Changes in the flexion relaxation response induced by lumbar muscle fatigue

<p>Abstract</p> <p>Background</p> <p>The flexion relaxation phenomenon (FRP) is an interesting model to study the modulation of lumbar stability. Previous investigations have explored the effect of load, angular velocity and posture on this particular response. However, the influence of muscular fatigue on FRP parameters has not been thoroughly examined. The objective of the study is to identify the effect of erector spinae (ES) muscle fatigue and spine loading on myoelectric silence onset and cessation in healthy individuals during a flexion-extension task.</p> <p>Methods</p> <p>Twenty healthy subjects participated in this study and performed blocks of 3 complete trunk flexions under 4 different experimental conditions: no fatigue/no load (1), no fatigue/load (2), fatigue/no load(3), and fatigue/load (4). Fatigue was induced according to the Sorenson protocol, and electromyographic (EMG) power spectral analysis confirmed that muscular fatigue was adequate in each subject. Trunk and pelvis angles and surface EMG of the ES L2 and L5 were recorded during a flexion-extension task. Trunk flexion angle corresponding to the onset and cessation of myoelectric silence was then compared across the different experimental conditions using 2 × 2 repeated-measures ANOVA.</p> <p>Results</p> <p>Onset of myoelectric silence during the flexion motion appeared earlier after the fatigue task. Additionally, the cessation of myoelectric silence was observed later during the extension after the fatigue task. Statistical analysis also yielded a main effect of load, indicating a persistence of ES myoelectric activity in flexion during the load condition.</p> <p>Conclusion</p> <p>The results of this study suggest that the presence of fatigue of the ES muscles modifies the FRP. Superficial back muscle fatigue seems to induce a shift in load-sharing towards passive stabilizing structures. The loss of muscle contribution together with or without laxity in the viscoelastic tissues may have a substantial impact on post fatigue stability.</p

Flexion Relaxation and Its Relation to Pain and Function over the Duration of a Back Pain Episode

BACKGROUND: Relaxation of the erector spinae often occurs in healthy individuals as full trunk flexion is achieved when bending forward from standing. This phenomenon, referred to as flexion relaxation is often absent or disrupted (EMG activity persists) in individuals reporting low back pain (LBP). METHODS AND RESULTS: Self-reported pain and disability scores were compared to EMG measures related to the flexion relaxation (FR) phenomenon by 33 participants with LBP at up to eight sessions over a study period of up to eight weeks. Fourteen participants served as a control group. In the protocol, starting from standing participants bent forward to a fully flexed posture, and then extended the trunk to return to standing position. A thoracic inclinometer was used to measure trunk posture. Surface electrodes located at the L2 and L5 levels recorded EMG amplitudes of the erector spinae. Ratios of EMG amplitudes recorded during forward bending to amplitudes at full flexion, and ratios of extension to full flexion were calculated. EMG amplitudes and their ratios were compared between control and LBP groups at the initial visit. No significant differences between groups were found except at the L5 location at full flexion. Correlations of the ratios to pain and function scores recorded in repeated sessions over the LBP episode also were compared between LBP group participants classified as having transient, recurrent or chronic symptoms. In another analysis participants were grouped by whether their symptoms resolved over the study period. CONCLUSIONS: The transient LBP group had significantly stronger correlations between pain and function to both ratios, than did those with more chronic LBP symptoms. Participants who experienced symptom resolution generally had stronger correlations of ratios to both pain and function than those with partial or no resolution. Improved understanding of these relationships may provide insight in clinical management of LBP

Exercise and manual auricular acupuncture: a pilot assessor-blind randomised controlled trial. (The acupuncture and personalised exercise programme (APEP) Trial)

<p>Abstract</p> <p>Background</p> <p>Evidence supports the use of exercise for chronic low back pain (CLBP); however, adherence is often poor due to ongoing pain. Auricular acupuncture is a form of pain relief involving the stimulation of points on the outer ear corresponding with specific body parts. It may be a useful adjunct to exercise in managing CLBP; however, there is only limited evidence to support its use with this patient group.</p> <p>Methods/Design</p> <p>This study was designed to test the feasibility of an assessor-blind randomised controlled trial which assess the effects on clinical outcomes and exercise adherence of adding manual auricular acupuncture to a personalised and supervised exercise programme (PEP) for CLBP. No sample size calculation has been carried out as this study aims to identify CLBP referral rates within the catchment area of the study site. The researchers aim to recruit four cohorts of n = 20 participants to facilitate a power analysis for a future randomised controlled trial. A computer generated random allocation sequence will be prepared centrally and used to allocate participants by cohort to one of the following interventions: 1) six weeks of PEP <it>plus </it>manual auricular acupuncture; 2) six weeks of PEP alone. Both groups will also complete a further six weeks of self-paced exercise with telephone follow-up support. In addition to a baseline and exit questionnaire at the beginning and end of the study, the following outcomes will be collected at baseline, and after 7, 13 and 25 weeks: pain frequency and bothersomeness, back-specific function, objective assessment and recall of physical activity, use of analgesia, perceived self-efficacy, fear avoidance beliefs, and beliefs about the consequences of back pain. Since this is a feasibility study, significance tests will not be presented, and treatment effects will be represented by point estimates and confidence intervals. For each outcome variable, analysis of covariance will be performed on the data, conditioning on the baseline value.</p> <p>Discussion</p> <p>The results of this study investigating the adjuvant effects of auricular acupuncture to exercise in managing CLBP will be used to inform the design of a future multi-centre randomised controlled trial.</p> <p>Trial Registration</p> <p>Current Controlled Trials ISRCTN94142364.</p

Load and speed effects on the cervical flexion relaxation phenomenon

<p>Abstract</p> <p>Background</p> <p>The flexion relaxation phenomenon (FRP) represents a well-studied neuromuscular response that occurs in the lumbar and cervical spine. However, the cervical spine FRP has not been investigated extensively, and the speed of movement and loading effects remains to be characterized. The objectives of the present study were to evaluate the influence of load and speed on cervical FRP electromyographic (EMG) and kinematic parameters and to assess the measurement of cervical FRP kinematic and EMG parameter repeatability.</p> <p>Methods</p> <p>Eighteen healthy adults (6 women and 12 men), aged 20 to 39 years, participated in this study. They undertook 2 sessions in which they had to perform a standardized cervical flexion/extension movement in 3 phases: complete cervical flexion; the static period in complete cervical flexion; and extension with return to the initial position. Two different rhythm conditions and 3 different loading conditions were applied to assess load and speed effects. Kinematic and EMG data were collected, and dependent variables included angles corresponding to the onset and cessation of myoelectric silence as well as the root mean square (RMS) values of EMG signals. Repeatability was examined in the first session and between the 2 sessions.</p> <p>Results</p> <p>Statistical analyses revealed a significant load effect (P < 0.001). An augmented load led to increased FRP onset and cessation angles. No load × speed interaction effect was detected in the kinematics data. A significant load effect (P < 0.001) was observed on RMS values in all phases of movement, while a significant speed effect (P < 0.001) could be seen only during the extension phase. Load × speed interaction effect was noted in the extension phase, where higher loads and faster rhythm generated significantly greater muscle activation. Intra-session and inter-session repeatability was good for the EMG and kinematic parameters.</p> <p>Conclusions</p> <p>The load increase evoked augmented FRP onset and cessation angles as well as heightened muscle activation. Such increments may reflect the need to enhance spinal stability under loading conditions. The kinematic and EMG parameters showed promising repeatability. Further studies are needed to assess kinematic and EMG differences between healthy subjects and patients with neck pain.</p

An exploration of differences between Japan and two European countries in the self-reporting and valuation of pain and discomfort on the EQ-5D.

PURPOSE: To investigate the systematic differences in the self-reporting and valuation of overall health and, in particular, pain/discomfort between three countries (England/UK, Japan, and Spain) on the EQ-5D. METHODS: Existing datasets were used to explore differences in responses on the EQ-5D descriptive system between Japan (3L and 5L), the UK (3L), England (5L), and Spain (5L), particularly on the dimension of pain/discomfort. The role of different EQ dimensions in determining self-reported overall health scores for the EuroQol visual analog scale (EQ-VAS) was investigated using ordinary least squares regression. Time trade-off (TTO) results from Japanese and UK respondents for the EQ-5D-3L as well as Japanese and English respondents for the EQ-5D-5L were compared using t tests. RESULTS: For the EQ-5D-3L, a higher percentage of respondents in Japan than in the UK reported 'no pain/discomfort' (81.6 vs 67.0%, respectively); for the EQ-5D-5L, the proportions were 79.2% in Spain, 73.2% in Japan, and 63-64% in England, after adjusting for age differences in samples. The 'pain/discomfort' dimension had the largest impact on respondents' self-reported EQ-VAS only for EQ-5D-3L in Japan. Using the EQ-5D-3L, Japanese respondents were considerably less willing to trade off time to avoid pain/discomfort than the UK respondents; for example, moving from health state, 11121 (some problems with pain/discomfort) to 11131 (extreme pain/discomfort) represented a decrement of 0.65 on the observed TTO value in the UK compared with 0.15 in Japan. Using the EQ-5D-5L, Japanese respondents were also less willing to trade off time to avoid pain/discomfort than respondents in England; however, the difference in values was much smaller than that observed using EQ-5D-3L data. CONCLUSIONS: This study provides evidence of between-country differences in the self-reporting and valuation of health, including pain/discomfort, when using EQ-5D in general population samples. The results suggest a need for caution when comparing or aggregating EQ-5D self-reported data in multi-country studies.Astellas Europe B

High-Density Electromyography Provides New Insights into the Flexion Relaxation Phenomenon in Individuals with Low Back Pain.

Recent research using high-density electromyography (HDEMG) has provided a more precise understanding of the behaviour of the paraspinal muscles in people with low back pain (LBP); but so far, HDEMG has not been used to investigate the flexion relaxation phenomenon (FRP). To evaluate this, HDEMG signals were detected with grids of electrodes (13 × 5) placed bilaterally over the lumbar paraspinal muscles in individuals with and without LBP as they performed repetitions of full trunk flexion. The root mean square of the HDEMG signals was computed to generate the average normalized amplitude; and the spatial FRP onset was determined and expressed as percentage of trunk flexion. Smoothing spline analysis of variance models and the contrast cycle difference approach using the Bayesian interpretation were used to determine statistical inference. All pain-free controls and 64.3% of the individuals with LBP exhibited the FRP. Individuals with LBP and the FRP exhibited a delay of its onset compared to pain-free controls (significant mean difference of 13.3% of trunk flexion).  They also showed reduced normalized amplitude compared to those without the FRP, but still greater than pain-free controls (significant mean difference of 27.4% and 11.6% respectively). This study provides novel insights into changes in lumbar muscle behavior in individuals with LBP