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.
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.
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.
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.
The increased intra-abdominal pressure (IAP) commonly observed when the spine is loaded during physical activities is hypothsized to increase lumbar spine stability.The mechanical stability of the lumbar spine is an important consideration in low back injury prevention and rehabilitation strategies. This study examined the effects of raised IAP and an abdominal belt on lumbar spine stability. Two hypotheses were tested: (1) An increase in IAP leads to increased lumbar spine stability, (2) Wearing an abdominal belt increases spine stability. Ten volunteers were placed in a semi-seated position in a jig that restricted hip motion leaving the upper torso free to move in any direction. The determination of lumbar spine stability was accomplished by measuring the instantaneous trunk stiffness in response to a sudden load release. The quick release method was applied in isometric trunk flexion, extension, and lateral bending. Activity of 12 major trunk muscles was monitored with electromyography and the IAP was measured with an intra-gastric pressure transducer. A two-factor repeated measures design was used (P < 0.05), in which the spine stability was evaluated under combinations of the following two factors: belt or no belt and three levels of IAP (0, 40, and 80% of maximum). The belt and raised IAP increased trunk stiffness in all directions, but the results in extension lacked statistical significance. In flexion, trunk stiffness increased by 21% and 42% due to 40% and 80% IAP levels respectively; in lateral bending, trunk stiffness increased by 16% and 30%. The belt added between 9% and 57% to the trunk stiffness depending on the IAP level and the direction of exertion. In all three directions, the EMG activity of all 12 trunk muscles increased significantly due to the elevated IAP. The belt had no effect on the activity of any of the muscles with the exception of the thoracic erector spinae in extension and the lumbar erector spinae in flexion, whose activities decreased. The results indicate that both wearing an abdominal belt and raised IAP can each independently, or in combination, increase lumbar spine stability. However, the benefits of the belt must be interpreted with caution in the context of the decreased activation of a few trunk extensor muscles.
Key words Lumbar spine; stability; Lumbar spine; intra-abdominal; pressure; Lumbar spine; abdominal belts; Lumbar spine; electromyography
The microscopic observation drug susceptibility assay (MODS) is a novel and promising test for the early diagnosis of tuberculosis (TB). We evaluated the MODS assay for the early diagnosis of TB in HIV-positive patients presenting to Pham Ngoc Thach Hospital for Tuberculosis and Lung Diseases in southern Vietnam. A total of 738 consecutive sputum samples collected from 307 HIV-positive individuals suspected of TB were tested by smear, MODS, and the mycobacteria growth indicator tube method (MGIT). The diagnostic sensitivity and specificity of MODS compared to the microbiological gold standard (either smear or MGIT) were 87 and 93%, respectively. The sensitivities of smear, MODS, and MGIT were 57, 71, and 75%, respectively, against clinical gold standard (MODS versus smear, P < 0.001; MODS versus MGIT, P = 0.03). The clinical gold standard was defined as patients who had a clinical examination and treatment consistent with TB, with or without microbiological confirmation. For the diagnosis of smear-negative patients, the sensitivities of MODS and MGIT were 38 and 45%, respectively (P = 0.08). The median times to detection using MODS and MGIT were 8 and 11 days, respectively, and they were 11 and 17 days, respectively, for smear-negative samples. The original bacterial/fungal contamination rate of MODS was 1.1%, while it was 2.6% for MGIT. The cross-contamination rate of MODS was 4.7%. In conclusion, MODS is a sensitive, specific, and rapid test that is appropriate for the detection of HIV-associated TB; its cost and ease of use make it particularly useful in resource-limited settings.
To determine if trunk muscle attributes are associated with balance and mobility performance among mobility-limited older adults.
Cross-sectional analysis of data from a randomized clinical trial.
Outpatient rehabilitation research center.
Community-dwelling older adults (N=70; mean age 75.9 y) with mobility limitations as defined by the Short Physical Performance Battery (SPPB).
Independent variables included physiologic measures of trunk extension strength, trunk flexion strength, trunk extension endurance, trunk extension endurance and leg press strength. All measures were well tolerated by the study subjects without the occurrence of any associated injuries or adverse events. The association of each physiologic measure with each outcome was examined, using separate multivariate models to calculate the partial variance (R2) of each trunk and extremity measure.
Main Outcome Measurements
Balance measured by the Berg Balance Scale (BBS) and Unipedal Stance Test (UST), and mobility performance as measured by the SPPB.
Trunk extension endurance (partial R2=.14, p=.02), and leg press strength (partial R2=.14, p=.003) accounted for the greatest amount of the variance in SPPB performance. Trunk extension endurance (partial R2=.17, p=.007), accounted for the greatest amount of the variance in BBS performance. Trunk extension strength (R2=.09, p=.03), accounted for the greatest amount of the variance in UST performance. The variance explained by trunk extension endurance equaled or exceeded the variance explained by limb strength across all three performance outcomes.
Trunk endurance and strength can be safely measured in mobility-limited older adults, and are associated with both balance and mobility performance. Trunk endurance and trunk strength are physiologic attributes worthy of targeting in the rehabilitative care of mobility-limited older adults.
Aged; Balance; Core; Impairments; Mobility; Rehabilitation; Trunk
Inexpensive, rapid, and reliable methods of detecting infection by and drug susceptibility of Mycobacterium tuberculosis (MTB) are crucial to the control of tuberculosis. The novel microscopic observation broth-drug susceptibility assay (MODS) detects early growth of MTB in liquid medium, allowing more timely diagnosis and drug susceptibility testing. Sputum samples from hospitalized patients in Peru were analyzed by using stains, culture, and PCR. Sensitivity of MODS (92%) compared favorably with the most sensitive of the other culture methods (93%). Sputum samples positive for tuberculosis were tested for susceptibility to isoniazid and rifampin with the microwell alamar blue assay (MABA) and MODS. In 89% of cases, there was concordance between MODS and MABA. Of the diagnostic and susceptibility testing methods used, MODS yielded results most rapidly (median, 9.0 and 9.5 days, respectively). MODS is a rapid, inexpensive, sensitive, and specific method for MTB detection and susceptibility testing; it is particularly appropriate for use in developing countries burdened by significant infection rates and increasing numbers of multiple-drug-resistant cases.
Pushing and pulling tasks account for 20% of occupational low-back injury claims. Primary torso muscle groups recruited during pushing tasks include rectus abdominis and the external obliques. However, analyses suggest that antagonistic co-contraction of the para spinal muscles is necessary to stabilize the spine during flexion exertions. The study quantified co-contraction and spinal load differences during isometric flexion and extension exertions. The goal was to provide insight into the mechanisms requiring greater co-contraction during trunk flexion exertions compared to extension exertions.
Electromyographic (EMG) signals were recorded from the trunk muscles of healthy volunteers during isometric trunk flexion and extension exertions. A biomechanical model was implemented to estimate total muscle force from the measured EMG and trunk moment data. A similar model estimated the muscle forces necessary to achieve equilibrium while minimizing the sum of squared muscle forces. The difference in these forces represented co-contraction. Spinal load attributed to co-contraction was computed.
Average co-contraction during flexion exertions was approximately twice the value of co-contraction during extension, i.e. 28% and 13% of total muscle forces respectively. Co-contraction accounted for up to 47% of the total spinal load during flexion exertions. Consequently, spinal compression during the flexion tasks was nearly 50% greater than during extension exertions despite similar levels of trunk moment.
Co-contraction must be considered when evaluating spinal load during pushing exertions. Results underscore the need to consider neuromuscular control of spinal stability when evaluating the biomechanical risks.
Low-back; Spine; Co-contraction; push
Side bridge endurance protocols have been suggested to evaluate lateral trunk flexor and/or spine stabilizer muscles. To date, no study has investigated muscle recruitment and fatigability during these protocols. Therefore the purpose of our study was to quantify fatigue parameters in various trunk muscles during a modified side bridge endurance task (i.e. a lateral isometric hold test on a 45° roman chair apparatus) and determine which primary trunk muscles get fatigued during this task. It was hypothesized that the ipsilateral external oblique and lumbar erector spinae muscles will exhibit the highest fatigue indices.
Twenty-two healthy subjects participated in this study. The experimental session included left and right lateral isometric hold tasks preceded and followed by 3 maximal voluntary contractions in the same position. Surface electromyography (EMG) recordings were obtained bilaterally from the external oblique, rectus abdominis, and L2 and L5 erector spinae. Statistical analysis were conducted to compare the right and left maximal voluntary contractions (MVC), surface EMG activities, right vs. left holding times and decay rate of the median frequency as the percent change from the initial value (NMFslope).
No significant left and right lateral isometric hold tests differences were observed neither for holding times (97.2 ± 21.5 sec and 96.7 ± 24.9 sec respectively) nor for pre and post fatigue root mean square during MVCs. However, participants showed significant decreases of MVCs between pre and post fatigue measurements for both the left and right lateral isometric hold tests. Statistical analysis showed that a significantly NMFslope of the ipsilateral external oblique during both conditions, and a NMFslope of the contralateral L5 erector spinae during the left lateral isometric hold test were steeper than those of the other side’s respective muscles. Although some participants presented positive NMFslope for some muscles, each muscle presented a mean negative NMFslope significantly different from 0.
Although the fatigue indices suggest that the ipsilateral external oblique and contralateral L5 erector spinae show signs of muscle fatigue, this task seems to recruit a large group of trunk muscles. Clinicians should not view this task as evaluating specifically lateral trunk flexors, but rather as providing an indication of the general endurance and stabilisation capacity of the trunk.
Side bridge test; Muscle fatigue; Trunk muscle; Functional testing
Cystic fibrosis is a multisystem disease where the main problems are existing in the respiratory system. Aerobic exercise programs are effective in increasing physical fitness and muscle endurance in addition to chest physiotherapy.
The aim of this study was to evaluate the effects of chest physiotherapy and aerobic exercise training on physical fitness in young children with cystic fibrosis.
Sixteen patients with cystic fibrosis, between the ages 5-13 years, were included in this study. All children were assessed at the beginning and at the end of 6 week of the training. Modified Bruce protocol was used for assessing the cardiovascular endurance. The sit-up test was used to evaluate the dynamic endurance of abdominal muscles, standing long jump was used to test power, sit and reach, trunk lateral flexion, trunk hyperextension, trunk rotation and forward bending tests were used to assess flexibility, 20 m shuttle run test and 10-step stair climbing tests were used to assess power and agility. All patients received chest physiotherapy and aerobic training, three days a week for six weeks. Active cycle of breathing technique and aerobic exercise training program on a treadmill were applied.
By evaluating the results of the training, positive progressions in all parameters except 20 m shuttle run and 10 stairs climbing tests were observed (p < 0.05). Active cycle of breathing techniques were used together with exercise training in clinically stable cystic fibrosis patients increases thoracic mobility (p < 0.05) and the physical fitness parameters such as muscle endurance, strength and speed (p < 0.05). Comparison of the results in sit and reach and forward bending tests were not significant (p > 0.05).
It is thought that in addition to medical approaches to the systems affected, the active cycle of breathing techniques along with aerobic training helps to enhance the aerobic performance, thoracic mobility and improves physical fitness in children with cystic fibrosis.
Cystic fibrosis; physical fitness; aerobic exercise; training
The 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.
Twenty-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.
The 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.
Previous 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.
The purpose of this study was to examine the effect of four methods of stabilization on maximal reciprocal isokinetic knee extension and flexion. Left knee extension/flexion was tested at 60°/s in 20 subjects. Warm-up consisted of five submaximal and one maximal effort followed by three maximal efforts in each of four randomized stabilization conditions: 1) Hands and back stabilization; the trunk was strapped to the back rest and the hands grasped the seat. 2) Back stabilization; the trunk was strapped to the back rest and the hands were folded across the chest. 3) Hand stabilization; the hands grasped the seat and the back rest was removed. 4) No stabilization; the hands were folded across the chest and the back rest was removed. One-way repeated measures ANOVA showed a significant effect of stabilization for knee extension (F(3,57)=17.44, p=.0001) and knee flexion (F(3,57)= 5.37, p=.002). Paired, two-tailed student's t-tests with Bonferroni correction showed that, in knee extension, no stabilization was significantly less than all others, p<.001. In addition, back stabilization was less than hands and back stabilization, p<.005. In knee flexion, no stabilization was significantly less than all others, p<.01. In conclusion, the method of trunk stabilization significantly affected maximal reciprocal isokinetic knee extension/flexion strength measurements. Maximal knee extension/flexion torque production was achieved when the trunk was strapped to the back support and when the hands grasped the seat.
Tuberculosis (TB) in children is rarely confirmed due to the lack of effective diagnostic tools; only 10 to 15% of pediatric TB is smear positive due to paucibacillary samples and the difficulty of obtaining high-quality specimens from children. We evaluate here the accuracy of Xpert MTB/RIF in comparison with the Micoroscopic observation drug susceptibility (MODS) assay for diagnosis of TB in children using samples stored during a previously reported evaluation of the MODS assay.
Ninety-six eligible children presenting with suspected TB were recruited consecutively at Pham Ngoc Thach Hospital in Ho Chi Minh City Viet Nam between May to December 2008 and tested by Ziehl-Neelsen smear, MODS and Mycobacterial growth Indicator (MGIT, Becton Dickinson) culture. All samples sent by the treating clinician for testing were included in the analysis. An aliquot of processed sample deposit was stored at −20°C and tested in the present study by Xpert MTB/RIF test. 183 samples from 73 children were available for analysis by Xpert. Accuracy measures of MODS and Xpert were summarized.
The sensitivity (%) in detecting children with a clinical diagnosis of TB for smear, MODS and Xpert were 37.9 [95% CI 25.5; 51.6], 51.7 [38.2; 65.0] and 50.0 [36.6; 63.4], respectively (per patient analysis). Xpert was significantly more sensitive than smear (P=0.046). Testing of additional samples did not increase case detection for MODS while testing of a second sputum sample by Xpert detected only two additional cases. The positive and negative predictive values (%) of Xpert were 100.0 [88.0; 100.0] and 34.1 [20.5; 49.9], respectively, while those of MODS were 96.8 [83.3; 99.9] and 33.3 [19.6; 49.5].
MODS culture and Xpert MTB/RIF test have similar sensitivities for the detection of pediatric TB. Xpert MTB RIF is able to detect tuberculosis and rifampicin resistance within two hours. MODS allows isolation of cultures for further drug susceptibility testing but requires approximately one week to become positive. Testing of multiple samples by xpert detected only two additional cases and the benefits must be considered against costs in each setting. Further research is required to evaluate the optimal integration of Xpert into pediatric testing algorithms.
Tuberculosis; GeneXpert MTB/RIF; MODS; Pediatric; Childhood
Nonlinear systems analyses of trunk kinematics were performed to estimate control of dynamic stability during repetitive flexion and extension movements.
Determine whether movement pace and movement direction of dynamic trunk flexion and extension influence control of local dynamic stability.
Summary of Background Data.
Spinal stability has been previously characterizedz in static, but not in dynamic movements. Biomechanical models make inferences about static spinal stability, but existing analyses provide limited insight into stability of dynamic movement. Stability during dynamic movements can be estimated from Lyapunov analyses of empirical data.
There were 20 healthy subjects who performed repetitive trunk flexion and extension movements at 20 and 40 cycles per minute. Maximum Lyapunov exponents describing the expansion of the kinematic state-space were calculated from the measured trunk kinematics to estimate stability of the dynamic system.
The complexity of torso movement dynamics required at least 5 embedded dimensions, which suggests that stability components of lumbar lordosis may be empirically measurable in addition to global stability of trunk dynamics. Repeated trajectories from fast paced movements diverged more quickly than slower movement, indicating that local dynamic stability is limited in fast movements. Movements in the midsagittal plane showed higher multidimensional kinematic divergence than asymmetric movements.
Nonlinear dynamic systems analyses were successfully applied to empirically measured data, which were used to characterize the neuromuscular control of stability during repetitive dynamic trunk movements. Movement pace and movement direction influenced the control of spinal stability. These stability assessment techniques are recommended for improved workplace design and the clinical assessment of spinal stability in patients with low back pain.
spine; stability; dynamics; neuromuscular control
Sensory information from mechanoreceptors in the skin, muscles, tendons, and joint structures plays an important role in joint stability. A joint injury can lead to disruption of the sensory system, which can be measured by proprioceptive acuity. When evaluating proprioception, assessment tools need to be reliable. The aim of this study was to assess the test-retest reliability of a device designed to measure knee proprioception.
Twenty-four uninjured individuals (14 women and 10 men) were examined with regard to test-retest reliability of knee kinesthesia, measured by the threshold to detection of passive motion (TDPM). Measurements were performed towards extension and flexion from the two starting positions, 20 degrees and 40 degrees knee joint flexion, giving four variables. The mean difference between test and retest together with the 95% confidence interval (test 2 minus test 1), the intraclass correlation coefficient (ICC2,1), and Bland and Altman graphs with limits of agreement, were used as statistical methods for assessing test-retest reliability.
The intraclass correlation coefficients ranged from 0.59 to 0.70 in all variables except one. No difference was found between test and retest in three of the four TDPM variables. TDPM would need to decrease between 10% and 38%, and increase between 17% and 24% in groups of uninjured subjects to be 95% confident of detecting a real change. The limits of agreement were rather wide in all variables. The variables associated with the 20-degree starting position tended to have higher intraclass correlation coefficients and narrower limits of agreement than those associated with 40 degrees.
Three TDPM variables were considered reliable for observing change in groups of subjects without pathology. However, the limits of agreement revealed that small changes in an individual's performance cannot be detected. The higher intraclass correlation coefficients and the narrower limits of agreement in the variables associated with the starting position of 20 degrees knee joint flexion, indicate that these variables are more reliable than those associated with 40 degrees. We, therefore, recommend that the TDPM be measured with a 20-degree starting position.
The differences between the metastatic property of moderately (Mod) and well (Wel) differentiated colorectal adenocarcinoma remain unclear. Since Mod is unable to form complete acini, therefore an epithelial-mesenchymal transition (EMT) can occur in that structure. Herein, we hypothesized that Mod metastasizes more easily than the Wel counterparts.
The medical records of 283 consecutive patients with Mod (n = 71) or Wel (n = 212) who underwent surgery were reviewed between January 1, 2001, and December 31, 2003, for actual 5-year overall survival. We examined the differences between the clinicopathological characteristics of the Mod and the Wel groups.
The lymph node involvement (p < 0.0001), lymphatic permeation, venous permeation, depth of invasion, liver metastasis, and carcinomatous peritonitis were significantly higher in the Mod group in comparison to the Wel group. The independent risk factors by a logistic regression analysis for lymph node involvement were as follows: lymphatic permeation, liver metastasis, and Mod (p = 0.0291, Relative Risk of 1.991: 95% Confidence Interval: 1.073-3.697). A Kaplan-Meier survival curve showed that Mod had a trend towards a poor survival (p = 0.0517).
Mod metastasizes to the lymph nodes more easily in comparison to Wel. Therefore, patients with Mod may be considered the existence of lymph node involvement.
Using a Cybex® trunk extension/flexion device, we measured the effects of rigid and semirigid lumbar/sacral supports on peak muscular torque, total work, and average power. Ten well-conditioned men, aged 21 to 35, performed three testing sessions each at 7-day intervals (one session with a rigid support, one session with a semirigid support, and one with no support). We selected four isokinetic testing speeds (30°/s, 60°/s, 90°/s, and 120°/s), complying with a standard Cybex trunk extension/flexion protocol. Differences between lumbar/sacral supports were analyzed using an analysis of variance (ANOVA) and Scheffé post hoc tests. Peak torque, total work, and average power were significantly different (p<.05) during trunk flexion at various isokinetic velocities. Trunk extension movements did not appear to be affected by the use of supports, but trunk flexion was significantly greater with the semirigid device and with no device than with the rigid support. We concluded that a rigid lumbar/sacral support decreases strength during movement tasks involving trunk flexion with resistance.
Assessment of shoulder mobility is essential for diagnosis and clinical follow-up of shoulder diseases. Only a few highly sophisticated instruments for objective measurements of shoulder mobility are available. The recently introduced DynaPort MiniMod TriGyro ShoulderTest-System (DP) was validated earlier in laboratory trials. We aimed to assess the precision (repeatability) and agreement of this instrument in human subjects, as compared to the conventional goniometer.
The DP is a small, light-weight, three-dimensional gyroscope that can be fixed on the distal upper arm, recording shoulder abduction, flexion, and rotation. Twenty-one subjects (42 shoulders) were included for analysis. Two subsequent assessments of the same subject with a 30-minute delay in testing of each shoulder were performed with the DP in two directions (flexion and abduction), and simultaneously correlated with the measurements of a conventional goniometer. All assessments were performed by one observer. Repeatability for each method was determined and compared as the statistical variance between two repeated measurements. Agreement was illustrated by Bland-Altman-Plots with 95% limits of agreement. Statistical analysis was performed with a linear mixed regression model. Variance for repeated measurements by the same method was also estimated and compared with the likelihood-ratio test.
Evaluation of abduction showed significantly better repeatability for the DP compared to the conventional goniometer (error variance: DP = 0.89, goniometer = 8.58, p = 0.025). No significant differences were found for flexion (DP = 1.52, goniometer = 5.94, p = 0.09). Agreement assessment was performed for flexion for mean differences of 0.27° with 95% limit of agreement ranging from −7.97° to 8.51°. For abduction, the mean differences were 1.19° with a 95% limit of agreement ranging from −9.07° to 11.46°.
In summary, DP demonstrated a high precision even higher than the conventional goniometer. Agreement between both methods is acceptable, with possible deviations of up to greater than 10°. Therefore, static measurements with DP are more precise than conventional goniometer measurements. These results are promising for routine clinical use of the DP.
Repeatability; Precision; Shoulder motion; Objective assessment; Dynaport; Gyroscope
Spinal stability is related to the recruitment and control of active muscle stiffness. Stochastic system identification techniques were used to calculate the effective stiffness and dynamics of the trunk during active trunk extension exertions. Twenty-one healthy adult subjects (10 males, 11 females) wore a harness with a cable attached to a servomotor such that isotonic flexion preloads of 100, 135, and 170 N were applied at the T10 level of the trunk. A pseudorandom stochastic force sequence (bandwidth 0–10 Hz, amplitude ±30 N) was superimposed on the preload causing small amplitude trunk movements. Nonparametric impulse response functions of trunk dynamics were computed and revealed that the system exhibited underdamped second-order behavior. Second-order trunk dynamics were determined by calculating the best least-squares fit to the IRF. The quality of the model was quantified by comparing estimated and observed displacement variance accounted for (VAF), and quality of the second-order fits was calculated as a percentage and referred to as fit accuracy. Mean VAF and fit accuracy were 87.8 ± 4.0% and 96.0 ± 4.3%; respectively, indicating that the model accurately represented active trunk kinematic response. The accuracy of the kinematic representation was not influenced by preload or gender. Mean effective stiffness was 2.78 ± 0.96 N/mm and increased significantly with preload (p< 0.001), but did not vary with gender (p = 0.425). Mean effective damping was 314 ± 72 N s/m and effective trunk mass was 37.0 ± 9.3 kg. We conclude that stochastic system identification techniques should be used to calculate effective trunk stiffness and dynamics.
Low back; Dynamics; Stiffness; Model
Insulators define chromosomal domains such that an enhancer in one domain cannot activate a promoter in a different domain. We show that the Drosophila gypsy insulator behaves as a cis-stimulatory element in the larval fat body. Transcriptional stimulation by the insulator is distance dependent, as expected for a promoter element as opposed to an enhancer. Stimulation of a test alcohol dehydrogenase promoter requires a binding site for a GATA transcription factor, suggesting that the insulator may be facilitating access of this DNA binding protein to the promoter. Short-range stimulation requires both the Suppressor of Hairy-wing protein and the Mod(mdg4)-62.7 protein encoded by the trithorax group gene mod(mdg4). In the absence of interaction with Mod(mdg4)-62.7, the insulator is converted into a short-range transcriptional repressor but retains some cis-stimulatory activity over longer distances. These results indicate that insulator and promoter sequences share important characteristics and are not entirely distinct. We propose that the gypsy insulator can function as a promoter element and may be analogous to promoter-proximal regulatory modules that integrate input from multiple distal enhancer sequences.
The goal of this paper was to determine if trunk antagonist activation is associated with impaired neuromuscular performance. To test this theory, we used two methods to impair neuromuscular control: strenuous exertions and fatigue. Force variability (standard deviation of force signal) was assessed for graded isometric trunk exertions (10, 20, 40, 60, 80 % of max) in flexion and extension, and at the start and end of a trunk extensor fatiguing trial. Normalized EMG signals for five trunk muscle pairs (RA – rectus abdominis, EO – external oblique, IO – internal oblique, TE – thoracic erector spinae, and LE – lumbar erector spinae) were collected for each graded exertion, and at the start and end of a trunk extensor fatiguing trial. Force variability increased for more strenuous exertions in both flexion (p<.001) and extension (p<.001), and after extensor fatigue (p<.012). In the flexion direction, both antagonist muscles (TE & LE) increased activation for more strenuous exertions (p<.001). In the extension direction, all antagonist muscles except RA increased activation for more strenuous exertions (p<.05) and following fatigue (p<.01). These data demonstrate a strong relationship between force variability and antagonistic muscle activation, irrespective of where this variability comes from. Such antagonistic co-activation increases trunk stiffness with the possible objective of limiting kinematic disturbances due to greater force variability.
Isometric trunk exertion; Trunk muscle recruitment; Force variability; Fatigue; Spine stability
MODS is a novel liquid culture based technique that has been shown to be effective and rapid for early diagnosis of tuberculosis (TB). We evaluated the MODS assay for diagnosis of TB in children in Viet Nam. 217 consecutive samples including sputum (n = 132), gastric fluid (n = 50), CSF (n = 32) and pleural fluid (n = 3) collected from 96 children with suspected TB, were tested by smear, MODS and MGIT. When test results were aggregated by patient, the sensitivity and specificity of smear, MGIT and MODS against “clinical diagnosis” (confirmed and probable groups) as the gold standard were 28.2% and 100%, 42.3% and 100%, 39.7% and 94.4%, respectively. The sensitivity of MGIT and MODS was not significantly different in this analysis (P = 0.5), but MGIT was more sensitive than MODS when analysed on the sample level using a marginal model (P = 0.03). The median time to detection of MODS and MGIT were 8 days and 13 days, respectively, and the time to detection was significantly shorter for MODS in samples where both tests were positive (P<0.001). An analysis of time-dependent sensitivity showed that the detection rates were significantly higher for MODS than for MGIT by day 7 or day 14 (P<0.001 and P = 0.04), respectively. MODS is a rapid and sensitive alternative method for the isolation of M.tuberculosis from children.
Reposition sense of lumbar curvature was assessed as a function of trunk flexion, trunk asymmetry, and target lumbar curvature using a repeated-measures design and an active-active proprioception paradigm.
The objectives of the research were to measure the ability of the subjects to sense and control the lumbar curvature in different lifting postures and to see if error in the lumbar curvature would increase in high-risk postures.
Summary of Background Data.
The risk of low back disorders (LBDs) is related to trunk posture, with greater risk reported in flexed and asymmetric trunk positions. Spinal posture, including trunk position and lumbar lordosis, influences spinal stability. Hence, the ability to accurately sense and control spinal curvature may be an important factor in the control of LBD risk.
Eleven subjects were trained to assume specified lumbar curvatures using visual feedback. The ability of the subjects to reproduce this curvature without feedback was then assessed. This procedure was repeated for different trunk postures, including flexion and asymmetry, and with different target lumbar curvatures.
These measurements demonstrated reposition error was increased in flexed trunk positions but was unchanged with trunk asymmetry. This increase in reposition error with flexion was diminished when the target posture and lumbar curvature were highly flexed and kyphotic.
This research suggests that it may be difficult to control spinal curvature in flexed positions, leading to an increased risk of injury. For jobs in which flexed working postures are unavoidable, therefore, it is important to minimize potentially unstable events such as slipping or shifting loads to avoid injury.
proprioception; lumbar; posture; lordosis
Although there are many studies demonstrating increased trunk activation under unstable conditions, it is not known whether this increased activation would translate into meaningful trunk strength with a prolonged training program. Additionally, while balance-training programs have been shown to improve stability, their effect on specific joint proprioception is not clear. Thus the objective of this study was to examine training adaptations associated with a 10-week instability-training program. Participants were tested pre- and post-training for trunk extension and flexion strength and knee proprioception. Forty-three participants participated in either a 10-week (3 days per week) instability-training program using Swiss balls and body weight as resistance or a control group (n = 17). The trained group increased (p < 0. 05) trunk extension peak torque/body weight (23.6%) and total work output (20.1%) from pre- to post-training while the control group decreased by 6.8% and 6.7% respectively. The exercise group increased their trunk flexion peak torque/body weight ratios by 18.1% while the control group decreased by 0.4%. Knee proprioception (combined right and left joint repositioning) improved 44.7% from pre- to post-training (p = 0.0006) and persisted (21.5%) for 9 months post-training. In addition there was a side interaction with the position sense of the right knee at 9 months showing 32.1% (p = 0.03) less deviation from the reference angle than the right knee during pre-testing. An instability-training program using Swiss balls with body weight as resistance can provide prolonged improvements in joint proprioception and core strength in previously untrained individuals performing this novel training stress which would contribute to general health.
Although traditional free weight resistance exercises have been recommended as most beneficial for improving strength and power in athletes (Behm et al., 2010b), an IT program using Swiss balls and body weight as a resistance may provide an alternative starting point for the sedentary untrained population.
As it is well documented that force or strength is decreased when unbalanced (Behm et al., 2010b) and balance-training programs improve balance (Behm and Kean 2006), this type of instability RT program can provide significant adaptations to improve trunk strength especially with the untrained.
This type of training should also be incorporated into a new program as the improvements in joint proprioception may help protect from joint injuries over a protracted period.
The finding that improved joint proprioception persists for months after training should be emphasized to those individuals whose training is regularly or inconsistently interrupted.
Instability resistance training; stability; back; abdominals
Depletion of the circulating actin-binding protein, plasma gelsolin (pGSN) has been described in critically ill surgical patients. We hypothesized that the extent of pGSN reduction might correlate with different outcome of burn patients. The study was performed to evaluate the prognostic implications of pGSN levels on the development of multiple organ dysfunction syndrome (MODS) and fatal outcome in a group of severely burn patients.
Methods and Findings
95 patients were included, and they were divided into three groups with different burn area: group I (n = 33), group II (n = 32) and group III (n = 30). According to whether there was development of MODS or not, patients were divided into MODS group (n = 28) and none-MODS group (n = 67); then the patients with MODS were further divided into non-survivor group (n = 17) and survivor group (n = 11). The peripheral blood samples were collected on postburn days (PBD) 1, 3, 7, 14, and 21. The levels of pGSN were determined and T cells were procured from the blood. The contents of cytokines (IL-2, IL-4 and IFN-γ) released by T cells were also measured. The related factors of prognosis were analyzed by using multivariate logistic regression analysis. The results showed that pGSN concentrations, as well as the levels of IL-2 and IFN-γ, decreased markedly on PBD 1–21, whereas, the levels of IL-4 increased markedly in all burn groups as compared with normal controls (P<0.05 or P<0.01), and there were obviously differences between group I and group III (P<0.05 or P<0.01). The similar results were found in MODS patients and the non-survivor group as compared with those without MODS and the survival group on days 3–21 postburn (P<0.05 or P<0.01). Moreover, as the pGSN levels decreased, the incidence of septic complication as well as MODS remarkably increased.
pGSN levels appear to be an early prognostic marker in patients suffering from major burns.
The cachexia-anorexia syndrome impacts on patients' physical independence and quality of life. New treatments are required and need to be evaluated using acceptable and reliable outcome measures, e.g. the assessment of muscle function. The aims of this study were to: (i) examine the acceptability and reliability of the Cybex NORM dynamometer to assess muscle function in people with non-small cell lung cancer or mesothelioma; (ii) compare muscle function in this group with healthy volunteers and; (iii) explore changes in muscle function over one month.
The test consisted of 25 repetitions of isokinetic knee flexion and extension at maximal effort while seated on a Cybex NORM dynamometer. Strength and endurance for the quadriceps and hamstrings were assessed as peak torque and total work and an endurance ratio respectively. Thirteen patients and 26 volunteers completed the test on three separate visits. Acceptability was assessed by questionnaire, reliability by intraclass correlation coefficients (ICC) and tests of difference compared outcomes between and within groups.
All subjects found the test acceptable. Peak torque and work done were reliable measures (ICC >0.80), but the endurance ratio was not. Muscle function did not differ significantly between the patient and a matched volunteer group or in either group when repeated after one month.
For patients with non-small cell lung cancer or mesothelioma, the Cybex NORM dynamometer provides an acceptable and reliable method of assessing muscle strength and work done. Muscle function appears to be relatively well preserved in this group and it appears feasible to explore interventions which aim to maintain or even improve this.
The dysfunction and decrease of endothelial progenitor cells (EPCs) may play a very important role in the initiation of organ dysfunction caused by trauma or severe sepsis. We aim to measure the number and function of EPCs in the progression of multiple organ dysfunction syndromes (MODS) caused by severe sepsis, which may help to understand the pathogenesis of MODS by the changing of EPCs.
A total of 40 pigs were randomly divided into two groups, which were subjected to hemorrhagic shock, resuscitation and endotoxemia (experimental group, n = 20) or acted as a control (control group, n = 20). The number and function of EPCs including adhesive, migratory and angiogenesis capacities were analyzed at different times in both groups.
All the animals in the experimental group developed MODS (100%) and 17 of 20 animals (85%) died due to MODS; the incidence of MODS and death of the animals in the control group were 0% (P < 0.01). The number, migratory and adhesive capacities of EPCs decreased sharply in the animals of the experimental group corresponding to the increasing severities of MODS, but the angiogenesis function increased gradually until death. The decrease in function of EPCs preceded the decrease in number of EPCs. The decrease in number and function of EPCs occurred prior to the occurrence of MODS.
For the first time, it was observed that the number and function of EPCs decreased sharply in the progression of MODS and that it was prior to the occurrence of MODS. The decrease in number and function of EPCs may be one of the main pathogenic factors of MODS.