Danik Lafond

Postural control during prolonged standing in persons with chronic low back pain

Prolonged standing has been associated with the onset of low back pain symptoms in working populations. So far, it is unknown how individuals with chronic low back pain (CLBP) behave during prolonged unconstrained standing (PS). The aim of the present study was to analyze the control of posture by subjects with CLBP during PS in comparison to matched healthy adults. The center of pressure (COP) position of 12 CLBP subjects and 12 matched healthy controls was recorded in prolonged standing (30min) and quiet stance tasks (60s) on a force plate. The number and amplitude of COP patterns, the root mean square (RMS), speed, and frequency of COP sway were analyzed. Statistical analyses showed that CLBP subjects produced less postural changes in the antero-posterior direction with decreased postural sway during the prolonged standing task in comparison to the healthy group. Only CLBP subjects were influenced by the prolonged standing task, as demonstrated by their increased COP RMS, COP speed and COP frequency in the quiet standing trial after the prolonged standing task in comparison to the pre-PS trial. The present study provides additional evidence that individuals with CLBP might have altered sensory-motor function. Their inability to generate responses similar to those of healthy subjects during prolonged standing may contribute to CLBP persistence or an increase risk of recurrent back pain episodes. Moreover, quantification of postural changes during prolonged standing could be useful to identify CLBP subjects prone to postural control deficits.

Postural development in school children: a cross-sectional study.

BackgroundLittle information on quantitative sagittal plane postural alignment and evolution in children exists. The objectives of this study are to document the evolution of upright, static, sagittal posture in children and to identify possible critical phases of postural evolution (maturation).MethodsA total of 1084 children (aged 4–12 years) received a sagittal postural evaluation with the Biotonix postural analysis system. Data were retrieved from the Biotonix internet database. Children were stratified and analyzed by years of age with n = 36 in the youngest age group (4 years) and n = 184 in the oldest age group (12 years). Children were analyzed in the neutral upright posture. Variables measured were sagittal translation distances in millimeters of: the knee relative to the tarsal joint, pelvis relative to the tarsal joint, shoulder relative to the tarsal joint, and head relative to the tarsal joint. A two-way factorial ANOVA was used to test for age and gender effects on posture, while polynomial trend analyses were used to test for increased postural displacements with years of age.ResultsTwo-way ANOVA yielded a significant main effect of age for all 4 sagittal postural variables and gender for all variables except head translation. No age × gender interaction was found. Polynomial trend analyses showed a significant linear association between child age and all four postural variables: anterior head translation (p < 0.001), anterior shoulder translation (p < 0.001), anterior pelvic translation (p < 0.001), anterior knee translation (p < 0.001). Between the ages of 11 and 12 years, for anterior knee translation, T-test post hoc analysis revealed only one significant rough break in the continuity of the age related trend.ConclusionA significant linear trend for increasing sagittal plane postural translations of the head, thorax, pelvis, and knee was found as children age from 4 years to 12 years. These postural translations provide preliminary normative data for the alignment of a childs sagittal plane posture.

Changes in the flexion relaxation response induced by lumbar muscle fatigue

BackgroundThe 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.MethodsTwenty 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.ResultsOnset 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.ConclusionThe 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.

Changes in the flexion-relaxation response induced by hip extensor and erector spinae muscle fatigue

BackgroundThe flexion-relaxation phenomenon (FRP) is defined by reduced lumbar erector spinae (ES) muscle myoelectric activity during full trunk flexion. The objectives of this study were to quantify the effect of hip and back extensor muscle fatigue on FRP parameters and lumbopelvic kinematics.MethodsTwenty-seven healthy adults performed flexion-extension tasks under 4 different experimental conditions: no fatigue/no load, no fatigue/load, fatigue/no load, and fatigue/load. Total flexion angle corresponding to the onset and cessation of myoelectric silence, hip flexion angle, lumbar flexion angle and maximal trunk flexion angle were compared across different experimental conditions by 2 × 2 (Load × Fatigue) repeated-measures ANOVA.ResultsThe angle corresponding to the ES onset of myoelectric silence was reduced after the fatigue task, and loading the spine decreased the lumbar contribution to motion compared to the hip during both flexion and extension. A relative increment of lumbar spine motion compared to pelvic motion was also observed in fatigue conditions.ConclusionsPrevious results suggested that ES muscles, in a state of fatigue, are unable to provide sufficient segmental stabilization. The present findings indicate that, changes in lumbar-stabilizing mechanisms in the presence of muscle fatigue seem to be caused by modulation of lumbopelvic kinematics.

COMPARISON BETWEEN ELDERLY AND YOUNG MALES' LUMBOPELVIC EXTENSOR MUSCLE ENDURANCE ASSESSED DURING A CLINICAL ISOMETRIC BACK EXTENSION TEST

OBJECTIVE Endurance of the back extensor muscles has become important for clinical decisions that guide interventions, particularly for chronic low back pain patients. Very little information is available regarding back muscle endurance in the elderly. The aim of this study was to investigate back extensor muscle endurance in healthy elderly subjects during a modified Sorensen test. METHODS Sixteen elderly and 20 young male adults participated in our cross-sectional study. The subjects performed a modified Sorensen test (on a 45 degrees Roman chair) to quantify lumbopelvic extensor muscle endurance. Pre and postfatigue back extension maximal voluntary force was assessed according to an isometric lift test in a semicrouched position. Endurance time, perceived exertion (Borg CR10 scale), and postfatigue reduction of lifting force were recorded and compared among groups. RESULTS Elderly subjects showed a trend toward decreased endurance time compared to young adults, but the difference was not significant. Similar perceived exertion and diminished maximal force after the fatiguing protocol were observed in both young and elderly subjects. Maximal isometric lift force was significantly associated with endurance time in young but not in elderly subjects. CONCLUSIONS Lumbopelvic extensor muscle endurance and perceived exertion do not differ between young and healthy elderly individuals. However, back muscle endurance seems to be modulated by different neurophysiologic factors in the elderly. Normative data on young adults should be interpreted with caution in assessing back fitness in elderly subjects.

Balance, Falls-Related Self-Efficacy, and Psychological Factors amongst Older Women with Chronic Low Back Pain: A Preliminary Case-Control Study

Objective. To investigate balance functions in older women and evaluate the association of the fear-avoidance beliefs model (FABM) factors with balance and mobility performance. Participants. Fifteen older women with CLBP was compared with age-matched pain-free controls (n = 15). Main Outcome Measures. Pain intensity, falls-related self-efficacy and intrinsic constructs in the FABM were evaluated. Postural steadiness (centre of pressure (COP)) and mobility functions were assessed. Linear relationships of FABM variables with COP and mobility score were estimated. Results. CLBP showed lower mobility score compared to controls. CLBP presented lower falls-related self-efficacy and it was associated with reduced mobility scores. FABM variables and falls-related self-efficacy were correlated with postural steadiness. Physical activity was reduced in CLBP, but no between-group difference was evident for knee extensor strength. No systematic linkages were observed between FABM variables with mobility score or postural steadiness. Conclusions. Back pain status affects balance and mobility functions in older women. Falls-related self-efficacy is lower in CLBP and is associated with reduced mobility. Disuse syndrome in CLBP elderly is partly supported by the results of this preliminary study.

Load and speed effects on the cervical flexion relaxation phenomenon

BackgroundThe 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.MethodsEighteen 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.ResultsStatistical 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.ConclusionsThe 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.

Rehabilitation program for traumatic chronic cervical pain associated with unsteadiness: a single case study

BackgroundNeck problems are often recurring or chronic. After pain, unsteadiness and balance problems are among the most frequent symptoms reported by chronic neck pain (CNP) patients. Altered sensorimotor control of the cervical spine and sensorimotor integration problems affecting postural control have been observed in CNP patients. Very few data are available regarding the post-intervention effects of rehabilitation programs on postural control in CNP.Case presentationThis is a case study of a traumatic CNP patient (a 45-year old female) with postural unsteadiness who participated in an 8-week rehabilitation program combining therapeutic exercises with spinal manipulative therapy. Pre-intervention data revealed that the postural control system was challenged when postural control sensory inputs were altered, particularly during the head-extended-backward condition. Post-intervention centre of pressure measurements indicated a drastic reduction in postural sway during trials with changes in neck orientation.ConclusionThis case report indicates that an 8-week rehabilitation program combining therapeutic exercises with spinal manipulative therapy may have had an effect on improvement of postural control in a trauma CNP patient with unsteadiness. These results warrant further studies to investigate the relationships between pain amelioration, sensorimotor control of the cervical spine, muscle fitness and postural steadiness.

Intrasession reliability and influence of breathing during clinical assessment of lumbar spine postural control

The aims of this study were to evaluate the influence of breathing when measuring lumbar postural control during a clinical progressive lumbar stabilization test (LST) and to estimate the intrasession reliability of the LST. The lumbar postural control index was calculated by using a biofeedback pressure unit. The LST was performed in two different positions (crook lying and upright) and two respiratory conditions (apnea and breathing) by 20 healthy individuals. The intrasession reliability of the lumbar postural control index of one trial was estimated with intraclass correlation coefficient (ICC) based on an Anova model. The results showed that the lumbar postural control index is similar between testing positions. There is an increase of the lumbar postural control index during breathing compared to the apnea. The reliability of the lumbar postural control index was fair to good (ICC 0.28–0.58). We also found that for the apnea, three trials had to be averaged to attain an ICC of 0.80 for both positions. The results of the present study indicate that the progressive LST can be similarly conducted in either supine or upright posture. Clinicians should be aware of the influence of breathing during LST. However, breathing could also serve as a clinical strategy to challenge lumbar spine postural control and stability during bracing therapeutic exercises.