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PubMed1999

An electromyography-assisted model to estimate trunk muscle forces during fatiguing repetitive trunk exertions.

During submaximal shortening muscle contraction, fatigue characteristically results in an increase in measured surface electromyography, whereas the maximum force that can be produced by muscle is reduced. This finding compromises researchers' ability to estimate muscle stress in a joint system such as the spine, which is composed of more muscles than degrees of freedom of the joint. A three-dimensional, electromyography-assisted, dynamic biomechanical model of spinal loading was developed and validated for use during fatiguing repetitive trunk extension exertions. A time-varying maximum muscle stress was included to model the effect of a change in the maximum force-producing capacity of the erector spinae muscle. Sixteen men performed submaximal isokinetic trunk extension endurance tests at 15 degrees per second. The exertion level (35% and 70% of their maximum dynamic extension torque) and repetition rate (5 and 10 repetitions per minute) of the tests were varied during four testing sessions. Using trunk muscle electromyography and the measured torque as input, the model predicted significant linear reductions in the maximum muscle stress in 78% of the endurance tests, which resulted in an estimated decrease in erector spinae force in 75% of the tests. Conversely, if the maximum muscle stress was assumed to be constant, the erector spinae force would have been predicted to increase in 73% of the tests. The magnitude of the change in predicted erector spinae maximum muscle stress and force depended on the exertion level and repetition rate. This model will allow researchers to assess the effects of changes in recruitment patterns of trunk muscles during dynamic trunk extension on the estimated spinal loading of the lumbar spine.

Abdominal Muscles↗

PubMed1999

Maximum isometric trunk muscle strength and activity at trunk axial rotation during sitting.

This study was performed to provide information relating to the twisted posture being characteristic of the driver of an agricultural tractor working in the field. The relationship of trunk axial strength and muscle activity to trunk twisting angle of prerotation was determined and quantified. Differences between tractor drivers and office workers, and between the two directions of twisting action were also studied. Nine male tractor drivers and nine male office workers performed isometric maximum efforts at about -40, -20, 0, 20 and 40 degrees of pre-set trunk twisting angles in both the clockwise and counterclockwise directions. Exerted torque, true angle of prerotation and muscle activity from left and right side of each of obliquus externus, rectus abdominis and erector spinae were measured simultaneously. The results showed that the subjects could exert the greatest torques when being prerotated in the opposite direction and the lowest torques when being prerotated in the same direction to the direction of exertion. The exerted torques were within the range of 65-145 Nm. There were large differences in obliquus externus and erector spinae activity due to the twisting direction. There were also changes in muscle activity from obliquus externus and rectus abdominis due to prerotation angle. The results raised questions concerning the involvement of the passive tissues and the use of deeper muscles during trunk axial rotation, which should be further investigated.

Abdominal Muscles↗

PubMedDate not supplied

Sheldon's trunk index and the growth of the thoracic and lumbar trunk.

The trunk index (TI), a ratio of the area of the thoracic trunk to that of the lumbar trunk, is measured on a somatotype photograph marked according to defined criteria. Photographs of 82 boys from the Harpenden Growth Study were measured at ages 5 to 18 years, in an order that obscured which photographs were of the same boy at different ages. Remeasurement two months later of 12 boys at each of ages 5, 11, and 18 years showed retest correlations of 0.97 or higher for thoracic and lumbar areas separately and of about 0.95 for their ratio. When 57 boys aged 17 to 20 years were measured by another worker, their TI values correlated 0.90 with those used in this study. Inter-age correlations among the unedited TI values were approximately 0.9 between ages a year apart and declined as age differences increased. Correlations with values at age 18 increased from about 0.7 at age 5 to 0.9 by age 16. Editing was done by remeasuring all values that deviated by more than 0.05 TI units from a regression line based on each subject's total array of values. In the edited data, correlations with TI values at age 18 increased, ranging from 0.8 at age 5 to 0.95 by age 16. Mean TI was quite stable, ranging only between 1.45 and 1.51 for the whole age span, with the lowest values appearing from 11 to 14 years. In 43 of the 59 boys whose series allowed determination of peak height velocity (PHV), a 'TI dip' appeared: one to three TI values fell more than 0.05 TI units below the boy's overall regression line shortly before PHV. Distance and velocity curves are given for growth of the thoracic and lumbar trunk areas. Peak velocity of growth of the lumbar area occurred on average a little earlier than that for the thoracic area; the TI dip was in part a result of this. Alterations of fat distribution as seen by skinfolds probably also contributed. Judging by their individual regression lines, about 80% of the boys showed no more than chance variation from a horizontal slope, their TI neither increasing nor decreasing overall. An additional 10% appeared to show significant slopes only because their series started or ended too near their TI dips. The remaining 10% of boys appeared to show real changes in TI as they grew. Examples of the most extreme changes are shown.

Adolescent↗

PubMed1997

Changes in trunk dynamics and spine loading during repeated trunk exertions.

STUDY DESIGN: Trunk and hip kinematic and spinal loading changes were documented as experienced subjects performed a set of standard free-dynamic lifting tasks at various intervals throughout a 5-hour repetitive manual materials handling session. OBJECTIVES: To document how spine loading changes as a function of repetitive lifting during an extended period of lifting cycles. SUMMARY OF BACKGROUND DATA: Many studies have evaluated spine loading as a function of a specific lifting task, but no studies could be found in the literature that evaluated how spine loading may change with repeated exposure to a lifting task. METHODS: Ten experienced material handlers were recruited. Each was required to transfer 11 pallets of 23 kg boxes at a rate of 125 lifts per hour. Before and after unloading each pallet, subjects were asked to perform a set of five standard free-dynamic lifting tasks. Electromyographic activities of 10 trunk muscles were recorded along with kinematic and kinetic data. An electromyography-assisted model was used to evaluate spine loading during the standard lifting tasks. RESULTS: Subjects significantly changed their motion patterns throughout the lifting session. Trunk range of motion, velocity, and acceleration decreased in the sagittal plane, whereas these same measures increased for the hip. Trunk moment also decreased by 7% during the standard lifts. These changes were accompanied by a redistribution of muscle recruitment patterns, resulting in a decrease in spine compression and an increase in anterior/posterior shear. CONCLUSIONS: This study has shown that spine loading patterns do indeed change with repetition, suggesting that one needs to monitor these changes throughout repetitive lifting tasks if low back disorder risk is to be minimized.

Adult↗

PubMed1996

Reproducibility of isometric trunk extension torque, trunk extensor endurance, and related electromyographic parameters in the context of their clinical applicability.

Testing the capacity of the trunk extensor muscles may be useful in the diagnosis of low back pain. In the present study, the reproducibility of measurements of maximum trunk extension force, trunk extension endurance, and related electromyographic parameters was investigated. Intraclass correlations indicated that the reproducibility of maximum force and endurance time was satisfactory. Nevertheless, the smallest difference in these parameters that could be attributed, with 95% confidence, to a change in the condition of a patient was, in general, more than 20%. On the electromyograms, the slopes of amplitude and frequency content appeared to be related to endurance time. The reproducibility of these parameters in terms of the intraclass correlation was again satisfactory; however, the smallest detectable difference generally exceeded 50%. The clinical applicability of the parameters studied is severely limited by a lack of reproducibility.

Adult↗

PubMed2001

Postural control of the trunk in response to lateral support surface translations during trunk movement and loading.

The postural response to translation of the support surface may be influenced by the performance of an ongoing voluntary task. This study was designed to test this proposal by applying lateral perturbations while subjects handled a load in the frontal plane. Measurements were made of medio-lateral displacement of the centre of pressure, angular displacement of the trunk and thigh in the frontal plane and intra-abdominal pressure. Subjects were translated randomly to the left and right in a variety of conditions that involved standing either quietly or with a 5 kg load in their left hand, which they were required either to hold statically or to lift or lower. The results indicate that when the perturbation occurred towards the loaded left side the subjects were able to return their centre of pressure, trunk and thigh rapidly and accurately to the initial position. However, when the perturbation occurred towards the right (away from the load) this correction was delayed and associated with multiple changes in direction of movement, suggesting decreased efficiency of the postural response. This reduced efficiency can be explained by a conflict between the motor commands for the ongoing voluntary task and the postural response, and/or by the mechanical effect of the asymmetrical addition of load to the trunk.

Abdomen↗

PubMed2006

Trunk muscle activation and associated lumbar spine joint shear forces under different levels of external forward force applied to the trunk.

High anterior intervertebral shear loads could cause low back injuries and therefore the neuromuscular system may actively counteract these forces. This study investigated whether, under constant moment loading relative to L3L4, an increased externally applied forward force on the trunk results in a shift in muscle activation towards the use of muscles with more backward directed lines of action, thereby reducing the increase in total joint shear force. Twelve participants isometrically resisted forward forces, applied at several locations on the trunk, while moments were held constant relative to L3L4. Surface EMG and lumbar curvature were measured, and an EMG-driven muscle model was used to calculate compression and shear forces at all lumbar intervertebral joints. Larger externally applied forward forces resulted in a flattening of the lumbar lordosis and a slightly more backward directed muscle force. Furthermore, the overall muscle activation increased. At the T12L1 to L3L4 joint, resulting joint shear forces remained small (less than 200N) because the average muscle force pulled backward relative to those joints. However, at the L5S1 joint the average muscle force pulled the trunk forward so that the increase in muscle force with increasing externally applied forward force caused a further rise in shear force (by 102.1N, SD=104.0N), resulting in a joint shear force of 1080.1N (SD=150.4N) at 50Nm moment loading. It is concluded that the response of the neuromuscular system to shear force challenges tends to increase rather than reduce the shear loading at the lumbar joint that is subjected to the highest shear forces.

Abdomen↗

PubMed2001

Effects of dynamic office chairs on trunk kinematics, trunk extensor EMG and spinal shrinkage.

Seated work has been shown to constitute a risk factor for low-back pain. This is attributed to the prolonged and monotonous low-level mechanical load imposed by a seated posture. To evaluate the potential health effects with respect to the low back of office chairs with a movable seat and back rest, trunk kinematics, erector spinae EMG, spinal shrinkage and local discomfort were assessed in 10 subjects performing simulated office work. On three separate occasions subjects performed a 3 h task consisting of word processing, computer-aided design and reading. Three chairs were used, one with a fixed seat and back rest and two dynamic chairs, one with a seat and back rest movable in a fixed ratio with respect to each other, and one with a freely movable seat and back rest. Spinal shrinkage measurements showed a larger stature gain when working on the two dynamic chairs as compared with working on the chair with fixed seat and back rest. Trunk kinematics and erector spinae EMG were strongly affected by the task performed but not by the chair type. The results imply that dynamic office chairs offer a potential advantage over fixed chairs, but the effects of the task on the indicators of trunk load investigated were more pronounced than the effects of the chair.

Adult↗

PubMed2004

Postural and trunk muscle response to sudden release during stoop lifting tasks before and after fatigue of the trunk erector muscles.

The effect of fatigue on the muscular and postural response to sudden release of different stoop lifting loads was studied. Ten male volunteers performed a series of stoop lifting trials before and after fatigue of the erector spinae. Trials were performed using loads of 20, 40, 60, and 80 N, and sudden release of load was triggered randomly on one of the repetitions using an electromagnetic release. The onset of release was registered by an accelerometer, centre of pressure (COP) motion was recorded via a forceplate, and EMG activities of the latissimus dorsi (LD), erector spinae (ES), rectus abdominus (RA), external oblique (EO) and internal oblique (IO) muscles were recorded. A slightly reduced lifting speed was seen after fatigue, particularly at the higher loads, but this had little effect on the perturbing force at release, which was dominated by the release load. A significant effect of fatigue was seen on the antero-posterior COP motion, with the postural disturbance being decreased after fatigue. Fatigue resulted in a significant increase in ES (p = 0.029) and LD (p = 0.015) relaxation times and, while the response patterns (relaxation, contraction or no response) of the anterior trunk muscles (RA, EO, IO) were not always consistent, the proportion of response by relaxation was greater after fatigue. This resulted in a lower incidence but longer duration of co-contraction of the ES-RA, ES-EO and ES-EO muscle groups following fatigue, such that the mean co-contraction duration of these groups showed no significant differences before and after fatigue. The response to sudden release is a balance between maintaining postural stability and at the same time preventing the trunk musculature from overloading the spine and risking tissue injury. While fatigue of the trunk extensors does not appear to increase either the risk of fall or stumble or the incidence of co-contraction following sudden release of stoop lifting tasks, the duration of co-contraction appears to increase following fatigue. Further study is required to quantify the loading on the spine during sudden release of different lifting tasks before and after more realistic fatigue conditions.

Abdominal Muscles↗

PubMed1987

Normal trunk muscle strength and endurance in women and the effect of exercises and electrical stimulation. Part 2: Comparative analysis of electrical stimulation and exercises to increase trunk muscle strength and endurance.

Several studies have shown positive correlations between muscle strength, flexibility, and the frequency of low-back pain. Weak trunk musculature and decreased endurance have thereby come to be identified as significant risk factors in the development of occupational back problems. Because it is widely accepted that exercise plays an important role in the conservative treatment and prevention of low-back pain, the goals of most rehabilitative programs involves improving the strength and endurance of the low-back pain patient. Whereas electrical stimulation has been shown to increase the muscle strength of the lower extremities, this effect has not been demonstrated for the trunk muscles. Part 2 is a prospective controlled study designed to document and to compare objectively the effects of electrical stimulation and exercise on trunk muscle strength. A total of 117 healthy women were divided randomly into four groups. Two groups received electrical stimulation with different electrical parameters, one group received exercises, and one group acted as a control group. The results showed that low-frequency electrical stimulation and exercises significantly (P less than .05) increased isokinetic back-muscle strength compared to the control and medium-high-frequency electrical stimulation groups. Both types of electrical stimulation, however, significantly increased (P less than .05) the endurance in the back muscles compared with the control and the exercise groups. This study showed that electrical stimulation may be a valuable treatment in the early care of low-back pain patients in maintaining and increasing strength and endurance of back muscles when a more active exercise program is too painful to perform.

Adolescent↗

PubMed1992

The influence of lordosis on axial trunk torque and trunk muscle myoelectric activity.

Force contributions from the facet complex and posterior ligaments during the generation of axial torque are a function of lordosis, and it has been speculated that these forces together with muscular contributions play a role in axial trunk twisting. This study investigated the electromyographic activity of the trunk musculature and torque-generating capacity of the lumbar spine under the conditions of normal lordosis, hyperlordosis, and hypolordosis. Eleven male subjects volunteered for this study. The subjects performed isometric twisting efforts and maximum dynamic twisting efforts at 30 degrees/sec. The myoelectric activity levels (normalized to maximal amplitude obtained from nontwist activities) were quite low despite maximal efforts to generate axial torque (for example: approximately 60% maximum voluntary contraction for latissimus dorsi and even lower for the abdominals). Furthermore, changes in lordosis did not produce any consistent changes in muscle activity, although a hyperlordotic spine produced significantly smaller axial torques, and a hypolordotic spine smaller still. Larger torques were measured during all three conditions of lordosis, as the subjects rotated toward an untwisted position, and lower torques as the subjects rotated away. The opposite trend was observed, however, in myoelectric activity of the agonistic side of latissimus dorsi, the thoracic level of erector spine, and the lumbar level of erector spinae, i.e., larger amplitudes were observed as the trunk was twisted away from the untwisted position. These data suggest that tissues other than muscle (i.e., passive tissue) contribute significantly to axial torque production and that the flexed and twisted spine is less able to resist applied axial torques, possibly increasing the risk of torsional injury.

Abdominal Muscles↗

PubMed2004

Abdominal Muscle Activity While Performing Trunk-Flexion Exercises Using the Ab Roller, ABslide, FitBall, and Conventionally Performed Trunk Curls.

OBJECTIVE: To compare the surface electromyographic activity of the abdominal musculature and rectus femoris (RF) muscle during trunk-flexion exercises using 3 abdominal exercise devices (Ab Roller, ABslide, and FitBall) and the traditional trunk curl. DESIGN AND SETTING: Each subject performed approximately 15 repetitions for each exercise condition. A repeated-measures, one-way multivariate analysis of variance was used to compare the mean integrated electric activity value for each muscle during each exercise condition. SUBJECTS: A total of 10 male and 13 female collegiate undergraduate students. MEASUREMENTS: Surface electromyographic activity was recorded for the upper rectus abdominis (URA), lower rectus abdominis (LRA), external oblique (EO), and RF during 5 consecutive repetitions of each exercise bout. The signal was amplified by a factor of 1000, rectified, and integrated. These integrated values were then divided by the time value for each exercise to give the mean integrated electromyography value. RESULTS: A significant difference existed among exercise conditions for the RF (P <.0001), with the ABslide and the FitBall having greater electric activity than the other exercise conditions. Activity was significantly different (P <.0009) for the URA, with the ABslide having the least electric activity. For the EO, exercising with the ABslide produced significantly greater electric activity (P <.0001) than all other exercise conditions. No significant difference was found across exercise conditions for the LRA (P <.051). CONCLUSIONS: Performing abdominal exercises with the Ab Roller, ABslide, and FitBall did not elicit greater activity of the URA and LRA than performing traditional trunk curls. Use of the ABslide elicited greater EO activity and significantly less URA activity than the other 3 modes. Both the ABslide and FitBall resulted in greater involvement of the hip flexors, an undesirable feature of abdominal exercises.

Journal Article↗

PubMed1998

Concurrent anomalies of the abdominal arteries: an extremely long coeliac trunk, an inferior phrenic trunk, and an aberrant right hepatic artery.

We present a case in which the branching pattern of the abdominal arteries contains multiple variations that to date have not been reported together. The anomalies encountered include an extremely long coeliac trunk, an inferior phrenic trunk (as one of the branches of the coeliac trunk) and an aberrant (replaced) right hepatic artery derived from the superior mesenteric artery.

Abdomen↗

PubMed2000

Aneurysm in the pulmonary trunk associated with atrial septal defect, a left coronary artery fistula to the pulmonary trunk, and valvular pulmonary stenosis.

A 78-year-old woman with an aneurysm in the pulmonary trunk associated with an atrial septal defect, left anterior descending coronary artery fistula to the pulmonary trunk and valvular pulmonary stenosis is reported. The aneurysm showed gradual dilatation over 16 years and was successfully treated using aneurysmorrhaphy. Although there has been some controversy regarding the optimum management for a pulmonary artery aneurysm, surgical correction is thought to be essential for aneurysms associated with congenital cardiac anomalies because of the high incidence of rupture.

Aged↗

PubMed1993

Supported angioplasty with synchronized retroperfusion in high-risk patients with left main trunk or near left main trunk obstruction.

To test the feasibility of synchronized retroperfusion (SRP) as a support device of percutaneous transluminal coronary angioplasty (PTCA) for high-risk patients, 10 patients with left main trunk or near left main trunk obstruction underwent PTCA with SRP. An 8.5F retroperfusion catheter was inserted from the antecubital vein into the coronary sinus. Arterial blood was supplied through the catheter into the myocardium with a retroperfusion pump during the diastolic phase by means of ECG triggering. In all patients, the narrowings were successfully dilated and an improvement of more than 20% in the luminal diameter stenosis was achieved; however, narrowing of more than 50% (58%) remained in one patient. In all patients, systemic hemodynamics was maintained for more than 30 seconds during balloon inflation. In seven patients, a 60-second balloon inflation was possible without any collapse of systemic hemodynamics. To test the protective effect of SRP on myocardial ischemia and impairment of systemic hemodynamics, balloon inflation without SRP was performed in eight patients after successful dilatation. The duration for balloon inflation with SRP (71 +/- 30 seconds; n = 8) was significantly longer than that without SRP (56 +/- 30 seconds; n = 8). The decrease in systolic aortic pressure, the increase in pulmonary diastolic pressure, and ST-T segment elevation in the precordial lead of ECG during balloon inflation with SRP were less than those during balloon inflation without SRP. After PTCA, angina was not provoked by exercise stress testing in any of the 10 patients. We concluded that SRP is a beneficial support device of PTCA for high-risk patients.

Aged↗

PubMed2005

Should the "elephant trunk" be skeletonized? Total arch replacement combined with stented elephant trunk implantation for Stanford type A aortic dissection.

OBJECTIVES: To eliminate the residual false lumen in the descending thoracic aorta and improve long-term outcomes of surgical intervention for Stanford type A aortic dissection, we performed the skeletonized "elephant trunk" procedure in the ascending aorta and aortic arch replacement combined with transaortic stented graft implantation into the descending aorta for both acute and chronic type A aortic dissection, and the short-term results were compared. METHODS: Between April 2003 and November 2004, 60 consecutive patients (mean age, 53 +/- 16.7; approximate range, 28-78 years) with acute (n = 36) or chronic (n = 24) type A aortic dissection underwent this procedure. Right axillary artery cannulation was used for cardiopulmonary bypass and selected cerebral perfusion. The stented graft, a 10-cm-long woven Dacron graft with a self-expandable stent, was implanted through the aortic arch during hypothermic circulatory arrest. Enhanced electric beam computed tomography was performed in each patient before discharge, 3 months after the operation, and once each year thereafter to evaluate the postoperative time course of the residual false lumen. RESULTS: Cardiopulmonary bypass time was 166 +/- 38 minutes, and average selective cerebral perfusion and lower body arrest time was 30 +/- 15 minutes. The in-hospital mortality was 3.3% (2/60). Thrombus obliteration of the residual false lumen in the descending thoracic aorta was observed in 92% and 85% of the acute and chronic aortic dissections, respectively, 3 months postoperatively. There was no late death during follow-up. CONCLUSIONS: The skeletonized elephant trunk procedure is an effective way of closing the residual false lumen of the descending aorta and might contribute to better long-term outcomes for both acute and chronic type A aortic dissection.

Acute Disease↗

PubMed1999

A technique for estimating activity in whole nerve trunks applied to the cervical sympathetic trunk, in the rabbit.

The changes in sympathetic outflow may be evaluated from the amplitude of the antidromic compound action potential (ACAP) according to the collision technique described by Douglas and Ritchie (Douglas, W.W. and Ritchie J.M., A technique for recording functional activity in specific groups of medullated and non-medullated fibers in whole nerve trunks. J. Physiol., 138(1957) 19-30). This technique was revised, taking into account the depressant action exerted by antidromic stimulation on sympathetic preganglionic neurones (SPNs). Cervical sympathetic nerve (CSN) of rabbits was used as experimental model. Stimulation frequencies of 0.2-0.5 Hz were found to be sufficiently low to avoid depressant actions on CSN spontaneous activity; they were employed to test the sensitivity of the technique during different experimental manoeuvres, such as changes in pulmonary-ventilation, baroreceptor unloading and arousal stimuli. In addition a procedure was devised to calibrate the ACAP amplitude: high frequency antidromic stimulation was used to induce a complete and transient inhibition of SPNs which allows to record the ACAP maximum amplitude. ACAPs recorded in various experimental conditions can then be expressed as percentage of this value.

Action Potentials↗

PubMed1991

Trunk muscle and lumbar ligament contributions to dynamic lifts with varying degrees of trunk flexion.

This study was done to assess the interplay between muscular and ligamentous sources of extensor moment during dynamic lifting with various loads and flexion angles of the trunk segment for 15 subjects lifting a total of 150 loads. Ligament forces predicted from an anatomically detailed biomechanical model did not generally contribute more than 60 Nm for most of the lifts because the lumbar spine was only flexed to a moderate and constant degree for each load condition. In contrast, additional moment demands associated with increases in hand load were supported by muscle. Although the compression forces on the L4-5 intervertebral disc were fairly insensitive to the interplay between the recruitment of muscle and ligament, the shear force was significantly higher with a greater degree of lumbar flexion. The risk of injury may be influenced more by the degree of lumbar flexion than the choice of stoop or squat technique.

Adult↗