Isometric Trunk Extensor Research Articles

Hamstring and knee injuries are associated with isometric hip and trunk muscle strength in elite Australian Rules and Rugby League players

ObjectivesThis study investigated relationships between isometric trunk and hip extensor strength, lumbar muscle morphology, and the risk of hamstring and knee ligament injuries in Australian Football League and National Rugby League players. DesignProspective cohort study. MethodsTrunk and hip extensor strength, multifidus and quadratus lumborum cross-sectional area were measured during the 2020 pre-season. Logistic regressions and decision trees were employed to explore associations between maximum strength, strength endurance, multifidus and quadratus lumborum cross-sectional area, age, previous injuries, and hamstring and knee ligament injury risk. ResultsGreater strength endurance [odds ratio = 0.42 (0.23–0.74), p = 0.004] and maximum strength [odds ratio = 0.55 (0.31–0.94), p = 0.039] reduced hamstring injury risk. Increased risk of knee ligament injuries was associated with larger multifidus [odds ratio = 1.66 (1.14–2.45), p = 0.008] and higher multifidus to quadratus lumborum ratio (odds ratio = 1.57 (1.13–2.23), p = 0.008]. Decision tree models indicated that low strength endurance (< 99 Nm) characterised hamstring strains, while high (≥ 1.33) multifidus to quadratus lumborum ratio mitigated risk. Knee ligament injuries were associated with larger (≥ 8.49 cm2) multifidus, greater (≥ 1.25) multifidus to quadratus lumborum ratio, and lower maximum strength (< 9.24 N/kg). ConclusionsPlayers with lower trunk and hip extensor maximum strength and strength endurance had increased risk of hamstring injuries, while knee ligament injury risk was elevated with larger multifidus cross-sectional area, higher multifidus to quadratus lumborum ratio, and lower maximum trunk and hip extensor strength.

Relationships between trunk morphology and strength with non-contact lower limb injuries in elite rugby league and Australian football players

Background: Non-contact lower limb injuries (NCLLI) are common within the National Rugby League (NRL) and Australian Football League (AFL). Smaller lumbar multifidus at L5 (LM L5) cross-sectional area (CSA) and lower levels of trunk and hip extension and knee flexion strength have been associated with increased NCLLI risk in AFL players. However, such associations have not been reported in the NRL. This study aims to explore relationships between NCLLI, trunk morphology and isometric trunk and hip extension strength in NRL and AFL players. Methods: NRL and AFL players had their LM L2-L5 and quadratus lumborum (QL) CSA (n=238), and isometric trunk and hip extension strength (n=153) measured using ultrasonography and a novel field-based test in preseason. Isometric trunk and hip extensor strength were measured using a 65s maximal voluntary isometric contraction (MVIC) protocol (5s MVIC, 5s off, 45s MVIC, 5s off, 5s MVIC). Team medical staff reported all NCLLIs sustained in the subsequent competitive season. The associations between LM and QL CSA, 5s and 45s MVIC, age, and previous injury, and prospectively occurring NCLLI were analysed using univariable and then multivariable logistic regression. Logistic regression analysis was also performed for the most sustained NCLLI (hamstring and knee). Results: Seventy-two players sustained a NCLLI in the 2020 competitive seasons (51 NRL, 21 AFL). From univariable logistic regression previous injury increased the risk of any NCLLI in NRL (OR=2.43, 95%CI=1.16-5.09, p=0.019). Reduced 5s MVIC (OR=1.00, 95%CI=1.00-1.01, p=0.012), increased QL CSA (OR=1.55, 95%CI=1.05-2.38, p=0.033) and lower ratio between LM and QL CSA (OR=0.03, 95%CI=0.01-0.60, p=0.02) increased NCLLI risk in AFL. Pooled hamstring injuries (n=28) were most common and were associated with lower 5s MVIC (OR=0.99, 95%CI=0.99-1.00, p=0.02) and 45s MVIC (OR=0.99, 95%CI=0.99-1.00, p=0.001). Pooled knee injuries (n=21) were associated with both reduced LM CSA (OR=1.35, 95%CI=1.08-1.70, p=0.018) and LM to QL ratio (OR=3.62, 95%CI=1.41- 9.66, p=0.043). Conclusions: Larger QL CSA and reduced levels of trunk and hip extension strength are observed in AFL players in preseason who sustain a NCLLI in the subsequent playing season. Only previous NCLLI was associated with future risk of NCLLI for NRL players. These results suggest that risk factors for NCLLI are football code specific, and prevention strategies should be tailored accordingly. Conflict of interest statement: My co-authors and I acknowledge that we have no conflict of interest relevant to the submission of this abstract.

Trunk muscle strength and back muscle endurance in construction workers with and without low back disorders

The aim of this study was to test the hypothesis that male workers exposed to heavy work and with no lifetime history of a low back disorder (group A) have better trunk muscle strength and back muscle endurance compared to male workers with the same work exposure but with a probable (group B) or definite low back disorder (group C). Group A (n = 42) was clinically negative on physical examination. Group B (n = 75) was clinically negative or uncertain and group C (n = 86) was clinically positive, with current or previous low back disorders occurring in both groups. Group A had a significantly higher mean intraindividual extension/flexion ratio, namely 1.29 versus 1.19, in group C. The mean values for maximum isometric trunk extension and flexion strength did not differ between the groups. The isometric trunk extensor endurance was significantly lower in group C than in both group A and group B

Features of trunk muscle weakness in patients with ankylosing spondylitis: A cross-sectional study

BackgroundAnkylosing spondylitis (AS) is an inflammatory autoimmune disorder that manifested with sacroiliitis at its early stage and developed extensive inflammation with syndesmophytes of the lumbar, thoracic and cervical spines at its later stage. In the present study, we characterized the trunk isometric strength in patients with AS with different disease severity, defined by the radiological images. MethodsIn a cross-sectional study conducted in a university-affiliated hospital, thirty-eight male AS patients (23 in the early AS group whose radiological findings showed no syndesmophyte, Modified Stoke Ankylosing Spinal Score (m-SASSS <3); and 15 in the syndesmophyte group, m-SASSS ≥24), and 22 healthy controls were recruited. All subjects received assessments of maximum isometric strength of trunk flexor and extensor muscles at a variety of trunk postures measured by an isokinetic device. ResultsUnder all examined trunk postures, the syndesmophyte AS patient group had the lowest isometric trunk muscle strength among the three groups. The flexion/extension ratio, defined by the ratio between isometric trunk flexor and extensor strengths, was highest among the three groups. ConclusionsTrunk muscle strength significantly decreases in patients with syndesmophyte AS. The decrease of trunk muscle is inhomogeneous, which is more profound in extensor than in flexor muscles.

The effects of six weeks of Core stabilization exercise on pain, Functional disability and Isometric strength of the trunk and lower extremities Muscle in women with patellofemoral pain syndrome

Abstract Background and Aim: The knee joint is most common of region for injury and musculoskeletal disorders in lower extremity. Patellofemoral pain syndrome is as a common cause of knee pain in subjects. The purpose of present study was to assess the effect of core stabilization exercises on pain, functional disability andstrength of muscles of thelower Extremity and trunk in females with patellofemoral pain syndrome. Materials and Methods: Subjects in this study were 20 female with patellofemoral pain syndrome participated. The subjects were randomly divided into two groups. 10 Subjects in the experimental group (age 32.13±1.95 yr, height 169.00±7.59 cm, weight 65.50±6.80 kg) and 10 Subjects in the control group (age 31.25±1.58 yr, height 170.00±7.46 cm, weight 67.50±14.39 kg) participated in this study. Then experimental group performed exercises for 6 weeks. The Visual Analogue Scale (VAS) and Western Ontario and McMaster Universities (WOMAC) questioners were used to measure rate of functional disability and pain pre and post six weeks in both groups. also was used the dynamometer for measure isometric strength pre and post six weeks. Data using descriptive and inferential statistics (independent t test to compare scores at pre-test and post hoc t test to compare pre- and post-test scores) were analyzed. Results: The results showed that Core stabilization exercises has a significant effect on pain reduction in experimental compared with control group (p= 0.003). The mean score of disability test also showed significant improvement in experimental compared with control group (p= 0.001). Also, the results showed that Isometric strenghtening trunk flexor (p= 0.005) and extensor (p= 0.036), hip flexor (p= 0.001) and extensor (p= 0.001), hip abductor (p= 0.001) external rotator (p= 0.019), knee flexor (p= 0.001) and extensor muscles (p= 0.001) improved significantly compared with control group. Conclusion: According to results of this study, core stabilization exercises can reduce pain and improved disability and muscles isometric strength in subjects with patellofemoral pain syndrome.

The relationship between isometric trunk muscle endurance and physical activity related energy expenditure in healthy young adults.

Despite the popularity of core stabilization, there is limited evidence as to the relationship between performance on tests of isometric trunk muscle endurance and physical activity levels in adults. To investigate the relationship between isometric trunk muscle endurance and physical activity related energy expenditure in healthy young adults. A total of 51 participants (24 female) participated in the study. Median age and body mass index were; 22 years (Min-max: 18-26 years) and 21.8 kg/m2 (Min-Max: 18.59-28.98 kg/m2), respectively. Participants completed the International Physical Activity Questionnaire. Isometric trunk muscle endurance was assessed with holding times of isometric trunk flexor, extensor, and lateral side bridge tests. Collected data were summarized based on median and interquartile ranges. The Spearman's correlation test was used to ascertain the relationship between isometric trunk muscle endurance and physical activity related energy expenditure. There were no gender differences in holding times of the trunk flexor and trunk extensor endurance tests (p> 0.05). Males showed higher endurance scores for side bridge test than females (p< 0.001). No difference was found in physical activity related energy expenditure between males and females. No correlation was observed between isometric trunk muscle endurance and physical activity related energy expenditure for either females or males (p> 0.05). According to our findings, trunk muscle endurance is not related to physical activity related energy expenditure in healthy young adults.

Trunk muscles strength as a risk factor for nonspecific low back pain: a pilot study.

ObjectiveTo investigate the effects of asymptomatic back muscle weakness and spinal deformity on low back pain (LBP).MethodsSixty healthy subjects without LBP participated in this study. Radiography and an isokinetic/isometric dynamometer were used to respectively measure spinal scoliosis/lordosis and the strength of the trunk flexors/extensors. After 2 years, 48 subjects visited the hospital again and LBP episodes, its severity and the Korean version of the Oswestry Disability Index were assessed. Differences between the group with LBP and the group without LBP were evaluated and the association with LBP incidence and severity was determined.ResultsSex, age, and trunk strength were significantly different in both group. Sex and age were significantly positive associated with LBP incidence. The isometric trunk flexor and extensor strength, maximum isokinetic trunk flexor and extensor strength were significantly and negatively associated with the LBP severity. The maximum isokinetic trunk extensor and maximum isometric trunk extensor strength was significantly negative associated with the LBP incidence.ConclusionLBP incidence is associated with isometric and isokinetic trunk extensor weakness, whereas LBP severity is associated with age, sex, isokinetic trunk extensor and flexor weakness, isometric trunk extensor and flexor weakness.

Improved function in women with persistent pregnancy-related pelvic pain after a single corticosteroid injection to the ischiadic spine: A randomized double-blind controlled trial

Background: Pregnancy-related low back and pelvic pain is a worldwide problem. A large proportion of women still experience disabling daily back pain 2 years after childbirth, resulting in major changes in activities and general well-being. In spite of this, the source of pain and effective treatment are uncertain. Objective: To evaluate the short-term effects on function of a single corticosteroid injection treatment to the ischiadic spine in women with persistent pregnancy-related pelvic pain (PPPP). Methods: Thirty-six women were allocated to injection treatment with slow-release triamcinolone and lidocain or saline and lidocain, given once at the sacrospinous ligament insertion on the ischiadic spine bilaterally with follow-up at 4 weeks. Outcome measures were Disability Rating Index (DRI), self-rated functional health (SF-36), gait speed and endurance (6MWT), and strength and endurance of trunk muscles (isometric trunk extensor and flexor tests). Results: Women in the triamcinolone group showed significantly improved DRI (p = 0.046), 6MWT (p = 0.016), and isometric trunk extensor tests (p = 0.004), as compared with the saline group. Close co-variation was shown between improved function and reduced pain intensity. Conclusions: Improved function was achieved among women with PPPP after a single injection treatment with slow-release corticosteroid. The effect was positively correlated to the reduced pain intensity.

Diagnostic accuracy and reliability of muscle strength and endurance measurements in patients with chronic low back pain

Dynamometric trunk muscle strength and endurance tests are performed widely within the rehabilitation management of chronic low back pain. The aim of this study was to examine the accuracy and long-term reliability of these measurements in patients with chronic low back pain. Cross-sectional study. Thirty-two patients with chronic low back pain, 19 healthy controls and 15 patients with chronic headache matched for age, sex and body mass index. Both patient groups and healthy controls performed isokinetic and isometric trunk extensor and flexor tests on a Biodex 2000 dynamometer. The Biering-Sørensen test served to examine back muscle endurance. Borg-Category-Ratio-Scales CR-10 rated participants' body experience immediately before and after the testing. Patients with chronic low back pain repeated measurements after 3 weeks. Among dynamometric tests, isokinetic measurements revealed the best area under the curve (AUC = 0.89) for the discrimination between patients with chronic low back pain and healthy controls. Reliability testing revealed highly significant learning effects for isometric trunk flexion and isokinetic measurements. The Biering-Sørensen test demonstrated excellent accuracy (AUC = 0.93) and no learning effects. Borg-category-ratio-scale ratings were not associated with the observed changes. In chronic low back pain dynamometric trunk muscle measures are limited to muscle function assessment purposes. Monitoring treatment outcome in these patients with these measures appears to be problematic because of learning effects. Based on our findings, we recommend the Biering-Sørensen test for management of chronic low back pain rehabilitation.

Swing Kinematics in Skilled Male Golfers Following Putting Practice

Control laboratory study consisting of preintervention and postintervention measurements. To determine the effects of a putting practice session on the kinematics of full golf swings made by skilled male golfers. Skilled golfers perform putting practice for prolonged periods. The combination of sustained trunk flexion with minimal trunk motion may affect the endurance capacity of the trunk extensor muscles. Because of their important role in the golf swing, any impairment of the trunk extensors may negatively influence full-swing kinematics, but this has not been previously evaluated. Three-dimensional swing kinematics and holding time on the Biering-Sørensen test of isometric trunk extensor endurance were evaluated in 29 skilled male golfers before and after performing a 40-minute putting task. After the intervention, peak segmental speeds were reduced and total swing duration increased (mean +/- SD, 36 +/- 55 milliseconds). There were reductions in the magnitude of pelvis and torso axial rotation during the downswing (mean +/- SD, -2.3 degrees +/- 2.6 degrees and -2.3 degrees +/- 4.7 degrees , respectively). The peak difference between torso rotation and pelvis rotation during early downswing was also significantly reduced by 0.9 degrees +/- 2.0 degrees (P<.05). The effects on pelvis and torso rotation were smallest for golfers with higher body mass index (BMI). Holding time on the Biering-Sørensen test after putting practice was significantly reduced by 25.7 +/- 23.8 seconds (P = .01). Changes in swing kinematics observed following 40 minutes of putting practice might have resulted from fatigue-related impairment of the trunk extensor muscles, a view supported by the poorer performance on the postintervention Biering-Sørensen test. Results showed that swing kinematics of golfers with high BMI were least affected by the putting practice. Harm, level 5.

Co-activation alters the linear versus non-linear impression of the EMG–torque relationship of trunk muscles

The use of electromyographic signals in the modeling of muscle forces and joint loads requires an assumption of the relationship between EMG and muscle force. This relationship has been studied for the trunk musculature and been shown to be predominantly non-linear, with more EMG producing less torque output at higher levels of activation. However, agonist–antagonist muscle co-activation is often substantial during trunk exertions, yet has not been adequately accounted for in determining such relationships. The purpose of this study was to revisit the EMG–moment relationship of the trunk recognizing the additional moment requirements necessitated due to antagonist muscle activity. Eight participants generated a series of isometric ramped trunk flexor and extensor moment contractions. EMG was recorded from 14 torso muscles, and the externally resisted moment was calculated. Agonist muscle moments (either flexor or extensor) were estimated from an anatomically detailed biomechanical model of the spine and fit to: the externally calculated moment alone; the externally calculated moment combined with the antagonist muscle moment. When antagonist activity was ignored, the EMG–moment relationship was found to be non-linear, similar to previous work. However, when accounting for the additional muscle torque generated by the antagonist muscle groups, the relationships became, in three of the four conditions, more linear. Therefore, it was concluded that antagonist muscle co-activation must be included when determining the EMG–moment relationship of trunk muscles and that previous impressions of non-linear EMG–force relationships should be revisited.

The Role of Genetics and Environment in Lifting Force and Isometric Trunk Extensor Endurance

Our understanding of what different back performance tests are measuring is limited. The purpose of this study was to investigate the relative contributions of genetics and unique and common environmental factors for 3 tests of back muscle performance in a classic twin analysis. The subjects were a population-based sample of 122 monozygotic and 131 dizygotic male twin pairs aged 35 to 69 years (mean=49.9, SD=7.7). Variance component analysis was applied to estimate genetic and environmental influences on isokinetic and psychophysical lifting and isometric trunk extensor endurance test performance. The Cholesky decomposition genetic factor model was used to estimate genetic and environmental correlations of these variables. Path analysis was applied to study determinants of isokinetic and psychophysical lifting and isometric trunk extensor endurance test performance. Genetic effects accounted for 60%, 33%, and 5% of the total variance of isokinetic and psychophysical lifting forces and isometric trunk extensor endurance, respectively, and unique environmental factors accounted for 35%, 49%, and 61% of the variance. Genetics had a dominant role in isokinetic lifting and unique environmental factors in isometric trunk extensor endurance. The relatively high role of genetics in lifting force suggests the potential to increase and sustain changes in back muscle force in the general population may be particularly challenging.

Maximum Trunk Flexion Angle during the Sit to Stand Is Not Determined by Knee or Trunk-Hip Extension Strength in Healthy Older Adults

When rising from a chair, older adults have been reported to use a strategy in which the trunk is flexed to a greater extent than young adults, a strategy attributed by some to concerns with the postural stability demands of the task. This study determined the extent to which maximum trunk flexion angle during a self-paced sit-to-stand from a standardized initial position was influenced by the maximum isometric strength of the knee and trunk/hip extensor muscles in older adults. The hypothesis was that the larger maximum trunk flexion angle attained by older adults when rising from a chair is related to the maximum isometric strength of the knee and trunk-hip extensor muscles. To test this hypothesis, maximum voluntary isometric strength of the trunk extensor and knee extensor muscles of 28 older men and women were measured. Trunk motion during the sit-to-stand by these adults was men assessed using motion analysis. Multiple regression was used to characterize the relationship between the maximum trunk flexion angle and maximum isometric knee extensor and trunk extensor muscle strength. The derived relationship was neither statistically significant nor biomechanically meaningful. This result suggests that the trunk flexion angle attained by healthy older adults when rising from a chair from a standardized initial position is not influenced by knee extension and trunk-hip extension strength as measured in the present study.

Quantification of erector spinae muscle fatigue during prolonged, dynamic lifting tasks.

A method was developed to quantify erector spinae fatigue resulting from repetitive dynamic lifting in the sagittal plane. This method was tested with the data from eight male subjects lifting inertial loads of 19 kg and 17 kg during sessions of 20 min and 2 h, respectively. Surface EMG electrodes were applied over sites representing the bilateral lumbar and thoracic erector spinae and external oblique muscles. Maximal and submaximal isometric trunk extensor contractions were performed at the start, intermittently throughout, and at the end of the dynamic lifting trials, within an apparatus designed to control spine posture in the upright standing position. These exertions were used to assess the decreases in strength, endurance and EMG mean power frequency (fw) as well as the increases in EMG amplitude that have been shown to accompany muscle fatigue. The average of the group for extensor strength decreased 17% and 21% (P < 0.05) and the endurance times decreased 60% and 62% (P < 0.01) for the 2-h and the 20-min session, respectively. The average endurance time decreased at least 10% for each subject in each session. Strength decreased at least 10% in all but 2 of 16 cases (both in the 20-min session). The average decreases in fw were 12% (lumbar) and 17% (thoracic; P < 0.05) in the 2-h sessions and 20% (lumbar; P < 0.05) and 14% (thoracic) in the 20-min sessions. There was also a significant increase in EMG amplitude (P < 0.05) for both muscle group in both sessions.(ABSTRACT TRUNCATED AT 250 WORDS)

Isometric trunk extensor endurance in young females

Series elastic stiffness of rat gastrocnemius medialis muscle was determined by means of sinusoidal movements (180 Hz, 0.25% of muscle length) for various contraction conditions. The effects of muscle length, activation level, velocity, prestretch, and temperature on the force-stiffness relationship were investigated. All force-stiffness curves were transformed to a linear force-α curve (Ettema and Huijing, 1993; Morgan, 1977) to distinguish mathematically two series elastic components; a force dependent and force independent compliance. For all isometric conditions a typical force-stiffness curve was found, where stiffness increased with force, and this increase levelled off at higher forces. Stiffness in dynamic shortening and lengthening contractions is related to force in a completely different way than in isometric condition. An increase in temperature caused a decrease in muscle stiffness for a given force, and the effects of muscle length, activation level, and prestretch were small. It was concluded that the series elastic component of skeletal-muscle-tendon complex is probably located in more than two morphologically identifiable elements. Furthermore, we concluded that using a single series elastic element in muscle modelling is not appropriate to describe muscle behaviour under all conditions that occur during in vivo activation.

Muscle fibre (hyper-)trophy and atrophy in relation to fibre angle

s-International Society of Biomechanics XIII Congress 1991 695 MUSCLE FIBRE (HYPER-)TROPHY AND ATROPHY IN RELATION TO FIBRE ANGLE. Peter A. Huijing and Hans W. Heslinga Faculteit Bewegingswetenschappen, Vrije Unlversiteit, Amsterdam, The Netherlands For pennate muscle it is generally accepted that fibre angle of attachment o an aponeumsis or bone is related to fibre volume. Fibre volume can be calculated as fibre length x &(fibre angle) x area of attachment. As fibre volume is constant during contraction, this means that fibre angles increase as the flbres shorten. It has been argued that a similar mechanism of angular change would be active during accommodation of changes of fibre volume as a consequence of hypertrophy or atrophy. The aim of the present work was to test the hypothesis of existence of a unique relationship between fibre angle and state of hypertrophy or atrophy of rat gastrocnemius medialis (GM). For that purpose geometry of GM at muscle optimum length (n=6) during adult growth and short length immobiiation was studied. During growth (age 10-14-16 weeks) fibre angle increased: me&SD 26S0f 3.25 to 32.3”f 3.30, while muscle volume increased by 20% and fibre diameter 5%. As a consequence of short length immobilization, starting at 10 weeks for 4 or 6 weeks periods, sizable atrophy occurred: Muscle volume decreased (776i80 mm3 to 474f123) by 39% and fibre diameter by 19% but certainly no decrease of fibre angles occurred (26.5Ok3.25 and 32.M4.60) even though aponeurosis length seemed fairly constant (21.6fi.9 and 2O.lfi.6 mm). It is concluded that fibre angle may increase with growth related hypextmphy but immobilization related atrophy did not cause fibre angle decrease. The hypothesized unique relationship was not found. Therefore it is concluded that other factors must play a role in the regulation of fibre angle. Considering the functional significance of fibre angles (e.g. Zuurbier and Huijing. this volume) this seems to be a notable result. ISOMETRIC TRUNK EXTENSOR ENDURANCE IN YOUNG FEMALES K. Jsrgensen and T. Nicolaisen August Krogh Institute, University of Copenhagen, Copenhagen. Denmark The aim of the present work was to study: 1) fibre distribution and capillary supply of the lumbar paravertebral muscles and 2) muscular endurance in young

Observations on intra-abdominal pressure and patterns of abdominal intra-muscular activity in man.

The aim was to investigate possible relationships between activities of the individual muscles of the ventrolateral abdominal wall and the development of pressure within the abdominal cavity. Intra-muscular activity was recorded bilaterally from transversus abdominis, obliquus internus, obliquus externus and rectus abdominis with fine-wire electrodes guided into place using real-time ultrasound. Intra-abdominal pressure was measured intragastrically using a micro tip pressure transducer. Six males were studied during loading and movement tasks with varied levels of intra-abdominal pressure. During both maximal voluntary isometric trunk flexion and extension, transversus abdominis activity and intra-abdominal pressure remained constant, while all other abdominal muscles showed a marked reduction during extension. When maximal isometric trunk flexor or extensor torques were imposed upon a maximal Valsalva manoeuvre, transversus abdominis activity and intra-abdominal pressure remained comparable within and across conditions, whereas obliquus internus, obliquus externus and rectus abdominis activities either markedly increased (flexion) or decreased (extension). Trunk twisting movements showed reciprocal patterns of activity between the left and right sides of transversus abdominis, indicating an ability for torque development. During trunk flexion--extension, transversus abdominis showed less distinguished changes of activity possibly relating to a general stabilizing function. In varied pulsed Valsalva manoeuvres, changes in peak intra-abdominal pressure were correlated with mean amplitude electromyograms of all abdominal muscles, excluding rectus abdominis. It is concluded that the co-ordinative patterns shown between the muscles of the ventrolateral abdominal wall are task specific based upon demands of movement, torque and stabilization. It appears that transversus abdominis is the abdominal muscle whose activity is most consistently related to changes in intra-abdominal pressure.

Trunk muscle strength and back muscle endurance in construction workers with and without low back disorders

The aim of this study was to test the hypothesis that male workers exposed to heavy work and with no lifetime history of a low back disorder (group A) have better trunk muscle strength and back muscle endurance compared to male workers with the same work exposure but with a probable (group B) or definite low back disorder (group C). Group A (n = 42) was clinically negative on physical examination. Group B (n = 75) was clinically negative or uncertain and group C (n = 86) was clinically positive, with current or previous low back disorders occurring in both groups. Group A had a significantly higher mean intraindividual extension/flexion ratio, namely 1.29 versus 1.19, in group C. The mean values for maximum isometric trunk extension and flexion strength did not differ between the groups. The isometric trunk extensor endurance was significantly lower in group C than in both group A and group B.

Comparison of Spinal Mobility and Isometric Trunk Extensor Forces with Electromyographic Spectral Analysis in Identifying Low Back Pain

This study compared conventional clinical measurements with electromyographic (EMG) spectral measurements for identification of individuals with low back pain (LBP). Twenty freshman sweep rowers were subjects for this study. Range-of-motion (ROM) measurements were taken for forward bending (FB), backward bending (BB) (double inclinometers), lateral bending (LB) (tape measure), and rotation (double-arm goniometer). Intratester reliability for ROM was also assessed. The Back Analysis System was used to determine static trunk extensor strength (ie, maximal voluntary contraction [MVC]) and to compute EMG spectral parameters from a paraspinal multi-electrode array. A two-group stepwise discriminant-analysis procedure for the ROM and MVC variables correctly identified 57% of the rowers with LBP and 63% of the rowers without LBP. A similar discriminant-analysis procedure for EMG spectral parameters correctly identified either 88% of the rowers with LBP and 100% of the rowers without LBP or 100% of the rowers with LBP and 88% of the rowers with LBP, depending on whether EMG measurements of recovery were calculated at 1 minute or at 2 minutes into the recovery period. Sensitivity (66%) and specificity (71%) results from the more traditional tests suggest that these techniques may be of limited usefulness for LBP screening or diagnosis.