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Between- and within-subject variance of motor variability metrics in females performing repetitive upper-extremity precision work
Centre for Musculoskeletal Research, Department of Occupational and Public Health Sciences, University of Gävle, Sweden.
Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation, Physiotherapy. Centre for Musculoskeletal Research, Department of Occupational and Public Health Sciences, University of Gävle, Sweden.ORCID iD: 0000-0002-2804-3200
Centre for Musculoskeletal Research, Department of Occupational and Public Health Sciences, University of Gävle, Sweden.
2015 (English)In: Journal of Electromyography & Kinesiology, ISSN 1050-6411, E-ISSN 1873-5711, Vol. 25, no 1, 121-129 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Elsevier, 2015. Vol. 25, no 1, 121-129 p.
Keyword [en]
precision motor control, kinematics reliability, repetitive work, pipetting, movement variability
National Category
Physiotherapy Neurosciences Sport and Fitness Sciences
URN: urn:nbn:se:umu:diva-95050DOI: 10.1016/j.jelekin.2014.10.011ISI: 000348289200018PubMedID: 25467549OAI: diva2:757056
Available from: 2014-10-21 Created: 2014-10-21 Last updated: 2015-03-06Bibliographically approved
In thesis
1. Sensorimotor control and cervical range of motion in women with chronic neck pain: Kinematic assessments and effects of neck coordination exercise
Open this publication in new window or tab >>Sensorimotor control and cervical range of motion in women with chronic neck pain: Kinematic assessments and effects of neck coordination exercise
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Sensomotorisk funktion och rörelseomfång i nacken hos kvinnor med långvarig nacksmärta : Utvärdering med rörelseanalys och effekter av nackkoordinationsträning
Abstract [en]

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.

Abstract [sv]

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.

Place, publisher, year, edition, pages
Umeå: Umeå Universitet, 2014. 61 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 1687
Neck pain, Rehabilitation, Coordination training; Resistance training; Postural balance; randomized controlled trial, Musculoskeletal pain; Biomechanics; Range of motion, Kinematics, Head Movements
National Category
urn:nbn:se:umu:diva-96172 (URN)978-91-7601-170-6 (ISBN)
Public defence
2014-12-04, Vårdvetarhuset, Aulan, Umeå, 09:00 (English)
Available from: 2014-11-13 Created: 2014-11-11 Last updated: 2015-01-21Bibliographically approved

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