The causality field (extrinsic and intrinsic factors) in industrial subacute low back pain patients

Electrically evoked force loss of the knee extensors is equivalent for young and old females and males

Data are scant on sex-related differences for electrically evoked contractions, which assess intrinsic contractile properties while limiting spinal and supraspinal adaptations to mitigate fatigue. Furthermore, the few studies that exist use stimulus frequencies considerably higher than the natural motor unit discharge rate for the target force. The purpose of this study was to compare force loss to electrically evoked contractions at a physiological stimulus frequency among young females (n = 12), young males (n = 12), old females (n = 11), and old males (n = 11). The quadriceps of the dominant leg were fatigued by 3 min of intermittent transcutaneous muscle belly stimulation (15 Hz stimulus train to initially evoke 25% of maximal voluntary force). Impairment of tetanic contractile impulse (area under the curve) did not differ between sexes for young or old adults or between age groups, with a pooled value of 55.2% ± 12.4% control at the end of fatigue. These data contrast with previous findings at 30 Hz, when the quadriceps of females had greater fatigue resistance than males for young and old adults. The present results highlight the impact stimulus frequency has on intrinsic fatigability of muscle; the findings have implications for future fatigue paradigms and treatment approaches when utilizing electrical stimulation for rehabilitation.

Novelty Fatigue was not different between sexes with a stimulation frequency comparable to discharge rates during voluntary contractions. These results highlight that stimulus frequency not only influences fatigue development but also between-group differences.

The effects of hypoxia on muscle deoxygenation and recruitment in the flexor digitorum superficialis during submaximal intermittent handgrip exercise

Background

Decreased oxygenation of muscle may be accentuated during exercise at high altitude. Monitoring the oxygen saturation of muscle (SmO₂) during hand grip exercise using near infrared spectroscopy during acute exposure to hypoxia could provide a model for a test of muscle performance without the competing cardiovascular stresses that occur during a cycle ergometer or treadmill test. The purpose of this study was to examine and compare acute exposure to normobaric hypoxia versus normoxia on deoxygenation and recruitment of the flexor digitorum superficialis (FDS) during submaximal intermittent handgrip exercise (HGE) in healthy adults.

Methods

Twenty subjects (11 M/9 F) performed HGE at 50% of maximum voluntary contraction, with a duty cycle of 2 s:1 s until task failure on two occasions one week apart, randomly assigned to normobaric hypoxia (FiO₂ = 12%) or normoxia (FiO₂ = 21%). Near-infrared spectroscopy monitored SmO₂, oxygenated (O₂Hb), deoxygenated (HHb), and total hemoglobin (tHb) over the FDS. Surface electromyography derived root mean square and mean power frequency of the FDS.

Results

Hypoxic compared to normoxic HGE induced a lower FDS SmO₂ (63.8 ± 2.2 vs. 69.0 ± 1.5, p = 0.001) and both protocols decreased FDS SmO₂ from baseline to task failure. FDS mean power frequency was lower during hypoxic compared to normoxic HGE (64.0 ± 1.4 vs. 68.2 ± 2.0 Hz, p = 0.04) and both decreased mean power frequency from the first contractions to task failure (p = 0.000). Under both hypoxia and normoxia, HHb, tHb and root mean square increased from baseline to task failure whereas O₂Hb decreased and then increased during HGE. Arterial oxygen saturation via pulse oximetry (SpO₂) was lower during hypoxia compared to normoxia conditions (p = 0.000) and heart rate and diastolic blood pressure only demonstrated small increases. Task durations and the tension-time index of HGE did not differ between normoxic and hypoxic trials.

Conclusion

Hypoxic compared to normoxic HGE decreased SmO₂ and induced lower mean power frequency in the FDS, during repetitive hand grip exercise however did not result in differences in task durations or tension-time indices. The fiber type composition of FDS, and high duty cycle and intensity may have contributed greater dependence on anaerobiosis.

Effectiveness of Workplace Interventions in Return-to-Work for Musculoskeletal, Pain-Related and Mental Health Conditions: An Update of the Evidence and Messages for Practitioners

Purpose The objective of this systematic review was to synthesize evidence on the effectiveness of workplace-based return-to-work (RTW) interventions and work disability management (DM) interventions that assist workers with musculoskeletal (MSK) and pain-related conditions and mental health (MH) conditions with RTW. Methods We followed a systematic review process developed by the Institute for Work & Health and an adapted best evidence synthesis that ranked evidence as strong, moderate, limited, or insufficient. Results Seven electronic databases were searched from January 1990 until April 2015, yielding 8898 non-duplicate references. Evidence from 36 medium and high quality studies were synthesized on 12 different intervention categories across three broad domains: health-focused, service coordination, and work modification interventions. There was strong evidence that duration away from work from both MSK or pain-related conditions and MH conditions were significantly reduced by multi-domain interventions encompassing at least two of the three domains. There was moderate evidence that these multi-domain interventions had a positive impact on cost outcomes. There was strong evidence that cognitive behavioural therapy interventions that do not also include workplace modifications or service coordination components are not effective in helping workers with MH conditions in RTW. Evidence for the effectiveness of other single-domain interventions was mixed, with some studies reporting positive effects and others reporting no effects on lost time and work functioning. Conclusions While there is substantial research literature focused on RTW, there are only a small number of quality workplace-based RTW intervention studies that involve workers with MSK or pain-related conditions and MH conditions. We recommend implementing multi-domain interventions (i.e. with healthcare provision, service coordination, and work accommodation components) to help reduce lost time for MSK or pain-related conditions and MH conditions. Practitioners should also consider implementing these programs to help improve work functioning and reduce costs associated with work disability.

The Assessment of Motor Fatigability in Persons With Multiple Sclerosis: A Systematic Review

Background. Persons with multiple sclerosis (PwMS) are often characterized by increased motor fatigability, which is a performance change on an objectively measured criterion after any type of voluntary muscle contractions. This review summarizes the existing literature to determine which protocols and outcome measures are best to detect or study motor fatigability and the underlying mechanisms in MS. Methods. Two electronic databases, PubMed and Web of Science, were searched for relevant articles published until August 2016 with a combination of multiple sclerosis, fatigability, muscle fatigue, and motor fatigue. Results. A total of 48 articles were retained for data extraction. A variety of fatigability protocols were reported; protocols showed differences in type (isometric vs concentric), duration (15 to 180 s), and number of contractions (fixed or until exhaustion). Also, 12 articles reported motor fatigability during functional movements, predominantly assessed by changes in walking speed; 11 studies evaluated the mechanisms underlying motor fatigability, using additional electrical nerve or transcranial magnetic stimulation. Three articles reported psychometrics of the outcomes. Conclusions. The disparity of protocols and outcome measures to study different aspects of motor fatigability in PwMS impedes direct comparison between data. Most protocols use maximal single-joint isometric contractions, with the advantage of high standardization. Because there is no head-to-head comparison of the different protocols and only limited information on psychometric properties of outcomes, there is currently no gold standard to assess motor fatigability. The disability level, disease phenotype, and studied limb may influence the assessment of motor fatigability in PwMS.

[Patients with low back pain. Psychosocial work-related factors and return to work - a literature review]

BACKGROUND

Since the 1990s work-related rehabilitation programs have gained more importance in orthopaedic rehabilitation. Although inception cohort studies of patients with low back pain have indicated the prognostic relevance of psychosocial work-related factors for return to work, these factors and the interaction of these factors with restrictions in functional capacity have been less extensively considered during the rehabilitation process so far.

METHODS

Systematic reviews on the course of low back pain were reviewed concerning the prognostic relevance of psychosocial work-related factors for return to work.

RESULTS

Seven reviews were comparable concerning the outcome analysed (return to work) and the populations considered (acute/subacute). These reviews confirmed that patients with low back pain and low social support from supervisors and colleagues, low decision latitude, high psychosocial work demands and a poor subjective prognosis have a lower chance of returning to work. The prognostic relevance of job satisfaction was contradictory.

CONCLUSION

Rehabilitation should be aimed at supporting and developing strategies for coping with psychosocial work stress.

A biomechanical assessment of isometric handgrip force and fatigue at different anatomical positions

The present work examined the handgrip force at different anatomical positions for both hands. Anthropometrics, handgrip force, and fatigue were obtained from a representative sample of 20 males randomly selected from the German Jordanian University students. The hand dynamometer first was calibrated with respect to the volunteer's maximal grip strength, and he was then asked to squeeze maximally until the grip force decreased to 50% of its maximal due to fatigue; this test was performed for both hands at different anatomical positions with 2 min of rest for recovery of muscle function. The results showed differences in the handgrip force between subjects of the same anatomical positions and for the different anatomical positions, differences in the time for 50% of the force maximal for both right hand and left hand, higher time required to achieve 50% of maximal handgrip force for the nondominant hand, and maximal handgrip force was obtained when arm adduction with 90 degrees forward at the elbow joint. Recommendations for future work are to measure fatigue time at different percentages, 25%, 50%, 60%, and 75% of maximal force and to investigate the factors affecting handgrip force over a larger sample.

Effects of patient – clinician disagreement in occupational low back pain: A pilot study

PURPOSE

To determine (1) patient--physical therapist and patient--physician agreement on clinical management of LBP, (2) patient perception of agreement between physical therapist and physician, (3) association between agreement and outcome (return to work, self-perceived disability).

METHOD

Thirty-five workers compensated for LBP responded to a telephone interview within 1 week of referral to physical therapy. They were asked about agreement with the physical therapist and the physician regarding the clinical management of their LBP and whether they thought the physical therapist was providing the treatment the physician would have thought appropriate. They completed a second interview upon returning to work or after 3 months. They answered questionnaires on self-perceived disability, psychological distress, coping strategies, and job satisfaction at both baseline and follow-up.

RESULTS

Nearly all patients (97.1%) agreed with the physical therapist and all believed the physical therapist was providing the treatment the physician would have thought appropriate. The 10 (28.6%) patients who disagreed with their physician on medical management of their LBP were less satisfied with the medical care (P=0.05), technical quality of the visit (P=0.01), and catastrophized more about their pain (P=0.03) than those who agreed. Disagreement was not associated with greater time off-work or greater self-perceived disability.

CONCLUSION

Patients who disagreed with their physician were less satisfied with their medical management, and catastrophized more about their pain than those who agreed, but disagreement was not associated with chronicity or disability. Studies with larger sample sizes should investigate the role of other factors, such as patient expectations, in the transition to chronicity.

Comparison of risk factors predicting return to work between patients with subacute and chronic non-specific low back pain: systematic review

The objective of the study was to provide an inventory of predictive instruments and their constituting parameters associated with return to work in patients with subacute (2-10 weeks pain duration) and chronic (10-24 weeks pain duration) non-specific low back pain (NSLBP). Data sources included systematic review in Medline, Embase, Cinahl, Central, PEDro, Psyndex, PsychInfo/PsycLit, and Sociofile up to September 2008, in reference lists of systematic reviews on risk factors, and of included studies. For the systematic review, two reviewers independently assessed study eligibility and quality, and extracted data. Disagreements were resolved by consensus. Risk factors were inventorised and grouped into a somatic and psychosocial domain. 23 studies reporting on subacute and 16 studies reporting on chronic patients were included. The studies on subacute patients reported on a total of 56 biomedical factors out of which 35 (63%) were modifiable and 61 psychosocial factors out of which 51 (84%) were modifiable. The corresponding values in studies on chronic patients were 44 biomedical [27 (62%) modifiable] and 61 [40 (66%) modifiable] respectively. Our data suggest that the interdisciplinary approach in patients at risk to develop persistent NSLBP is justified in both, the subacute and chronic disease stages. Psychosocial interventions might be more effective in subacute stages since a higher proportion of modifiable risk factors were identified in that group.

Prediction of sickness absence in patients with chronic low back pain: a systematic review

OBJECTIVES

To provide evidence of predictors for sickness absence in patients with non-specific chronic low back pain (CLBP), distinguishing predictors aimed at the decision to report sick (absence threshold) and decision to return to work (return to work threshold).

METHODS

Medical and psychological databases were searched, as well as citations from relevant reviews. In- and exclusion criteria were applied. Two reviewers assessed the methodological quality of the papers independently.

RESULTS

Many different predictors were studied, and few factors were studied more than once. Consistent evidence was found for own expectations of recovery only as predictor for the decision to return to work. Patients with higher expectations had less sickness absence at the moment of follow-up measurement. As expected, different predictors were found aiming at the absence threshold or the return to work threshold. Furthermore, predictors varied also with the measurement instruments used, timing of follow-up measurements, and definition of outcomes. Until now, too few studies are available to overcome several potential sources of heterogeneity.

CONCLUSIONS

No core set of predictors exists for sickness absence in general. The characteristics of the study including the decision to report sick or to return to work determined the influence of several predictors on sickness absence in patients with CLBP. Further research and use of a core set of measurements and uniform definitions are needed to predict sickness absence and return to work in patients with CLBP.

Outcome determinants of subacute low back pain

STUDY DESIGN

Descriptive prognostic study.

OBJECTIVES

To identify outcome determinants of subacute low back pain.

SUMMARY OF BACKGROUND DATA

The factors predicting recovery from prolonged back pain among working adults are largely unknown.

MATERIALS AND METHODS

One hundred sixty-four employed patients with subacute (duration of pain 4-12 weeks) daily low back pain were recruited from primary health care to a randomized study. Data on potential predictive factors were collected before randomization. In multiple regressions using repeated measures analysis, the treatment received was adjusted when determining the impact of the predictive factors. Dependent outcome variables used were pain, perceived functional disability, generic health-related quality of life, satisfaction with care, days on sick leave, use of health care, and costs of health care consumption measured, at 3-, 6-, and 12-month follow-ups.

RESULTS

Age and intensity of pain at baseline predicted most of the outcomes. The perceived risk of not recovering was a stronger determinant of outcome than gender, education, or self-rated health status (which did not have any predictive value) or body mass index, expectations of treatment effect, satisfaction with work, or the presence of radicular symptoms below the knee (only slight predictive value). The only factors predicting the duration of sick leave were the duration of sick leave at baseline and the type of occupation.

CONCLUSION

Age and intensity of pain are the strongest predictors of outcome. Accumulation of days on sick leave is predicted by the duration of sick leave at entry and the type of work, but not by pain, perceived disability, or satisfaction with work.

Employment-related factors in chronic pain and chronic pain disability

BACKGROUND

Disability is a multifactorial phenomenon. Social scientists suggest that nonclinical factors, including age, education, and job status, correlate with disability.

OBJECTIVE

Do employment-related factors predict chronic pain and/or chronic pain disability?

METHODOLOGY

The literature search identified 15 observational studies to provide the evidence about this question.

RESULTS

Review topics included job satisfaction, type of work, modified work and work autonomy, other employment-related factors, and socioeconomic status. Most subjects in the studies had low back pain. The studies used return to work as an outcome predicting chronic pain disability.

CONCLUSIONS

Lack of modified work and lack of work autonomy predicted chronic pain disability (level 2). There was limited evidence (level 3) that lack of job satisfaction, perception of difficult job conditions and demands, heavy physical demands of the job, private rather than public employment, and lower socioeconomic group predict chronic pain disability. The number of years employed varied as a predictor in different studies (level 4b).