Acute exercise as active inference in chronic musculoskeletal pain, effects on gait kinematics and muscular activity in patients and healthy participants: a study protocol for a randomised controlled laboratory trial

INTRODUCTION

Chronic musculoskeletal pain is a highly prevalent, complex and distressing condition that may negatively affect all domains of life. In view of an active inference framework, and resting on the concept of allostasis, human movement per se becomes a prerequisite for health and well-being while chronic pain becomes a sign of a system unable to attenuate an allostatic load. Previous studies on different subgroups of chronic pain conditions have demonstrated alterations in gait kinematics and muscle activity, indicating shared disturbances in the motor system from long-term allostatic load. We hypothesise that such alterations exist in heterogenous populations with chronic musculoskeletal pain, and that exposure to acute and controlled exercise may attenuate these alterations. Therefore, the main aim of this study is to investigate the acute effects of exercise on gait kinematics and activity of the back and neck muscles during diverse walking conditions in patients with chronic musculoskeletal pain compared with a reference sample consisting of healthy participants.

METHODS AND ANALYSIS

This two-sample two-armed parallel randomised controlled laboratory trial will include 40 participants with chronic musculoskeletal pain (>3 months) and 40 healthy participants. Participants will be randomly allocated to either 30 min of aerobic exercise or rest. Primary outcomes are gait kinematics (walking speed, step frequency, stride length, lumbar rotation, gait stability) and muscular activity (spatial and temporal) of the back and neck during diverse walking conditions. Secondary outcomes are variability of gait kinematics and muscle activity and subjective pain ratings assessed regularly during the trial.

ETHICS AND DISSEMINATION

The study has been approved by the Regional Ethics Review Board in Uppsala, Sweden (#2018/307). Findings will be disseminated via conference presentations, publications in peer-reviewed journals and engagement with patient support groups and clinicians.

TRIAL REGISTRATION NUMBER

NCT03882333.

Evaluation of content validity and feasibility of the eVISualisation of physical activity and pain (eVIS) intervention for patients with chronic pain participating in interdisciplinary pain rehabilitation programs

BACKGROUND

Chronic pain negatively influences most aspects of life, including aerobic capacity and physical function. The "eVISualisation of physical activity and pain" (eVIS) intervention was developed to facilitate individualized physical activity for treatment in interdisciplinary pain rehabilitation programs (IPRPs). The objective of this study was to evaluate the content validity and feasibility of the eVIS intervention prior to an effectiveness trial.

METHODS

In order to determine pre-clinical content validity, experts (n = 10) (patients, caregivers, researchers) participated in three assessment rounds using a Likert-scale survey where relevance, simplicity, and safety were rated, whereafter the intervention was revised. Item-content validity index (I-CVI), average, and overall CVI were used to quantify ratings. To determine content validity and feasibility in the clinical context, experts (n = 8) (patients and physiotherapists) assessed eVIS after a 2-3-week test trial, with the feasibility aspects acceptability, demand, implementation, limited efficacy-testing, and practicality in focus. Additional expert interviews (with physiotherapists, physicians) were conducted on two incomplete areas.

RESULTS

The intervention was iteratively revised and refined throughout the study. After three assessment and revision rounds, the I-CVI ratings for relevance, simplicity, and safety ranged between 0.88 and 1.00 (≥0.78) in most items, giving eVIS "excellent" content validity. In the IPRP context, the intervention emerged as valid and feasible. Additional interviews further contributed to its content validity and clinical feasibility.

CONCLUSIONS

The proposed domains and features of the eVIS intervention are deemed valid in its content and feasible in the IPRP context. The consecutive step-by-step evaluation process enabled careful intervention development with revisions to be made in close collaboration with stakeholders. Findings implicate a robust base ahead of the forthcoming effectiveness trial.

Effectiveness of the eVISualisation of physical activity and pain intervention (eVIS) in Swedish Interdisciplinary Pain Rehabilitation Programmes: study protocol for a registry-based randomised controlled clinical trial

INTRODUCTION

Living with chronic pain often involves negative consequences. Interdisciplinary Pain Rehabilitation Programmes (IPRP) is considered superior to single-treatment measures in patients with chronic pain. Despite this, effects emerge suboptimal and more than 20% of patients deteriorate in patient-reported physical health outcomes after IPRP. A novel e-Health intervention, eVISualisation (eVIS) of physical activity and pain, was systematically developed to facilitate individualisation of physical activity levels. By adding elements of data collection, visualisation and communication of objectively measured physical activity and patient-reported outcomes (pain intensity, interference of pain, pharmaceutical consumption) to existing treatment modalities in IPRP, the IPRP team acquires prerequisites to adapt advice and physical activity prescriptions and to evaluate set activity goals. The overall aim is twofold. First, the aim is to evaluate the feasibility of the subsequent registry-based randomised controlled clinical trial (R-RCT). Second, the aim is to prospectively evaluate the effectiveness of the eVIS-intervention as a supplement to IPRP on our defined primary (physical health) and secondary outcomes.

METHODS AND ANALYSIS

In the R-RCT, recruitment of 400 patients with chronic pain will be performed at 15 IPRP units. A random allocation to either IPRP + eVIS or to control group that will receive IPRP only will be performed. Data from the initial 30 participants completing the study period (6 months) will be included in a pilot study, where key feasibility outcomes (recruitment, randomisation, implementation, treatment integrity, data collection procedure, preliminary outcome measures) will be evaluated. Outcome variables will be extracted from the web application Pain And TRaining ON-line (PATRON) and from six national registries. Multivariate statistics and repeated measure analyses will be performed. Quality-adjusted life years and incremental cost-effectiveness ratio will be calculated for cost-effectiveness evaluation.

ETHICS/DISSEMINATION

The Swedish Ethics Review Board granted approval (Dnr 2021/02109). Results will be disseminated through peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT05009459. Protocol V.1.

The value of interdisciplinary treatment for sickness absence in chronic pain: A nationwide register-based cohort study

BACKGROUND

Interdisciplinary treatment (IDT) is an internationally recommended intervention for chronic pain, despite inconclusive evidence of its effects on sickness absence.

METHODS

With data from 25,613 patients in Swedish specialist healthcare, we compared sickness absence, in the form of both sick leave and disability pensions, over a 5-year period between patients either allocated to an IDT programme or to other/no interventions (controls). To obtain population-average estimates, a Markov multistate model with theory-based inverse probability weights was used to compute both the proportion of patients on sickness absence and the total sickness absence duration.

RESULTS

IDT patients were more likely than controls to receive sickness absence benefits at any given time (baseline: 49% vs. 46%; 5-year follow-up: 36% vs. 35%), and thereby also had a higher total duration, with a mean (95% CI) of 67 (87, 48) more days than controls over the 5-year period. Intriguingly, sick leave was higher in IDT patients (563 [552, 573] vs. 478 [466, 490] days), whereas disability pension was higher in controls (152 [144, 160] vs. 169 [161, 178] days).

CONCLUSION

Although sickness absence decreased over the study period in both IDT patients and controls, we found no support for IDT decreasing sickness absence more than other/no interventions in chronic pain patients.

SIGNIFICANCE

In this large study of chronic pain patients in specialist healthcare, sickness absence is compared over a 5-year period between patients in an interdisciplinary treatment programme and other/no interventions. Sickness absence decreased over the study period in bothgroups; however, there was no support forthat it decreased more with interdisciplinary treatment than alternative interventions.

Feasibility of high dose medical exercise therapy in patients with long-term symptomatic knee osteoarthritis

Purpose: High repetition high dose medical exercise therapy (MET) is a promising treatment for patients with musculoskeletal pain. However, little is known regarding the feasibility of MET in patients with symptomatic knee osteoarthritis (OA). The aim of this study was to investigate the feasibility of MET in patients with symptomatic knee pain with radiographic verified OA.Methods: Patients with symptomatic knee osteoarthritis were recruited to a group-based high repetitive high dose MET intervention for 12 weeks in a primary health care setting. Indicators of feasibility included processes (recruitment, program adherence, and exercise compliance), and scientific feasibility (safety and pain evaluated by using the Visual Analogue Scale (VAS)).Results: Out of 31 individuals with symptomatic knee OA, 29 (93%) were included in this study. A total of 26 patients (90%) completed the intervention and 83% reached an attendance rate of ≥30 treatments. No adverse events were reported, and a majority of the patients reported a pain intensity <30 mm (VAS) throughout the intervention period. The results showed a 70% reduction of median pain intensity between baseline (33 mm, IQR: 39), and post-assessment (10 mm, IQR: 25, P = .003).Conclusion: These findings support an overall positive feasibility of MET for patients with symptomatic knee OA. The results also demonstrated that achieving a high dose of exercises might be challenging for this population. Thus, individual variations in exercise dose may be a confounding factor when evaluating high dose MET in future clinical studies.

The Context Matters: A Retrospective Analysis of Life Stage at Chronic Pain Onset in Relation to Pain Characteristics and Psychosocial Outcomes

BACKGROUND

Developmental life stage at chronic pain onset differs among chronic pain patients. Although pain affects multiple life domains, it is unknown whether the timing of chronic pain onset relates to pain characteristics and psychosocial outcomes. The purpose of this retrospective study was to investigate differences in pain characteristics and psychosocial outcomes in patients at different developmental life stages at chronic pain onset.

METHODS

Cross-sectional baseline data from the Swedish Quality Registry for Pain Rehabilitation (2009 to 2016) were used, selecting the middle-aged patients (45-65 years, n=6225) reporting chronic nonmalignant pain. Patients were categorized into three groups, depending on their developmental life stage at chronic pain onset: early onset (age ≤30 years), intermediate onset (age 31-45 years), and late onset (age ≥46 years). Pain characteristics and psychosocial outcomes were assessed with validated self-reported measures.

RESULTS

One-way MANCOVA indicated differences in number of pain locations and psychosocial outcomes among the groups. Post hoc analysis showed differences in the trends for how groups differed on outcome domains. Overall, patients with earlier chronic pain onset showed significantly poorer psychosocial outcomes and more spreading of pain.

CONCLUSION

Developmental life stage at chronic pain onset is associated with different pain outcomes. Pain onset early in life is linked to worse outcomes in multiple domains, pointing to a need for identifying these patients early.

Musculoskeletal disorders and their associations with health- and work-related factors: a cross-sectional comparison between Swedish air force personnel and army soldiers

BACKGROUND

The high numbers of musculoskeletal disorders (MSD) among soldiers in the Swedish Armed Forces has led to the implementation of an effective prevention program, the musculoskeletal screening protocol (MSP), including questionnaires, physical tests and individual intervention of their MSD. A corresponding MSP for the Swedish Air Force is also needed due to earlier reported high prevalence of MSD. We therefore investigated the prevalence of MSD in Swedish Air Force personnel (AF) and compared this to Swedish Army deployed soldiers (DS). Individual, health- and work-related factors associated with MSD were also investigated.

METHODS

Cross-sectional questionnaire-based study on 166 male AF and 185 DS. AF consisted of fighter pilots, helicopter pilots and rear crew from one Swedish air base.

RESULTS

The one-year and point prevalence, respectively, of MSD were significantly higher for AF compared to DS with regard to both the upper quarter of the body (i.e. neck, shoulder and thoracic regions) (AF = 54.8 and 31.3%, DS = 26.1 and 13.6%, p = 0.01) and the lumbar region (AF = 38.0 and 18.7%, DS = 22.2 and 7.1%, p = 0.00). No significant differences were present between fighter pilots, helicopter pilots and rear crew regarding MSD prevalence. Factors significantly associated with having both upper quarter and lumbar regions MSD were group (i.e. greater odds for AF than DS) and self-reported physical health as less than excellent. Additionally, being older and taller were also factors associated with lumbar region MSD.

DISCUSSION

Despite a generally healthy lifestyle, MSD were commonly reported by AF and DS, with generally higher prevalence in AF who mainly reported MSD in the upper quarter of the body. The results from this study indicate that the MSP can be a meaningful tool to prevent MSD in air force personnel and that questions regarding general health and MSD in specific body regions should be included in screening protocols. The development of the preventive program MSP is therefore recommended for the Swedish Air Force.

Prognostic factors for improved physical and emotional functioning one year after interdisciplinary rehabilitation in patients with chronic pain: Results from a national quality registry in Sweden

OBJECTIVE

To investigate prognostic factors for physical and emotional functioning following interdisciplinary multimodal pain rehabilitation, by targeting patients' baseline characteristics and health measures.

METHODS

A prospective cohort of 2,876 patients from 38 specialist clinics across Sweden, who were completing interdisciplinary multimodal pain rehabilitation programmes, was followed through the Swedish Quality Registry for Pain Rehabilitation, from initial assessment to 12-month follow-up. Using logistic regression, baseline data were regressed to predict improvement in Physical functioning and Emotional functioning, fused by principal component analyses using the 36-item Short Form Health Survey (SF-36) and the Hospital Anxiety and Depression Scale (HADS).

RESULTS

Employment status emerged as having the largest effect sizes in both Physical functioning and Emotional functioning; Working: odds ratio (OR) 2.05 (95% confidence interval (95% CI) 1.64-2.56) and OR 1.59 (95% CI 1.27-1.98), respectively. Strong beliefs in restored health, better initial emotional health, lower levels of pain and pain interference, and younger age all predicted Physical functioning. European origin, higher levels of general activity, and sense of life control all predicted Emotional functioning. Worse initial physical and emotional health predicted the corresponding dependent outcomes.

CONCLUSION

Employment was consistently found to be an important prognostic factor, suggesting the significance of avoiding delay in interdisciplinary multimodal pain rehabilitation. A positive treatment expectancy was of importance. In general, multidimensional measures indicated that better initial status was more favourable; however, inconsistency implies a complex prognostic picture.

The importance of emotional distress, cognitive behavioural factors and pain for life impact at baseline and for outcomes after rehabilitation – a SQRP study of more than 20,000 chronic pain patients

Background and aims

Although literature concerning chronic pain patients indicates that cognitive behavioural variables, specifically acceptance and fear of movement/(re)injury, are related to life impact, the relative roles of these factors in relation to pain characteristics (e.g. intensity and spreading) and emotional distress are unclear. Moreover, how these variables affect rehabilitation outcomes in different subgroups is insufficiently understood. This study has two aims: (1) to investigate how pain, cognitive behavioural, and emotional distress variables intercorrelate and whether these variables can regress aspects of life impact and (2) to analyse whether these variables can be used to identify clinically meaningful subgroups at baseline and which subgroups benefit most from multimodal rehabilitation programs (MMRP) immediately after and at 12-month follow-up.

Methods

Pain aspects, background variables, psychological distress, cognitive behavioural variables, and two life impact variables were obtained from the Swedish Quality Registry for Pain Rehabilitation (SQRP) for chronic pain patients. These data were analysed mainly using advanced multivariate methods.

Results

The study includes 22,406 chronic pain patients. Many variables, including acceptance variables, showed important contributions to the variation in clinical presentations and in life impacts. Based on the statistically important variables considering the clinical presentation, three clusters/subgroups of patients were identified at baseline; from the worst clinical situation to the relatively good situation. These clusters showed significant differences in outcomes after participating in MMRP; the subgroup with the worst situation at baseline showed the most significant improvements.

Conclusions

Pain intensity/severity, emotional distress, acceptance, and life impacts were important for the clinical presentation and were used to identify three clusters with marked differences at baseline (i.e. before MMRP). Life impacts showed complex relationships with acceptance, pain intensity/severity, and emotional distress. The most significant improvements after MMRP were seen in the subgroup with the lowest level of functioning before treatment, indicating that patients with complex problems should be offered MMRP.

Implications

This study emphasizes the need to adopt a biopsychosocial perspective when assessing patients with chronic pain. Patients with chronic pain referred to specialist clinics are not homogenous in their clinical presentation. Instead we identified three distinct subgroups of patients. The outcomes of MMRP appears to be related to the clinical presentation. Thus, patients with the most severe clinical presentation show the most prominent improvements. However, even though this group of patients improve they still after MMRP show a complex situation and there is thus a need for optimizing the content of MMRP for these patients. The subgroup of patients with a relatively good situation with respect to pain, psychological distress, coping and life impact only showed minor improvements after MMRP. Hence, there is a need to develop other complex interventions for them.

A longitudinal observational study of back pain incidence, risk factors and occupational physical activity in Swedish marine trainees

OBJECTIVES

To evaluate the occurrence of low back pain (LBP) and LBP that limits work ability, to identify their potential early risks and to quantify occupational physical activity in Swedish Armed Forces (SwAF) marines during their basic 4 month marine training course.

DESIGN

Prospective observational cohort study with weekly follow-ups.

PARTICIPANTS

Fifty-three SwAF marines entering the training course.

OUTCOMES

Incident of LBP and its related effect on work-ability and associated early risks. Occupational physical activity, as monitored using accelerometers and self-reports.

RESULTS

During the training course, 68% of the marines experienced at least one episode of LBP. This yielded a LBP and LBP limiting work ability incidence rate of 13.5 (95% CI 10.4 to 17.8) and 6.3 (95% CI 4.2 to 10.0) episodes per 1000 person-days, respectively. Previous back pain and shorter body height (≤1.80 m) emerged as independent risks for LBP (HR 2.5, 95% CI 1.4 to 4.3; HR 2.0, 95% CI 1.2 to 3.3, respectively), as well as for LBP that limited work ability (HR 3.6, 95% CI 1.4 to 8.9; HR 4.5, 95% CI 2.0 to 10.0, respectively). Furthermore, managing fewer than four pull-ups emerged as a risk for LBP (HR 1.9, 95% CI 1.2 to 3.0), while physical training of fewer than three sessions per week emerged as a risk for LBP that limited work ability (HR 3.0, 95% CI 1.2 to 7.4). More than 80% of the work time measured was spent performing low levels of ambulation, however, combat equipment (≥17.5 kg) was carried for more than half of the work time.

CONCLUSIONS

Incidents of LBP are common in SwAF marines' early careers. The link between LBP and previous pain as well as low levels of exercise highlights the need for preventive actions early on in a marine's career. The role of body height on LBP needs further investigation, including its relationship with body-worn equipment, before it can effectively contribute to LBP prevention.

Who benefits from multimodal rehabilitation - an exploration of pain, psychological distress, and life impacts in over 35,000 chronic pain patients identified in the Swedish Quality Registry for Pain Rehabilitation

Background

Chronic pain patients frequently suffer from psychological symptoms. There is no consensus concerning the prevalence of severe anxiety and depressive symptoms and the strength of the associations between pain intensity and psychological distress. Although an important aspect of the clinical picture is understanding how the pain condition impacts life, little is known about the relative importance of pain and psychological symptoms for individual’s life impact. The aims of this study were to identify subgroups of pain patients; to analyze if pain, psychological distress, and life impact variables influence subgrouping; and to investigate how patients in the subgroups benefit from treatments.

Methods

Background variables, pain aspects (intensity/severity and spreading), psychological distress (depressive and anxiety symptoms), and two life impact variables (pain interference and perceived life control) were obtained from the Swedish Quality Registry for Pain Rehabilitation for chronic pain patients and analyzed mainly using advanced multivariate methods.

Results

Based on >35,000 patients, 35%–40% had severe anxiety or depressive symptoms. Severe psychological distress was associated with being born outside Europe (21%–24% vs 6%–8% in the category without psychological distress) and low education level (20.7%–20.8% vs 26%–27% in the category without psychological distress). Dose relationships existed between the two psychological distress variables and pain aspects, but the explained variances were generally low. Pain intensity/severity and the two psychological distress variables were significantly associated (R²=0.40–0.48; P>0.001) with the two life impact variables (pain interference and life control). Two subgroups of patients were identified at baseline (subgroup 1: n=15,901–16,119; subgroup 2: n=20,690–20,981) and the subgroup with the worst situation regarding all variables participated less in an MMRP (51% vs 58%, P<0.001) but showed the largest improvements in outcomes.

Conclusion

The results emphasize the need to assess both pain and psychological distress and not take for granted that pain involves high psychological stress in the individual case. Not all patients benefit from MMRP. A better matching between common clinical pictures and the content of MMRPs may help improve results. We only partly found support for treatment resistance in patients with psychological distress burden.

Prevalence and potential risk factors of flight-related neck, shoulder and low back pain among helicopter pilots and crewmembers: a questionnaire-based study

BACKGROUND

Flight-related neck, shoulder and low back pain are the most common musculoskeletal disorders among helicopter pilots and their crewmembers, thus becoming a growing concern. Information on the combined prevalence of these types of pain and related risks are scarce. The aim of this study was therefore to estimate pain prevalence and to evaluate potential risk factors for neck pain among helicopter pilots and crewmembers within the armed forces, the airborne police and airborne rescue organizations in Austria.

METHODS

Among a cohort of 104 helicopter pilots and 117 crewmembers (69.8% compliance), demographics, flying experience, use of Night Vision Goggles (NVG), helicopter type flown, prevalence and intensity of musculoskeletal symptoms (pain was defined as any reported pain experience, ache or discomfort) were collected by an online-based questionnaire.

RESULTS

For helicopter pilots the 12-month prevalence of neck pain was 67.3%, followed by low back (48.1%) and shoulder pain (43.3%). Among crewmembers, the 12-month pain prevalence were 45.3, 36.8 and 30.8% among the neck, lower back and shoulder, respectively. During this period, 41.8% of these helicopter pilots had experienced 8-30 pain days in the areas of neck (45.7%), shoulder (37.8%) and lower back (42.0%) whereas 47.8% of crewmembers self-reported 1-7 days of neck (54.7%), low back (44.2%) and shoulder (44.4%) pain in the previous year. The 3-month prevalence of neck pain was 64.4% followed by low back (42.3%) and shoulder pain (38.5%) for helicopter pilots. Among crewmembers, 41.9% suffered from neck, 29.9% from low back and 29.1% from shoulder pain the previous 3 months. Multivariate regression analysis revealed NVG use (OR 1.9, 95% CI, 1.06-3.50, p = 0.032), shoulder pain (OR 4.9, 95% CI, 2.48-9.55, p < 0.001) and low back pain (OR 2.3, 95% CI, 1.21-4.31, p = 0.011) to be significantly associated with neck pain.

CONCLUSIONS

The 12- and 3-month prevalence of neck, shoulder and low back is considerably high among both, helicopter pilots and crewmembers confirming the existence of this growing concern. The use of NVG devices, shoulder and low back pain in the previous 12 months represent independent risk factors for neck pain. These findings highlight the need for longitudinal studies.

Inter-rater and test-retest reliability of movement control tests for the neck, shoulder, thoracic, lumbar, and hip regions in military personnel

Strategies are needed to mitigate the high rates and related risks of musculoskeletal complaints and injuries (MSCI) in the military aviator community. Previous work on Swedish Armed Forces (SwAF) soldiers have shown that proper screening methods have been successful in reducing early discharge from military training. Research has pointed at the importance of optimal spinal movement control in military aviators. The aim of this work was to investigate the inter-rater and test-retest reliability of a battery of clinical tests for evaluating movement control in the neck, shoulders, thoracic, lumbar, and hip regions in a population of SwAF military personnel. Inter-rater and test-retest reliability of 15 movement control tests were assessed by crude and prevalence-adjusted kappa coefficient. The study included 37 (inter-rater) and 45 (test-retest) SwAF personnel and was performed with two physiotherapists simultaneously observing and rating the movements on the first occasion and repeated with one physiotherapist on the second occasion. For inter-rater reliability, the kappa coefficient ranged from .19 to .95. Seven tests showed substantial to almost perfect agreement (kappa > .60). With the adjusted kappa, three more tests reached the level of substantial agreement. The corresponding values for test-retest reliability ranged from .26 to .65. Substantial agreement was attained for two tests, three with adjusted kappa. The following tests can reliably be used when screening for biomechanically less advantageous movement patters in military aviators: Shoulder flexion, and rotation, Neck flexion in sitting and supine, Neck extension and rotation in sitting, Pelvic tilt, Forward lean and Single and Double knee extension tests. Grading criteria for tests in supine and quadruped positions need to be further elaborated.

Movement control tests for the lumbopelvic complex. Are these tests reliable and valid?

This study evaluated inter- and intra-observer reliability and discriminative validity of three movement control tests: 1) standing knee-lift test; 2) static lunge test; and 3) dynamic lunge test. Thirty-eight subjects, 21 with low-back pain and 17 healthy, were video-recorded while performing the tests. Four physical therapists scored the tests according to a standardized protocol and calculated a composite score for each test based on the number of incorrect test components. Inter-observer reliability for the composite scores ranged between 0.68 and 0.80 (ICC 2,k) and intra-observer reliability between 0.54 and0.82 (ICC 2,1). The separate test components ranged between 0.32 and 0.91 (κ_free) for inter-observer reliability and 0.42 and1.00 for intra-observer reliability. Test components showing the highest values were: back extension; arm lowering; and shoulders moving backwards. Components hip hitch, trunk lateral flexion, knee not lifted straight up and hips moving backwards did not reach accepted thresholds. Discriminative validity ranged between 0.47 and 0.56 (AUC). As our results showed an overall good agreement for the composite, scores and for the majority of the included test components the tests can be considered reliable enough. As the tests' discriminative ability was close to "none", they should, however, not be used for diagnostic purposes but should be further evaluated toward predicted validity.

Neck Muscle EMG-Force Relationship and Its Reliability During Isometric Contractions

BACKGROUND

Susceptible to injury, the neck is subject to scientific investigations, frequently aiming to elucidate possible injury mechanisms via surface electromyography (EMG) by indirectly estimating cervical loads. Accurate estimation requires that the EMG-force relationship is known and that its measurement error is quantified. Hence, this study examined the relationship between EMG and isometric force amplitude of the anterior neck (AN), the upper posterior neck (UPN), and the lower posterior neck (LPN) and then assessed the relationships' test-retest reliability across force-percentiles within and between days.

METHODS

EMG and force data were sampled from 18 participants conducting randomly ordered muscle contractions at 5-90% of maximal voluntary force during three trials over 2 days. EMG-force relationships were modeled with general linear mixed-effects regression. Overall fitted lines' between-trial discrepancies were evaluated. Finally, the reliability of participants' fitted regression lines was quantified by an intraclass correlation coefficient (ICC) and the standard error of measurement (SEM).

RESULTS

A rectilinear model had the best fit for AN while positively oriented quadratic models had the best fit for UPN and LPN, with mean adjusted conditional coefficients of determination and root mean square errors of 0.97-0.98 and 4-5%, respectively. Overall EMG-force relationships displayed a maximum 6% between-trial discrepancy and over 20% of maximal force, and mean ICC was above 0.79 within day and 0.27-0.61 between days across areas. Corresponding SEM was below 12% both within and between days across areas, excluding UPN between days, for which SEM was higher.

CONCLUSIONS

EMG-force relationships were elucidated for three neck areas, and provided models allow inferences to be drawn from EMG to force on a group level. Reliability of EMG-force relationship models was higher within than between days, but typically acceptable for all but the lowest contraction intensities, and enables adjustment for measurement imprecision in future studies.

Does a dynamic chair increase office workers' movements? - Results from a combined laboratory and field study

PURPOSE

Dynamic chairs have the potential to facilitate movements that could counteract health problems associated with sedentary office work. This study aimed to evaluate whether a dynamic chair can increase movements during desk-based office work.

METHODS

Fifteen healthy subjects performed desk-based office work using a dynamic office chair and compared to three other conditions in a movement laboratory. In a field study, the dynamic office chair was studied during three working days using accelerometry.

RESULTS

Equivocal results showed that the dynamic chair increased upper body and chair movements as compared to the conventional chair, but lesser movements were found compared to standing. No differences were found between the conditions in the field study.

CONCLUSIONS

A dynamic chair may facilitate movements in static desk-based office tasks, but the results were not consistent for all outcome measures. Validation of measuring protocols for assessing movements during desk-based office work is warranted.

Neck Muscle Strain in Air Force Pilots Wearing Night Vision Goggles

INTRODUCTION

Flight-induced neck pain is common in high performance jet pilots, with incidents frequently attributed to high G_z flight maneuvers. The additional load of helmet-mounted night vision goggles (NVG) is believed to increase the risk, possibly from neck muscle strain in counteracting muscles. Hence, the aim was to investigate the effect of NVG on neck muscle strain as well as on the activity level distribution through a simulated flight session in air force pilots.

METHODS

In this post hoc randomized crossover trial, four senior air force pilots each completed two identical 1.5-h dynamic flight simulations in a human centrifuge: one with a standard helmet and NVG, and one with a standard helmet only. Simulations included repeated exposure to 3-7 G_z, during which neck muscle activity was recorded bilaterally from the anterior neck, the upper and lower posterior neck, and the upper shoulders. The number of muscle activities surpassing 50% of maximum voluntary electrical activity (MVE) and total time of activity at each MVE percentile were compared between NVG and control flights.

RESULTS

There was no overall effect in number of neck strain activities between NVG and control flights; however, significantly more activities emerged in the anterior neck. In addition, MVE percentile data showed a tendency of higher activity in the lower posterior neck during NVG flights.

CONCLUSIONS

The results showed that the additional load of helmet-mounted NVG increases neck muscle strain in anterior stabilizing muscles, indicating that the inertia of head-worn NVG elevates the risk of flight-related neck pain. Pousette MW, Lo Martire R, Linder J, Kristoffersson M, Äng BO. Neck muscle strain in air force pilots wearing night vision goggles. Aerosp Med Hum Perform. 2016; 87(11):928-932.

Decelerations of Parachute Opening Shock in Skydivers

INTRODUCTION

High prevalence of neck pain among skydivers is related to parachute opening shock (POS) exposure, but few investigations of POS deceleration have been made. Existing data incorporate equipment movements, limiting its representability of skydiver deceleration. This study aims to describe POS decelerations and compare human- with equipment-attached data.

METHODS

Wearing two triaxial accelerometers placed on the skydiver (neck-sensor) and equipment (rig-sensor), 20 participants made 2 skydives each. Due to technical issues, data from 35 skydives made by 19 participants were collected. Missing data were replaced using data substitution techniques. Acceleration axes were defined as posterior to anterior (+ax), lateral right (+ay), and caudal to cranial (+az). Deceleration magnitude [amax (G)] and jerks (G · s-1) during POS were analyzed.

RESULTS

Two distinct phases related to skydiver positioning and acceleration direction were observed: 1) the x-phase (characterized by -ax, rotating the skydiver); and 2) the z-phase (characterized by +az, skydiver vertically oriented). Compared to the rig-sensor, the neck-sensor yielded lower amax (3.16 G vs. 6.96 G) and jerk (56.3 G · s-1 vs. 149.0 G · s-1) during the x-phase, and lower jerk (27.7 G · s-1 vs. 54.5 G · s-1) during the z-phase.

DISCUSSION

The identified phases during POS should be considered in future neck pain preventive strategies. Accelerometer data differed, suggesting human-placed accelerometry to be more valid for measuring human acceleration.Gladh K, Lo Martire R, Äng BO, Lindholm P, Nilsson J, Westman A. Decelerations of parachute opening shock in skydivers. Aerosp Med Hum Perform. 2017; 88(2):121-127.

Free Fall Acrobatics to Reduce Neck Loads During Parachute Opening Shock: Evaluation of an Intervention (ACROPOSE)

Introduction

Neck pain is a widespread health problem in the skydiver athlete population, epidemiologically linked to repeated exposure to parachute opening shock (POS). During POS, a parachutist is subjected to considerable deceleration forces. This study aims to evaluate the use of preventive free fall acrobatics to reduce the biomechanical load on the neck of parachutists during parachute opening.

Methods and analysis

Interventional study with a cross-over, within-subject, repeated measures design. Two consecutive skydives are made on the same day with random ordering of either an ‘intervention jump’ or a ‘control jump’. The intervention jump contains two acrobatic elements prior to main parachute extraction: Reducing parachute deployment airspeed and positioning the human body head high. The primary outcome measure is the magnitude of initial Gx deceleration. All other directions of accelerations will be measured as well, as will magnitudes of multidirectional jerks (rates of changes of accelerations) and lower neck torque. Repeated within group measures analysis of variance will be used to quantify effects, and regression used to test for relationships between the elements of the intervention.

Ethics and dissemination

Regional Medical Research Ethics Committee of Stockholm approval 2015/1189-31. The intervention protocol has been systematically prevalidated with an emphasis on participant safety. The study will be conducted in compliance with the Declaration of Helsinki, and its results published in peer-reviewed journals, preferably Open Access, to maximise access for the target athlete population.

Trial registration number

NCT02625896. Pre-results.

Risk factors for back pain in marines; a prospective cohort study

Background

It is recognised that back pain (BP) is a debilitating medical problem in the soldier community, which limits operational readiness as well as work ability. As such, identification of risk factors is a necessity for effective preventive actions, but also regarded as important from a safety perspective. The aim of this prospective cohort study was therefore to identify risk factors for back pain and BP limiting work ability in active duty marines within a 6 and 12-month period.

Methods

Demographic characteristics, health-related factors and occupational exposure information, as gathered from questionnaires, as well as clinical test of movement control among 137 Swedish marines were regressed with multivariable logistic regressions, and strength of associations was presented as odds ratio (OR) with 95 % confidence intervals (CI). BP within 6 and 12 months were used as primary outcomes, whereas BP limiting work ability within 6 and 12 months served as secondary outcomes.

Results

Previous BP and tall body height (≥1.86 m) emerged as risk factors for back pain within 6 months (OR 2.99, 95 % CI 1.22–7.30; OR 2.81, 95 % CI 1.16– 6.84, respectively), and 12 months (OR 6.75, 95 % CI 2.30–19.80; 2.75, 95 % CI 1.21–6.29, respectively). Previous BP was also identified as risk factor for BP limiting work ability within 12 months (OR 6.64, 95 % CI 1.78–24.78), and tall body height emerged as a risk within both six (OR 4.30, 95 % CI 1.31–14.13) and 12 months (OR 4.55, 95 % CI 1.53–13.57) from baseline.

Conclusions

Marines with a history of BP are at risk of further BP episodes, which, thus, emphasise the importance of early BP preventive actions. Tall body height also emerged as an important risk which may reflect that personal equipment and work tasks are not adapted for the tallest marines. While this should be considered when introducing new work equipment, further studies are warranted to clarify the underlying mechanism of this association.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-016-1172-y) contains supplementary material, which is available to authorized users.

Development and validation of a web-based questionnaire for surveying the health and working conditions of high-performance marine craft populations

BACKGROUND

High-performance marine craft crews are susceptible to various adverse health conditions caused by multiple interactive factors. However, there are limited epidemiological data available for assessment of working conditions at sea. Although questionnaire surveys are widely used for identifying exposures, outcomes and associated risks with high accuracy levels, until now, no validated epidemiological tool exists for surveying occupational health and performance in these populations.

AIM

To develop and validate a web-based questionnaire for epidemiological assessment of occupational and individual risk exposure pertinent to the musculoskeletal health conditions and performance in high-performance marine craft populations.

METHOD

A questionnaire for investigating the association between work-related exposure, performance and health was initially developed by a consensus panel under four subdomains, viz. demography, lifestyle, work exposure and health and systematically validated by expert raters for content relevance and simplicity in three consecutive stages, each iteratively followed by a consensus panel revision. The item content validity index (I-CVI) was determined as the proportion of experts giving a rating of 3 or 4. The scale content validity index (S-CVI/Ave) was computed by averaging the I-CVIs for the assessment of the questionnaire as a tool. Finally, the questionnaire was pilot tested.

RESULTS

The S-CVI/Ave increased from 0.89 to 0.96 for relevance and from 0.76 to 0.94 for simplicity, resulting in 36 items in the final questionnaire. The pilot test confirmed the feasibility of the questionnaire.

CONCLUSIONS

The present study shows that the web-based questionnaire fulfils previously published validity acceptance criteria and is therefore considered valid and feasible for the empirical surveying of epidemiological aspects among high-performance marine craft crews and similar populations.

The abdominal drawing-in manoeuvre for detecting activity in the deep abdominal muscles: is this clinical tool reliable and valid?

OBJECTIVE

The abdominal drawing-in manoeuvre (ADIM) is a common clinical tool for manually assessing whether a preferential activation of the deep abdominal muscles in patients with low back pain (LBP) is 'correct' or not. The validity and reliability of manual assessment of the ADIM are, however, as yet unknown. This study evaluated the concurrent and discriminative validity and reliability of the manually assessed ADIM.

DESIGN

Single-blinded cross-sectional study.

SETTINGS

General population in Stockholm County, Sweden.

PARTICIPANTS

The study sample comprised 38 participants seeking care for LBP, and 15 healthy subjects.

MEASURES

The manual ADIM was assessed as correct or not following a standard procedure. Ultrasound imaging (USI) was used as the concurrent reference (gold standard) for the manually assessed ADIM by calculating a ratio of the change in muscle thickness between the resting and the contracted states: the correlation between manual test and USI was calculated. Discriminative validity was analysed by calculating sensitivity and specificity. A sample of 24 participants was analysed with κ coefficients for interobserver reliability between two raters.

RESULTS

The concurrent validity between the manual ADIM and the ADIM-USI ratios showed poor correlations (r=0.13-0.40). The discriminative validity of the manually assessed ADIM to predict LBP showed a sensitivity/specificity of 0.30/0.73, while the ADIM-USI ratio to predict LBP showed 0.19/0.87. The interobserver reliability for the manually assessed ADIM revealed substantial agreement: K=0.71, CI (95%) 0.41 to 1.00.

CONCLUSIONS

Although the interobserver reliability of the manually assessed ADIM was high, the concurrent and discriminative validity were both low for examining the preferential activity of the deep abdominal muscles. Neither the manually assessed ADIM nor the ultrasound testing discriminated between participants with LBP and healthy subjects regarding preferential activity of the transversus muscle as this ability/inability was also present in healthy subjects.

Validation of a free fall acrobatics intervention protocol to reduce neck loads during parachute opening shock

Background

Elevated neck pain prevalence among skydivers is associated with exposure to repeated parachute opening shock (POS). A study is planned to evaluate a preventive free fall acrobatics intervention, but prior assessment of the protocol is necessary given the complex and safety-critical study environment.

Aim

To validate an intervention protocol to reduce POS neck loads.

Methods

A protocol was developed based on observational data and theoretical calculations. Six experts rated each component of the protocol on a four-point Likert scale, regarding relevance, simplicity/feasibility and safety, and responded to open-ended questions. Two iterations were made, each followed by consensus panel protocol revisions. The content validity index (CVI) was used to quantify ratings. A measure of universal agreement (CVI/UA) was computed as the proportion of components that achieved a rating ≥3 by all raters. For safety, a high-sensitivity CVI/UA was computed with a rating of no <4 (highest score) as acceptable.

Results

CVI/UA for relevance increased from 0.80 in the first assessment to 1.00 in the second; for simplicity from 0.50 to 0.63; and for safety from 0.70 to 1.00. High-sensitivity CVI/UA for safety increased from 0.10 to 0.75. Responses to open-ended questions included safety concerns for free fall stability, altitude awareness and concerns over comprehensibility.

Conclusions

The proposed protocol has been improved in assessed relevance, simplicity and safety, and is considered validated for the start of the empirical trial. To what degree complex interventions should be preceded by open prevalidation is discussed.

Musculoskeletal pain and limitations in work ability in Swedish marines: a cross-sectional survey of prevalence and associated factors

OBJECTIVES

To estimate the prevalence of self-rated musculoskeletal pain and pain limiting work ability in Swedish Armed Forces (SAF) marines, and to study factors potentially associated with pain limiting work ability for the most prevalent pain regions reported.

DESIGN

Population-based, cross-sectional survey.

PARTICIPANTS

There were 272 SAF marines from the main marine battalion in Sweden included in the study.

OUTCOMES

Self-assessed musculoskeletal pain and pain limiting the marines' work ability within a 6-month period, as obtained from structured questionnaires. The association of individual, health and work-related factors with musculoskeletal pain limiting work ability was systematically regressed with multiple logistic models, estimating OR and 95% CI.

RESULTS

Musculoskeletal pain and pain limiting work ability were most common in the back, at 46% and 20%, and lower extremities at 51% and 29%, respectively. Physical training ≤1 day/week (OR 5.3, 95% CI 1.7 to 16.8); body height ≤1.80 m (OR 5.0, 95% CI 1.6 to 15.1) and ≥1.86 m (OR 4.4, 95% CI 1.4 to 14.1); computer work 1/4 of the working day (OR 3.2, 95% CI 1.0 to 10.0) and ≥1/2 (OR 3.3, 95% CI 1.1 to 10.1) of the working day were independently associated with back pain limiting work ability. None of the studied variables emerged significantly associated with such pain for the lower extremities.

CONCLUSIONS

Our findings show that musculoskeletal pain and resultant limitations in work ability are common in SAF marines. Low frequency of physical training emerged independently associated with back pain limiting work ability. This suggests that marines performing physical training 1 day per week or less are suitable candidates for further medical evaluation and secondary preventive actions. While also associated, body height and computer work need further exploration as underlying mechanisms for back pain limiting work ability. Further prospective studies are necessary to clarify the direction of causality.

Neck muscle activity in skydivers during parachute opening shock

This observational study investigated skydiver neck muscle activity during parachute opening shock (POS), as epidemiological data recently suggested neck pain in skydivers to be related to POS. Twenty experienced skydivers performed two terminal velocity skydives each. Surface electromyography quantified muscle activity bilaterally from the anterior neck, the upper and lower posterior neck, and the upper shoulders; and two triaxial accelerometers sampled deceleration. Muscle activity was normalized as the percentage of reference maximum voluntary electrical activity (% MVE); and temporal muscle activity onset was related to POS onset. Our results showed that neck muscle activity during POS reached mean magnitudes of 53-104% MVE, often exceeding reference activity in the lower posterior neck and upper shoulders. All investigated muscle areas' mean temporal onsets occurred <50 ms after POS onset (9-34 ms latencies), which is consistent with anticipatory motor control. The high muscle activity observed supports that the neck is under substantial strain during POS, while temporal muscle activation suggests anticipatory motor control to be a strategy used by skydivers to protect the cervical spine from POS. This study's findings contribute to understanding the high rates of POS-related neck pain, and further support the need for evaluation of neck pain preventative strategies.

Is active sitting as active as we think?

The aim of this study was to compare the biomechanical characteristics of sitting on a stool without a backrest (so as to encourage active sitting), sitting on a conventional office chair and standing in healthy participants. Thirteen healthy participants performed a keyboard-writing task during four (stable and unstable) sitting conditions and standing. Body segment positions and posture, postural sway and muscle activity of neck and trunk muscles were assessed with a motion capture system, a force plate and surface electromyography. The results showed that body segment positions, postural sway and trunk muscle activity were relatively similar for the stools without backrests compared with standing. All sitting conditions showed lower vertical upper body alignment, less anterior pelvic tilt and larger hip angles, compared with standing (p = 0.000). Unexpectedly, the muscle activity levels and total postural sway, sway velocity and sway in M/L and A/P directions were lower (p = 0.000) for the conditions that encouraged active sitting and standing, compared with the conventional office chair conditions.

PRACTITIONER SUMMARY

Thirteen healthy participants performed a keyboard-writing task during different sitting conditions and standing and were analysed regarding posture, postural sway and trunk muscle activity. Surprisingly, less postural sway and less muscle activity were observed during the conditions that encourage active sitting, compared with sitting on a conventional office chair.

Inter- and intra-observer reliability of clinical movement-control tests for marines

BACKGROUND

Musculoskeletal disorders particularly in the back and lower extremities are common among marines. Here, movement-control tests are considered clinically useful for screening and follow-up evaluation. However, few studies have addressed the reliability of clinical tests, and no such published data exists for marines. The present aim was therefore to determine the inter- and intra-observer reliability of clinically convenient tests emphasizing movement control of the back and hip among marines. A secondary aim was to investigate the sensitivity and specificity of these clinical tests for discriminating musculoskeletal pain disorders in this group of military personnel.

METHODS

This inter- and intra-observer reliability study used a test-retest approach with six standardized clinical tests focusing on movement control for back and hip. Thirty-three marines (age 28.7 yrs, SD 5.9) on active duty volunteered and were recruited. They followed an in-vivo observation test procedure that covered both low- and high-load (threshold) tasks relevant for marines on operational duty. Two independent observers simultaneously rated performance as "correct" or "incorrect" following a standardized assessment protocol. Re-testing followed 7-10 days thereafter. Reliability was analysed using kappa (κ) coefficients, while discriminative power of the best-fitting tests for back- and lower-extremity pain was assessed using a multiple-variable regression model.

RESULTS

Inter-observer reliability for the six tests was moderate to almost perfect with κ-coefficients ranging between 0.56-0.95. Three tests reached almost perfect inter-observer reliability with mean κ-coefficients > 0.81. However, intra-observer reliability was fair-to-moderate with mean κ-coefficients between 0.22-0.58. Three tests achieved moderate intra-observer reliability with κ-coefficients > 0.41. Combinations of one low- and one high-threshold test best discriminated prior back pain, but results were inconsistent for lower-extremity pain.

CONCLUSIONS

Our results suggest that clinical tests of movement control of back and hip are reliable for use in screening protocols using several observers with marines. However, test-retest reproducibility was less accurate, which should be considered in follow-up evaluations. The results also indicate that combinations of low- and high-threshold tests have discriminative validity for prior back pain, but were inconclusive for lower-extremity pain.