Markku Kankaanpää

The effect of lumbar fatigue on the ability to sense a change in lumbar position. A controlled study.

STUDY DESIGN A cross-sectional study in patients with recurrent/chronic low back trouble and healthy control subjects. OBJECTIVE To evaluate the effect of paraspinal muscle fatigue on the ability to sense a change in lumbar position. SUMMARY OF BACKGROUND DATA Protection against spinal injury requires proper anticipation of events, appropriate sensation of body position, and reasonable muscular responses. Lumbar fatigue is known to delay lumbar muscle responses to sudden loads. It is not known whether the delay is because of failure in the sensation of position, output of the response, or both. METHODS Altogether, 106 subjects (57 patients with low back trouble [27 men and 30 women] and 49 healthy control subjects [28 men and 21 women]) participated in the study. Their ability to sense a change in lumbar position while seated on a special trunk rotation unit was assessed. A motor rotated the seat with an angular velocity of 1 degree per second. The task in the test involved reacting to the perception of lumbar movement (rotation) by releasing a button with a finger movement. The test was performed twice, before and immediately after a fatiguing procedure. During the endurance task, the participants performed upper trunk repetitive extensions against a resistance, with a movement amplitude adjusted between 25 degrees flexion and 5 degrees extension, until exhaustion. RESULTS Patients with chronic low back trouble had significantly poorer ability than control subjects on the average to sense a change in lumbar position (P = 0.007), which was noticed before and after the fatiguing procedure. Lumbar fatigue induced significant impairment in the sensation of position change (P < 0.000001). CONCLUSIONS Lumbar fatigue impairs the ability to sense a change in lumbar position. This feature was found in patients and control subjects, but patients with low back trouble had poorer ability to sense a change in lumbar position than control subjects even when they were not fatigued. There seems to be a period after a fatiguing task during which the available information on lumbar position and its changes is inaccurate.

Back and hip extensor fatigability in chronic low back pain patients and controls

OBJECTIVE To compare the lumbar paraspinal and gluteus maximus muscle fatigability between chronic low back pain patients and healthy controls by using electromyographic (EMG) spectral analysis during a maximal isometric endurance task. DESIGN A cross-sectional comparative study between chronic low back pain patients and healthy control subjects. SETTING Physical medicine and rehabilitation clinic in Finland. SUBJECTS Twenty women with nonspecific chronic low back pain (longer than 3 months) and 15 healthy controls. INTERVENTION Subjects performed maximal voluntary isometric back extensions (MVC) at 30 degrees forward flexion in a specially designed measurement unit. A 50% MVC load was used in isometric endurance test. OUTCOME MEASURES Low back pain intensity was assessed by using the visual analogue scale and functional disability by the Oswestry disability index. Time to endurance was measured. Bipolar surface EMG recordings were made over the lumbar paraspinal muscles (L3-L4, L5-S1) and over the gluteus maximus muscles. Average EMG (aEMG%), and initial spectral median frequency (MFinit) and change over time (MFslope) were computed. RESULTS Pain intensity and functional disability were higher and MVC and time to endurance were lower in the chronic low back pain group (p < .05). Similar muscle activity levels (aEMG%) and MFinit indicated similar muscle loading in both groups at the beginning of the endurance test. EMG spectral decreases (MFslope) indicated that lumbar paraspinal muscle fatigability was similar in both groups. In the chronic low back pain group, the gluteus maximus fatigued faster than in the control group (greater MFslope, p < .05). However, the shorter endurance time indicated greater fatigability in the chronic low back pain group in general (p < .05). CONCLUSIONS The chronic low back pain patients were weaker and fatigued faster than the healthy controls. The EMG fatigue analysis results suggest that the gluteus maximus muscles are more fatigable in chronic low back pain patients than in healthy control subjects during a sustained back extension endurance test.

Interexaminer reliability of low back pain assessment using the McKenzie method.

Study Design. A test–retest design was used. Objective. To assess interexaminer reliability of the McKenzie method for performing clinical tests and classifying patients with low back pain. Summary of Background Data. Clinical methods and tests classifying patients with nonspecific low back pain have been based mainly on symptom duration or extent of pain referral. The McKenzie mechanical diagnostic and classification approach is a widely used noninvasive, low-technology method of assessing patients with low back pain. However, little is known about the interexaminer reliability of the method, previous studies having yielded conflicting results. Methods. For this study, 39 volunteers with low back pain, mean age 40 years (range, 24–55 years), were blindly assessed by two physical therapists trained in the McKenzie method. The variability of two examiners for binary decisions was expressed by the kappa coefficient, and by the proportion of observed agreement, as calculated from a 2 × 2 contingency table of concordance. Results. On the basis of pure observation alone, agreement among clinical tests on the presence and direction of lateral shift was 77% (&kgr; = 0.2;P < 0.248) and 79% (&kgr; = 0.4;P < 0.003), respectively. Agreement on the relevance of lateral shift and the lateral component according to symptom responses was 85% (&kgr; = 0.7;P < 0.000) and 92% (&kgr;= 0.4;P < 0.021), respectively. Using the repeated movements and static end-range loading strategy to define the centralization phenomenon and directional preference, agreement was 95% (&kgr; = 0.7;P < 0.002) and 90% (&kgr; = 0.9;P < 0.000), respectively. When patients with low back pain were classified into the McKenzie main syndromes and into specific subgroups, agreement was 95% (&kgr; = 0.6;P < 0.000) and 74% (&kgr; = 0.7;P < 0.000), respectively. Conclusions. Interexaminer reliability of the McKenzie lumbar spine assessment in performing clinical tests and classifying patients with low back pain into syndromes were good and statistically significant when the examiners had been trained in the McKenzie method.

Age, sex, and body mass index as determinants of back and hip extensor fatigue in the isometric Sørensen back endurance test

OBJECTIVE To study the ability of a widely used isometric back endurance test to measure lumbar back erector muscle fatigue and to assess the influence of age, sex, and body mass index (BMI) on back and hip extensor muscle fatigability (EMG spectral indices). DESIGN Cross-sectional study of men and women without back problems. SETTING Occupational health center and rehabilitation clinic in Finland. SUBJECTS Experiment 1 consisted of 233 consecutive occupational health center customers (133 women, 100 men) without back problems. Experiment 2 consisted of 20 healthy women. INTERVENTION Subjects performed the isometric Sørensen back endurance test up to 240sec in experiment 1 and to the limit of endurance in experiment 2. OUTCOME MEASURES Raw surface EMG was recorded bilaterally over the belly of lumbar erector spinae muscles at L1-L2 and L4-L5 levels in experiment 1, and bilaterally over the medial paraspinal muscles at L1-L2, L3-L4, and L5-S1 levels and over the major hip extensor muscles (gluteus maximus and biceps femoris) in experiment 2. In both experiments, time to endurance was recorded (in experiment 1 up to 240sec). The EMG spectral median frequency (MF) decrease over time was used for the assessment of back and hip extensor fatigability. RESULTS In experiment 1, the rate of change in paraspinal MF was greater in men than in women, indicating greater paraspinal fatigability in men. Multiple regression analysis indicated that the rate of MF decrease (fatigue) during the test was dependent on age and BMI in both sexes and that the effects of age and BMI were more pronounced in women than in men. Correlation analysis revealed that the rate of paraspinal muscle MF decrease was associated with endurance time and BMI in women and with endurance time and age in men. In experiment 2, the paraspinal muscles, as well as the hip extensor muscles, biceps femoris, and gluteus maximus, showed clear decreases in MF during the isometric endurance test in women. MF decrease was highly related to endurance time and BMI in women. CONCLUSIONS Lumbar paraspinal muscle fatigability during the Sørensen test is influenced by subject characteristics. Further, the hip extensor muscles also significantly fatigue, indicating load sharing between back and hip extensor muscles during the test. According to these results, the validity of this widely used back endurance test in specifically measuring lumbar paraspinal muscle endurance is questionable, as is the direct comparison of test results between women and men.

Back and hip extensor muscle function during Therapeutic exercises

BACKGROUND Therapeutic exercises are widely used in the treatment of low back problems. Clinical knowledge about targeting the load in these exercises, however, is insufficient. This study assessed the L2 and L5 level paraspinal and gluteus maximus muscle activities in different therapeutic exercises. Intramuscular and surface electromyography (EMG) measurements were obtained to study whether surface EMG measurements can be used in the assessment of multifidus muscle function. METHODS Eleven healthy subjects (5 men, 6 women) 21 to 38 years of age volunteered for the study. The subjects performed 18 different therapeutic exercises. During the exercises paraspinal EMG was recorded using fine wire and surface electrodes. The normalized peak and average muscle EMG activities (percentage of amplitude in maximal voluntary contraction [MVC]) during each task were determined. RESULTS The correlations between the average intramuscular and surface activities of the normalized EMG (% of MVC) at the L2 and L5 levels were .928 and .950, respectively. The peak and average EMG amplitudes of the exercises were below 50% and 25% of MVC, respectively. At the L5 level, the multifidus peak and average EMG amplitudes (% MVC) were higher in women than in men, whereas no significant difference was found at the L2 level. In women, the normalized multifidus EMG amplitude was higher at the L5 level than at the L2 level, whereas no significant difference was found in men. In both sexes, the normalized EMG amplitude was higher in the multifidus than in the longissimus muscle. CONCLUSION Surface EMG measurements may be used in the assessment of multifidus muscle function. Simple therapeutic exercises are effective in activating the lumbar paraspinal muscles.

Lumbar paraspinal muscle function, perception of lumbar position, and postural control in disc herniation-related back pain.

Study Design. A follow-up study evaluating postural control, lumbar movement perception, and paraspinal muscle reflexes in disc herniation-related chronic low back pain (LBP) before and after discectomy. Objectives. To assess the effect of discectomy on postural control, lumbar perception, and reflex activation of paraspinal muscles during sudden upper limb loading. Summary of Background Data. Impaired muscle function, postural control, and lumbar proprioception have been observed in LBP. However, they have not been studied in sciatica patients after surgery. Methods. The study included 20 patients selected for an operation for chronic LBP caused by disc herniation and 15 controls without chronic LBP. The paraspinal muscle responses for upper limb loading during unexpected and expected conditions were measured by surface electromyography. The ability to sense lumbar rotation was assessed in a previously validated motorized trunk rotation unit in the seated position. The postural control was measured with a vertical force platform. Pain, disability, and depression scores were recorded. Results. Patients had poorer lumbar perception (P = 0.012) and postural control (P < 0.05) than did healthy controls. The postural control remained unchanged, but lumbar perception (P = 0.054) and the lumbar feed-forward control (P = 0.043) improved after the surgery. Conclusions. The results demonstrate impaired lumbar proprioception and postural control in sciatica patients. During short-term follow-up after operative treatment, postural control does not seem to change, but impaired lumbar proprioception and feed-forward control of paraspinal muscles seem to recover.

Lumbar paraspinal muscle fatigability in repetitive isoinertial loading: EMG spectral indices, Borg scale and endurance time

Abstract The purpose of this study was to develop a submaximal repetitive isoinertial back muscle endurance test by defining the relationships between the power spectral indices of paraspinal muscle electromyographic (EMG) activities, endurance time and a subjective estimate of fatigue (Borg scale). Bilateral surface EMG recordings were obtained over the lumbar paraspinal muscles in ten individuals who were currently free from back pain. All subjects performed repetitive upper trunk extensions (25° flexion and 5° extension, 30 repetitions per min), while movement below the third lumbar vertebral body was mechanically restricted. The load level depended upon upper body mass, sex, and age. The tests continued for as long as the subjects were able to maintain the required repetition rate (endurance time). Median (MF) and mean power frequency (MPF) slopes were calculated by performing a fast Fourier transformation after confirmation of EMG stationarity by recurrence quantification analysis. MF and MPF correlations with endurance time/Borg scale were measured for the first 60 s (0.60–0.88/0.42–0.86), the first 90 s (0.62–0.89/0.52–0.90), the first 120 s (0.50–0.76/0.41–0.73), and the entire repetitive run (0.63–0.88/0.54–0.90). To test for the reproducibility of the spectral indices, EMGs were recorded for 2 min during repetitive loading from the same subjects on two consecutive days. Corresponding spectral slopes of MF and MPF were correlated at 60 s (0.36–0.93), 90 s (0.58–0.92), and 120 s (0.70–0.94) at the L3–L4 and L5–S1 levels, indicating good reproducibility of results from alternate recording sessions at the L5–S1 level. It is concluded that paraspinal muscle spectral indices (MF and MPF) measured before the onset of total muscle fatigue are good predictors of endurance time and are closely related to the subjective perception of fatigue.

Novel parameters of surface EMG in patients with Parkinson’s disease and healthy young and old controls

The aim of this study was to evaluate a variety of traditional and novel surface electromyography (SEMG) characteristics of biceps brachii muscle in patients with Parkinsons disease (PD) and compare the results with the healthy old and young control subjects. Furthermore, the aim was to define the optimal biceps brachii loading level that would most likely differentiate patients from controls. The results indicated that such nonlinear SEMG parameters as %Recurrence, %Determinism and SEMG distribution kurtosis, correlation dimension and sample entropy were significantly different between the PD patients and healthy controls. These novel nonlinear parameters, unlike traditional spectral or amplitude parameters, correlated with the Unified Parkinsons Disease Rating Scale (UPDRS) and finger tapping scores. The most significant between group differences were found in the loading condition where no additional weights were applied in isometric elbow flexion. No major difference of SEMG characteristics was detected between old and young control subjects. In conclusion, the novel SEMG parameters can differentiate the patients with PD from healthy control subjects and these parameters may have potential in the assessment of the severity of PD.

Impaired Lumbar Movement Perception in Association With Postural Stability and Motor- and Somatosensory-Evoked Potentials in Lumbar Spinal Stenosis

Study Design. A descriptive study of the associations between different neurophysiologic findings in patients with lumbar spinal stenosis. Objectives. To evaluate the ability to sense a change in lumbar position and the associations between lumbar movement perception, postural stability, and motor-evoked potentials and somatosensory-evoked potentials. Summary of Background Data. Patients with low back pain have impaired postural control and impaired lumbar proprioception. Altered motor-evoked potentials and somatosensory-evoked potentials have been often observed in lumbar spinal stenosis. Methods. The study included 26 patients with clinically and radiologically diagnosed lumbar spinal stenosis. Their ability to sense lumbar rotation was assessed in a previously validated motorized trunk rotation unit in the seated position. The abilities to indicate the movement direction and the movement magnitude were used as indexes of the ability to sense the lumbar rotatory movement. The postural stability was measured with a vertical force platform. The motor-evoked potentials were elicited by transcranial and lumbar stimulation and recorded from anterior tibialis muscles. The somatosensory-evoked potentials were elicited by transcutaneous electrical stimulation of the tibial nerve at the ankle. Results. Twenty patients (76.9%;P = 0.006) reported the wrong movement direction. Furthermore, the patients consistently localized the movement sensation in their shoulders instead of the lumbar region. The altered motor-evoked potentials and somatosensory-evoked potentials were observed in 11 and 16 patients, respectively. Abnormal motor-evoked potentials had inconsistent associations with impaired movement perception and postural stability and abnormal somatosensory-evoked potentials had no associations with other findings. Conclusions. Many patients with lumbar spinal stenosis have difficulties in sensing the lumbar rotational movement, which may indicate impaired proprioceptive abilities. Abnormal motor-evoked potentials and somatosensory-evoked potentials are also frequent in lumbar spinal stenosis but do not necessarily occur in the same patients as the abnormal ability to sense trunk movement. These new findings add to our understanding of the pathophysiology of lumbar spinal stenosis.

Surface EMG and acceleration signals in Parkinson’s disease: feature extraction and cluster analysis

We present an advanced method for feature extraction and cluster analysis of surface electromyograms (EMG) and acceleration signals in Parkinson’s disease (PD). In the method, 12 different EMG and acceleration signal features are extracted and used to form high-dimensional feature vectors. The dimensionality of these vectors is then reduced by using the principal component approach. Finally, the cluster analysis of feature vectors is performed in a low-dimensional eigenspace. The method was tested with EMG and acceleration data of 42 patients with PD and 59 healthy controls. The obtained discrimination between patients and controls was promising. According to clustering results, one cluster contained 90% of the healthy controls and two other clusters 76% of the patients. Seven patients with severe motor dysfunctions were distinguished in one of the patient clusters. In the future, the clinical value of the method should be further evaluated.