Background: Cervical strength and stability is often addressed in rehabilitation of people with neck pain. These functions may be associated with emergence and retention of neck pain in cases where the neck strength does not meet daily demands. However, clear empiric support for these notions are lacking, partly due to a scarcity of well controlled dynamometry studies with large samples. First, clarification is needed whether neck strength is in fact reduced in people with neck pain and to resolve the diagnostic performance of neck strength tests.

Purpose: To compare neck muscle strength of women with non-specific long-term neck pain and healthy controls. Also, to assess the diagnostic performance of neck strength tests by assessing their discriminative ability to discern women with and without neck pain.

Methods: The study had a cross-sectional design with data on cervical strength derived from the baseline measurement of a randomized controlled trial (RCT). 80 women with long-term non-specific neck pain (NP) were compared with 40 healthy women (CON). The NP group was a subsample from the RCT selected so that there were no group differences (NP-CON) for body weight and physical activity. Cervical strength assessment included dynamometry of cervico-thoracic extension (CTE) and flexion (CTF) in sitting and cranio-cervical flexion (CCF) in standing, all performed with isometric maximum voluntary contraction (iMVC). Independent samples Mann-Whitney U test and T-test were used to assess group differences for iMVC of the tests. Diagnostic accuracy was further assessed with a receiver operating characteristic (ROC) curve by plotting the true positive rate (sensitivity) as a function of the false positive rate (1 - specificity). The area under the ROC curve (AUC) with 95% confidence interval was used to determine discriminative ability of the tests. The optimal cut-off value to discern NP from CON with corresponding sensitivity and specificity was also determined.

Results: Women with neck pain produced significant lower iMVC in CTE (28%), CTF (26%) and CCF (33%) (all p< 0.001). The ability of CTE, CTF and CCF to discriminate between NP and CON showed moderate accuracy (AUC 0.83, 0.78 and 0.73, respectively). The cut-off value of 165.7 N in CTE had a sensitivity of 0.725 and a specificity of 0.8. The corresponding values for CTF and CCF were 85.8 N (sensitivity 0.8; specificity 0.692) and 4.2 Nm (sensitivity 0.575; specificity 0.9).

Conclusion(s): The neck pain group had less neck muscle strength than controls in all tests. The diagnostic performance of the neck strength tests, judged as discriminative ability to discern neck pain from control participants, were moderate. These results support earlier findings of reduced neck strength in people with neck pain. Also, neck strength tests may have a complementary value in the assessment of neck pain persons.

Implications: The results highlights that impaired neck strength, both in global cervico-thoracic and deep cranio-cervical muscles, is most likely a characteristic of people with long-term neck pain. The study also shows that strength tests could be used with fairly good discriminative precision and may thereby be valuable assessment tools.

Besvär ifrån kroppens muskler och leder såsom nack- och ryggbesvär är fortfarande ett stort problem inom arbetslivet. Muskuloskeletal diagnos är den vanligaste orsaken till lång sjukfrånvaro inom privat sektor och näst vanligast inom kommuner och landsting. Orsakerna till dessa besvär kan vara relaterade till exponering både under arbete och på fritid, men även till individfaktorer. Vår forskargrupp har en bred ansats för att fylla kunskapsluckor inom detta område och kommer att presentera resultat från flera forskningsprojekt i symposiet Arbete, individ och nacksmärta.

Långvarigt sittande har blivit alltmer vanligt förekommande i många yrkesgrupper. Långvarigt sittande och låg fysisk aktivitet har också uppmärksammats som ett betydande hälsoproblem i dagens arbetsliv och även som en möjlig riskfaktor för smärta i nacke-skuldra. Men forskningen om betydelsen av långvarigt sittande för smärta i nacke-skuldra är fortfarande begränsad. Likaså är det oklart om huvudets hållning vid sittandet och nackens funktion, exempelvis nackens rörelsefunktion och styrka, har betydelse för besvärsutveckling. Statiskt arbete med nacken i vridna och böjda positioner misstänks vara en riskfaktor för nack-skuldersmärta i yrken såsom tandläkare, men det är oklart varför vissa exponerade individer drabbas medan andra inte får ont. För de med långvarig smärta krävs ofta rehabiliterande åtgärder, och hur väl dessa åtgärder lyckas kan även det vara beroende av individens fysiska och psykosociala arbetsmiljö. Individens arbetsmiljö påverkar således inte bara risken för om man får besvär utan kan också ha betydelse för hur rehabiliteringen av besvären lyckas.

Syftet med detta symposium är att presentera studier från Centrum för belastningsskadeforskning som handlar om nacksmärta i arbetslivet, sammanfatta kunskapsläget inom området och diskutera hur arbetet kan utformas för att bli hållbart och inkluderande. De forskningsexempel som presenteras berör stillasittande och hållning i arbetslivet och dess tänkbara konsekvenser för nacksmärta och hälsa, riskfaktorer för nacksmärta i tandläkaryrket och arbetsmiljöns betydelse för resultatet av rehabilitering vid nacksmärta. Symposiet avslutas med en frågestund och gemensam diskussion.

Background: Cervical range of motion (ROM) is commonly assessed in clinical practice and research. In a previous study we decomposed active cervical sagittal ROM into contributions from lower and upper levels of the cervical spine and found level- and direction-specific impairments in women with chronic non-specific neck pain. The present study aimed to validate these results and investigate if the specific impairments can be explained by the neutral posture (defining zero flexion/extension) or a movement strategy to avoid large gravitationally induced torques on the cervical spine.

Methods: Kinematics of the head and thorax was assessed in sitting during maximal sagittal cervical flexion/extension (high torque condition) and maximal protraction (low torque condition) in 120 women with chronic non-specific neck pain and 40 controls. We derived the lower and upper cervical angles, and the head centre of mass (HCM), from a 3-segment kinematic model. Neutral head posture was assessed using a standardized procedure.

Findings: Previous findings of level- and direction-specific impairments in neck pain were confirmed. Neutral head posture was equal between groups and did not explain the direction-specific impairments. The relative magnitude of group difference in HCM migration did not differ between high and low torques conditions, lending no support for our hypothesis that impairments in sagittal ROM are due to torque avoidance behaviour.

Interpretation: The direction- and level-specific impairments in cervical sagittal ROM can be generalised to the population of women with non-specific neck pain. Further research is necessary to clarify if torque avoidance behaviour can explain the impairments.

Kinematic motor variability is extensively studied in occupational, clinical and sports biomechanics, but the consistency of most motor variability metrics have never been reported. In this study, fourteen subjects performed a repetitive pipetting task on three separate days. Movements of hand, arm and pipette tip were recorded in 3D and used to compute shoulder elevation, elbow flexion and shoulder-arm coordination angles, as well as pipette-tip endpoint precision. Cycle-to-cycle motor variability was quantified using linear dispersion measures of standard kinematics properties such as peak velocity, range of motion, and inter-segmental relative phase. Between- and within-subject consistencies of these variability metrics were quantified by variance components estimated using a nested random effects model. For most metrics, the variance between subjects was larger than that between days and cycles. Entering the variance components in statistical power equations showed that for most metrics, a total of 80-100 subjects will be required to detect a 20% difference between two groups with sufficient power, while this difference can typically be detected  in repeated-measures (paired) designs using 25 subjects. The reported between- and within-subject variance components can be used as a data base to facilitate efficient designs of future studies of kinematic motor variability.

Objective: To evaluate the effect of neck coordination exercise on sensorimotor function in women with neck pain compared with best-available treatment and sham treatment. Design: Observer-blinded randomized controlled trial with short-term and 6-month follow-ups. Subjects: Women with chronic non-specific neck pain were randomized to 3 groups: neck coordinationexercise with a novel training device; strength training for the neck and shoulders; or massage. Each group had 36 participants. Methods: The intervention period was 11 weeks with 22 individually supervised sessions. Primary outcomes were postural sway measures and precision of goal-directed arm movements. Secondary outcomes were range of motion for the neck, peak speed of axial rotation, and neck pain. A repeated measures multivariate analysis of variance (MANOVA) was conducted separately on the primary outcomes for the short-term and 6-month evaluations and on the sensorimotor secondary outcomes for the 6-month effect. The 6-month effect on pain was analysed with a repeated measures analysis ofvariance (ANOVA). Results: No significant treatment effects in favour of neck coordination exercise were found for short-term or 6-month evaluations. Conclusion: Neck coordination exercise is no better than strength training and massage in improvingsensorimotor function. Further research should investigate the use of cutoffs for sensorimotordysfunctions prior to proprioceptive or coordinative training.

Introduction: Neck pain is a common problem in society and is more prevalent among women. The consequences of neck pain for the individual often include activity and participation limitations, thus affecting many dimensions of life. There is still a lack of understanding of the underlying mechanisms of the disorder and likewise of efficient rehabilitation for people with neck pain. However, coordination exercises have shown promising short-term effects. To carry this line of research forward, there is a need to improve methods for objective characterization of impairments and to investigate novel methods of rehabilitation.

Aims: To characterize impairments of active cervical range of motion of the upper and lower cervical levels in women with chronic neck pain with a novel method (Study I and II) and identify the influence of head posture and movement strategies (Study II). Further, to investigate the effects of a novel method for neck coordination exercise on sensorimotor function and neck pain (study III) and the consistencies of motor variability metrics in a goal directed arm movement task to aid the design of future clinical research (Study IV).

Methods: All studies were laboratory based with kinematic assessments of neck movements (Study I-III), balance (Study III) and goal directed arm movements (Study III, IV). The studies had designs that were: cross-sectional (I and II), randomized controlled trial (III) or test-retest reliability study (IV). Participants in Study I (n=135) and II (n=160) were women with chronic non-specific neck pain and healthy controls. In Study III, women with chronic non-specific neck pain (n=108) were randomized into three different individually supervised 11 week interventions. Study IV included healthy women (n=14).

Results: It was found that cervical range of motion impairments in women with non-specific neck pain were direction- and level-specific; impairments were greater in extension in the upper and flexion in the lower levels of the cervical spine. The magnitude of impairments in range of motion was associated to self-ratings of functioning and health. Possible group differences in natural head posture were rejected as a cause for the direction specific effects. Neither could the effects be explained by a strategy to minimize torque in the cervical spine during movement execution. The neck coordination training was not superior to strength training (best-available) and massage treatment (sham) in improving sensorimotor functions or pain according to short-term and 6 months follow ups. The results from the study of the goal directed movement task showed that between and within-subject sizes of most motor variability metrics were too large to make the test suitable for application in clinical research.

Conclusions: Women with chronic non-specific neck pain have direction- and level-specific impairments in cervical sagittal range of motion. The underlying causes of these specific impairments remains unresolved, but the direction specific impairments are not related to natural head posture. The clinical validity of the method of characterization of cervical range of motion was supported and it can be useful in future clinical research. The novel method of neck coordination exercise showed no advantages on sensorimotor functions or pain compared with best-available treatment in women with chronic non-specific neck pain.

Långvarig smärta i nacken är vanligt förekommande och orsakar både personligt lidande och stora kostnader för samhället. Långvariga nackbesvär är vanligare hos kvinnor än hos män. Det saknas kunskap om effektiva rehabiliteringsmetoder, men forskning har indikerat att träning som förbättrar nackens koordination kan vara effektivt. För att uppnå bättre rehabiliteringsresultat är det viktigt att utveckla metoder för att objektivt mäta funktionsnedsättningar och att utveckla samt utvärdera nya rehabiliteringsmetoder.

Syftet med avhandlingen kan sammanfattas i tre delar: Att detaljerat mäta nedsättningar i nackens rörelseomfång hos kvinnor med långvarig nacksmärta; att utvärdera effekten av en ny metod för nackkoordinationsträning på rörelsefunktion och smärta hos kvinnor med långvarig nacksmärta; samt att utvärdera ett nytt test för att mäta precision och koordination vid målriktade armrörelser och ämnat för framtida klinisk forskning.

Resultaten visade att kvinnor med långvarig nacksmärta hade specifika nedsättningar i nacken rörelseomfång; i övre nackregionen var bakåtböjning mer begränsad medan i nedre nackregionen var framåtböjning mer begränsad. Vi kunde utesluta att resultaten berodde på skillnader i huvudets normala hållning. Graden av rörelsebegränsning i nacken uppvisade samband med personernas självskattade funktion, symtom och hälsa. Nackkoordinationsträningen var inte var bättre än styrketräning eller massage för att förbättra rörelsefunktion eller för att minska smärta. Det nya testet för armrörelser var inte lämpat för kliniska studier av rörelseprecision.

Slutsatserna från avhandlingsarbetet är att kvinnor med långvarig nacksmärta har begränsningar i nackens rörelseomfång vid framåt- och bakåtböjning av huvudet som är specifika vad gäller nivå i halsryggen och riktning. Att graden av rörelsebegränsning uppvisade samband med självskattad funktion, symtom och hälsa styrker testets kliniska validitet. Ytterligare forskning behövs för att förstå orsakerna bakom de specifika nedsättningarna. Nackkoordinationsträningen som utvärderades kan inte rekommenderas för kvinnor med långvarig nacksmärta eftersom korttidsuppföljning och 6-månadersuppföljning visade att träningsformen inte var bättre än styrketräning eller massage, vare sig när det gällde att förbättra sensomotorisk funktion eller att minska smärta.

Reduced cervical range of motion (ROM) is a common finding in people with neck pain. With few exceptions, only the angle between head and thorax has been measured. Our aim was to use an extended model to compare active cervical flexion and extension, separate for upper and lower cervical levels, between people with chronic non-traumatic neck pain and controls. We also investigated associations between ROM measures, symptoms and self-rated functioning. In this cross-sectional study, 102 subjects with neck pain and 33 healthy controls participated. An electromagnetic tracker system was used to measure the kinematics to construct a three-segment model including the thorax, cervical spine and head. Neutral flexion/extension were defined at subjects’ self-selected seated posture. We found that in the neck pain group, extension in the upper cervical levels and predominately flexion for the lower levels were reduced. The ratio between ROM for the upper and lower levels was altered in the neck pain group so that the lower levels contributed to a lesser extent to the total sagittal ROM compared to controls. These findings could not be explained by a greater forward head posture but must have other origins. For the neck pain group, ROM measures were weakly associated to pain and self-rated functioning. Altogether, this implies that using a three-segment model for assessment of ROM can be a valuable improvement for characterisation of patients and treatment evaluation.

AIM: Several studies have reported reduced cervical range of motion (ROM) in people with neck pain. Different methodologies have been used, but with a few exception they measure only head-trunk relationship and do not discriminate between upper and lower cervical motion. Recent strategies for treatment of neck pain condition include retraining the function of the deep cervical flexors that act in cranio-cervical movements. Thus objective measures of cervical ROM in flexion-extension that includes determination of cervical level can be valuable for treatment evaluation.

The aim of the present study was to compare cervical flexion and extension, separate for upper and lower cervical levels, between people with chronic neck pain and controls. Also, the association between upper and lower cervical ROM and self rated characteristics was studied.

METHODS: In a cross-sectional study design, 135 subjects (non-traumatic neck pain: n = 102, controls: n = 33) performed three trials of maximum active cervical flexion and extension. Subjects were seated in a chair with belts crossed over the chest. An electromagnetic tracker system was used to register the kinematics to construct a three-segment model including the trunk, cervical spine and head. The angle for the upper cervical level was defined as the angle between the head and the cervical spine segments. The angle for the lower cervical level was defined as the angle between the cervical spine and the trunk segments. Pressure pain thresholds, pain ratings as well as self ratings of functioning and physical activity were assessed.

RESULTS: Total ROM was reduced in the neck pain group for both the lower (controls: mean = 26.5, SD=6.7, neck pain: mean=19.0, SD =6.5 degrees) and the upper cervical levels (controls: mean = 84.7, SD = 7.9, neck pain: mean = 73.0, SD = 11.2 degrees). This reduction was direction specific: in the upper cervical level only extension was reduced and in the lower cervical level the reduction was predominately in flexion. Multivariate regression analysis revealed that lower level of physical activity, greater impairments of physical functioning, self reported problems with head movements and lower pressure pain thresholds were related to a greater reduction in ROM in the neck pain group.

CONCLUSION: Reduction of ROM is present for both the upper and lower levels of the cervical spine in people with non-traumatic neck pain. For the upper cervical level this reduction is direction specific so that only extension is reduced. The limited extension range of the upper cervical spine in the neck pain group could reflect a habituated sitting posture that includes a more extended upper cervical spine. Alternatively it could reflect an impaired functioning of the deep cervical flexors. For the lower cervical level the reduction was mainly limited to flexion. This could be a reflection of a ‘head forward posture’ that has previously been reported in people with neck pain. The associations between self rated characteristics and range of motion variables supports the validity of this methodology in research on neck pain conditions.

Introduction:Several studies have reported impaired postural control in people with neck pain. Many of these studies have analysed centre of pressure data from a force plate in quiet standing but to our knowledge none has investigated the kinematics of postural sway in people with neck pain. From studies on healthy controls there are two well established strategies of maintaining upright stance: hip and ankle strategies. Recent work has shown that these co-exist simultaneously. The purpose of this study is to investigate these kinematic strategies in people with neck pain. This could give a greater understanding of the mechanisms behind the postural control impairments and give implications for specific rehabilitation interventions.Methods:Seventy subjects (neck pain n=44, controls n=26) stood with their feet together, arms crossed and their eyes closed for 180 s. An electromagnetic tracker was used to record the kinematics for a two segment model (leg, trunk). An in-phase pattern between these segments corresponds to ankle strategy and an anti-phase pattern to hip-strategy. The strength of the in-phase pattern was quantified using coherence analysis.Results:Preliminary results indicate that people with neck pain rely less on ankle strategy in quiet standing than healthy controls. There were no differences in variability of the segment angles between groups. However people with neck pain tended to stand with a greater degree of extension in the hip.Conclusion:It’s generally considered that hip-strategy is used more when the difficulty of the task is higher. One speculative interpretation to the weaker ankle strategy in the neck pain group is that they perceived the task as more demanding. The method of coherence analysis used in this study can be a valuable tool in future studies for understanding postural sway in people with spinal pain.