities and the trunk.

Instrumented treadmills offer the potential to generate standardized walking perturbations, which are particularly rapid and powerful. However, technical requirements to release adequate perturbations regarding timing, duration and amplitude are demanding. This study investigated the test-retest reliability and validity of a new treadmill perturbation protocol releasing rapid and unexpected belt perturbations to provoke muscular reflex responses at lower extremities and the trunk. Fourteen healthy participants underwent two identical treadmill walking protocols, consisting of 10 superimposed one-sided belt perturbations (100ms duration; 2m/s amplitude), triggered by a plantar pressure insole 200ms after heel contact. Delay, duration and amplitude of applied perturbations were recorded by 3D-motion capture. Muscular reflex responses (within 200ms) were measured at lower extremities and the trunk (10-lead EMG). Data was analyzed descriptively (mean±SD). Reliability was analyzed using test-retest variability (TRV%) and limits of agreement (LoA, bias±1.96∗SD). Perturbation delay was 202±14ms, duration was 102±4ms and amplitude was 2.1±0.01m/s. TRV for perturbation delay, duration and amplitude ranged from 5.0% to 5.7%. LoA reached 3±36ms for delay, 2±13ms for duration and 0.0±0.3m/s for amplitude. EMG amplitudes following perturbations ranged between 106±97% and 909±979% of unperturbed gait and EMG latencies between 82±14ms and 106±16ms. Minor differences between preset and observed perturbation characteristics and results of test-retest analysis prove a high validity with excellent reliability of the setup. Therefore, the protocol tested can be recommended to provoke muscular reflex responses at lower extremities and the trunk in perturbed walking.

On the relevance of surrogate parameter deduction in biomedical research: mediated regression analysis for variance explanation of cervical range of motion.

PURPOSE: Research on cervical range of motion (ROM) often includes age and body mass index (BMI) as potential variables to explain inter-individual variances. The BMI may not be a predictor of ROM but an age-affected surrogate parameter: the described effect of BMI on ROM is, thus, suspected being partially or completely mediated by age. METHODS: Healthy and adult volunteers (n = 139, 65 female, age 19-75 years, BMI 24.2 ± 3.8 kg m-2) performed five repetitive maximal cervical movements in the sagittal plane to assess maximal ROM (primary outcome). After the examination of underlying assumptions, data were analysed by mediation regression analyses using a SPSS-macro provided by Hayes. ROM represented the outcome variable, independent variable was BMI and mediator variable was age. Total as well as direct and indirect effects were calculated: (1) for all subjects included and (2) for subject with a BMI <35 kg m-2. RESULTS: Analysis including all subjects revealed both a direct (-1.1, s e .46, p < .05, 95 %CI -2; -1.7) and an existing indirect effect (mediated by age, -2.4, s e .33, p < .05, 95 %CI -3.1; -1.8) of BMI on ROM. Analysis without obese 2 subjects showed no direct effect of BMI (effect -1, s e .54, p > .05, 95 %CI -2.1; +.1) but a systematic indirect effect, mediated by age, on ROM (effect -2.4, s e .33, p < .001, 95 %CI -3.1; -1.8). CONCLUSIONS: After the withdrawal of the surrogate parameter BMI, age explains 53 % of maximal ROM. No impact of BMI on ROM was detected after excluding highly obese participants. Our results illustrate the relevance of including each supposable predictor in causal mediation models development.

Is remote stretching based on myofascial chains as effective as local exercise? A randomised-controlled trial.

Lower limb stretching based on myofascial chains has been demonstrated to increase cervical range of motion (ROM) in the sagittal plane. It is, however, unknown whether such remote exercise is as effective as local stretching. To resolve this research deficit, 63 healthy participants (36 ± 13 years, ♂32) were randomly assigned to one of three groups: remote stretching of the lower limb (LLS), local stretching of the cervical spine (CSS) or inactive control (CON). Prior (M1), immediately post (M2) and 5 min following intervention (M3), maximal cervical ROM was assessed. Non-parametric data analysis (Kruskal-Wallis tests and adjusted post hoc Dunn tests) revealed significant differences between the disposed conditions. With one exception (cervical spine rotation after CSS at M2, P > .05), both LLS and CSS increased cervical ROM compared to the control group in all movement planes and at all measurements (P < .05). Between LLS and CSS, no statistical differences were found (P > .05). Lower limb stretching based on myofascial chains induces similar acute improvements in cervical ROM as local exercise. Therapists might consequently consider its use in programme design. However, as the attained effects do not seem to be direction-specific, further research is warranted in order to provide evidence-based recommendations.

Neuromuscular response of the trunk to sudden gait disturbances: Forward vs. backward perturbation.

The study aimed to analyse neuromuscular activity of the trunk comparing four different perturbations during gait. Thirteen subjects (28±3yrs) walked (1m/s) on a split-belt treadmill, while 4 (belt) perturbations (F1, F2, B1, B2) were randomly applied. Perturbations differed, related to treadmill belt translation, in direction (forward (F)/backward (B)) and amplitude (20m/s(2) (1)/40m/s(2) (2)). Trunk muscle activity was assessed with a 12-lead-EMG. EMG-RMS [%] (0-200ms after perturbation; normalized to RMS of normal gait) was analyzed for muscles and four trunk areas (ventral left/right; dorsal left/right). Ratio of ventral:dorsal muscles were calculated. Muscle onset [ms] was determined. Data analysis was conducted descriptively, followed by ANOVA (post hoc Tukey-Kramer (α=0.05)). All perturbations lead to an increase in EMG-RMS (428±289%). F1 showed the lowest and F2 the highest increase for the flexors. B2 showed the highest increase for the extensors. Significant differences between perturbations could be observed for 6 muscles, as well as the 4 trunk areas. Ratio analysis revealed no significant differences (range 1.25 (B1) to 1.71 (F2) between stimuli. Muscle response time (ventral: 87.0±21.7ms; dorsal: 88.4±17.0ms) between stimuli was only significant (p=0.005) for the dorsal muscles. Magnitude significantly influences neuromuscular trunk response patterns in healthy adults. Regardless of direction ventral muscles always revealed higher relative increase of activity while compensating the walking perturbations.

Influence of Load on Three-Dimensional Segmental Trunk Kinematics in One-Handed Lifting: A Pilot Study.

Stability of the trunk is relevant in determining trunk response to different loading in everyday tasks initiated by the limbs. Descriptions of the trunk's mechanical movement patterns in response to different loads while lifting objects are still under debate. Hence, the aim of this study was to analyze the influence of weight on 3-dimensional segmental motion of the trunk during 1-handed lifting. Ten asymptomatic subjects were included (29 ± 3 y; 1.79 ± 0.09 m; 75 ± 14 kg). Subjects lifted 3× a light and heavy load from the ground up onto a table. Three-dimensional segmental trunk motion was measured (12 markers; 3 segments: upper thoracic area [UTA], lower thoracic area [LTA], lumbar area [LA]). Outcomes were total motion amplitudes (ROM;[°]) for anterior flexion, lateral flexion, and rotation of each segment. The highest ROM was observed in the LTA segment (anterior flexion), and the smallest ROM in the UTA segment (lateral flexion). ROM differed for all planes between the 3 segments for both tasks (P < .001). There were no differences in ROM between light and heavy loads (P > .05). No interaction effects (load × segment) were observed, as ROM did not reveal differences between loading tasks. Regardless of weight, the 3 segments did reflect differences, supporting the relevance of multisegmental analysis.

Estimation of loads on human lumbar spine: A review of in vivo and computational model studies.

Spinal loads are recognized to play a causative role in back disorders and pain. Knowledge of lumbar spinal loads is required in proper management of various spinal disorders, effective risk prevention and assessment in the workplace, sports and rehabilitation, realistic testing of spinal implants as well as adequate loading in in vitro studies. During the last few decades, researchers have used a number of techniques to estimate spinal loads by measuring in vivo changes in the intradiscal pressure, body height, or forces and moments transmitted via instrumented vertebral implants. In parallel, computational models have been employed to estimate muscle forces and spinal loads under various static and dynamic conditions. Noteworthy is the increasing growth in latter computational investigations. This paper aims to review, compare and critically evaluate the existing literature on in vivo measurements and computational model studies of lumbar spinal loads to lay the foundation for future biomechanical studies. Towards this goal, the paper reviews in separate sections models dealing with static postures (standing, sitting, lying) as well as slow and fast dynamic activities (lifting, sudden perturbations and vibrations). The findings are helpful in many areas such as work place safety design and ergonomics, injury prevention, performance enhancement, implant design and rehabilitation management.