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Introduction: The objective of this study was to find the immediate as well as short-term effect on pelvic alignment and forward arm reach distance in sitting among stroke patients following thoracic spine and abdominal muscles taping along with conventional therapy. Methods: Thirty subjects with stroke attending the physiotherapy programme at Department of Physiotherapy at a tertiary care hospital underwent this randomized controlled experimental study. Subjects in the experimental group received taping, along with conventional physiotherapy treatment, for restricting thoracic kyphosis and facilitating abdominal muscles. Subjects in the control group received only conventional physiotherapy treatment. To assess the change in pelvic alignment and forward arm reach distance while sitting, Palpation MeterTM (PALMTM) and sit and reach test were used, respectively. Results: In the experimental group, pelvic obliquity was corrected (4.1 ± 0.94) and anterior pelvic tilt revealed improvement (4.9 ± 2.1, p value < 0.001). In the control group, no improvement in pelvic alignment was recorded. Improvement in forward arm reach distance was similar in both groups ( p value = 0.804). Conclusion: Taping as an adjunctive treatment method to physiotherapy can cause immediate as well as short-term improvement of pelvic alignment in sitting, following stroke. It also, immediately improves the sit and reach distance in the same population.

Objective: To investigate the effect of a new therapeutic approach, using an oscillating rod to strength the pelvic floor and deep abdominal musculature and to speed up recovery of continence after radical prostatectomy. Design: Prospective randomized controlled clinical trial. Setting: Inpatient uro-oncology rehabilitation clinic. Subjects: Ninety-three (intervention group (IG)) and ninety-one patients (control group (CG)) with urinary incontinence after prostatectomy were examined. Intervention: All patients were randomly allocated to either standard pelvic floor muscle exercises and oscillating rod therapy (IG) or standard pelvic floor muscle exercises and relaxation therapy (CG). Main outcome measures: Urinary incontinence (1- and 24-hour pad test) was assessed, and health-related quality of life (HRQL; Functional Assessment of Cancer Therapy-Prostate (FACT-P) questionnaire) was measured for all patients before and after three weeks of treatment. Results: One hundred and eighty-four patients (mean (SD) age: 64.1 (6.94) years) completed the study. The IG showed a significant reduction in urinary incontinence (1-hour pad test: P = 0.008, 24-hour pad test: P = 0.012) and a significant improvement of HRQL ( P = 0.017) compared with CG. Continence was significantly improved in both groups (1-hour pad test: 22.6–8.5 g (IG) vs. 23.0–18.1 g (CG)/24-hour pad test: 242.9–126.7 g (IG) vs. 237.6–180.9 g (CG)). Conclusion: The study demonstrated that a combination of conventional continence exercises and the new oscillation rod training increased abdominal and pelvic floor musculature and speeded up recovery of continence after radical prostatectomy.

Background: External rotation (ER) strengthening of the shoulder is an integral component of rehabilitative and preventative programs for overhead athletes. A variety of shoulder ER strengthening exercises are reported, including those intended to integrate the core musculature. The purpose of this study was to examine ER torque and electromyographic (EMG) activation of shoulder and trunk muscles while performing resisted isometric shoulder ER in 3 positions (standing, side lying, and side plank). Hypothesis: Significantly greater force and shoulder muscle activation would be generated while side lying given the inherent stability of the position, and greater trunk muscle activation would be generated in the less stable plank position. Study Design: Quasi-experimental repeated-measures study. Level of Evidence: Level 5. Methods: A convenience sample of 25 healthy overhead recreational athletes (9 men, 16 women) participated in this study. EMG electrodes were placed on the infraspinatus, posterior deltoid, middle trapezius, multifidi, internal obliques, and external obliques. EMG signals were normalized to a maximal isometric contraction. Participants performed resisted isometric ER in standing, side-lying, and side plank positions. Results were analyzed using a repeated-measures analysis of variance with post hoc Bonferroni corrections (α = 0.05). Results: There was no significant difference in ER torque between positions (α = 0.05). A significant difference in EMG activity of shoulder and trunk musculature between positions was found in 7 of the 8 muscles monitored. Significantly greater EMG activity in the infraspinatus, middle trapezius, and the nondominant external and internal obliques was found in the side plank position as compared with standing and side lying. Conclusion: While there was no difference in ER torque between the 3 exercise positions, EMG activity of the shoulder and trunk muscles was dependent on body position. Clinical Relevance: If a clinician is seeking to integrate trunk muscle activation while performing shoulder ER strengthening, the side plank position is preferred as compared with standing or side lying.

The Sorensen test has been widely used in assessing the isometric endurance of trunk muscles. In this study, a modified Sorensen test was performed using four different upper body offload conditions (0%, 25% 50% and 75%) and surface EMG (sEMG) was used to determine fatigue characteristics in lumbar muscles. Results showed that the offloading of the upper body has a statistically significant impact on the slope of the EMG median frequency, which is representative of lumbar muscle fatigue responses. The first 25% offloading significantly decreased the fatigue response in the lumbar region. In addition, the 25% offload condition was significantly different from the 75% offload condition. However, the slopes of 25% and 50% offload conditions are not statistically different from each other and same for 50% and 75% offload conditions.

Low back pain (LBP) is often cited as a common condition at all levels of dance. Evidence suggests that reduced endurance of the trunk muscles can predispose an individual to LBP. The purpose of this study was to examine differences in trunk muscle endurance in a sample of tertiary level dance students with and without LBP. Seventeen full-time female dance students were divided into two groups: dance students with LBP (N = 11), and without LBP (N = 6). All participants provided informed consent, and the study was approved by an institutional ethics review board. Participants performed four isometric tests that assess trunk muscle endurance: the right and left side plank, double straight leg raise (DSLR), and the Sorensen test. A modified version of the Osaka City University test was used to assess the presence of LBP. A significant difference (p < 0.05) between groups was observed for the right and left side plank, as well as the DSLR test, and students with LBP displayed lower levels of endurance compared to those without. No other significant differences were found. This study offers some evidence that reduced trunk muscle endurance is present among dancers with LBP and provides direction for future research into back health among dancers.

The increasingly popular practice of using a stability ball (exercise/fitness ball) as a sitting surface runs counter to conventional human factors/ergonomics guidelines for seated workspace design. Employees sitting on stability balls in an office environment present safety risks that might be justifiable if the practice has a definitive benefit to the promotion of health. However, the published studies and best evidence to date call into question even the theoretical basis for this practice and do not suggest significant health benefits. First, biomechanical studies do not confirm the intended trunk muscle activation. Second, energy expenditure studies show a small (if any) increase in metabolic demand that is unlikely to be effective in combating sedentary work risk factors. Until studies demonstrate more conclusive benefits, the practice of stability ball sitting should be viewed skeptically as a general workplace recommendation in the interest of health or wellness.

The aim of this study was to compare the EMG patterns of trunk muscles throughout the golf swing, performed with two different clubs, and also to describe the activity patterns in the average golfer. Nine male golfers performed ten swings using the pitching wedge and the 4-iron, alternately. Surface electromyography (EMG) was recorded from trunk muscles of both sides: rectus abdominis (RA), external oblique (EO), erector spinae (ES) and gluteus maximus (GM). 3D high-speed video analysis was used for determination of golf swing phases. Muscles had their highest activation during the forward swing and acceleration phases. The highest mean activation regarding the maximal EMG (EMGMAX), was found in the right EO (59–67% EMGMAX) and in the GM of the trailing leg (62–72% EMGMAX). In the majority of the cases and phases, trunk muscles showed higher mean values of EMG activation when golfers performed with 4-iron club. However, no club effect was verified in trunk muscles.

Objective: The aim of this study was to evaluate the efficacy of a 9-day accommodation protocol on reducing perceived discomfort while sitting on a stability ball (SB); trunk muscle activity levels and lumbar spinal postures were also considered. Background: Previous studies have compared SB sitting with office chair sitting with few observed differences in muscle activity or posture; however, greater discomfort during SB sitting has been reported. These findings may indicate an accommodation period is necessary to acclimate to SB sitting. Method: For this study, 6 males and 6 females completed two separate, 2-hr sitting sessions on an SB. Half the participants completed a 9-day accommodation period between the visits, whereas the other half did not use an SB during the time. On both occasions, self-reported perceived discomfort ratings were collected along with erector spinae and abdominal muscle activity and lumbar spinal postures. Results: Discomfort ratings were reduced in female participants following the accommodation; no effects on muscle activation or lumbar spine postures were observed. Conclusion: Accommodation training may reduce perceived low-back discomfort in females. Trunk muscle activity and lumbar spine postures during seated office work on an SB did not differ between groups; however, greater sample power was required to conclusively address these variables. Application: Regarding whether to use an SB in place of a standard office chair, this study indicates that females electing to use an SB can decrease discomfort by following an accommodation protocol; no evidence was found to indicate that SB chair use will improve trunk strength or posture, even following an accommodation period.

The purpose of current study was to investigate the effects of vertical ground accelerations induced by simulated wave motions on trunk muscle activation and trunk kinematics during manual materials handling tasks. Sixteen subjects performed lifting, lowering and static weight-holding tasks under ten different combinations of load mass and vertical acceleration of the ground surface (ten different effective loads). The results showed that this effective load had a significant effect on the peak sagittal plane angular acceleration during lifting and peak sagittal plane angular deceleration during lowering. The EMG results indicate that the boat motions tend to amplify the effects of the slant of the lifting surface.

Single dynamometric measures are sometimes used to characterize overall muscle strength. This study examined the legitimacy of that practice by assessing how dynamometer measures of grip and knee extension strength related to manual muscle-test grades of each upper and lower limb and of the trunk. Based on correlations and principal component analysis, grip dynamometry can be used to characterize upper limb strength but not lower limb strength; knee extension dynamometry can be used to characterize lower limb and trunk strength.

The ability to assess the loads on the spine in industry using biologically-assisted models has been limited by the current capability to obtain accurate muscle activities that could be entered into an EMG-assisted model. One crucial aspect of EMG-assisted models is the capability to capture the antagonistic coactivity in dynamic lifting conditions. However, limitations of electromyography equipment make it difficult to assess the muscle activity in industry. The overall project developed a complex engine using fuzzy average with fuzzy cluster distribution techniques in combination with neural network structure. The objective of the current study was compare the predicted spine loads for the actual and predicted muscle activities during sagittal lifting conditions. The model fidelity of the EMG-assisted spine load model was actually improved with the predicted EMG as compared to the actual EMG with improved r-square and average absolute error values. Furthermore, the three-dimensional spine loads were almost identical for the predicted EMG as compared to the actual EMG (within 35 N in each plane). The compression forces predicted within 1% while shear forces were within 11%. Overall, the new neuro-fuzzy engine provides an accurate estimation of the coactivity pattern during lifting that can now be applied in industrial settings where traditional muscle activity assessment methods are subjected to noise or are difficult to administer.

The Valsalva manoeuvre remains a popular medical topic, with more than 100 publications per annum, 300 years after its first mention by Antonio Valsalva in Bologna in 1704 in his classical ‘De aure humana tractatus’.1 In current usage it usually means: an acute rise in intrathoracic and intra abdominal pressure, brought about by contraction of the trunk muscles, right down to the pelvic floor, against a ‘stop’, at the glottis, but also more peripherally by the tongue in the nasopharynx, or at the lips and nostrils, or even outside the body, as in the blowing up of a column of mercury in a manometer. It is done automatically, and very briefly, in coughing and sneezing; and for longer periods in bodily functions like defaecation and parturition; or, more deliberately, in heavy lifting; in various sports; and in the blowing of wind instruments.

Asymmetric trunk postures and trunk dynamics have been implicated as risk factors for occupational low back disorders. Muscle fatigue has also been cited as an ergonomic issue, though not directly linked to an increased risk of low back injury. This paper investigates the effect of trunk extensor muscle fatigue on muscle activity levels during symmetric and asymmetric trunk extension exertions. The results show that muscle fatigue alters both flexor and extensor muscle activity patterns in asymmetric trunk extensions earlier than in sagittally-symmetric trunk extensions. This quickened fatigue response to asymmetric trunk motions could be a contributor to the increased risk of low back injury seen in occupational tasks that include asymmetric trunk lifting.

The main objective of this study was to demonstrate feasibility of predicting the electromyographic (EMG) activities of trunk muscles in manual lifting tasks. The applied data-driven fuzzy model with relational rule network utilized trunk dynamics as input variables, including sagittal and lateral trunk moments, pelvic tilt and rotation angles, and sagittal, lateral, and twist trunk angles. The data for model training and testing were randomly selected from a data set of EMG time domain values collected for 20 male college students. The utilized EMG data represented a total of 24 combinations of weight (15, 30, 50) lifted, asymmetry (0–60 degrees), and the origin and destination of lift (floor-waist, floor-102 cm, knee-waist, knee-102 cm), with two replications of each condition. The model was trained using the data for ten subjects and 18 randomly selected trials, and was then tested based on the EMG data for another ten subjects using randomly selected 6 trials. The model allowed for estimating EMG responses (in time domain) for the ten trunk muscles with the mean absolute error ranging from 0.91% to 11.8%. The study showed that it is feasible to estimate the time domain EMG responses of human trunk muscles due to manual lifting tasks with the acceptable level of accuracy.

Antagonist coactivation levels of trunk muscles were determined quantitatively using three coactivation measures: the sum of antagonist NEMG, the sum of antagonist force, and the sum of antagonist moment. Twelve male subjects performed isometric voluntary exertions gradually increasing to maximum efforts in six directions: flexion/extension, left/right lateral bending, and clockwise/counter-clockwise twisting. Coactivation levels were assessed at 10, 20, 30, 40, 50, 60, 70, 80, and 90% MVE in six directions. Antagonist coactivation was dependent on the magnitude and direction of the exertion moment, while it showed different patterns according to the coactivation measures. Twisting moments induced highest coactivation in all three measures.

Infantile autosomal recessive spinal muscular atrophy (type I) represents a lethal disorder leading to progressive symmetric muscular atrophy of limb and trunk muscles. Ninety-six percent cases of spinal muscular atrophy type I are caused by deletions or mutations in the survival motoneuron gene (SMN1) on chromosome 5q11.2-13.3. However, a number of chromosome 5q-negative patients with additional clinical features (respiratory distress, cerebellar hypoplasia) have been designated in the literature as infantile spinal muscular atrophy plus forms. In addition, the combination of severe spinal muscular atrophy and neurogenic arthrogryposis has been described. We present clinical, molecular, and autopsy findings of a newborn boy presenting with generalized muscular atrophy in combination with congenital bone fractures and extremely thin ribs but without contractures. (J Child Neurol 2002;17:718-721).

Seven male subjects performed 8 cable lifting and hanging tasks, while trunk kinematics and electromyographic data often trunk muscles were obtained. The objectives of the study were to evaluate trunk muscle recruitment and spine loads resulting from performance of this task in different postures and with different load magnitudes. The eight tasks were combinations of four postures (standing, stooping, kneeling on one knee or both knees) and two levels of load (0 N or 100 N load added to existing cable weight). Results indicated that changes in posture and changes in load magnitude both affected muscle co-activation; however, the influence of these variables were quite different in nature. Increased load magnitude resulted in a generalized increase in the co-activation of all trunk muscles, no matter which posture was employed (p < 0.05). Changes in posture significantly affected trunk muscle recruitment patterns (p < 0.05); however, the posture effect typically involved a relatively small subset of trunk muscles. No significant interactions were detected (p > 0.05), indicating that posture and load effects are both independent and additive.

The prediction of muscle forces around the low back is a key aspect in the calculation of spinal loads. Artificial Neural Networks (ANNs) are suited to handle this prediction problem, and have been employed in the past in similar efforts. This paper evaluates the performance of an ANN in predicting trunk muscle forces, whose values were estimated from measurements of myoelectric activity during various high-magnitude static trunk exertions. Sensitivity of the ANN to its two user-adjustable parameters, Muscle Self-Inhibition and Muscle Inhibition, is also evaluated. Results indicate moderate agreement between predicted forces and forces estimated from measured myoelectric activity (average R2s in the 0.50s), although some muscles were well predicted (R2s in the 0.80s). The model iterations resulting from variations in the ANN Inhibition parameters varied only slightly in terms of prediction performance levels, suggesting that this particular ANN model may be limited by other factors, including inter-individual differences in motor control strategies.

This paper discusses development of a neuro-fuzzy expert model for predicting electromyographic (EMG) responses of trunk muscles in manual lifting based on task. The model utilizes two task variables, i.e. trunk moment and trunk velocity, as inputs, and ten muscle activities as outputs. The input and output variables are represented using the fuzzy membership functions. Initial fuzzy rules are generated by neural networks using true EMG data. The refined fuzzy rules are used to derive the prediction model. The model was developed based on EMG data for 8 subjects, and validated using the EMG data for another 4 subjects. The model allowed to predict the normalized EMG values with the mean absolute error ranging from 4.97% to 13.16% (average = 8.43%, SD=2.87%), and average value of the mean absolute difference between the real and predicted EMG of 6.4% (SD=3.39%). It is concluded that prediction of EMG responses in manual lifting tasks is feasible, and that model performance could be improved by increasing the number of lifting task variables.

This study evaluated the differences in biomechanical model performance and predicted spinal loading on L5/S1 for controlled sagittally symmetric lifting exertions, utilizing three different EMG-assisted biomechanical models comprising different torso anatomical inputs. The first model was based on muscle lines-of-action and prediction of cross-sectional areas from an historical biomechanical model. The second model was based upon observations from an MRI study on torso geometry. The third model consisted of a hybrid approach, where geometric inputs from MRI observations were supplemented with lines-of-action observed from cadaver studies, where necessary. To evaluate the models, spinal loading and model performance was evaluated for thirty-five males performing sagittally symmetric lifting tasks starting from 55 deg trunk flexion to upright neutral. All three models resulted in comparable and acceptable model performance. However, differences were observed in predicted spinal loading. The hybrid model resulted in smaller compression force and sagittal plane shear force when compared to the MRI-only model, and smaller sagittal plane shear forces when compared to the historical biomechanical model. These results indicate that the geometric representation of the torso anatomy needs to be considered when evaluating spinal loading predicted from different biomechanical models for comparison to tolerance estimates in attempts to evaluate risk of injury.

The purpose of this study was to determine the effects of repetitive lifting on trunk muscle activity and spine kinematics during an intense, forty minute, asymmetrical lifting and lowering task. Contrary to many previous sagittal plane materials handling studies, the asymmetrical task did result in differences in kinematics between lifting and lowering. Further, there were few consistent effects of fatigue on trunk muscle activity and only spine flexion was observed to decrease over the course of the trials. However, some individual subjects did demonstrate fatigue related changes that may have increased their risk of injury if performed over prolonged periods.

There is a trade-off between the risk of low-back injury associated with tissue overload versus the risk of spinal instability. The benefit of antagonistic co-contraction in helping to prevent low-back pain associated with instability injury during manual materials handling tasks was examined. Ten healthy males performed sagittal lifting tasks while trunk motion, reaction loads, and EMG activity were recorded. A biomechanical model was developed to compute spinal load and spinal stability during the tasks. Antagonistic co-contraction was found to be beneficial in terms of the stability versus spinal load, i.e. compression increased 12–18% while stability increased 36–64%. Stability was a minimum at low trunk moments, e.g. upright postures. Conversely, as trunk moment increased the risk of stability failure was reduced but the risk of spinal tissue overload injury was increased. To compensate, subjects recruited antagonistic co-contraction less in high moment conditions and more in low moment conditions.

The accurate description of trunk muscle coactivation, and more specifically antagonist muscle activity, has recently been the focus of a great deal of research in the spine biomechanics literature. The research presented in this paper is an empirical approach to the problem. Electromyographic (EMG) data were collected from 28 subjects as they performed simulated lifting tasks. These EMG data were collected from the right and left pairs of the erector spinae, latissimus dorsi, rectus abdominis, external obliques and internal obliques as subjects performed a variety of trunk extension exertions. Nine repetitions of each combination of independent variables were performed by each subject. Included in these exertions were asymmetric postures and dynamic (isokinetic and constant acceleration) exertions. The data collected during these trials were used to develop marginal distributions of trunk muscle activity as well as a 10 × 10 correlation matrix that described how the muscles cooperated in the development of these extension torques. These elements were then combined to generate multivariate distributions describing the coactivation of the trunk musculature.

The Minimum Intensity Compression (MIC) model developed by Bean, Chaffin, and Schultz (1988) and the Sum of the Cubed Intensities (SCI) model developed by Crowninshield and Brand (1981) have been used to predict trunk muscle forces during external loads. The models require muscle geometries (moment arms, lines of action, and cross-sectional areas) as inputs. This paper reports on a computer simulation conducted to evaluate the changes in trunk muscle forces predicted by the MIC and SCI models with changes in inputs. Two muscle geometries were used for a 10-muscle set one reported by Han, Ann, Goel, Takeuchi, and McGowan (1992) and a second formed by a compilation of several studies. The results indicate that regions of muscle activity and magnitude vary greatly between the models and associated inputs. Muscle EMG data indicating active and inactive loading conditions reported by Lavender, Tsuang, Hafezi, Andersson, Chaffin, and Hughes (1992) are significantly predicted by the model combinations for some right side muscles.

In this study, comparisons were made among three representative methods for predicting compressive forces on the lumbosacral disc: LP-based model, double LP-based model and EMG-assisted model. Two subjects simulated lifting tasks that were frequently performed in the refractories industry in Korea, in which vertical distance, frontal plane horizontal distance, and weight of load were varied. To calculate the L5/S1 compressive forces, EMG signals from six trunk muscles were measured and postural data were recorded using the Motion Analysis System. The EMG-assisted model was shown to reflect well all three factors considered here. On the other hand, the compressive forces of the two LP-based models were significantly affected only by weight of load. Furthermore, relatively low correlation was observed between the compressive force of the EMG-assisted model and the 1991 NIOSH lifting index(LI), while highly positive correlation was observed between that of the two LP-based models and LI.

To investigate the effects of MMH task conditions on the activity and fatigue of the trunk musculature, EMG signals from eight major trunk muscles were analyzed during 120 minutes of repetitive dynamic lifting tasks. Two independent task variables were the work strategy of weight and lifting frequency combination and the body posture. The dependent variables were the amplitude of EMG signals and the amount of median power frequency (MPF) decrease over time for the eight trunk muscles. The results of the study indicated that the recruitment and the level of force exertions of the trunk muscles during manual lifting tasks are a function of the direction and the weight of the external load. The different activities of the muscles due to given task conditions also influence the fatiguing process of the individual muscle. The muscles in the dorsal part of trunk were activated during the symmetric task conditions, while the muscles on the contralateral side to the workload were more strongly activated during the asymmetric task conditions. The decreasing trends of MPF were found in some activated muscles, and they were more pronounced for the asymmetric posture than for the symmetric posture. It was also seen that the muscles became fatigued faster for light load-high frequency conditions than for heavy load-low frequency conditions.

The need for an alternative mailbag to the conventional U.S. postal mailbag, which hangs at the side over one shoulder, was investigated. Based on the results of a pilot study, two types of alternative mailbags, both including waist support and one that splits the load into two parts, are recommended. The metabolic energy requirement and lateral trunk muscle fatigue resulting from the use of the alternative mailbags were compared with those resulting from the conventional U.S. postal mailbag. The alternative mailbags resulted in no significant change in metabolic load. Both alternative mailbags resulted in significantly less lateral trunk muscle fatigue. It is proposed that this reduction in fatigue would result in reduced musculoskeletal stress and reduced potential for back injury.

Asymmetric material handling frequently results in lateral bending of the torso. Each of these factors have been linked via epidemiological investigations to the incidence of low back disorders (LBD). Very little literature is available which describes the response of the trunk muscles in situations which would be analogous to handling materials while bent to the side. Such activities are observed frequently in industrial settings, especially during the initial and final portions of a lift. The objective of the current study was to describe the internal response of the trunk muscles as asymmetric loads were applied to the laterally bent torso. Specifically, this investigation quantified the electromyographic activities (EMG) of 8 trunk muscles under conditions where the trunk was isometrically loaded while the trunk was maintained in a 20 degree laterally bent posture. Moments with a magnitudes of 20 and 40 Nm were applied to fifteen subjects. The direction of the external moments was varied in 30 degree increments completely around the subjects. The EMG data indicates that the muscles showed the greatest activity when they were in opposition to the load's sagittal and frontal plane moment. The muscle showing the largest response was the External Oblique. Significant activity was also observed under conditions in which muscles were creating an antagonistic moment in either the sagittal plane, the frontal plane, or in both planes.

In an effort to understand the mechanism of low back disorders, researchers have developed EMG driven biomechanical models which estimate the magnitude of the internal reaction forces of the spine (compression and shear), by using information about the activity of the muscles of the trunk. But, because the trunk ls multi-dimensional in nature, there is variability in the relative contribution of the various muscles, which implies variability in the reaction forces of the spine. Therefore, it may be more appropriate to discuss the range of spine reaction forces during a lift as opposed to the mean spine reaction force. The present research was an attempt to model the muscle forces stochastically and to develop a simulation model which predicts trunk muscle EMG that could occur during a lift. The simulated EMGs which resulted were then input into an EMG driven biomechanical model so the variability in spine reaction forces could be quantified. Under simple sagittally symmetric isometric conditions, compression which occurred at three standard deviations above the mean was 12% higher than that of the mean. The results for anterior shear (24% higher) and lateral shear (50% higher) showed even larger Increases.

The present investigation describes the electromyographic (EMG) response of eight trunk muscles during the application of loads to the torso while subjects maintained a twisted posture. The external moments of 20 and 40 Nm were applied to a harness system as each of the 10 subjects twisted 25 degrees. The applied moment direction was varied in 3 0 degree increments completely around the subjects (0 to 33 0 degrees). Surface EMG was used to monitor the left and right Latissimus Dorsi, Erector Spinae, External Oblique, and Rectus Abdominus. Multivariate and univariate analyses of variance (MANOVA and ANOVA) procedures showed significant main effects for all muscles and a significant moment magnitude by moment direction interaction effect in 6 of the 8 muscles. The greatest muscle activity was observed in the right Erector Spinae and the left External Oblique muscles. The results are also compared with an earlier study in which a similar loading paradigm was used as subject maintained a neutral upright posture.

Trunk muscle activity of twelve healthy males with coal mining experience was examined while each subject lifted a box under various conditions. The independent variables were four levels of posture (kneeling, stooped under a 1.2 m roof, stooped under a 1.6 m roof, and standing), height to which the box was lifted (35 cm or 70 cm), and weight of the lifting box (15 kg, 20 kg, or 25 kg). The dependent variables were the peak EMG values recorded during a lift for each of eight trunk muscles (left and right erectores spinae, left and right latissimus dorsi, left and right external oblique, and left and right rectus abdominis). Posture and weight of lift significantly affected peak activity of the left and right erectores spinae, the left and right latissimus dorsi muscles, and the right external oblique muscle. The latissimus dorsi muscle activity was highest in the low stooping posture, and was lowest in the kneeling posture, while erectores spinae activity was highest in the kneeling posture and decreased as the trunk became more flexed. Thus, the muscle activity during lifting tasks is affected by restricting a worker's posture. Consequently, many lifting guidelines and recommendations currently in use may not be directly applicable to work being performed in restricted postures.

The aim of the paper is to show the physiological effects and effects on selected health variables caused by work site trunk muscle training in vocational groups with a large work related mechanical exposure of the back. A total of 10 male hospitalporters and 23 female nurse assistents and home helpers paticipated bi-weekly - one hour per session - in a 12 weeks submaximal(50–55% MVC) muscle training programme. The main findings was that the endurance capacity of the trunk extensor muscles increased by 50%, while their strength only increased marginally Moreover was the pain level of the lumbar back reduced significantly. Minimizing muscle fatigue of the paravertebral muscles is probably one relevant way to to reduce the magnitude of occupational elated low back problems. This goal can be obtained by using two different but equal important concepts: Ergonomic (including work organization) changes and maintenance of the strength and endurance of the trunk muscles of the working force.

Twelve subjects participated in an investigation of the biomechanical stresses of asymmetric lifting in stooped and kneeling postures. Three factors were manipulated in this study: Posture (stooped or kneeling), height of lift (35 or 70 cm), and weight of lift (15, 20, or 25 kg). Subjects were required to lift or lower a box every 10 seconds for a period of 2 minutes. Electromyography (EMG) of eight trunk muscles was collected during a lift in this period. The EMG data, normalized to maximum extension and flexion exertions in each posture, were input to a biomechanical model and used to predict compression and shear forces at the L3 level of the lumbar spine. Results from the EMG-driven biomechanical model indicated that compression was greater when lifting to a higher shelf (p < 0.001), and indicated a significant interaction between posture and the weight of the lifting box (p < 0.01). Peak lateral shear was not significantly affected by any main effects or interactions (p < 0.05). Anterior shear was increased with increasing height of lift (p < 0.001), and also by the posture x weight interaction (p < 0.01). A multivariate analysis of variance (MANOVA) indicated a complex relationship for recruitment of the eight trunk muscles, with the triple interaction being significant (p < 0.001). The results of this investigation will be used to evaluate safe loads for lifting in these restricted postures.

Introduction Lumbar spine fusion (LSF) may be performed in the treatment of several spinal disorders if conservative treatment fails. Decreased physical activity due to pain together with spinal fusion may cause muscle atrophy and therefore decrease the trunk muscle strength. Previously, the average trunk muscle strength in flexion and in extension were reported to be 564 and 629 N, respectively, in control population compared with those of 375 and 404 N in patients 2 months after disc herniation surgery (Häkkinen et al, 2003). In healthy people trunk extensor strength has been reported to be greater than flexor strength, that is, extensor/flexor strength ratio is more than 1 (Yahia et al, 2011). Objective The aim of the present study was to evaluate the influence of lumbar spine fusion to the flexion and extension strength of the trunk muscles at 1 year follow-up after the surgery. Material and Methods Altogether 195 patients (66% females, mean [SD] age 61 [12] years and body weight 78 [15] kg) undergoing instrumented LSF attended the present study. Indications for surgery were degenerative spondylolisthesis, spondylolysis, spinal stenosis, disc herniation or degeneration, postoperative conditions or scoliosis. The median (IQR) duration of preoperative back pain was 31 (18, 66) months. Isometric flexion and extension strength of the trunk muscles was measured using a strain-gauge dynamometer and back pain was measured using visual analogue scale (VAS 0–100 mm) preoperatively and at 1 year after surgery. Results Mean (SD) preoperative trunk flexion and extension strength levels were 295 (172) and 205 (144) N, respectively. A year after the surgery, mean (95% CI) trunk flexion strength increased by 69 (53–85) N ( p Conclusion The trunk muscle strength in patients with chronic back pain undergoing LSF is low. After LSF some improvement can be found, however, still 1 year after the surgery the trunk muscle strength remains low. Moreover, the flexion strength is better than extension strength, which is in contrast to results of healthy people in previous studies. Therefore, after the spinal fusion surgery the rehabilitation should aim at improving muscle strength and special attention should be paid to correct the imbalance between trunk flexion and extension muscles.

Introduction The goal of postoperative rehabilitation after lumbar spine fusion (LSF) is to decrease pain and disability; however, back function should also be taken into account. Low trunk muscle strength has been reported in patients after LSF and it correlates with poor disability1. To increase the trunk muscle strength after fusion surgery the training should also include more intensive exercises. Exercises that are performed lumbar spine in a neutral position allow loading without the strain of fused segment. The purpose of present study was to determine trunk extensor muscle activity during different exercises and evaluate association between pain during loading and muscle activation in patients after LSF. Materials and Methods A total of 22 patients (50%women) with mean (SD) age of 59 (17) years who had undergone LSF 3 to 11 months earlier participated in the study. The indications for surgery were spondylolysis, degenerative olisthesis, spinal stenosis, and degenerative disk disease. Bilateral surface electromyography (EMG) activity of trunk extensor muscles (longissimus at the L1 level and multifidus at L5) was measured during dynamic upper limb exercise (bilateral shoulder flexion in the standing position). The load was individually adjusted using a pull machine so that each subject was able to perform 10 repetitions per set. In addition, lower limb exercise (right hip extension in the four-point kneeling position) with 10 repetitions and static back extension exercise (in the Biering-Sorensen test position) were studied. The starting and finishing points of the fifth repetition in the upper and lower limb exercises were determined from simultaneous EMG and video analysis, and this period was used for analysis. In static trunk extension exercise, the first 3 seconds were taken to analysis. The raw EMG signal was rectified and averaged. Then, the reference EMG activities obtained from maximal isometric trunk extension strength measurement (reference value) were used to normalize the EMG-activation levels collected for trunk muscle exercises. The intensity of back and leg pain during the past week and during the exercises was assessed by visual analogue scale (VAS, 0–100). Results The mean (SD) trunk extension strength was 341 (204) N. The highest activation in the longissimus was measured during the static back extension exercise. The activity on the right side was 104% and on the left side 83% when compared with the reference values. The corresponding values during bilateral shoulder flexion were 65 and 62%. The highest activity levels of the multifidus (62% on the right side and 64% on the left side) were also measured during the static back extension exercise. Activity levels of multifidus were 55% on the right side and 52% on the left side during bilateral shoulder flexion and 34% and 27% during right hip extension exercise. EMG activities of longissimus ( p Conclusion Static back extension exercise elicited the highest longissimus and multifidus muscle activity. Bilateral shoulder flexion exercise in the standing position also elicited muscle activity that may be high enough to develop muscle endurance and strength characteristics. All studied exercises are feasible in the postoperative rehabilitation after lumbar fusion surgery because pain intensity remained at relatively low level. All studied exercises are performed in the lumbar spine in the neutral position, thus strain of fused segment is minimized. I confirm having declared any potential conflict of interest for all authors listed on this abstract Yes Disclosure of Interest None declared Tarnanen SP, et al. 2012, Submitted

The present study investigated the effect of warning time and magnitude of an external loading on the trunk muscular response to sudden loading conditions while in a non-sagittally symmetric posture. Eleven subjects were asked to catch falling weights of three magnitudes (3, 6, and 9 kg) with four levels of warning time (0, 100, 200, and 400 ms) in an asymmetric posture. For each of the eight muscles sampled with surface electrodes the integrated electromyographic (EMG) signal was interpreted in terms of its peak value, mean value, onset rate, and lead/lag time with reference to the weight drop. Results show monotonic relations between muscle force and levels of warning time, and muscle force and levels of weight. In addition, muscular forces in the left posterior trunk musculature ranged between two and five times greater than the right posterior trunk musculature in response to sudden loading conditions. This experiment demonstrates how sudden asymmetric loading, and specifically sudden loading without adequate warning time may be involved in the development of low back pain.

Scaling bars are frequently used in underground mining for removing loose material from the roof and the walls. Previous research has demonstrated the scaling bar to be one of the hand tools more frequently involved in underground mining muscular-skeletal injuries. The present experiment investigated the role of seam height, scaling method and selected parameters of scaling bar design. Fourteen subjects worked in simulated mine environment and participated in all conditions of the experiment. Electromyographic (EMG) data was collected to study the relative involvement of six trunk muscles, and dynamometer output measured subjects' ability to use each bar and method effectively. Results suggest the parameters of weight and weight distribution to be important in scaling bar design. Also EMG data showed differences with tool parameters and the method used. Asymmetric loadings to the spine were found to be more extreme in the low roof conditions. These results suggest recommendations concerning tool design and proper training.

The purpose of this study was to examine the lifting capacity of low-seam coal miners in four restricted work postures (roof heights of 36″, 40″, 44″, and 48″), investigate the associated metabolic costs, and to examine electromyographic (EMG) data from eight trunk muscles during the lifting procedure. Subjects were thirteen underground miners accustomed to handling materials in restricted work postures. Each subject performed two twenty-minute periods of asymmetric lifting in each of four postures during the day of testing. The frequency of lifting was 10 lifts per minute. A specially designed lifting box incorporated microswitches in one handle of the box and another in the bottom of the box, in order to examine the trunk muscle function at specific points during the lfting cycle. The data collected will be used by the Bureau of Mines to make recommendations for lifting materials in low-seam coal mines.

Low back pain is a condition which, at some time, affects over half of the world's population and is also the number one cause of physical limitation for persons under 45 years of age. The etiology of most low back pain largely is unknown. However, it is known that after injury the biomechanics of the back change drastically. The present study investigates the ability of normal men and women to move and exert force with the back (as is done during lifting). Twenty men and women were monitered as they attempted to exert maximal force with the back under isometric and isokinetic conditions. The back angle and velocity of movement were controlled while torque, intra-abdominal pressure and the electromyographic activity of the ten trunk muscles monitored. The relationship between isometric and isokinetic exertions was determined as well as the interactive contribution of muscle forces and abdominal pressure to spinal loading. These results suggest new manual material handling implications as well as a new method for employee screening.

The literature has reported that there is a link between sudden unexpected load handling and the risk of a low back injury. It was hypothesized that sudden unexpected loads would create excessive forces upon the trunk due to the overcompensation of the trunk muscles. An experiment was performed to test this theory and quantify the degree of overcompensation. Subjects were asked to hold a box in a static lift position while weights ranging from 5 to 20 pounds were dropped into the box from a constant height. Under some conditions (expected) the subjects were permitted to observe the weight drop while under other conditions (unexpected) the subjects were deprived of visual and auditory cues during the weight drop. Generally, it was found that during sudden unexpected loading the trunk response resembled an expected loading of twice the weight value. These findings may provide guidelines for work situations where unexpected loading conditions are common.

The purpose of this study was to investigate muscle recruitment patterns for a task routinely performed in industry, under conditions which might be encountered in industry rather than in a controlled laboratory setting. Subjects encountered two asymmetric loading conditions (minimal and substantial) and two trunk motion speed conditions (normal and fast) and performed several repetitions of each condition. Electromyographic (EMG) voltage data pertaining to four pairs of trunk muscles were collected for analysis. The timing of certain events in each signal (start, peak, and end times of elevated activity) were determined. From these events, networks were constructed which portrayed average muscle recruitment order results which were found to occur under all loading and velocity conditions encountered by the subjects. Only two event-pairs were found to occur consistently for all subjects. Event-pairs which were related to changes in resistance or velocity were found for each subject. Some subjects shared event-pairs, but only one pair was found to occur for all subjects.