Prolonged computer use, especially if fatigue ensues, is associated with visual and musculoskeletal symptoms. The aim was to determine the time-course of perceived fatigue in the wrist, forearm, shoulder and eyes during a 60-min mouse task (painting rectangles), and whether object size and/or mouse use demands were of influence. Also, we investigated performance (number of rectangles painted), and whether perceived fatigue was paralleled by local muscle fatigue or tissue oxygenation. Ten women performed the task for three conditions (crossover design). At condition 1, rectangles were 45 × 25 mm, square paint cursor size 1.3 × 1.3 mm, and mousepointer movement ratio 1:26. At condition 2, the same cursor size and mousepointer movement ratio was used, but rectangles were smaller. At condition 3, the smaller rectangles were used, but the cursor size was also smaller and mousepointer movement ratio was 1:8. The results showed increased self-reported fatigue over time, with the observed increase greater for the eyes, but no change in physiological responses. Condition 2 resulted in higher performance and increased eye fatigue. Perceived fatigue in the muscles or physiological responses did not differ between conditions. In conclusion, computer work tasks imposing high visual and motor demands, and with high performance, seemed to have an influence on eye fatigue. 

SAMMANFATTNING

Detta pilotprojekt har utförts under våren 2010 på Arlandas terminal 4 av en ergonom (Eva Bergsten) vid Högskolan i Gävle, Centrum för Belastningsskadeforskning (CBF), på uppdrag av Transports yrkes- och arbetsmiljönämnd (TYA). Projektet var en förstudie till det större huvudprojektet "Skadefria flygplanslastare" som TYA under våren sökte och sedermera beviljades pengar för att genomföra.

Huvudprojektets övergripande syfte är att kartlägga och beskriva flygplanslastarnas arbetsförhållanden utifrån ett ergonomiskt helhetsperspektiv med hänsyn tagen till fysiska, psykosociala, tekniska, organisatoriska och kognitiva faktorer vid ramp och sorteringsarbete.

Syftet med pilotprojektet var att inför huvudprojektet

• göra en litteratursammanställning på området: vad har man redan beforskat när det gäller flygplanslastning i Sverige och internationellt?
• ta fram och testa frågeformulär och observationsmetoder för den större datainsamlingen i huvudprojektet
• ta reda på vilka företagsdata som kan och bör samlas in i huvudprojektet

En genomgång av publicerade artiklar och så kallad grå litteratur (ej vetskapligt granskade artiklar och rapporter) gjordes för att se vilken kunskap som redan finns på området, och för att identifiera kunskapsluckor inför den skarpa planeringen av huvudprojektet. En styrgrupp, en projektledare och en projektgrupp samt fyra mindre arbetsgrupper var redan tillsatta av TYA och Transportfacken med namngivna personer vilket underlättade uppdraget.

Utifrån telefonkontakter, möten och intervjuer med nyckelpersoner i handlingbolag, på Transport, AFA, försäkringskassan och arbetsmiljöverket kunde väsentlig information inhämtas som fick ligga till grund för att sammanställa ett frågeformulär angående flygplanslastarnas fysiska och psykosociala arbetsförhållanden, baserat på vetenskapliga grunder. Frågeformuläret testades på ett 20-tal personer, lastare, skyddsombud, huvudskyddsombud och ombudsmän på Transport och reviderades därefter. Mycket och värdefull information om vilka relevanta företagsdata som finns tillgängliga och hos vilken aktör, och vilka som inte kan påräknas i huvudstudien, har också kunnat kartläggas.

En genomgång av vetenskapliga observationsmetoder gjordes och en valdes ut för att testas vid lastning av en narrow body aircraft som metodmässigt bedömdes vara ett svårt arbetsmoment att observera och studera.

Pilotprojektet har resulterat i basen till ett frågeformulär som dock fortfarande kan revideras om det vid samtal med de fyra arbetsgrupperna uppkommer relevanta tillägg. Observation av lastning och lossning av narrow body aircraft samt dokumentation med videokamera visade sig vara möjligt, och metoden som testades (REBA) kan användas för att komplettera de i huvudprojektet planerade heldagsmätningarna med teknisk utrustning av arbetsställningar.

Litteraturgenomgången av 17 artiklar/rapporter som lokaliserats i en omfattande sökning visade att de största belastningsergonomiska riskerna i arbetet verkar uppstå i samband med att lasta och lossa en narrow body aircraft och det på grund av de trånga lastutrymmena som tvingar lastarna till ogynnsamma arbetsställningar. Det finns också några få studier som styrker att vissa hjälpmedel och arbetsmetoder skulle kunna minska antalet dåliga arbetsställningar, muskulär belastning, kompressionskrafter i ryggen och fysiologisk ansträngning, och att bagagets vikt har betydelse för belastningen. Däremot kan man inte i litteraturen finna några studier av hur olika organisatoriska lösningar påverkar lastarnas arbetsställningar och den belastning de i övrigt utsätts för. Enskilda arbetsmoment har studerats men ingen har tittat på hur belastningsmönstret ser ut för lastarna under ett helt arbetsskift.

Besvärsfrekvensen bland flygplanslastare är, enligt den funna litteraturen hög vad gäller rygg, nacke, axlar och knän. Någon större kartläggning av detta eller hur sjukfrånvaron ser ut har inte gjorts i Sverige. Inte heller har man i Sverige eller något annat land tittat på psykosociala faktorer och dess betydelse för flygplanslastares arbetsförhållanden.

Resultaten av det här pilotprojektet ligger till grund för de "kunskapsluckor" som vi rekommenderar (i Kapitel 4) att huvudstudien arbetar vidare med, i överensstämmelse med dess övergripande målsättning och den projektplan som tagits fram av projektgruppen.

Sammanfattning

Arbetsmiljöprojektet Skadefria cargo- och flygplanslastare har utförts på uppdrag av Svenska Transportarbetareförbundet och Svenska Flygbranschen med syfte att kartlägga flygplanslastarnas arbetsförhållanden och att komma med förslag på förbättringsåtgärder för att minska belastningsrelaterade skador och sjukdomar i branschen.

Projektledningsgruppen har bestått av fem personer: Eva Bergsten, ergonom, anställd av projektet; Erik Alphonse, projektledare, TYA; Reidar Pettersson, arbetsmiljökonsult, Arbetsmiljölotsen; Svend Erik Mathiassen, professor, Centrum för belastningsskadeforskning vid Högskolan i Gävle; och Dan Holmberg, regionalt skyddsombud, Transportarbetareförbundet.

Projektet som omfattade 14 bolag (11 handling, 3 cargo) på sex flygplatser (Arlanda, Malmö, Göteborg, Växjö, Skavsta och Arvidsjaur) startades våren 2010 och avslutades våren 2012, efter en inledande pilotstudie våren 2010 som finansierades av TYA. Inom projektet har 1 039 enkäter distribuerats med frågor om psykosociala arbetsförhållanden, upplevd arbetsbelastning, trötthet och besvär. Svarsfrekvensen var 72 procent. Heldagsmätningar av arbetsställningar för rygg och armar har genomförts på 5-6 lastare per flygplats samtidigt som lastarna filmats och fyllt i dagböcker. Fokusgrupper har intervjuats och data om till exempel sjukskrivningar och olyckstillbud har samlats in från företagen.

Parallellt med den vetenskapliga delen har projektet haft en praktisk del med fyra arbetsgrupper bestående av representanter från både arbetsgivar- och arbetstagarsidan. Grupperna har träffats två gånger per termin och jobbat inom områdena: I) fysisk belastning och arbetsskadestatistik, II) arbetsorganisation, schemaläggning och psykosocial arbetsmiljö, III) hjälpmedel och metoder samt IV) utbildning och utveckling.

Våra resultat visar att besvärsfrekvenserna i muskler och leder är relativt höga. Det finns arbetsmoment i lastaryrket som är ogynnsamma och som ökar risken för besvär, framför allt i axlar/skuldra, rygg och handleder/händer. De arbetsuppgifter som en lastare har skiljer sig inte så mycket åt mellan de olika flygplatserna, men det finns betydande skillnader i hur ofta och hur länge uppgifterna förekommer. Vid vissa flygplatser är således flyglastararbetet mera varierat än vid andra, vilket förmodligen har en betydelse för risken att utveckla besvär.

Överlag fanns det hjälpmedel för de mest belastande arbetsmomenten, men också brister i hur dessa används.

Inom den psykosociala arbetsmiljön visade projektet på ett behov av att förbättra ledarskapet och lastarnas inflytande i planering och genomförande av det egna arbetet. Bättre feedback i form av stöd och uppmuntran från ledare efterfrågades också.

Arbetsgrupperna, som löpande delgavs resultaten från den vetenskapliga kartläggningen, utvecklade i enlighet med projektets målsättning ett antal åtgärdsförslag, med stöd i kartläggningen. Förslagen, som presenteras i denna rapport, är av generell natur. Flera av förslagen omfattar ett flertal möjliga delåtgärder och initiativ, som naturligtvis måste anpassas för och prioriteras av det enskilda bolaget utifrån dess egna förutsättningar. Mot bakgrund av våra projektresultat vill vi dock generellt rekommendera samtliga bolag att lägga en viss prioritet på de psykosociala arbetsförhållandena i sitt förbättringsarbete. Det fanns även uppenbara möjligheter att förbättra den fysiska belastningsprofilen, särskilt genom att bredda arbetsinnehållet på vissa flygplatser, och genom en mera effektiv användning av tekniska hjälpmedel. Samtidigt är det viktigt att framhålla att lastaryrket även har många goda sidor i form av ett rörligt och spännande arbete med ett bra socialt klimat.

Vår bedömning är att de förslag till förändringar i arbetsmiljö och arbetsvillkor som föreslås i denna rapport skulle leda till en bättre arbetsmiljö men sannolikt också kunna påverka effektiviteten i arbetet i positiv riktning.

Projektet Skadefria cargo- och flygplanlastare är föremål för en avhandling vilket betyder att vidare analyser av insamlade data kommer att ske. Resultaten kommer framöver att publiceras i vetenskapliga tidsskrifter.

Introduction

Flight baggage handlers are mainly engaged in sorting luggage or cargo, loading and unloading it to and from the airplanes. The Vocational Training and Working Environment Council, TYA - formed by employer’s and employee’s organizations in the transportation sector - initiated a scientific study in 2009 to investigate the prevalence of musculoskeletal disorders and their suspected determinants in six Swedish airports involving a total of about 1000 handlers in 14 cargo- and handling companies. Encouraged by an initial literature review, the present field study was designed to contain qualitative, questionnaire-based, and observational surveys of working conditions, as well as extensive direct measurements of postures using full-shift inclinometry. This paper reports the design and results of the questionnaire part of the study.

Method

All baggage handlers working at least half-time (n=1044) were encouraged to fill in an extensive questionnaire handed out at the workplace by a research team member. In general the researcher collected the questionnaires at the same occasion. The questionnaire addressed general health, work capacity and physical exposures in relevant handling tasks. It also included a modified version of the Copenhagen Psychosocial Questionnaire (COPSOQ), the Nordic Council of Minister’s Questionnaire (NMQ) on disorders, and the SOFI-questionnaire measuring perceived fatigue.

Results

The response rate was 73%. The prevalence of musculoskeletal disorders in the back, shoulders and wrists during the last 12 months was 70%, 60% and 45%. Positive effects of devices used for reducing perceived physical load were confirmed. The handlers expressed a low confidence in the leadership, and insufficient feedback, information and influence at work. Fatigue particularly occurred in the dimensions lack of energy and physical discomfort.

Discussion

The observed prevalence of low back pain (70%) is high, and in parity with results among nurses in Sweden (64%; Josephson et al. 1997) and China (56%; Smith et al. 2004). Further examination of questionnaires, interviews and direct posture measurements will identify determinants to consider for intervention to reduce the prevalence of disorders among the baggage handlers.

Josephson M, et al. Occup Environ Med 1997;54:681-685.

Smith DR, et al. Occup Med 2004;54:579-582

The aim was to investigate how Swedish small and medium enterprises (SMEs) within the manufacturing industry carry out work environment improvements, and to study if managers consider profitability to be associated with issues in the work environment. Workplace observations and interviews (n=60) with company managers were carried out. Forty-five enterprises were affiliated with an occupational health service, typically in order to get quick access to health care, rather than getting help planning and implementing changes. Fifty-eight managers believed that healthy work environments would have at least some positive effect on company profitability. Incentives for work environment improvements were external, individual and organizational and varied between companies of different sizes. External requirements from The Swedish Work Environment Authority and from established or potential customers were prioritized incentives in SMEs with < 50 employees. Organizational and individual incentives such as incident- and accident reports, productivity, health and sick-leave were prioritized in SMEs with >50 employees. Irrespective of company size, well-being among work-force was consistently mentioned as an important factor for successful business. Small companies urged quick decisions and actions while medium companies had more planned, systematic and organized work environment activities. Deliberate work environment improvements for increased profitability were for instance, changes to eliminate risks, reduce manual work and resolve planning and coordination problems in production that led to stress.

Two ambiguous figures (Mach's book-figure and the AMBEGUJAS phenomenon) have been studied. They show colour shifts synchronised with the shifts of their alternative phases. The perceived concave phase appeared to have chromatic surface colour, but the perceived convex phase can appear to be in coloured illumination and shadow (film colour). The two perceived reversible shapes of the Mach figure (the book and the tent) and the three perceived alternative shapes of the Mondrians used in the AMBEGUJAS phenomenon (a roof, a ceiling, and a tile) all can appear to have chromatic surface colours in their concave phases but appear to have coloured illumination and shadow in their convex phases

Background

A major problem with rehabilitation interventions for neck pain is that the condition may have multiple causes, thus a single treatment approach is seldom efficient. The present study protocol outlines a single blinded randomised controlled trial evaluating the effect of tailored treatment for neck-shoulder pain. The treatment is based on a decision model guided by standardized clinical assessment and functional tests with cut-off values. Our main hypothesis is that the tailored treatment has better short, intermediate and long-term effects than either non-tailored treatment or treatment-as-usual (TAU) on pain and function. We sub-sequentially hypothesize that tailored and non-tailored treatment both have better effect than TAU.

Methods

120 working women with minimum six weeks of nonspecific neck-shoulder pain aged 20-65, are allocated by minimisation with the factors age, duration of pain, pain intensity and disability in to the groups tailored treatment (T), non-tailored treatment (NT) or treatment-as-usual (TAU). Treatment is given to the groups T and NT for 11 weeks (27 sessions evenly distributed). An extensive presentation of the tests and treatment decision model is provided. The main treatment components are manual therapy, cranio-cervical flexion exercise and strength training, EMG-biofeedback training, treatment for cervicogenic headache, neck motor control training. A decision algorithm based on the baseline assessment determines the treatment components given to the each participant of T- and NT-groups. Primary outcome measures are physical functioning (Neck Disability Index) and average pain intensity last week (Numeric Rating Scale). Secondary outcomes are general improvement (Patient Global Impression of Change scale), symptoms (Profile Fitness Mapping neck questionnaire), capacity to work in the last 6 weeks (quality and quantity) and pressure pain threshold of m. trapezius. Primary and secondary outcomes will be reported for each group with effect size and its precision.

Discussion

We have chosen not to include women with psychological ill-health and focus on biomedical aspects of neck pain. Future studies should aim at including psychosocial aspects in a widened treatment decision model. No important adverse events or side-effects are expected. Trial registration: Current Controlled Trials registration ISRCTN49348025. Key words: Neck, trapezius, myalgia, neck-shoulder pain, RCT, individualized treatment, rehabilitation, physiotherapy, tailored

Denna skrift vänder sig till dig som har ständig värk i rygg eller nacke, eller som vid flera tillfällen haft en diffus smärta i rygg eller nacke. Här kan du läsa om vilka åtgärder forskare rekommenderar och vad du själv kan göra för att minska värken. Forskningen om vilka åtgärder som hjälper har gjort framsteg och även för dig som haft långvarig värk finns det goda möjligheter att minska smärtan.

Purpose: To assess overall reliability and validity of a neck-specific questionnaire, the Profile Fitness Mapping neck questionnaire (ProFitMap-neck), on three chronic neck pain groups. Method: Participating groups were as follows: whiplash associated disorders, inpatient care (IP-WAD, n = 127); nonspecific neck pain, inpatient care (IP-NS, n = 83) and nonspecific neck pain subjects (non-IP-NS, n  = 104). All groups answered the ProFitMap-neck and the SF-36, whereas non-IP-NS also answered the Neck Disability Index (NDI) and the Functional Self-Efficacy Scale (SES). Internal consistency, test–retest reliability and components of convergent construct, face and content validity were determined for the ProFitMap-neck. Results: The ProFitMap-neck showed good internal consistency in all three groups, and ICC test–retest reliability (0.80–0.91). Good correlation (0.66–0.78) and highest agreement was reached with NDI. According to the International Classification of Functioning, Disability and Health, the symptom scale of the ProFitMap-neck was mainly classified to the domain of impairments–body functions, and the functional limitation scale to the activity limitation domain. Conclusion: The results indicate that the ProFitMap-neck is valid for measuring symptoms and functional limitations in people with chronic neck pain. The combination of a composite total score of symptoms and function as well as separate scores of each domain makes ProFitMap-neck suitable for research as well as in clinical practice.

Implications for Rehabilitation

• The ProFitMap-neck can be used as a valid self-assessment tool for measuring symptoms and functional limitations in people belonging to the most prevalent categories of neck pain.

• The combination of the symptom and functional limitation questionnaire scores in a total score can be used for an overall clinical judgment.

This study investigated temporal changes in movement strategy and performance during fatiguing short-cycle work. Eighteen participants performed six 7-minutes work blocks with repetitive reaching movements at 0.5 Hz, each followed by a 5.5-minute rest break for a total duration of one hour. Electromyography (EMG) was collected continuously from the upper trapezius muscle, the temporal movement strategy and timing errors were obtained on a cycle-to-cycle basis, and perceived fatigue was rated before and after each work block. Clear signs of fatigue according to subjective ratings and EMG manifestations developed within each work block, as well as during the entire hour. For most participants, timing errors gradually increased, as did the waiting time at the near target. Changes in temporal movement strategy were negatively correlated with changes in the level and variability of EMG, suggesting that an adaptive temporal strategy offset the development of unstable motor solutions in this fatiguing, short-cycle work

This study investigated the effect of work pace on workload, motor variability and fatigue during light assembly work. Upper extremity kinematics and electromyography (EMG) were obtained on a cycle-to-cycle basis for eight participants during two conditions, corresponding to "normal" and "high" work pace according to a predetermined time system for engineering. Indicators of fatigue, pain sensitivity and performance were recorded before, during and after the task. The level and variability of muscle activity did not differ according to work pace, and manifestations of muscle fatigue or changed pain sensitivity were not observed. In the high work pace, however, participants moved more efficiently, they showed more variability in wrist speed and acceleration, but they also made more errors. These results suggest that an increased work pace, within the range addressed here, will not have any substantial adverse effects on acute motor performance and fatigue in light, cyclic assembly work. STATEMENT OF RELEVANCE: In the manufacturing industry, work pace is a key issue in production system design and hence of interest to ergonomists as well as engineers. In this laboratory study, increasing the work pace did not show adverse effects in terms of biomechanical exposures and muscle fatigue, but it did lead to more errors. For the industrial engineer, this observation suggests that an increase in work pace might diminish production quality, even without any noticeable fatigue being experienced by the operators.

Background: Musculoskeletal disorders have been associated with computer use among office workers and lack of variation caused by too little exposure diversity between work tasks has been proposed as an important etiological factor. However there is little information on the diversity of occupations and information and communication technologies (ICT) used by office workers and none which extends beyond the traditional workday. Whilst direct observation is expected to provide the most accurate data, it is resource intensive and self report and sampling alternatives may be a viable alternative.

Method: This paper describes direct observation and self-report data on the occupations and ICT use of 24 Australian office workers in their natural environments at work and away-from-work, over 12 hours of a working day.

Results: Participants were observed for a mean [SD] for 642[40] minutes, 67% of which was at the workplace. Productive occupations (405[122] minutes) accounted for 63% of the observation period, compared to 17% for instrumental (106[57] minutes), 12% for self-care (75[46] minutes) and 8% for leisure occupations (54[39] minutes). Non ICT tasks occurred during 44% of the observation period (285[89] minutes); New ICT accounted for 36 % (234[118] minutes), Old ICT accounted for 15% (98[73] minutes), and Combined ICT tasks 4% (24[30] minutes). The proportions of occupations and ICT use differed between work and away-from-work. Computer-based New ICT was most used for work tasks. Observed and self-reported time on occupations and ICT were similar, though with some differences. Self-reported time on occupations and ICT was similar for the first day and the subsequent 4 days.

Conclusion: The first detailed description of occupations and ICT used by office workers at work and away-from-work shows that the variety of Old, New, Combined and Non-ICT used for performing typical work and non-work tasks offered a diversity of exposures for the workers. This information provides an important step for further investigations into exposure variation in this group, and possible musculoskeletal health risks.

Background: Reports in the popular media are that school children use modern information and communication technology (ICT) on a regular basis for a variety of purposes, however little has been documented in the scientific literature about how school children spend their time and the different types of ICT they use.

Method: This paper describes the observed occupations and ICT use of nine Australian primary school children in their natural environments at school and away-from-school during one school day, and compares self-reported exposures with direct observations. Self-reported discomfort scores were obtained throughout the day.

Results: The study identified that paper-based ICT (Old ICT) was used mostly for productive occupations at school, while electronics-based (New ICT) was used mostly during leisure in away-from-school locations. Tasks involving no ICT (Non ICT) accounted for the largest proportion of time in both locations during self-care, leisure and instrumental occupations. End-of-day self-reported time performing different occupations was consistent with data from independent observations. Self reported time using Old ICT and New ICT was marginally over-estimated, and time spent using Non-ICT was marginally under-estimated.

Conclusion: The children in this study used a variety of ICT in the performance of daily occupations in their natural environments. New ICT use was primarily for leisure, but time spent was less than reported among other child studies. Discomfort reports among the participants were low. Children’s self-reports of daily occupations and ICT use has utility as an exposure assessment metric.

Background: There are concerns that insufficient variation in postural and muscle activity associated with modern information and communication technology (ICT) tasks presents a risk for musculoskeletal ill-health among school children. However, scientific knowledge on physical exposure variation in this group is limited.

Method: Postures of the head, upper back and upper arm, and muscle activity of the right and left upper trapezius and right forearm extensors were measured over 10-12 hours in nine school children using different types of ICT at school and away-from-school. Variation in postures and muscle activity was quantified using two indices, EVA_sd and APDF_(90-10).

Results: Paper-based (Old) ICT tasks produced postures that were less neutral but more variable than electronics-based (New ICT) and Non-ICT tasks. Non-ICT tasks involved mean postures similar to New ICT tasks, but with greater variation. Variation of muscle activity was similar between ICT types in the right and left upper trapezius muscles. Non-ICT tasks produced more muscle activity variation in the right forearm extensor group compared to New and Old ICT tasks.

Conclusion: Different ICT tasks produce different degrees of variation of postures and muscle activity. Combining tasks that use different ICT may increase overall exposure variation. More research is needed to determine what degree of postural and muscle activity variation is associated with reduced risk of musculoskeletal ill-health.

Muscle oxygenation responses are reportedly greater in the distal muscle region than in the proximal muscle region. We combined near infrared spectroscopy and electromyography (EMG) to determine whether regional differences in oxygenation are associated with differences in (1) muscle activation and/or (2) fatigue development. Nine males performed 2-min sustained isometric knee extensions at 15% and 30% maximum voluntary contraction during which oxygenation and EMG were recorded simultaneously from proximal and distal locations of the vastus lateralis muscle. Near infrared spectroscopy variables for oxygen saturation (StO2%) were initial slope at contraction onset, peak drop, and recovery slope at contraction end. Electromyography produced the root mean square to indicate muscle activation and mean power frequency changes over time (decreasing slope) to indicate fatigue development. For StO2%, significantly greater peak drop and steeper recovery slope were found for the distal muscle region than for the proximal muscle region. Root mean square, however, was not different between locations. Mean power frequency decreased throughout the contractions but changes were not different between locations. Our results indicate that for modest submaximal contractions, regional differences in oxygenation are not associated with differences in muscle activation or with fatigue development (as interpreted by changes in mean power frequency over time).

This study determined the day-to-day reliability of NIRS-derived oxygenation responses (ΔStO 2%) for isometric contractions and for cuff occlusion. Twenty-four subjects (12 males and 12 females) were tested on two days (4-6 days interval). Variables generated were: (i) ΔStO 2% for isometric contractions (10%, 30%, 50% and 70% MVC) for descending trapezius (TD) and extensor carpi radialis (ECR) muscles; (ii) slope changes in total haemoglobin (HbTslope) and deoxyhaemoglobin (HHbslope) for the ECR using upper arm venous (VO, 50 mmHg) and arterial occlusion (AO, 250 mmHg); (iii) recovery slopes (Rslope) for oxygen saturation (StO2) following isometric contractions and AO. For each variable an intraclass correlation (ICC) was calculated to assess the ability to differentiate between subjects, and limits of agreement (LOA) were computed to assess day-to-day consistency of the measurement. ICCs for ΔStO2% were lowest at 10% MVC for both ECR (0.58) and TD (0.55), and highest at 30% MVC for ECR (0.95) and at 70% MVC for TD (0.79). For both muscles, LOA for ΔStO 2% was lowest at 10% and highest at 50% and 70% MVC. ICC for HbTslope was 0.17. For HHbslope ICC was higher for AO (0.83) than for VO (0.73), and LOA was lower for AO. For the ECR Rslope ICCs ranged 0.88–0.90 for contraction, but was lower for AO (0.33); LOA was lowest at 70% MVC. For trapezius Rslope ICCs ranged 0.63–0.73 and LOA was lowest at 30% MVC. For this study establishing reliability data for the ECR and TD, and including variables commonly reported, are expected to have meaning for future NIRS studies of work-related upper-extremity pain as well as for other NIRS research and clinical applications.

We examined the effect of a low-level sustained contraction on the muscle contractile properties, hemodynamics and oxygenation of the flexor digitorum superficialis muscle (FDS) of the finger. We tested the hypothesis that hemodynamics and oxygenation, reflecting the muscle metabolic characteristics, would recovery more quickly than the muscle contractile properties. Eleven subjects (26 ± 4 yrs) were equipped with electrodes for electrical stimulation and a near-infrared spectroscopy (NIRS) probe on the forearm over the FDS. The experimental protocol consisted of three baselines measurements (-60 min, -30 min, pre-exercise), immediately after a sustained 15-min contraction of the FDS at 10% maximal voluntary contraction (post-exercise), and after 30 min, 60 min and 120 min of recovery. For each time point, participants were subjected to a battery of test that included upper arm venous occlusion (at rest), a computer-mouse point and click task (standardized voluntary task), and electrical stimulation. For venous occlusion (50 mmHg, 1 min), slopes were calculated for NIRS-derived total hemoglobin (HbTslope) and deoxyhemoglobin (HHbslope) as estimates of blood flow and oxygen consumption, respectively. The computer-mouse task entailed using the mouse to point and click on targets presented on the screen during which NIRS signals were monitored for determination of change in total hemoglobin (ΔHbT) and oxygen saturation (ΔStO2%). Electrical stimulation (2 Hz, 5 trains of 15 twitches) provided twitch force (Tw-force), contraction time (CT) and one-half relaxation time (½RT) data. Statistical analysis revealed significant changes over time for all contractile parameters as well as for HHbslope (P < 0.05 for each). Post-hoc testing demonstrated significant decreases for Tw-force post-exercise and at 60 min; for CT at post-exercise, 30 min and 60 min; and for ½RT at post-exercise and at 30 min. HHbslope was significantly higher post-exercise as compared to pre-exercise. During the computer-mouse point and click task, no significant differences were detected forΔHbT, however,ΔStO2% showed a tendency to decrease, albeit not significant (P = 0.11). Further testing showedΔStO2% was significantly lower post-exercise and at 30 min as compared to pre-exercise. The present study shows that NIRS provides insight into muscle hemodynamics and oxygenation for low-level sustained activity to fatigue. The overall quick recovery of hemodynamic and oxygenation responses, and a more prolonged recovery of contractile responses confirms our hypothesis, and this may fit well with the classical definition of low frequency fatigue.

A study was conducted to investigate the influence of different approaches to arranging the pace and temporal organisation of repetitive assembly and disassembly tasks on both average performance and its variability and to compare assembly and disassembly times derived with psychophysical methods to a more traditional methods-time measurement (MTM) approach. The conditions studied were a traditional assembly line arrangement, where assemblies were started at a pace of 110 MTM (repeated on two occasions), a batch condition, where subjects were required to complete 36 assemblies within the total amount of time allowed at 110, MTM and a psychophysical condition, where subjects were allowed to choose their pace (repeated on two occasions). Overall, the results suggest that the mean time spent working in each cycle (the 'on-time') remained fairly constant across conditions, while the idle 'off-time' in between on-times was shorter and of less varied duration in the more autonomous batch and psychophysical conditions. During the second psychophysical (self-paced) condition, subjects completed a significantly higher number of assemblies than during the 110 MTM line condition. The higher pace was achieved through reduction in mean off-times and the potential implications for musculoskeletal risk are discussed. Statement of Relevance: Higher levels of autonomy over work pace, which intuitively would be beneficial from an ergonomics standpoint, actually led to subjects selecting to organise work such that off-times (idle times) were reduced. In contrast, active 'on' times were not affected much by autonomy. These results point to a reason that piecework would be associated with increased risk for musculoskeletal disorders.

Nackbesvär är vanligt förekommande och utgör en betydande orsak till ohälsa och inskränkt arbetsförmåga. Vanligen går det inte att klarlägga organisk orsak till långvariga nackbesvär men mycket tyder på att de oftast är ett komplext tillstånd där både biologiska och psykosociala faktorer är av betydelse. Forskning har visat på samband mellan långvariga nackbesvär och störningar i olika sensomotoriska funktioner och att graden av funktionspåverkan ofta är kopplad till graden av upplevda besvär. Undersökning av sensomotorisk funktion kan därför vara en viktig del i bedömningen av denna patientgrupp. Forskning har även visat att det finns evidens för positiva effekter av sensomotorisk träning vid nackbesvär på kort sikt, medan kunskap om långtidseffekter saknas. Vid träning av sensomotorisk funktion är det viktigt att beakta grundläggande kunskap inom motorisk inlärning för att öka möjligheterna till bestående träningseffekter och att dessa överförs till vardagliga situationer.

The prevalence of work-related muscle pain (WRMP) is large in the general population in the industrialized world. Despite significant advances over recent years in some research areas, the mechanisms of why WRMP occurs and the pathophysiological mechanisms behind the disorders are still unclear. One suggested explanation is that WRMP is caused initially by a limitation of the local muscle circulation and oxidative metabolism. There is a lack of objective methods to gauge the development and diagnosis of WRMP.

Near infrared spectroscopy (NIRS) is a non-invasive technique that allows for determinations of oxygenation and blood flow. The purpose of this thesis was to evaluate NIRS (1) as a method for measuring muscle oxygenation and hemodynamics for the extensor carpi radialis (ECR) and trapezius descendens muscles (TD), and (2) to investigate whether variables measured by NIRS differed between patients diagnosed with WRMP and healthy subjects.

Several variables of NIRS were produced and investigated. These included muscle oxygenation (StO₂%), changes during contractions (∆StO₂%) and StO₂% recovery (Rslope), total hemoglobin (HbT) as an indication of blood volume and its changes during contractions (∆HbT). In addition, for the ECR, by applying an upper arm venous occlusion (VO) HbTslope increase as a surrogate of blood flow, and for both VO and arterial occlusion (AO) HHbslope increase (i.e. deoxyhemoglobin slope) as a surrogate of oxygen consumption were variables of interest.

A first objective was to determine how StO₂% and HbT responded to various contraction forces and how it related to muscle activation measured by electromyography (EMG). For both muscles isometric contractions of 10, 30, 50 and 70% of maximal voluntary contraction (MVC) were maintained for 20 s each by healthy males and females; additionally a 10% MVC contraction was sustained for 5 min. For the different contraction levels, predictable relationships were seen between ∆StO₂% and force, and between ∆StO₂% and EMG RMS amplitude. The general trend was a decrease in ∆StO₂% with increasing force and increasing EMG. Females showed a tendency for a higher oxygen use (i.e., drop in StO₂%) for the ECR over force levels than males and a higher RMS% MVC for the TD. For the 10% MVC contraction sustained for 5 min gender specific changes over time for HbT and RMS for the ECR, and for StO₂% for the TD muscle were seen.

A second objective was to determine the day-to-day reliability of NIRS variables for the ECR and TD muscles at group level (Pooled data) and at gender level (males and females). Measurements were performed on two occasions separated by 4-6 days and intraclass correlation coefficients (ICC) and limits of agreement (LOA) were determined as reliability and reproducibility indicators, respectively. Variables tested were ∆StO₂% during submaximal isometric contractions of 10, 30, 50 and 70% MVC and StO₂% recovery (Rslope) after contractions and after AO. For the ECR, HbTslope as an indication of blood flow (using VO) and HHbslope as a surrogate of oxygen consumption for both VO and AO were computed. For ∆StO₂% for the ECR the highest ICC was at 30% MVC for both the pooled data and at gender level. For the TD ICCs were comparably high for 30, 50, 70 % MVC (for both muscles the ∆StO₂% at 10% MVC showed the lowest ICC). Further, females showed a higher ICC than males for contraction levels of 50 and 70% MVC. For both muscles, LOA for ∆StO₂% was lowest at 10% and highest at 50 and 70% MVC. For the ECR Rslope ICCs were high for all contraction levels, but was lower for AO; LOA was lowest at 70% MVC. For the TD, Rslope ICCs were also high for all contraction levels and LOA was lowest at 30 % MVC. ICC for HbTslope was the lowest of all variables tested. For HHbslope ICC was higher for AO than for VO, and LOA was lower for AO.

A third objective was to determine if there were differences between healthy subjects and patients diagnosed with WRMP in ∆StO₂% and ∆HbT responses during varying submaximal contractions (10, 30, 50 and 70% MVC), and StO₂% recovery (Rslope) immediately after contractions and AO. Additional variables tested in the ECR at rest were HHbslope to indicate oxygen consumption (using AO) and HbTslope as an indication of blood flow. There were no differences between groups in ∆StO₂% and ∆HbT variables during the contractions or Rslope in the recovery after contractions or AO. Furthermore, HbTslope was not different between groups However, oxygen consumption for the ECR and StO₂% for the TD at rest were significantly greater for healthy subjects compared to patients.

A fourth objective was to determine if there were differences in StO₂% and HbT between healthy subjects and WRMP patients during a 12 min sustained contraction of 15 % MVC. In addition, the protocol included a recovery period of 30 min. Prior to contraction, as well as during the recovery period, HbTslope as a surrogate of blood flow was determined for the ECR. Neither the ECR nor the TD exhibited significant differences between groups for StO₂% and HbT during the contraction. For the TD patients showed a lower StO₂% value at rest and throughout the contraction than healthy subjects. For the ECR HbT during the sustained contraction the general trend was an initial decrease with gradual increase throughout the contraction for both groups. For HbTslope no differences were seen between patients and healthy subjects before the sustained contraction and during the recovery period for both muscles.

NIRS is deemed a suitable technique for assessing physiological measurements of the upper extremity, including for day-to-day testing.

NIRS was not able to distinguish between the patients with WRMP and controls. A concern in the thesis is the characteristics of the patient group in being equally active in recreational sports, actively working, and similar in muscle strength as controls. Thus, applying NIRS for studying a more severe patient group could yield different results.

The aim was to investigate the relationship between oxygen saturation (StO(2)%) measured with near-infrared spectroscopy (NIRS) and myoelectric activity (root mean square, RMS) for the extensor carpi radialis (ECR) and trapezius muscles. In addition, gender differences were examined for submaximal (10-70% MVC) and sustained (10% MVC for 5 min) isometric contractions. Thirteen males and 15 females participated. Changes in StO(2)% (∆StO(2)%) and RMS, expressed as percentages of maximum, were calculated for each submaximal contraction. A good correlation between ∆StO(2)% and RMS was seen for the ECR (r = -0.53) and a moderate correlation seen for the trapezius muscle (r = -0.44). The ANOVA showed a significant decrease in ECR-∆StO(2)% over force with females demonstrating a tendency for larger changes than males. ECR-RMS increased over force with no impact of gender. For the trapezius, ∆StO(2)% decreased over force but was not gender dependent. Trapezius-RMS increased over force with females demonstrating a tendency for greater change than males. For the sustained contraction, ECR-StO(2)% changed over time but was not gender dependent. ECR-RMS increased over time with females showing a greater response than males. Trapezius-StO(2)% changed over time and differed between genders, i.e., males increased while females decreased. RMS increased over time similarly for both genders. In conclusion, our data show that the ECR and trapezius aerobic demands during isometric contractions are negatively correlated to electromyography (EMG) RMS. The present study also suggests some gender specificity for forearm and shoulder myoelectric activity and oxygenation for submaximal and sustained contractions.

Purpose. To describe limitations in 12 activities at baseline, after multidisciplinary rehabilitation and at a 6-month follow-up for patients with spinal pain and, further, to investigate whether low limitation in any of the activities or in the mean score at baseline might predict increased working time at follow-up. Method. A prospective cohort study of 302 patients, 22- to 63-years old, who participated in multidisciplinary rehabilitation because of chronic neck, thoracic and/or lumbar pain. Data from the Disability Rating Index questionnaire were obtained at baseline, after the 4-week rehabilitation programme, and at the 6-month follow-up. Two subgroups are described: patients who at baseline (1) worked full-time or (2) were on part- or full-time sick leave. Results. The degree of limitation in the 12 activities (items) showed large variations in median scores (7-91). Both subgroups showed significant improvements in most activities after rehabilitation, which remained at the follow-up. Nevertheless, in the sick-leave group, patients who had increased their working time at follow-up (62%) were still very limited in running, heavy work, and lifting heavy objects. In logistic regressions, low limitation in standing bent over a sink at baseline was the only single activity that predicted increased working time at the follow-up: odds ratio (OR) 1.93 (95% CI 1.1-3.5). OR for the mean score was 1.8 (1.0-3.3). Conclusion. A profile of the separate activities demonstrates the large variation in the degree of limitation, which is concealed in a mean score. The single items can be useful when evaluabing interventions. However, to predict increased working time after rehabilitation, the mean score, as well as the activity standing bent over a sink, proved useful.

In order to test the feasibility and sensitivity of the ergonomic exposure assessment tool Quick Exposure Check (QEC), a pilot-study was conducted. The aim was to test QEC in different occupational groups to compare the exposure in the most common work task with the exposure in the work task perceived as the most strenuous for the neck/shoulder region, and to test intra-observer reliability. One experienced ergonomist observed 23 workers. The mean observation time was 45 minutes, waiting time and time for complementary questions included. The exposure scores varied between the different occupational groups as well as between workers within the occupational groups. Eighteen workers rated their most common work task as also being the most strenuous for the neck/shoulder region. For the remaining five workers, the mean exposure score were higher both for the neck and shoulder/arm in the most common work task. Intra-observer reliability shows agreement in 86% of the exposure interactions in the neck and in 71% in the shoulder/arm. QEC seems to fulfill the expectations of being a quick, sensible and practical exposure assessment tool that covers physical risk factors in the neck, upper extremities and low back.

INTRODUCTION

Quick Exposure Check (QEC¹) and Rapid Upper Limb Assessment (RULA²) are two ergonomic risk assessment tools that have been designed to be useful for ergonomists assessing musculoskeletal risk factors in upper extremities at workplaces.

AIM

The aim was to describe the variation between and within ergonomists assessments using QEC and RULA, and to compare the two tools regarding within-observer agreement.

SUBJECTS & METHODS

Twenty ergonomists observed five different work tasks twice with three weeks in between, watching video clips. They made ergonomic risk assessments using both QEC and RULA.

The observed work tasks were: Window replacement, nailing a wooden pallet, toilet cleaning, instrumentation in an operating theatre, and sorting post.

For the statistical analyses, percent agreement and kappa value was used.

RESULTS

There was a variation in assessments between the ergonomists in all positions and movements both when using QEC and RULA, except from assessing armposition when observing window replacement using QEC, where all ergonomists assessed the same position (figure 1).

The ergonomists had higher percent agreement between observation one and two using QEC compared with RULA (table 1).

CONCLUSION

There was a variation when assessing positions and movements in different worktasks both between ergonomists and within the same ergonomist using both QEC and RULA. However the agreement between two observations within observers was higher for QEC.

Performance of certain cognitive tasks either during physical load or in rest pauses between boosts might lead to slowing of muscle fatigue and fatigue related decline in performance. Seventeen right-handed healthy volunteers (age 24±1.4, 8 males) participated in this study, aiming to investigate the effect of the level of the cognitive information processing – 1) passive perception of audio stimuli, 2) active stimuli discrimination, 3) active stimuli discrimination following motor response - on motor task performance (handgrip test 30% and 7% of MVC) and muscle fatigue development. Cognitive tasks show the following effects on motor work: i) Perceived fatigue during 30 % MVC (fatiguing) condition developed slower if participant pressed button in response to deviant acoustic stimuli, as compared to passive listening. Counting task, an active task without motor component, took the intermediate position and did not differ significantly from two other cognitive tasks. ii) MVC after 30% MVC (fatiguing) condition tended to decrease stronger when accompanied with passive listening in comparison with both active tasks. iii) Motor task performance during 30% MVC (fatiguing) condition was better for active cognitive task with motor component than for passive task. Active task without motor component took the intermediate position and did not differ significantly from both the other cognitive tasks.

Muscle load can affect performance of concurrent cognitive task. This effect is often explained by limited resources in the voluntary attention system. To examine whether earlier stages of cognitive information processing might be affected, we recorded the Mismatch Negativity component (MMN) of the auditory event-related brain potential before, during and after sustained handgrip at 7% and 30% of maximal voluntary contraction. MMN is an index of automatic detection of a deviating auditory event. MMN was not affected by force level. However, its amplitude at fronto-central sites decreased during the fatiguing 30% contraction, while it tended to increase during the light 7% work. Thus, muscle fatigue may affect auditory information processing at preattentive and preconscious stages, which could modify cognitive performance

Epidemiological research provides strong evidence for a link between repetitive work (RW) and the development of chronic trapezius myalgia (TM). The aims were to further elucidate if an accumulation of sensitising substances or impaired oxygenation is evident in painful muscles during RW. Females with TM (n=14) were studied during rest, 30 min RW and 60 min recovery. Microdialysate samples were obtained to determine changes in [glutamate], [PGE2], [lactate], and [pyruvate] relative to work. Muscle oxygenation (%StO2) was assessed using near-infrared spectroscopy. During work all investigated substances, except PGE2, increased significantly: [glutamate] (54%, P<0.0001), [lactate] (26%, P<0.005), [pyruvate] (19%, P<0.0001), while the %StO2 decreased (P<0.05). During recovery [PGE2] decreased (P<0.005), [lactate] remained increased (P<0.001), [pyruvate] increased progressively (P<0.0001), and %StO2 had returned to baseline. Changes in substance concentrations and oxygenation in response to work indicate normal increase in metabolism but no ongoing inflammation in subjects withTM.

Rationalizations generally have a negative effect on health and known risk factors for musculoskeletal disorders. These effects may be reduced by paying attention to modifiers as worker participation and a resonant management style. In this study a participatory approach was used in the food industry in order to improve ergonomics and productivity. The food industry shows a high prevalence of musculoskeletal disorders, and repetitive manual work occurs extensively. Prototypes of new packaging solutions were developed in three cases, and compared in a simulated production to the existing production system through direct measurements of working postures and muscle activity, ratings of physical load, and general productivity data. Measured and rated ergonomic exposures showed that workload was significantly lower for the prototypes, in all three cases. In two cases, the number of handling operations included in the packaging operations were greatly reduced with the prototype package, as were production costs. The impact on disorders of the obtained load reductions is difficult to assess, but we believe that in “critical” situations like this, even small improvements may have an effect. This study shows that workloads during manual handling of packages as well as production costs can be reduced by applying participative development of packages.

Visual strain and discomfort may contribute to the generation of work-related musculoskeletal disorders among e.g. computer workers. A positive correlation on a group level between eye-lens accommodation and trapezius muscle activity has been reported. In this study we investigated the possibility of a direct, fast, connection between lens accommodation and trapezius muscles activity. The subjects focused alternately on Near and Far targets, with a mean switch time of 5 s, through four different lenses. The cross-correlation, R(tau) was computed, between the time signals of accommodation and electromyography (EMG) from 23 subjects. In the overall mean R(tau) of 736 curves, a small but significant correlation peak (0.019) with a delay (of the EMG signal) of about 0.3 s, revealed a small common component in the two signals. Among the lenses, the positive lens (3.5 D), showed the highest correlation peak (0.040). The correlation may be caused by a direct “hard-wired” connection between the ciliary and trapezius muscles. But it could also be caused indirectly by the subject’s need for a more stable head in a more demanding visual task. The latter is supported by the result that the correlation was the highest in the positive lens condition. The present correlation is however weak and it has probably a low practical importance.

Background

The trapezius muscle is a neck muscle that is susceptible to chronic pain conditions associated with repetitive tasks, commonly referred to as chronic work-related myalgia, hence making the trapezius a muscle of clinical interest. To provide a basis for further investigations of the proteomic traits of the trapezius muscle in disease, two-dimensional difference gel electrophoresis (2D-DIGE) was performed on the healthy trapezius using vastus lateralis as a reference. To obtain as much information as possible from the vast proteomic data set, both one-way ANOVA, with and without false discovery rate (FDR) correlation, and partial least square projection to latent structures with discriminant analysis (PLS-DA) were combined to compare the outcome of the analysis.

Results

The trapezius and vastus lateralis showed significant differences in metabolic, contractile and regulatory proteins, with different results depending on choice of statistical approach and pre-processing technique. Using the standard method, FDR correlated one-way ANOVA, 42 protein spots differed significantly in abundance between the two muscles. Complementary analysis using immunohistochemistry and western blot confirmed the results from the 2D-DIGE analysis.

Conclusions

The proteomic approach used in the present study combining 2D-DIGE and multivariate modelling provided a more comprehensive comparison of the protein profiles of the human trapezius and vastus lateralis muscle, than previously possible to obtain with immunohistochemistry or SDS-PAGE alone. Although 2D-DIGE has inherent limitations it is particularly useful to comprehensively screen for important structural and metabolic proteins, and appears to be a promising tool for future studies of patients suffering from chronic work related myalgia or other muscle diseases.

Work related musculoskeletal disorders are the dominating causes of reported ill-health in industrialized countries. These chronic pain conditions are one of the most costly public health problems in Europe and North America. When work related musculoskeletal disorders are considered to be of muscular origin and the trapezius muscle is affected, the common appellation is trapezius myalgia. Since little is known about the genesis or how it is maintained, it is of great importance to better understand the pathophysiology of trapezius myalgia; doing so will better enable recommendations for prevention, treatment and rehabilitation. Several hypotheses have been presented based on biochemical alterations in the muscle, suggesting increased signaling of inflammatory substances and altered metabolism. Previous research has not been able to present the comprehensive picture of the muscle in pain. Thus there is a demand for more comprehensive research regarding the biochemical milleu of the chronic trapezius muscle.

Proteomic and metabolomic methods allow non-targeted simultaneous analyses of a large number of proteins and metabolites. The main emphasis in this thesis is on a proteomic method, two-dimensional differential gel electrophoresis (2D-DIGE). The method is validated to human skeletal muscle biopsy research with laboratory specific settings. In the baseline study, there were 14 metabolic, contractile, structural and regulatory proteins that differed significantly in abundance when trapezius and vastus lateralis muscles were compared. Using the validated 2D-DIGE method and the baseline study, a comparison between healthy and myalgic muscles was made. Biopsies from female cleaners with and without myalgia were compared to obtain results from women with the same type of work exposure. In the multivariate model, 28 identified unique proteins separated healthy and myalgic muscle and were grouped according to function: metabolic (n=10), contractile (n=9), regulatory (n=3), structural (n=4), and other (n=2). Finally, a second screening method, metabolomics, was introduced to analyze differences in metabolite content as a complement to and verification of the proteomic results. Gas chromatography-mass spectrometry (GC-MS) was performed on muscle interstitial fluid samples obtained with microdialysis, and differences in the abundance of extracellular metabolites were revealed.

 The 2D-DIGE method is a reliable method to analyze human skeletal muscle. The outcomes of the proteomic analyses were dependant on the statistical approach. Systematic differences in protein and metabolite content were detected using a multivariate approach. Univariate analyses were used to analyze individual proteins for their significance. The significant proteins in the baseline study were predominately related to muscle fiber type which correlated with the differences in fiber type content between trapezius and vastus lateralis. The proteomic and metabolomics studies where myalgic and healthy muscles were compared provide us with new clues and new aspects regarding the pathophysiology of the myalgic muscle.

Technically advanced methods employed in the thesis enabled an explorative screening of proteins of relevance for the pathophysiology of the myalgic muscle. The results of these analyses may contribute to the formulation of future hypothesis that need to be further evaluated.

The aim of the present study was to investigate reactions in trapezius muscle blood flow (MBF), muscle activity, heart rate variability (HRV) and systemic blood pressure (BP) to autonomic tests in subjects with chronic neck-shoulder pain and healthy controls. Changes in muscle activity and blood flow due to stress and unfavourable muscle loads are known underlying factors of work-related muscle pain. Aberration of the autonomic nervous system (ANS) is considered a possible mechanism. In the present study, participants (n = 23 Pain, n = 22 Control) performed autonomic tests which included a resting condition, static hand grip test (HGT) at 30% of maximal voluntary contraction, a cold pressor test (CPT) and a deep breathing test (DBT). HRV was analysed in time and frequency domains. MBF and muscle activity were recorded from the upper trapezius muscles using photoplethysmography and electromyography (EMG). The pain group showed reduced low frequency-HRV (LF) and SDNN during rest, as well as a blunted BP response and increased LF-HRV during HGT (∆systolic 22 mm Hg; ∆LF(nu) 27%) compared with controls (∆systolic 27; ∆LF(nu) 6%). Locally, the pain group had attenuated trapezius MBF in response to HGT (Pain 122% Control 140%) with elevated trapezius EMG following HGT and during CPT. In conclusion, only HGT showed differences between groups in systemic BP and HRV and alterations in local trapezius MBF and EMG in the pain group. Findings support the hypothesis of ANS involvement at systemic and local levels in chronic neck-shoulder pain.

The aim of the study was to investigate autonomic nervous system regulation, physical activity (PA) and perceived stress and energy during daily activities in subjects with chronic muscle pain in the neck-shoulders (trapezius myalgia) (n = 23) and symptom-free controls (n = 22). Subjects underwent 24-h objective ambulatory monitoring of heart rate variability (HRV) and PA, and reported their perceived stress and energy in a diary. Standard HRV measures were extracted in time and frequency domains. The volume and pattern of different types of activities were quantified in terms of intensity and duration of walking, and time spent sitting, standing and lying during the 24-h measurement. Results showed shortened inter beat-intervals (higher heart rate) and reduced HRV in the pain group, most pronounced during sleep (p < 0.05). For overall PA, the pain group showed increased lying time, compared to controls (p < 0.05). A different activity pattern was found in the pain group, with reduced leisure time PA and increased PA during morning hours, in comparison with controls (p < 0.05). Both groups demonstrated low levels of perceived stress, whereas reduced energy was observed in the pain group (p < 0.05). In conclusion, monitoring of 24-h HRV demonstrated diminished HRV among persons with chronic neck-shoulder pain. This reflected aberration in autonomic regulation, suggesting reduced parasympathetic activation and increased sympathetic tone as an element in maintenance of chronic muscle pain.