Low back pain suppresses preparatory and triggered upper-limb activation after sudden upper-limb loading.
ABSTRACT A cross-sectional comparative study between healthy controls and patients with chronic low back pain (LBP).
To assess the effect of chronic LBP on biceps brachii muscle activation during sudden upper-limb loading.
Chronic LBP is related to altered trunk muscle function. However, it is not known if these changes are also found in upper-limb function, indicating a general effect.
Surface electromyographic recordings were made from the biceps brachii bilaterally from 22 control subjects without chronic LBP and 29 patients with chronic LBP. Electromyography was recorded during expected and unexpected limb loading, with the activation pattern recorded for analysis at 150 milliseconds before loading, and 3 consecutive 50 milliseconds periods following loading. RESULTS.: Chronic LBP patients had decreased biceps brachii activation before expected perturbation (P = 0.035) and during the third 50-millisecond period (from 100 to 150 milliseconds) after unexpected perturbation (P = 0.010). During the first 2, 50-millisecond periods (from 0 to 100 milliseconds) after the perturbation, the activation was similar.
Chronic LBP did not affect reflex activation of biceps brachii muscles but decreased preparatory and triggered reactions. The finding indicates that back pain may disturb higher level information processing in motor control.
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ABSTRACT: HintergrundZiel der Studie war die Untersuchung der posturalen Kontrolle während externer über die Füße eingeleiteter Störungen bei Patienten mit chronischem nichtspezifischem Rückenschmerz (CNRS). Zudem wurde der Einfluss der visuellen Information (Augen offen vs. Augen geschlossen) auf die posturale Kontrolle untersucht. Material und MethodenEs wurden 8Patienten mit CNRS (Alter: 40±12Jahre; Body Mass Index, BMI: 23±2kg/m2) ohne degenerative Bandscheibenerkrankung der Wirbelsäule (Befund der Magnetresonanztomografie) und 12gesunde Vergleichspersonen (Alter: 28±7Jahre; BMI: 21±3kg/m2) untersucht. Mittels Oberflächenelektromyografie (OEMG) wurde die posturale Kontrolle bei 5Rumpf- und 5Beinmuskeln sowie einem Beckenmuskel bei distalen lateralen Störungen analysiert. ErgebnisseGesunde (Mittelwert±Standardabweichung: 96,42±64,77µV) zeigten im Vergleich zu Patienten mit CNRS (56,29±39,63µV) eine signifikant (F=6,00; p<0,05) größere erste Maximalamplitude der muskulären Reflexantwort des M. gluteus medius während externer Störungen im aufrechten Stand. Beide Gruppen zeigten für ausgewählte Beinmuskeln ein signifikant größeres Integral der ersten Reflexantwort bei geschlossenen Augen im Vergleich zu offenen Augen. SchlussfolgerungPatienten mit CNRS zeigen eine veränderte reflektorische Antwort des M. gluteus medius, welche mit einer verminderten Beckenstabilisierung einhergehen könnte. BackgroundThe aim of this study was to examine postural control in patients with chronic non-specific low back pain (CNRS). Furthermore the influence of visual information (eyes open versus eyes closed) was analyzed. Material and methodsA total of 8patients with CNRS and 12healthy control subjects were examined. Surface electromyography (SEMG) recordings were made from 5trunk and 5lower limb muscles as well as one hip muscle during application of distal lateral perturbation. ResultsHealthy controls (mean±standard deviation: 96.42±64.77µV) showed a significantly higher maximum amplitude of the gluteus medius muscle in comparison to patients with CNRS (56.29±39.63µV). Furthermore activation of several lower limb muscles was found to be dependent on visual information. ConclusionPatients showed an altered reflex response of the gluteus medius muscle which could be associated with reduced hip stability. SchlüsselwörterRückenschmerz–Posturale Kontrolle–Visuelle Information–Beckenmuskulatur–Elektromyografie KeywordsLow back pain–Postural balance–Visual information–Hip muscle–ElectromyographyDer Schmerz 07/2011; 25(2):199-206. · 1.02 Impact Factor
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ABSTRACT: Chronic low back pain (CLBP) is often accompanied by an abnormal motor performance. However, it has not been clarified yet whether these deviations also occur during motor tasks not involving the back and whether the performance is influenced by pain and pain-related cognitions. Therefore, the aim of the present study is to get insight in the contribution of both pain experience and pain-related cognitions to general motor task performance in CLBP. 13 CLBP patients and 15 healthy subjects performed a hand-function task in three conditions: sitting, lying prone (lying) and lying prone without trunk support (provoking). The last condition was assumed to provoke pain-related cognitions, which was considered successful when a patients' pain expectancy on a numeric rating scale was at least 1 point higher than actual pain experienced. Subjects' performance was expressed in reaction time and movement time. Repeated measures analysis of variance was performed to detect main effect for group and condition. Special interest was given to group*condition interaction, since significant interaction would indicate that patients and healthy subjects performed differently throughout the three conditions. Patients were slower throughout all conditions compared to healthy subjects. With respect to the provoking condition, patients showed deteriorated performance compared to lying while healthy subjects' performance remained equal between these two conditions. Further analysis of patients' data showed that provocation was successful in 54% of the patients. Especially this group showed deteriorated performance in the provoking condition. It can be concluded that CLBP patients in general have worse motor task performance compared to healthy subjects and that provoking pain-related cognitions further worsened performance.BMC Musculoskeletal Disorders 09/2011; 12:211. · 1.88 Impact Factor
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ABSTRACT: INTRODUCTION: Impaired muscle function and lumbar proprioception have been observed in lumbar spinal stenosis (LSS) but those have not been studied in LSS patients with age-matched controls. We assessed lumbar movement perception and paraspinal and biceps brachii (BB) muscle responses during sudden upper limb loading in age-matched healthy subjects and patients with LSS. METHODS: The study included 30 patients selected for an operation due to LSS and 30 age-matched controls without chronic back pain. The paraspinal and BB muscle responses for upper limb loading during unexpected and expected conditions were measured by surface EMG. The ability to sense lumbar rotation was assessed in a previously validated motorized trunk rotation unit in a seated position. Pain, disability and depression scores were recorded. RESULTS: Patients had poorer lumbar perception (mean difference 2.3 ± 0.6°, P < 0.001) and longer paraspinal muscle response latencies [mean difference 4.6 ± 0.6 ms (P = 0.033)] than age-matched healthy controls. Anticipation increased paraspinal and BB muscle activation prior to the load perturbation (P < 0.001) but less in LSS patients than in controls [9 vs. 30 %, P = 0.016 (paraspinals); 68 vs. 118 %, P = 0.047 (BB)]. CONCLUSIONS: The observed impairments in lumbar proprioception and activation of paraspinal and upper limb muscles indicate an extensive loss of both sensory and motor functions in LSS. The main new finding was decreased anticipatory muscle activation during expected upper limb loading reflecting involvement of central movement control mechanisms.European Spine Journal 11/2012; · 2.47 Impact Factor