Effects of chronic low back pain on trunk coordination and back muscle activity during walking: changes in motor control

Low back pain (LBP) is often accompanied by changes in gait, such as a decreased (preferred) walking velocity. Previous studies have shown that LBP diminishes the normal velocity-induced transverse counter-rotation between thorax and pelvis, and that it globally affects mean erector spinae (ES) activity. The exact nature and causation of these effects, however, are not well understood. The aim of the present study was to examine in detail the effect of walking velocity on global trunk coordination and ES activity as well as their variability to gain further insights into the effects of non-specific LBP on gait. The study included 19 individuals with non-specific LBP and 14 healthy controls. Gait kinematics and ES activity were recorded during treadmill walking at (1) a self-selected (comfortable) velocity, and (2) sequentially increased velocities from 1.4 up to maximally 7.0 km/h. Pain intensity, fear of movement and disability were measured before the experiment. The angular movements of thorax, lumbar and pelvis were recorded in three dimensions. ES activity was recorded with pairs of surface electrodes. Trunk–pelvis coordination and mean amplitude of ES activity were analyzed. In addition, invariant and variant properties of trunk kinematics and ES activity were studied using principal component analysis (PCA). Comfortable walking velocity was significantly lower in the LBP participants. In the transverse plane, the normal velocity-induced change in pelvis–thorax coordination from more in-phase to more antiphase was diminished in the LBP participants, while lumbar and pelvis rotations were more in-phase compared to the control group. In the frontal plane, intersegmental timing was more variable in the LBP than in the control participants, with additional irregular movements of the thorax. Rotational amplitudes were not significantly different between the LBP and control participants. In the LBP participants, the pattern of ES activity was affected in terms of increased (residual) variability, timing deficits, amplitude modifications and frequency changes. The gait of the LBP participants was characterized by a more rigid and less variable kinematic coordination in the transverse plane, and a less tight and more variable coordination in the frontal plane, accompanied by poorly coordinated activity of the lumbar ES. Pain intensity, fear of movement and disability were all unrelated to the observed changes in coordination, suggesting that the observed changes in trunk coordination and ES activity were a direct consequence of LBP per se. Clinically, the results imply that conservative therapy should consider gait training as well as exercises aimed at improving both intersegmental and muscle coordination.     

非特异性腰痛患者坐-立位脊柱序列变化的研究

目的:研究非特异性腰痛(nonspecific low back pain,NLBP)患者坐-立位脊柱序列变化的特点。方法 :选择NLBP患者50例,其中男15例,女35例,年龄为48.0±10.7岁;同时招募50名健康志愿者作为对照组,其中男17例,女33例,年龄为45.2±10.6岁。采用脊柱形态测量仪(Spinalmouse誖)分别测量两组坐位及立位胸椎后凸角(thoracic kyphosis,TK)、腰椎前凸角(lumbar lordosis,LL)、骶骨倾角(sacral inclination,SacHipJ)、倾角(inclination,Incl)。采用Wilcoxon检验,分别对比各组坐位和立位的脊柱参数;采用Mann-Whitney U检验,对比两组立位脊柱参数、坐位脊柱参数及坐-立位脊柱参数变化量(difference value,D);采用Spearman检验,评估NLBP组腰痛的视觉模拟量表(visual analogue scale,VAS)评分与坐位LL、立位LL及D-LL的相关性;以30～39岁、40～49岁、50～59岁、60～69岁分为四个年龄段,采用Kruskal-Wallis H检验,对比NLBP组各年龄段坐位LL、立位LL及D-LL的差异。结果:立位变为坐位时,两组的TK、LL、SacHipJ均变小(P0.05),Incl均增大(P0.05);立位时,两组参数无统计学差异(P0.05);坐位时,NLBP组LL较对照组大,Incl较对照组小(P0.05);NLBP组D-TK、D-LL、D-Incl均较对照组小(P0.05)。NLBP组的VAS评分与立位及坐位LL相关性无统计学意义(P0.05),与D-LL呈弱的负相关(rs=-0.293,P0.05)。NLBP组坐位LL、立位LL及D-LL不同年龄段间的差异无统计学意义(P0.05)。结论:NLBP患者坐-立位脊柱序列不同于健康人群,表现为坐位时LL较健康受试者大,而从立位转变为坐位时,除骨盆后旋外,胸椎与腰椎曲度变小及躯干前移的变化量均较健康受试者小。     

Biomechanical effects of sitting with adjustable ischial and lumbar support on occupational low back pain: evaluation of sitting load and back muscle activity

Background  

Compared to standing posture, sitting decreases lumbar lordosis, increases low back muscle activity, disc pressure, and pressure on the ischium, which are associated with occupational LBP. A sitting device that reduces spinal load and low back muscle activities may help increase sitting comfort and reduce LBP risk. The objective of this study is to investigate the biomechanical effect of sitting with a reduced ischial support and an enhanced lumbar support (Off-Loading) on load, interface pressure and muscle activities.     

Function of back extensor muscles in upright standing position and during sitting with identical back posture--an electromyography study

PROBLEM: There is a controversial discussion about the loading of the spine by the force of the extending muscles of the back in upright sitting with the back curved as in upright standing. Experimental studies investigating this issue are still lacking. METHODS: In the study presented in this paper we measured in 30 subjects the activity of the extending back muscles both in a natural upright standing posture and in sitting with identical posture of the back as recommended in some back training programs. To this end we recorded the electromyographical surface activity of the back muscles at four levels of the spine in both postures. The EMG activities were intraindividually normalized with reference to the respective activity recorded at maximum voluntary isometric contraction (MVC). RESULTS: At three of the four levels of the spine examined, the group averages of the EMG activity in sitting were significantly higher than in standing (p < 0.001). The maximum activity enhancement evaluated was 48% at Th12. The force of the lower back muscles in sitting with a posture of the back as in natural upright standing could be estimated to be at least greater than 30% of the force at MVC. CONCLUSION: The force needed to enforce in sitting a posture of the back identical to the posture at natural standing entails lower back muscle fatigue in a few minutes. The results of our study agree with recent experimental findings about an increased loading of the spine in lordotic sitting.     

The role of paraspinal muscle spindles in lumbosacral position sense in individuals with and without low back pain

STUDY DESIGN: A two-group experimental design with repeated measures on one factor was used. OBJECTIVES: To investigate the role of paraspinal muscle spindles in lumbosacral position sense in individuals with and without low back pain. SUMMARY OF BACKGROUND DATA: Proprioceptive deficits have been identified in patients with low back pain. The underlying mechanisms, however, are not well documented. METHODS: Lumbosacral position sense was determined before, during, and after lumbar paraspinal muscle vibration in 23 young patients with low back pain and in 21 control subjects. Position sense was estimated by calculating the mean absolute error, constant error, and variable error between six criterion and reproduction sacral tilt angles. RESULTS: Repositioning accuracy was significantly lower in the patient group than in healthy individuals (absolute error difference between groups = 2.7 degrees, P < 0.0001). Multifidus muscle vibration induced a significant muscle-lengthening illusion that resulted in an undershooting of the target position in healthy individuals (constant error = -3.1 degrees, P < 0.0001). Conversely, the position sense scores of the patient group did not display an increase in negative directional error but a significant improvement in position sense during muscle vibration (P < 0.05). No significant differences in absolute error were found between the first and last trial in the healthy individuals (P >/= 0.05) and in the patient group (P > 0.05). CONCLUSIONS: Patients with low back pain have a less refined position sense than healthy individuals, possibly because of an altered paraspinal muscle spindle afference and central processing of this sensory input. Furthermore, muscle vibration can be an interesting expedient for improving proprioception and enhancing local muscle control.     

Repositioning error in low back pain. Comparing trunk repositioning error in subjects with chronic low back pain and control subjects

STUDY DESIGN: Repositioning error of the trunk was tested in 20 subjects with chronic low back pain and in 20 control subjects. The 3Space Tracker (Polhemus, Colchester, VT), a device that measures three-dimensional position in space, was used to determine the subject's trunk position. OBJECTIVES: To determine whether repositioning error is different in subjects with chronic low back pain than in control subjects. SUMMARY OF BACKGROUND DATA: Proprioception allows the body to maintain proper orientation during static and dynamic activities. In peripheral joint injuries, researchers have demonstrated a loss of some aspects of proprioception and improvement in outcome with retraining. Although the components of proprioception in subjects with low back pain have not been well studied, it is thought that these persons lose some elements of proprioception that can be measured in a quantifiable way. If so, then rehabilitation to improve these deficits is important. In this pilot study, one aspect of proprioception, repositioning error, was examined. METHODS: The subjects attempted to replicate target positions of the trunk in flexion, extension, lateral bending, and lateral rotation. Repositioning error was calculated as the absolute difference between the actual and the subject-replicated target positions. RESULTS: No significant difference was found in repositioning error between the control subjects and the persons with chronic low back pain. CONCLUSIONS: Because proprioception is complex and entails the use of many afferent receptors, it is difficult to measure any one afferent deficiency discretely. The authors believe that this study, in which one aspect of proprioception was measured in an indirect manner, provides important background information on low back position sense. Further studies analyzing aspects of proprioception in subjects with low back pain are recommended.     

中国急/慢性非特异性腰背痛诊疗专家共识

<正>腰背痛(low back pain,LBP)是一类严重影响患者生活质量的常见病症,可导致患者运动功能障碍,甚至丧失生活自理能力。每年由腰背痛所产生的直接或间接经济损失数额巨大。据统计,仅1998年,美国因腰背痛治疗的总医疗支出较上一年增加了263亿美元~([1]),每年用于支付腰背部损伤性疼痛的劳动赔偿费用占年度总赔偿额度的     

Lumbopelvic kinematics and trunk muscle activity during sitting on stable and unstable surfaces

STUDY DESIGN: A single-group comparative study. OBJECTIVES: To compare lumbopelvic kinematics and muscle activation patterns while sitting on stable and unstable surfaces. BACKGROUND: Unstable surfaces are commonly used during the rehabilitation of certain low back pain disorders. The benefits postulated are increased muscle activity and facilitation of sustainable midrange positions via neuromuscular control. The use of unstable sitting devices in the workplace is controversial, as the postulated increase in muscle activity is thought to lead to a muscle fatigue/pain response. However, little evidence exists for or against the ability of these devices to alleviate or prevent spinal pain. METHODS AND MEASURES: This study included 26 healthy adults (14 male, 12 female). Fastrak 3-dimensional motion analysis detected lumbar curvature, pelvic tilt, and postural sway during sitting on a stable and unstable surface over 5-minute periods. Surface electromyography was used to measure activity in the superficial lumbar multifidus, transverse fibers of internal oblique, and iliocostalis lumborum pars thoracis. RESULTS: Spinal postures were similar for sitting on a stable and unstable surface. Significant increases in postural sway were detected (P = .013) in 3 dimensions of movement during sitting on an unstable surface. Gender differences were noted. No EMG amplitude or variance differences were detected between seating conditions. CONCLUSIONS: Preliminary data show that sitting on unstable surfaces induces greater spinal motion, but does not significantly alter the lumbosacral posture nor the amount of activity in the superficial trunk muscles under investigation.     

The association between isoinertial trunk muscle performance and low back pain in male adolescents

The literature reports inconsistent findings regarding the association between low back pain (LBP) and trunk muscle function, in both adults and children. The strength of the relationship appears to be influenced by how LBP is qualified and the means by which muscle function is measured. The aim of this study was to examine the association between isoinertial trunk muscle performance and consequential (non-trivial) low back pain (LBP) in male adolescents. Healthy male adolescents underwent anthropometric measurements, clinical evaluation, and tests of trunk range of motion (ROM), maximum isometric strength (STRENGTH) and peak movement velocity (VEL), using an isoinertial device. They provided information about their regular sporting activities, history and family history of LBP. Predictors of “relevant/consequential LBP” were examined using multivariable logistic regression. LBP status was reassessed after 2 years and the change from baseline was categorised. At baseline, 33/95 (35%) subjects reported having experienced consequential LBP. BMI, a family history of LBP, and regularly playing sport were each significantly associated with a history of consequential LBP (p < 0.05). 85/95 (89%) boys participated in the follow-up: 51 (60%) reported no LBP at either baseline or follow-up (never LBP); 5 (6%) no LBP at baseline, but LBP at follow-up (new LBP); 19 (22%) LBP at baseline, but none at follow-up; and 10 (12%) LBP at both time-points (recurrent/persistent LBP). The only distinguishing features of group membership in these small groups were: fewer sport-active in the “never LBP” group); worse trunk mobility, in the “persistent LBP” group, lower baseline sagittal ROM in the “never LBP” and “new LBP” (p < 0.05). Regular involvement in sport was a consistent predictor of LBP. Isoinertial trunk performance was not associated with LBP in adolescents.     

Reproducibility of postural control measurement during unstable sitting in low back pain patients

Background  

Postural control tests like standing and sitting stabilometry are widely used to evaluate neuromuscular control related to trunk balance in low back pain patients. Chronic low back pain patients have lesser postural control compared to healthy subjects. Few studies have assessed the reproducibility of the centre of pressure deviations and to our knowledge no studies have investigated the reproducibility of three-dimensional kinematics of postural control tests in a low back pain population. Therefore the aim of this study was to assess the test-retest reproducibility of a seated postural control test in low back pain patients.     

Exercise and nonspecific low back pain: a literature review

We reviewed the literature to clarify the effects of exercise in preventing and treating nonspecific low back pain. We evaluated several characteristics of exercise programs including specificity, individual tailoring, supervision, motivation enhancement, volume, and intensity. The results show that exercise is effective in the primary and secondary prevention of low back pain. When used for curative treatment, exercise diminishes disability and pain severity while improving fitness and occupational status in patients who have subacute, recurrent, or chronic low back pain. Patients with acute low back pain are usually advised to continue their everyday activities to the greatest extent possible rather than to start an exercise program. Supervision is crucial to the efficacy of exercise programs. Whether general or specific exercises are preferable is unclear, and neither is there clear evidence that one-on-one sessions are superior to group sessions. Further studies are needed to determine which patient subsets respond to specific characteristics of exercise programs and which exercise volumes and intensities are optimal.     

An analysis of the relationship between activity and pain in chronic and acute low back pain

We studied the temporal relationship between pain and activity in patients with acute or chronic low back pain. We studied 15 patients with acute low back pain and 15 patients with chronic low back pain over 3 wk. The activity levels were collected automatically using a wrist accelerometer and were sampled every minute. The pain levels were recorded at least every 90 min using a pocket-sized electronic diary. The time series from each patient were then analyzed using the cross-correlation function at various time offsets. We found that during the first 7 days of acute low back pain, there was a significant (P < 0.01) degree of cross-correlation between activity and pain. On average, pain followed activity by approximately 30 min. As these patients improved and reported less pain, the relationship between activity and pain disappeared. There was no such relationship at any point among the patients with chronic low back pain.     

Lumbosacral position sense during pelvic tilting in men and women without low back pain: test development and reliability assessment.

STUDY DESIGN: A single group test-retest design to evaluate the reproducibility of lumbosacral position sense measurements. OBJECTIVES: To develop a measure of position sense in the lumbosacral area and to determine test-retest reliability. BACKGROUND: Proprioception, muscle control, and coordination training could be the key issues in resolving neuromuscular dysfunction in patients with low back pain, but there are no standard ways to assess these parameters. METHODS AND MEASURES: A piezoresistive accelerometer attached to the skin over the sacrum was used to research the repositioning accuracy of active pelvic tilting, between days, of 14 young nonimpaired subjects (20 to 26 years of age) in standing. RESULTS: The mean absolute error for repositioning accuracy (the difference between criterion and matching positions) was 1.81 degrees (+/- 0.85). The intraclass correlation coefficient between measurements obtained on days 1 and 2 was moderate (R = 0.51). The average standard error of measurement associated with the intraclass correlation coefficient was 0.5 degree (95% confidence interval = +/- 0.99 degree). CONCLUSIONS: These findings suggest that the proposed test is sensitive with moderate test-retest reliability to examine lumbosacral position sense in healthy subjects. Further adjustments in the testing protocol are needed to improve the test-retest reliability.     

The effect of trunk muscle exercises in patients over 40 years of age with chronic low back pain

Previous studies of trunk muscle strength in patients with chronic low back pain (CLBP) have mainly reported on patients aged younger than 40 years. However, no such investigation has yet been done in middle-aged patients. Trunk muscle strength and the effect of trunk muscle exercises were investigated in patients with CLBP aged more than 40 years. Trunk muscle strengths were measured in a LBP group (52 patients) and a control group (60 volunteers) and the results for the two groups were compared. The LBP group was divided into three subgroups. Group A had only age-related spondylosis and group B had disk herniation and spondylolisthesis with age-related spondylotic change. Both these groups were able to continue exercises. Group C was made up of patients who had abandoned the exercise program. Trunk muscle strength and symptoms were assessed in each group. Both flexion and extension strength were decreased in the LBP group compared with the control group, with the reduction in extension strength being most marked. In both groups A and B, muscle strength increased and clinical symptoms improved. In contrast, no change was seen in group C. In older patients with CLBP, reduction of muscle strength was more marked in the spinal extensors than in the spinal flexors. It was confirmed that trunk muscle strengthening exercises are useful for increasing muscle strength and improving symptoms in such patients. Received for publication on July 15, 1999; accepted on Nov. 9, 1999