Biomechanical analysis of breastfeeding positions and their effects on lumbopelvic curvatures and lumbar muscle responses.

This study aimed to analyze the position of the lumbopelvic region and lumbar muscle activity in the most common breastfeeding positions. We recorded the curvatures of the lumbar spine and pelvis by means of an electrogoniometer, and the muscle activation levels of the erector spinae with electromyography, in 34 women in erect standing and breastfeeding their children in several positions. Both side lying and clutch-hold positions showed a greater degree of lumbar spine flexion compared to standing. In all sitting postures it was observed that the pelvis was placed in retroversion when compared to standing and side lying. In muscle activity, it was observed that the activation intensity of the right erector in the right side-supported side lying position was significantly lower compared to the rest of breastfeeding postures and standing. Side lying may be a better position to avoid muscle fatigue.

Where do archers hurt? Epidemiology of injuries during archery practice.

BACKGROUND: The risk of injury in archery is supposedly low. However, relations between pain, shooting phases and types of bow have not been studied. OBJECTIVE: Understanding the biomechanical mechanisms of archery-related injuries. METHODS: Online survey for archers from all types of bow. Variables were analyzed using contingency tables and chi-squared tests. RESULTS: 396 surveys were completed. 36.9% of the archers had practiced archery for more than 10 years, 23.3% between 5 and 10 years. Olympic recurve bow was the most commonly used (38.2%), followed by traditional (23.3%) and compound (22.0%). 57.3% of the archers suffered some kind of injury during archery practice. Drawing shoulder (28.2%) and neck/back injuries (19.9%) were the most prevalent, preventing 50.3% of those who suffered them from continuing archery practice. There was a moderate association between drawing arm injuries and symptomatology in the drawing phase, especially in the shoulder region (0.55), elbow (0.20), and hand (0.13), and to a lesser extent in the neck/back (0.28). CONCLUSIONS: Our results show that injury chronicity is frequent on archery. Correlations between types of bow, phases of the shoot and areas of pain could be a starting point for future studies on the repercussions of different types of injuries in archery practice.

Validation of the patients-specific functional scale in patients with haemophilia.

INTRODUCTION: A complete functional assessment is essential to measure health status and treatment effects in patients with haemophilia. The Patient-Specific Functional Scale (PSFS) is a reliable, valid, simple and quick scale that measures physical function in patients with musculoskeletal disorders. However, the reliability and validity of the PSFS have not been evaluated in patients with haemophilia. AIM: The aim of this study was to validate the Patient-Specific Functional Scale in patients with haemophilia. METHODS: Twenty-eight patients with haemophilia participated in the study. They completed the PSFS and the Haemophilia Activity List (HAL) scales by telephone during an initial session, and then repeated the assessment in a follow-up session 1 week apart. Reliability was analysed by the internal correlation coefficient (ICC), the standard error of measurement (SEM) and the smallest detectable change (SDC). The concurrent validity of the PSFS was determined by correlating the initial score of the PSFS scale to the initial score of the HAL scale. Correlations were calculated by means of scatter plots and Pearson product-moment r correlation coefficient. RESULTS: ICC and SEM values showed excellent reliability for the PSFS scale, with a SDC of 1. A significant moderate correlation was found between the results of the PSFS and the HAL (r = .57, P < .001). CONCLUSION: The PSFS is a reliable and valid scale to measure the functionality of people with haemophilia.

Determining the optimal maximal and submaximal voluntary contraction tests for normalizing the erector spinae muscles.

BACKGROUND: This study aimed to identify which maximum voluntary isometric contraction (MVIC) and sub-MVIC tests produce the highest activation of the erector spinae muscles and the greatest reduction in inter-individual variability, to put them forward as reference normalization maneuvers for future studies. METHODS: Erector spinae EMG activity was recorded in 38 healthy women during five submaximal and three maximal exercises. RESULTS: None of the three MVIC tests generated the maximal activation level in all the participants. The maximal activation level was achieved in 68.4% of cases with the test performed on the roman chair in the horizontal position (96.3 ± 7.3; p < 0.01). Of the five submaximal maneuvers, the one in the horizontal position on the roman chair produced the highest percentage of activation (61.1 ± 16.7; p < 0.01), and one of the lowest inter-individual variability values in the normalized signal of a trunk flexion-extension task. CONCLUSIONS: A modified Sorensen MVIC test in a horizontal position on a roman chair and against resistance produced the highest erector spinae activation, but not in 100% of participants, so the execution of several normalization maneuvers with the trunk at different inclinations should be considered to normalize the erector spinae EMG signal. A modified Sorensen test in a horizontal position without resistance is the submaximal maneuver that produces the highest muscle activation and the greatest reduction in inter-individual variability, and could be considered a good reference test for normalization.

Effects of pregnancy on lumbar motion patterns and muscle responses.

BACKGROUND CONTEXT: The kinematics of the lumbar region and the activation patterns of the erector spinae muscle have been associated with the genesis of low back pain, which is one of the most common complications associated with pregnancy. Despite the high prevalence of pregnancy-related low back pain, the biomechanical adaptations of the lumbar region during pregnancy remain unknown. PURPOSE: This study analyzes lumbar spine motion and the activation pattern of the lumbar erector spinae muscle in healthy pregnant women. STUDY DESIGN: A case-control study. PATIENT SAMPLE: The study involved 34 nulliparous women (control group) and 34 pregnant women in the third trimester (week 36 ± 1). OUTCOME MEASURES: We recorded the parameters of angular displacement of the lumbar spine in the sagittal plane during trunk flexion-extension, and the EMG activity of the erector spinae muscles during flexion, extension, eccentric and concentric contractions, and the myolectrical silence. METHODS: The participants performed several series of trunk flexion-extension movements, which were repeated 2 months postpartum. The position of the lumbar spine was recorded using an electromagnetic motion capture system. EMG activity was recorded by a surface EMG system and expressed as a percentage of a submaximal reference contraction. RESULTS: Antepartum measurements showed a decrease (relative to control and postpartum measurements) in lumbar maximum flexion (52.5 ± 10.5° vs 57.3 ± 7.7° and 58.7 ± 8.6°; p < .01), the percentage of lumbar flexion during forward bending (56.4 ± 5.6% vs 59.4 ± 6.8% and 59.7 ± 5.6%; p < .01), and the time keeping maximum levels of lumbar flexion (35.7 ± 6.7% vs 43.8 ± 5.3% and 50.1 ± 3.7%; p < .01). Higher levels of erector spinae activation were observed in pregnant women during forward bending (10.1 ± 4.8% vs 6.3 ± 2.4% and 6.6 ± 2.7%; p < .01) and eccentric contraction (12.1 ± 5.2% vs 9.4 ± 3.1% and 9.1 ± 2.9%; p < .01), as well as a shortened erector spinae myoelectric silence during flexion. CONCLUSIONS: Pregnant women show adaptations in their patterns of lumbar motion and erector spinae activity during trunk flexion-extension. These changes could be associated with the genesis of pregnancy-related low back pain, by means of biomechanical protection mechanisms against the increase on abdominal mass and ligamentous laxity.

Changes in trunk posture and muscle responses in standing during pregnancy and postpartum.

The aim of this study was to analyze the position of the lumbopelvic region and the muscle activation of erector spinae and biceps femoris muscles in a group of pregnant women in the third trimester. The hypothesis was that pregnancy-related biomechanical and morphological changes modify the position of the lumbopelvic region and the activation of extensor muscles. The position of the lumbar spine and pelvis in the sagittal plane, and the EMG activity of the erector spinae and biceps femoris muscles, were recorded during standing in 34 nulliparous and 34 pregnant women in the third trimester, and also two months after birth in the group of pregnant women. No significant differences in the position of the lumbar spine or pelvis between the group of pregnant women and nulliparous or postpartum were observed. A significant increase was observed in the EMG activity of the erector spinae (4.6% vs 2.4% and 2.1% in the nulliparous group and postpartum respectively) and the biceps femoris (3.4% vs 1.2% and 1.4%) in pregnant women compared to the other two groups (p <0.01). We conclude that pregnant women in the third trimester show no alterations in lumbopelvic position compared to nulliparous and postpartum women. However, there is an increase of the EMG activity of the trunk extensors. These results indicate that the extensor muscles of the trunk show, in static positions, adaptive responses to the increase of anterior loads during pregnancy.

Effects and underlying mechanisms of unstable shoes on chronic low back pain: a randomized controlled trial.

OBJECTIVE: To investigate the effects that wearing unstable shoes has on disability, trunk muscle activity, and lumbar spine range of motion (ROM) in patients with chronic lower back pain (CLBP). DESIGN: Randomized controlled trial. SETTING: Orthopedic Surgery Service. PARTICIPANTS: We randomized 40 adults with nonspecific CLBP either to an unstable shoes group ( n = 20) or to the control group ( n = 20). INTERVENTION: The participants in the unstable shoes group were advised to wear these shoes for a minimum of six hours a day for four weeks. Control group participants were asked to continue wearing their regular shoes. OUTCOME MEASURES: Our primary outcome was measurement of back-related dysfunction, assessed using the Roland-Morris Disability Questionnaire. Secondary outcomes included changes in electromyographic (EMG) activity of erector spinae (ES), rectus abdominis (RA), internus obliquus (IO), and externus obliquus (EO) muscles, and changes in lumbar spine ROM. RESULTS: Between-group analysis highlighted a significant decrease in disability in the unstable shoes group compared to the control (-5, 95% confidence interval (CI) = -8.4 to -1.6). Our results revealed a significant increase in the percentage of RA, ES, IO, and EO EMG activity and in lumbar spine ROM in the unstable shoes group compared to the control group. Moreover, our results showed a significant negative correlation between disability and the percentage of ES, RA, and IO muscle activity at the end of the intervention. CONCLUSION: This study shows that the use of unstable shoes contributes to improvements in disability, which are likely related to increased trunk muscle activity and lumbar spine ROM.

Effects of Myofascial Release in Nonspecific Chronic Low Back Pain: A Randomized Clinical Trial.

STUDY DESIGN: Double-blind, randomized parallel sham-controlled trial with concealed allocation and intention-to treat analysis. OBJECTIVE: To investigate the effects of an isolate myofascial release (MFR) protocol on pain, disability, and fear-avoidance beliefs in patients with chronic low back pain (CLBP). SUMMARY OF BACKGROUND DATA: MFR is a form of manual medicine widely used by physiotherapists in the management of different musculoskeletal pathologies. Up to this moment, no previous studies have reported the effects of an isolated MFR treatment in patients with CLBP. METHODS: Fifty-four participants, with nonspecific CLBP, were randomized to MFR group (n = 27) receiving four sessions of myofascial treatment, each lasting 40 minutes, and to control group (n = 27) receiving a sham MFR. Variables studied were pain measured by means Short Form McGill Pain Questionnaire (SF-MPQ) and visual analog scale (VAS), disability measured with Roland Morris Questionnaire, and fear-avoidance beliefs measured with Fear-Avoidance Beliefs Questionnaire. RESULTS: Subjects receiving MFR displayed significant improvements in pain (SF-MPQ) (mean difference -7.8; 95% confidence interval [CI]: -14.5 to -1.1, P = 0.023) and sensory SF-MPQ subscale (mean difference -6.1; 95% CI: -10.8 to -1.5, P = 0.011) compared to the sham group, but no differences were found in VAS between groups. Disability and the Fear-Avoidance Beliefs Questionnaire score also displayed a significant decrease in the MFR group (P < 0.05) as compared to sham MFR. CONCLUSION: MFR therapy produced a significant improvement in both pain and disability. Because the minimal clinically important differences in pain and disability are, however, included in the 95% CI, we cannot know whether this improvement is clinically relevant. LEVEL OF EVIDENCE: 2.

Lumbopelvic flexibility modulates neuromuscular responses during trunk flexion-extension.

Various stimuli such as the flexibility of lumbopelvic structures influence the neuromuscular responses of the trunk musculature, leading to different load sharing strategies and reflex muscle responses from the afferents of lumbopelvic mechanoreceptors. This link between flexibility and neuromuscular response has been poorly studied. The aim of this study was to investigate the relationship between lumbopelvic flexibility and neuromuscular responses of the erector spinae, hamstring and abdominal muscles during trunk flexion-extension. Lumbopelvic movement patterns were measured in 29 healthy women, who were separated into two groups according to their flexibility during trunk flexion-extension. The electromyographic responses of erector spinae, rectus abdominis and biceps femoris were also recorded. Subjects with greater lumbar flexibility had significantly less pelvic flexibility and vice versa. Subjects with greater pelvic flexibility had a higher rate of relaxation and lower levels of hamstring activation during maximal trunk flexion. The neuromuscular response patterns of the hamstrings seem partially modulated by pelvic flexibility. Not so with the lumbar erector spinae and lumbar flexibility, despite the assertions of some previous studies. The results of this study improve our knowledge of the relationships between trunk joint flexibility and neuromuscular responses, a relationship which may play a role in low back pain.

Effects of unstable shoes on trunk muscle activity and lumbar spine kinematics.

BACKGROUND: In patients with neuromuscular disease and a forced vital capacity (FVC) of <30% of the predictive value, scoliosis correction operation was Background. An unstable shoe was developed as a walking device to strengthen the lower extremity muscles and reduce joint loading. A large number of studies have reported increased electromyographic (EMG) activity throughout the gait cycle in most of the lower limb muscles, and significant kinematic changes in the lower extremity. However, no studies have investigated the effects of wearing unstable shoes on spine kinematics and trunk muscle activity during gait. AIM: To compare trunk muscle activity and lumbar spine range of motion (ROM) during gait using an unstable shoe and a conventional stable control shoe. DESIGN: Cross-sectional study. SETTING: A Biomechanics laboratory. POPULATION: Forty-eight healthy voluntary participants (24.5±5.6 years and 22.7±6.8 kg/m2). METHODS: Subjects underwent gait analysis while simultaneously collecting surface EMG data of erector spinae (ES) and rectus abdominis (RA) and lumbar spine sagittal plane ROM while treadmill walking wearing regular shoes and unstable shoes. RESULTS: The results showed that the unstable shoes resulted in significantly higher ES and RA EMG muscle activity levels in all gait phases compared to control shoes (P<0.001). In addition, the unstable shoe condition showed a significantly higher mean (mean difference: 3.1º; 95% CI 2.2º to 4º) and maximum (mean difference: 4.5º; 95% CI 2.6º to 6.5º) lumbar spine extension values (P<0.001). CONCLUSIONS: Unstable shoes increase trunk muscle activity (ES, RA) and lumbar lordosis during gait compared to control shoes. CLINICAL REHABILITATION IMPACT: Based on these findings, the use of unstable shoes may have potential implications in promoting spine tissue health, particularly in strengthening trunk muscles in healthy population or in low back pain treatment.

A comparison of lumbopelvic motion patterns and erector spinae behavior between asymptomatic subjects and patients with recurrent low back pain during pain-free periods.

OBJECTIVES: The purpose of this study was to determine the patterns of lumbopelvic motion and erector spinae (ES) activity during trunk flexion-extension movements and to compare these patterns between patients with recurrent low back pain (LBP) in their pain-free periods and matched asymptomatic subjects. METHODS: Thirty subjects participated (15 patients with disc herniation and recurrent LBP in their pain-free periods and 15 asymptomatic control subjects). A 3-dimensional videophotogrammetric system and surface electromyography (EMG) were used to record the angular displacements of the lumbar spine and hip in the sagittal plane and the EMG activity of the ES during standardized trunk flexion-extension cycles. Variables were maximum ranges of spine and hip flexion; percentages of maximum lumbar and hip flexion at the start and end of ES relaxation; average percentages of EMG activity during flexion, relaxation, and extension; and flexion-extension ratio of myoelectrical activity. RESULTS: Recurrent LBP patients during their pain-free period showed significantly greater ES activation both in flexion and extension, with a higher flexion-extension ratio than controls. Maximum ranges of lumbar and hip flexion showed no differences between controls and patients, although patients spent less time with their lumbar spine maximally flexed. CONCLUSIONS: This study showed that reduced maximum ranges of motion and absence of ES flexion-relaxation phenomenon were not useful to identify LBP patients in the absence of acute pain. However, these patients showed subtle alterations of their lumbopelvic motion and ES activity patterns, which may have important clinical implications.

Absence of circumflex artery with superdominant right coronary: a classic anatomical dissection study.

PURPOSE: We report a very unusual case of variant coronary artery anatomy, discovered during anatomical dissection in a medical school. METHODS: The heart from a very advanced age donor was dissected using classic anatomical techniques RESULTS: The right coronary artery showed a superdominant pattern, extending beyond the crux of the heart and circling the atrioventricular groove almost completely. It followed the usual path of the absent circumflex artery, and ended as a slender branch which almost reached the origin of the anterior interventricular artery. CONCLUSIONS: To our knowledge, these are the first reported dissection images of this kind of coronary artery variation. It may have clinical consequences, either leading to more accelerated atherosclerotic changes or causing technical difficulties during cardiac surgery.

Effects of treadmill running and fatigue on impact acceleration in distance running.

The effects of treadmill running on impact acceleration were examined together with the interaction between running surface and runner's fatigue state. Twenty recreational runners (11 men and 9 women) ran overground and on a treadmill (at 4.0 m/s) before and after a fatigue protocol consisting of a 30-minute run at 85% of individual maximal aerobic speed. Impact accelerations were analysed using two lightweight capacitive uniaxial accelerometers. A two-way repeated-measure analysis of variance showed that, in the pre-fatigue condition, the treadmill running decreased head and tibial peak impact accelerations and impact rates (the rate of change of acceleration), but no significant difference was observed between the two surfaces in shock attenuation. There was no significant difference in acceleration parameters between the two surfaces in the post-fatigue condition. There was a significant interaction between surface (treadmill and overground) and fatigue state (pre-fatigue and post-fatigue). In particular, fatigue when running overground decreased impact acceleration severity, but it had no such effect when running on the treadmill. The effects of treadmill running and the interaction need to be taken into account when interpreting the results of studies that use a treadmill in their experimental protocols, and when prescribing physical exercise.

Effect of custom-made and prefabricated insoles on plantar loading parameters during running with and without fatigue.

Controversy exists whether custom-made insoles are more effective in reducing plantar loading compared to prefabricated insoles. Forty recreational athletes ran using custom-made, prefabricated, and the original insoles of their running shoes, at rest and after a fatigue run. Contact time, stride rate, and plantar loading parameters were measured. Neither the insole conditions nor the fatigue state modified contact time and stride rate. Addressing prevention of running injuries, post-fatigue loading values are of great interest. Custom-made insoles reduced the post-fatigue loading under the hallux (92 vs. 130 kPa, P < 0.05), medial midfoot (70 vs. 105 kPa, P < 0.01), and lateral midfoot (62 vs 96 kPa, P < 0.01). Prefabricated insoles provoked reductions in post-fatigue loading under the toes (120 vs. 175 kPa, P < 0.05), medial midfoot (71 vs. 105 kPa, P < 0.01), and lateral midfoot (68 vs. 96 kPa, P < 0.01). Regarding both study insoles, custom-made insoles reduced by 31% and 54% plantar loading under the medial and lateral heel compared to the prefabricated insoles. Finally, fatigue state did not influence plantar loading regardless the insole condition. In long-distance races, even a slight reduction in plantar loading at each foot strike may suppose a significant decrease in the overall stress experienced by the foot, and therefore the use of insoles may be an important protective mechanism for plantar overloading.

Effect of overground vs treadmill running on plantar pressure: influence of fatigue.

The differences produced when running on a treadmill vs overground may call into question the use and validity of the treadmill as a piece of equipment commonly used in research, training, and rehabilitation. The aim of the present study was to analyze under pre/post fatigue conditions the effect of treadmill vs overground on plantar pressures. Twenty-seven recreational runners (17 men and 10 women) ran on a treadmill and overground at two speeds: S1=3.33 m/s and S2=4.00 m/s, before and after a fatigue protocol consisting of a 30-min run at 85% of their individual maximal aerobic speed (MAS). Contact time (CT in seconds), peak pressure (PP in kPa), and relative load (RL in %) were analyzed under nine foot zones of the left foot using an in-shoe plantar pressure device. A two-way repeated measures ANOVA showed that running on a treadmill increases CT (7.70% S1 and 9.91% S2), modifies the pressure distribution and reduces PP (25.98% S1 and 31.76% S2), especially under the heel, medial metatarsals, and hallux, compared to running overground. Moreover, on both surfaces, fatigue (S2) led to a reduced stride frequency (2.78%) and reduced PP on the lateral heel and hallux (15.96% and 16.35%, respectively), and (S1) increased relative load on the medial arch (9.53%). There was no significant interaction between the two factors analyzed (surface and fatigue). Therefore, the aforementioned surface effect, which occurs independently of the fatigue state, should be taken into account when interpreting the results of studies that use the treadmill in their experimental protocols, and when prescribing physical exercise on a treadmill.

Psychometric properties and factor structure of the Spanish version of the HC-PAIRS questionnaire.

OBJECTIVE: To develop a Spanish version of the Health Care Providers' Pain and Impairment Relationship Scale (HC-PAIRS) and to test its psychometric properties. METHODS: A forward and backward translation methodology was used to translate the questionnaire, which was then applied to 206 participants (174 physiotherapy students and 32 family physicians). The intraclass correlation coefficient was calculated to assess test-retest reliability. Internal consistency was evaluated using Cronbach's alpha and item analysis. Construct validity was measured using Pearson correlation coefficients between HC-PAIRS and FABQ, FABQ-Phys, FABQ-Work and the responses given by participants to three clinical case scenarios. An exploratory factor analysis was carried out following the Kaiser normalization criteria and principal axis factoring with an oblique rotation (quartimax). Sensitivity to change was assessed after a teaching module. RESULTS: Test-retest reliability was ICC 0.50 (p < 0.01) and Cronbach's alpha was 0.825. The HC-PAIRS scores correlated significantly with the scores of the FABQ and also with the recommendations for work and activity given by the participants in the three clinical case scenarios. Sensitivity to change test showed an effect size of 1.5, which is considered a large change. Factor analysis suggests that the Spanish version of HC-PAIRS measures a unidimensional construct. CONCLUSION: The Spanish version of the HC-PAIRS has proven to be a reliable, valid and sensitive instrument to assess health care providers' attitudes and beliefs about LBP. It can be used in evaluating clinical practice and in undergraduate acquisition of skills and knowledge.

White-to-white corneal diameter, pupil diameter, central corneal thickness and thinnest corneal thickness values of emmetropic subjects.

PURPOSE: This report assesses white-to-white corneal diameter, pupil diameter, central corneal thickness and thinnest corneal thickness values in a large sample of emmetropic subjects. METHODS: Three hundred and seventy-nine eyes of 379 young healthy emmetropic subjects were analyzed by means of scanning-slit corneal topography. The age of the subjects ranged from 18 to 53 years (mean ± SD = 29 ± 7). The mean of five consecutive measurements of the central corneal thickness, the thinnest corneal thickness, the white-to-white corneal diameter, and the photopic pupil diameter was recorded. RESULTS: The central corneal thickness ranged from 528 to 588 µm; the thinnest corneal thickness ranged from 504 to 574 µm; the white-to-white corneal diameter ranged from 11.5 to 12.3 mm; and the pupil diameter ranged from 3.0 to 4.7 mm. The central and the thinnest corneal thickness were positively correlated (r = 0.94, p < 0.001), and the pupil diameter was significantly higher in females (p < 0.001). CONCLUSIONS: This study shows that there are no differences in white-to-white corneal diameter, central corneal thickness, and thinnest corneal thickness between emmetropic females and males. However, pupil diameters are greater in emmetropic females.

Reliability and validity of a new objective tool for low back pain functional assessment.

STUDY DESIGN: Classification and functional assessment model for nonspecific low back pain (LBP) patients and controls on the basis of kinematic analysis parameters. OBJECTIVE: Develop a logistic regression model using kinematic analysis variables to (1) discriminate between LBP patients and controls and (2) obtain objective parameters for LBP functional assessment. SUMMARY OF BACKGROUND DATA: Functional assessment of spinal disorders has been carried out traditionally by means of subjective scales. Objective functional techniques have been developed, which usually involve the application of external loads or the analysis of highly standardized trunk flexion-extension maneuvers. Few studies have used everyday activities such as sit-to-stand or lifting an object from the ground. They have shown that the motion patterns of LBP patients differ from those of healthy subjects. Nevertheless, very few studies have tried to correlate objective findings to the results of subjective scales, and no previous study has developed a LBP classification and functional assessment model on the basis of kinematic analysis of everyday activities. METHODS: Sixteen controls and 39 LBP patients performed a sit-to-stand task, and lifted three different weights from a standing position. The vertical forces exerted and the relative positions of the lower limb and the cervical, thoracic, lumbar, and sacroiliac regions were recorded. Reliability was determined from repetitions of the tests performed by the control group. Binary logistic regression analyses were computed. The results of the selected regression equation were correlated to the Oswestry Disability Index scale results, to check the validity of the procedure for the measurement of functional disability. RESULTS: Reliability of the parameters was good. The selected regression model used two variables, and correctly classified 97.3% of the patients. High correlations were found between the results of this regression equation and the Oswestry Disability Index scale. CONCLUSION: It is possible to distinguish LBP patients from healthy subjects by means of the biomechanical analysis of everyday tasks. This kind of analysis can produce objective and reliable indexes about the patients' degree of functional impairment.

Is activation of the back muscles impaired by creep or muscle fatigue?

STUDY DESIGN: Intervention study on healthy human subjects. OBJECTIVE: To determine whether reflex activation of the back muscles is influenced by muscle fatigue or soft tissue creep in the spine. SUMMARY OF BACKGROUND DATA: Reflex contraction of the back muscles normally acts to limit spinal flexion, and hence protect the underlying spine from injury. However, repeated flexion allows bending moments on the spine to increase. Impaired reflexes as a result of fatigue or soft tissue creep may be contributing factors. METHODS: A total of 15 healthy volunteers (8 females/7 males aged 23-55 years) underwent 2 interventions, on separate days: (a) sitting flexed for 1 hour to induce creep and (b) performing the Biering-Sorensen test to induce back muscle fatigue. Before and after each intervention, reflex activation of the erector spinae in response to sudden trunk flexion (initiated by a Kin-Com dynamometer) was monitored bilaterally at T10 and L3 using surface electromyography (EMG) electrodes. These recordings indicated the onset latency of reflex activation, the peak EMG, and time to peak, at each site. Measurements before and after each intervention and between muscle sites were compared using a 2-way repeated measures Analysis of Variance. RESULTS: Spinal creep was confirmed by an increase in maximum flexion of 2.3 degrees +/- 2.5 degrees (P = 0.003), and fatigue by a significant fall in median frequency at one or more sites. Following creep, onset latency increased from 60 +/- 12 milliseconds to 96 +/- 26 milliseconds (P < 0.001) but there was no change in peak EMG or time to peak EMG. Differences between sites (P = 0.004) indicated greater latencies in lumbar compared to thoracic regions, especially after creep. Muscle fatigue had no significant effects on any of the measured parameters. CONCLUSION: Prolonged spinal flexion can impair sensorimotor control mechanisms and reduce back muscle protection of the underlying spine. The effect is due to time-dependent "creep" in soft tissues rather than muscle fatigue.

Trunk muscle activation patterns and spine kinematics when using an oscillating blade: influence of different postures and blade orientations.

OBJECTIVE: To compare trunk muscle activation patterns and trunk kinematics when using an oscillating blade in standing and unsupported sitting postures, and with different orientations of the blade. DESIGN: A cross-sectional survey of trunk muscle activities and lumbar motion. SETTING: Biomechanics research laboratory. PARTICIPANTS: Healthy men (N=13). INTERVENTIONS: An oscillating blade was held with 2 hands and oscillated with vertical and horizontal orientations of blade. These exercises were performed both in an erect standing position and in an erect sitting position. MAIN OUTCOME MEASURES: Surface electromyography from 14 trunk and 2 shoulder muscles, together with lumbar angular displacement in the 3 planes of motion, were measured while subjects used an oscillating blade at different performance variations. Electromyographic signals were normalized to isometric maximal voluntary contraction (MVC) amplitudes. RESULTS: With the exception of internal oblique and anterior deltoid for the horizontal condition, and erector spinae at L5 level for the vertical condition, the subject's posture had no effect on trunk muscular recruitment when using the oscillating blade. The vertical blade orientation resulted in higher amplitudes of spine rotation on the horizontal plane and produced the greatest activation levels of the internal oblique (47% MVC), pectoralis major (33% MVC), and external oblique (23% MVC). On the other hand, the horizontal orientation resulted in the greatest activation levels of erector spinae at T9 level (28% MVC), latissimus dorsi (26% MVC), and rectus abdominis (17% MVC). CONCLUSIONS: Muscle activation and spine motion from using an oscillating blade were not affected by the standing or sitting posture of the subject. The choice of blade orientation was more important, because it defined the main group of muscles recruited during the exercise.