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At least 235 records · Page 13Linked to original sources

PubMed2006

Extensive deployment of the stented elephant trunk is associated with an increased risk of spinal cord injury.

OBJECTIVE: Thoracic aortic aneurysm repair with the stented elephant trunk technique seems to be associated with an increased risk of spinal cord injury. We investigated whether severe atherosclerosis of the distal landing zone or extensive deployment of the stented elephant trunk is associated with increased risk of spinal cord injury. METHODS: Twenty-five patients underwent thoracic aortic aneurysm repair with the stented elephant trunk technique. The study population included 19 men and had a mean age of 73 +/- 7 years. All patients underwent a median sternotomy with cardiopulmonary bypass and selective cerebral perfusion. The elephant trunk was fixed with a Z-stent distal to the aneurysm during hypothermic circulatory arrest. Thirteen patients underwent concomitant total aortic arch replacement. RESULTS: Six (24%) patients had spinal cord injury. The presence of severe atherosclerosis at the distal landing zone demonstrated a tendency to increase the incidence of spinal cord injury (36% vs 9%, P = .1218). More distal deployment of the stented elephant trunk was significantly associated with increased risk of spinal cord injury (T8.0 +/- 0.6 vs T6.5 +/- 1.1, P = .0043). Univariate logistic regression analysis identified a history of abdominal aortic aneurysm repair (P = .0296) and the vertebral level of the distal landing zone (P = .0249) as significant independent risk factors for spinal cord injury, and only the latter was significant in multivariate analysis (P = .0396). The combination of a distal landing zone of T7 or greater and a history of abdominal aortic aneurysm repair was the strongest predictor for spinal cord injury (71% vs 6%, P = .0047). CONCLUSIONS: Spinal cord injury after stented elephant trunk deployment might be related to occlusion of the excessive intercostal arteries or thromboembolism. Patients with a history of abdominal aortic aneurysm repair who require extensive deployment of the stented elephant trunk seem to be at a higher risk for spinal cord injury.

Aged↗

PubMed2004

Redefining the head-trunk interface for the neural crest.

The head-trunk interface lies at the occipito-cervical boundary, which corresponds to the somite 5/6 level. Previous studies have demonstrated that neural crest cells also behave differently either side of this boundary and that this may be due to intrinsic differences between cranial and trunk crest. However, it is also possible that some of the observed differences between cranial and trunk crest are assigned by environmental cues. We have therefore scrutinised the behaviour of the neural crest cells generated either side of the occipito-cervical boundary in chick and, interestingly, find that both behave in a truncal fashion by traversing the anterior half of their adjacent somites. Furthermore, although not previously described, we find that transient DRGs form opposite somites 4 and 5. Crest cells produced anterior of the somite 3/4 boundary avoid the somites and behave in a non-truncal fashion; these cells populate the pharyngeal arches, and thus contribute to the developing head. We have further shown, via somite transplantations, that differential behaviour of the posterior versus anterior occipital crest is assigned by the somites. If somites 1 to 3 are replaced by trunk somites, then the anterior occipital crest will behave in a truncal fashion by invading the somites. Correspondingly, if these anterior occipital somites are transplanted in place of trunk somites, they perturb the migration of trunk crest. Thus, for the neural crest, the head-trunk interface does not lie at the occipito-cervical boundary, but rather lies at the somite 3/4 level and is defined by the somites. The fact that this boundary lies at the somite 3/4 level in chick is significant as it reflects the more ancient posterior occipital boundary; in fish, only the first three somites contribute to the occipital bone.

Animals↗

PubMed1995

Trunk movements in older subjects during sit-to-stand.

Sitting to standing (STS) is an activity that is performed many times during the course of a day and is an important prerequisite to the achievement of many functional goals. This article presents the results from a pilot study, the purpose of which was to develop a method for investigating the activity of sit-to-stand. The study describes STS timing and patterns of trunk movement during standing up in a population of 30 normal older adult subjects (mean age, 61.6 years; SD, 7.7 years). Data were gathered using a three-dimensional movement analysis system, CODA-3. Time taken to stand up was recorded, as were the trunk movements of pelvic and shoulder rotation, trunk lateral flexion, pelvic and shoulder lateral shift, and backward shoulder movement to achieve stance. Results show that normal subjects stood up quickly (mean, 1.67 sec; SD, .27 sec; range, 1.26 to 2.13 sec), and despite large amounts of trunk forward flexion and upward motion necessary to achieve the task of standing up, only small amounts of trunk rotation, trunk lateral flexion, and trunk lateral shift were measured during the activity. The identification of these movements characteristics may be beneficial in assisting with analysis of the STS movement pattern.

Aged↗

PubMed2003

Assessment of trunk function in single and multi-level spinal stenosis: a prospective clinical trial.

OBJECTIVE: To clarify the biomechanical indicators of single- and multi-level stenosis and to determine the biomechanical outcome of selective conservative decompression. DESIGN: This study is a prospective clinical trial examining trunk function in spinal stenosis patients operated using a conservative procedure in an orthopaedic clinic. BACKGROUND: Although several clinical studies have examined the instability and motion characteristics of operated lumbar spinal canal stenosis, few if any studies have prospectively examined the biomechanical outcome of lumbar spinal canal stenosis surgery. METHODS: Comprehensive pre- and post-operative trunk dynamometer strength and motion analysis tests were performed on 36 patients operated for lumbar canal stenosis. Surgical treatment efficacy was evaluated within a three variable crossed factorial design considering stenosis classification, number of operative levels, and changes in several trunk biomechanical outcomes from pre- to post-operative assessment. Patients were evaluated after a minimum one-year follow-up. RESULTS: Pre-operatively there were no differential effects associated with stenosis classification or number of operated levels. There was a significant post-operative increase in isometric trunk extension torque and flexion-extension power and a return to a more normal trunk extension-flexion torque ratio. Patients with mixed, single level stenosis demonstrated greater trunk extension power both pre- and post-operatively compared to other patients. CONCLUSIONS: Conservative surgical treatment of lumbar spinal stenosis produced a marked improvement in the functional mechanical status of the low back. RELEVANCE: This study assists clinicians and researchers to understand trunk function following conservative surgical treatment of lumbar spinal stenosis.

Decompression, Surgical↗

PubMed1997

Fatigue-related EMG responses of trunk muscles to a prolonged, isometric twist exertion.

OBJECTIVE: To determine the responses of the trunk muscles to fatigue during sustained, isometric axial torque exertions. DESIGN: Electromyographic (EMG) amplitude and frequency parameters were used to investigate the effects of prolonged contractions on the recruitment patterns of trunk muscles, with special emphasis on those antagonistic and stabilizing muscles not contributing directly to the required axial torque. BACKGROUND: High levels of muscle coactivity have been observed during axial torque generation in the trunk. It has been suggested that this serves to enhance postural stability of the spine during potentially injurious twist exertions. Muscle fatigue decreases force-generating capacity but the resulting effects on muscle recruitment, and the subsequent consequences for postural stability, have not been explored previously during the production of axial torques in the spine. METHODS: Eleven male and 11 female subjects maintained an isometric axial torque exertion to the left (40% of maximum) until volitional exhaustion in an upright standing posture. Maximum axial torques were measured before and after the trial. The average EMG amplitude (AEMG) and mean power frequency (MPF) of seven bilateral trunk muscles (representing agonists, antagonists and trunk stabilizers) were continuously monitored throughout the trial. RESULTS: The average decrease in maximum torque was 18.5% and the average endurance time was 163 +/- 52 s. Evidence of muscle fatigue was provided by significant MPF decreases in 12 of the 14 muscles monitored (P < 0.05) with a overall average decrease of 20.4%. There was a significant increase in AEMG with time for 11 of the 14 muscles monitored (P < 0.05). These increases in activation were linked to increases in muscle force for most of the antagonistic and stabilizing muscles. Gender effects were rarely observed. CONCLUSIONS: Fatigue results in an change in the recruitment patterns of trunk muscles. Muscles serving as antagonists and trunk stabilizers during prolonged axial twist exertions increased their force levels in response to fatigue.

Journal Article↗

PubMed2000

The effect of lumbar back support tension on trunk muscle activity.

OBJECTIVE: Assess the effect of different controlled lumbar back support tightness levels on trunk muscle activity. DESIGN: Two-way repeated measure design assessing lumbar back support tension and submaximal trunk extension moments on trunk muscle electromyographic activity. BACKGROUND: Biomechanical studies on lumbar back supports often use electromyography (EMG) to assess the affect on trunk muscle activity. However, the lumbar back support may alter the electromyographic signal by changing the electrode-muscle distance. METHODS: Subjects performed trunk extensions at three static submaximal extension moment levels (25%, 50% and 75% MVC) while stabilized at the hips and shoulders, with the back support tensioned to three different tightness levels (44.5, 66.7 and 89.0 N) as well as a no-back support condition. RESULTS: Statistical analysis failed to find a significant effect (P</=0.05) of lumbar back support tension on the average normalized EMG across the 10 trunk muscles sampled. CONCLUSIONS: For static experimental tasks, as long as electrodes are protected from direct contact with the back support, studies assessing the effect of lumbar back supports on the trunk muscles via EMG during static tasks are not subject to confounding due to differences in tensions across subjects. RelevanceThe results of this study suggest that variable tensions from previous studies for static exertions with lumbar back supports do not significantly alter the pick-up volume of protected electrodes.

Adult↗

PubMed2001

Trunk sway measures of postural stability during clinical balance tests: effects of a unilateral vestibular deficit.

This research evaluated whether quantified measures of trunk sway during clinical balance tasks are sensitive enough to identify a balance disorder and possibly specific enough to distinguish between different types of balance disorder. We used a light-weight, easy to attach, body-worn apparatus to measure trunk angular velocities in the roll and pitch planes during a number of stance and gait tasks similar to those of the Tinetti and CTSIB protocols. The tasks included standing on one or two legs both eyes-open and closed on a foam or firm support-surface, walking eight tandem steps, walking five steps while horizontally rotating or pitching the head, walking over low barriers, and up and down stairs. Tasks were sought, which when quantified might provide optimal screening for a balance pathology by comparing the test results of 15 patients with a well defined acute balance deficit (sudden unilateral vestibular loss (UVL)) with those of 26 patients with less severe chronic balance problems caused by a cerebellar-pontine-angle-tumour (CPAT) prior to surgery, and with those of 88 age- and sex-matched healthy subjects. The UVL patients demonstrated significantly greater than normal trunk sway for all two-legged stance tasks especially those performed with eyes closed on a foam support surface. Sway was also greater for walking while rotating or pitching the head, and for walking eight tandem steps on a foam support surface. Interestingly, the patients could perform gait tasks such as walking over barriers almost normally, however took longer. CPAT patients had trunk sway values intermediate between those of UVL patients and normals. A combination of trunk sway amplitude measurements (roll angle and pitch velocity) from the stance tasks of standing on two legs eyes closed on a foam support, standing eyes open on a normal support surface, as well as from the gait tasks of walking five steps while rotating, or pitching the head, and walking eight tandem steps on foam permitted a 97% correct recognition of a normal subject and a 93% correct recognition of an acute vestibular loss patient. Just over 50% of CPAT patients could be classified into a group with intermediate balance deficits, the rest were classified as normal. Our results indicate that measuring trunk sway in the form of roll angle and pitch angular velocity during five simple clinical tests of equilibrium, four of which probe both stance and gait control under more difficult sensory conditions, can reliably and quantitatively distinguish patients with a well defined balance deficit from healthy controls. Further, refinement of these trunk sway measuring techniques may be required if functions such as preliminary diagnosis rather than screening are to be attempted.

Discriminant Analysis↗

PubMed2002

Effect of pregnancy on trunk range of motion when sitting and standing.

BACKGROUND: During pregnancy, apposition of body segments and changes in trunk mobility and motion control due to increased mass and dimensions may reduce the functional range of motion of the trunk segments. Although static postures have been investigated, dynamic trunk motion during pregnancy in sitting and standing has had very limited investigation. METHODS: Included in the study was a volunteer sample of convenience of nine primiparous and multiparous women. Twelve nulliparous females formed a control group. The subjects were filmed while performing maximum seated and standing trunk forward flexion, side-to-side flexion and seated axial rotation. A repeated measures anova was used to investigate systematic changes in the motion of the pelvic and thoracic segments and the thoracolumbar spines during pregnancy. RESULTS: As pregnancy progressed, there was no significant decrease in the range of side-to-side flexion. For forward flexion and axial rotation, motion of the thoracic segment and the thoracolumbar spine was significantly reduced. Movement of the pelvis was less affected. Base of support width was increased for forward flexion and side-to-side flexion. CONCLUSIONS: In late pregnancy, strategies such as increasing the width of the base of support and reducing obstruction from other body parts were used to minimize the effects of increased trunk mass and girths. Not all trunk segment motion was affected equally. The differing effect on individual trunk segment motion may lead to altered movement patterns during functional tasks.

Adult↗

PubMed2003

Effect of fatigue on torque output and electromyographic measures of trunk muscles during isometric axial rotation.

OBJECTIVES: To examine the changes in torque output resulting from fatigue, as well as changes in electromyographic measures of trunk muscles during isometric axial rotation and to compare these changes between directions of axial rotation. DESIGN: Subjects performed fatiguing right and left isometric axial rotation of the trunk at 80% of maximum voluntary contraction while standing upright. SETTING: A rehabilitation center. PARTICIPANTS: Twenty-three men with no history of back pain. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Surface electromyographic signals were recorded from 6 trunk muscles bilaterally. The primary torque in the transverse plane and the coupling torques in sagittal and coronal planes were also measured. RESULTS: During the fatiguing axial rotation contraction, coupling torques of both sagittal and coronal planes were slightly decreased and no difference was found between directions of axial rotation. Decreasing median frequency and an increase in electromyographic amplitude were also found in trunk muscles with different degrees of changes in individual muscles. There were significant differences (P<.05) between right and left axial rotation exertions in median frequency slope of external oblique, internal oblique, latissimus dorsi, and iliocostalis lumborum muscles, but no such difference was found in median frequency slope of rectus abdominis and multifidus muscles. This could be attributed to different functional roles among the muscles. Similar differences (P<.05) between right and left axial rotation in median frequency slope were also detected in the electromyographic amplitude slope of the trunk muscles. Coefficient of variation of the torque output and electromyographic activation in most of the trunk muscles increased during the fatigue process. CONCLUSION: The changing coupling torque, different fatigue rate, and activation changes of trunk muscles, as well as the increase in variability during fatiguing axial rotation exertion, could affect the internal loading and stability of the spine; this needs to be further quantified in future studies.

Abdominal Muscles↗

PubMed2001

Vitamin D status, trunk muscle strength, body sway, falls, and fractures among 237 postmenopausal women with osteoporosis.

The aim of this study was to identify factors associated with fractures in patients with postmenopausal osteoporosis. The overall hypothesis was that trunk muscle strength, body sway and hypovitaminosis D would influence daily activities and the likelihood of falls and fractures. - In 237 women (mean age 62.9+/-7.4 years) osteoporosis was defined by a T-score at the femoral neck below -2.5 SD. Trunk muscle strength was determined using isokinetic dynamometry and body sway was measured according to Lord et al. Limitations in everyday life were assessed and the history of falls was documented. A fracture was defined as a vertebral height reduction of more than 20% or at least 4 mm. The assessment was carried out using the Spine Deformity Index (SDI) and was confirmed by an experienced radiologist. Pearson coefficients of correlation were calculated. - After correction for age, significant associations were found for body sway and 25-hydroxyvitamin D (p<0.001), body sway and falls (p<0.001), body sway and rib fractures (p<0.01), trunk muscle strength and limitations in everyday life (p<0.001), trunk muscle strength and SDI (p<0.001), trunk muscle strength and bone density (p<0.001), and bone density and 25-hydroxyvitamin D (p<0.001). No significant correlation was found for trunk muscle strength and 25-hydroxyvitamin D (p=0.712). - Findings suggest that hypovitaminosis D is associated with increased body sway and an elevated risk for falls and falls-related fractures. Musculoskeletal rehabilitation should include strengthening exercises for the trunk muscles and training of neuromuscular co-ordination and balance.

Accidental Falls↗

PubMed2000

Evaluation of waist circumference, waist-to-hip ratio, and the conicity index as screening tools for high trunk fat mass, as measured by dual-energy X-ray absorptiometry, in children aged 3-19 y.

BACKGROUND: A central fat pattern has adverse health implications in both children and adults. Because adiposity tracks from childhood into adulthood, the ability of simple anthropometric techniques to correctly measure truncal adiposity in childhood needs to be assessed. OBJECTIVES: We sought to assess the validity of waist circumference, waist-to-hip ratio (WHR), and the conicity index as indicators of trunk fat mass in children and adolescents. DESIGN: Trunk fat mass (kg) was measured with dual-energy X-ray absorptiometry in 278 girls and 302 boys aged 3-19 y. Receiver operating characteristic (ROC) curves and areas under the curves (AUCs) for the ROCs were calculated to compare the relative abilities of the anthropometric measures to correctly identify children with high trunk fat mass (z score for our study population of > or =1). RESULTS: The 80th percentile for waist circumference correctly identified 89% of girls and 87% of boys with high trunk fat mass (sensitivity) and 94% of girls and 92% of boys with low trunk fat mass (specificity). Waist circumference performed significantly better as an index of trunk fat mass than did WHR or the conicity index, as shown by the AUCs in girls and boys, respectively: waist circumference AUCs = 0.97 and 0.97, conicity index AUCs = 0.80 and 0.81, and WHR AUCs = 0.73 and 0.71. Our cutoffs for high trunk fat mass and high waist circumference are provided for both sexes for each year of age. CONCLUSION: Waist circumference provides a simple yet effective measure of truncal adiposity in children and adolescents.

Abdomen↗

PubMed2003

Impairments of trunk movements following left or right hemisphere lesions: dissociation between apraxic errors and postural instability.

Stroke patients present with apraxic or postural deficits involving trunk movements. Praxis and posture control have been associated with the functions of the left and the right hemisphere, respectively. For the first time, in this study the occurrence of apraxic and postural components in trunk movement deficits following right and left hemisphere lesions were investigated in the same participants. Twenty-three patients with left (L/pt), 12 with right (R/pt) hemisphere lesion, and 30 healthy controls were evaluated with a 21-item test assessing the imitation of meaningless, symbolic and reaching movements presented twice on visual or proprioceptive modality. Erroneous, motor responses of the trunk were classified as postural (compensations to overcome stability or asymmetry deficits) or apraxic (execution errors not due to biomechanical constraints). Postural instability reactions were significantly more frequent among the R/pts, whilst apraxic responses were overwhelming within the L/pts. The findings are consistent with the view that the left hemisphere is dominant for praxis and suggest that this dominance be extended to trunk praxis. The results also support the hypothesis that trunk postures are coded in relation to the environment by a representational system. A widespread network, mainly sitting in the right hemisphere, subserves this postural system. The distinction between praxic and postural deficits in executing trunk movements should be kept in mind when evaluating trunk movement difficulties shown by stroke patients, in following up their recovery or when tailoring rehabilitation programmes.

Adult↗

PubMed2005

Trunk muscle composition as a predictor of reduced functional capacity in the health, aging and body composition study: the moderating role of back pain.

BACKGROUND: Cross-sectionally, lower trunk muscle attenuation (higher fat infiltration) has been associated with poorer physical function in older adults. We hypothesize that lower trunk muscle attenuation will be associated with lower functional capacity 3 years later and that back pain status will moderate this relationship. METHODS: The study sample consisted of a biracial cohort of well functioning men (739) and women (788) aged 70-79 years from the Pittsburgh site of the Health, Aging and Body Composition (Health ABC) study. Computed tomography was used to measure trunk muscle area and attenuation of the lumbar paraspinal, lateral abdominal, and rectus abdominus muscles at baseline. The Health ABC Physical Performance Battery (usual and narrow walk, chair stands, and standing balance) was used to measure functional capacity at the first and fourth annual clinic visits. RESULTS: Regardless of back pain status, average trunk muscle attenuation (but not muscle area) was positively associated with overall physical performance, particularly balance (p <.01), in a fully adjusted model. The association between trunk attenuation and functional capacity was significantly stronger in participants with at least moderate back pain in the year prior to baseline (p <.05 for interaction; attenuation x back pain). Participants with moderate to extreme back pain had a greater decline in function over time (p <.05). CONCLUSIONS: Older adults with poorer trunk muscle composition (higher fat infiltration) exhibit reduced functional capacity, especially balance, 3 years later. Improving trunk muscle composition may be an important yet overlooked approach to maintain function and potentially reduce balance impairments, particularly in persons with a history of back pain.

Aged↗

PubMed1987

Head and trunk movement responses in healthy children to induced versus self-induced lateral tilt.

The purpose of our study was to determine head and trunk movement responses that occur in healthy 7-year-old children during induced and self-induced lateral tilt. Twenty subjects, while tailor sitting on a tiltboard, participated in three trials of both induced and self-induced left and right lateral displacements. Measurements of neck and trunk lateral flexion; trunk counterrotation; and neck, trunk, and body anterior-posterior movement were obtained from slide transparencies made at three stages of tilt (original position, initial tilt, and full tilt). For each subject in the two test conditions, changes in these measurements between the stages of tilt were determined and compared. Based on the results of multivariate analysis of variance procedures, we concluded that 1) a significant difference in trunk counterrotation existed between the two types of tilt, with the greatest degree of counterrotation occurring with induced displacement; 2) no significant difference existed in neck or trunk lateral flexion; and 3) no significant differences existed in neck, trunk, or body anterior-posterior movement between tilts. We also found that a wide variability of response existed among the children over the three testing trials. Clinical application of our results suggests that different and unique motor programs exist for automatic and willed balance responses. These differences should be considered when planning treatment strategies.

Biometry↗

PubMed1990

Relationship between trunk muscle torque and bone mineral content of the lumbar spine and hip in healthy postmenopausal women.

The purpose of the study was to determine the relationship between trunk muscle strength and bone mineral density (BMD). Fifty-six postmenopausal women, aged 38 to 73 years, were examined. The BMD of lumbar vertebrae L2-4, the femoral neck, the Ward's triangle, and the greater trochanter was measured with dual-photon absorptiometry. Isometric and isokinetic torque and work measurements obtained on a trunk testing unit were used to assess trunk flexor and extensor strength. Correlation analysis demonstrated a statistically significant relationship between most trunk torque and work measurements and BMD. The trunk extensors generally provided higher correlations with BMD than did the trunk flexors, and the isokinetic extension torque values demonstrated higher correlations than the isometric extension values in every case. Linear backward-regression models, based on the subjects' weight and trunk flexor and extensor torque and work measurements, demonstrated multiple-correlation coefficients of .67, .58, .43, and .65 in predicting the BMD of the L2-4 region, femoral neck, Ward's triangle, and greater trochanter region, respectively. Estrogen therapy status did not affect the linear regression models. These data suggest a positive relationship in postmenopausal women between flexor and extensor torque values and BMD at the lower lumbar spine and proximal femur.

Adult↗

PubMed1988

1988 Volvo award in biomechanics. The triaxial coupling of torque generation of trunk muscles during isometric exertions and the effect of fatiguing isoinertial movements on the motor output and movement patterns.

Previous studies have shown that reduction of precise motor control accompanies local muscular fatigue. The effects of isodynamic fatiguing of flexion and extension trunk movements on the movement patterns and the motor output of the trunk were investigated. Twenty male subjects with no history of low-back pain for the past 6 months volunteered for the study. A triaxial dynamometer was used that simultaneously provided measurement of torque, angular position and velocity of each axis. Resistances were set independently for each axis by an interfaced computer. The subjects performed trunk flexion and extension movement against a sagittal plane resistance equal to 70% of their maximum isometric extension strength in the upright position. The minimum resistances in the coronal and transverse planes were set up at 7 Newton meters. The subjects were asked to perform trunk movement as quickly and as accurately as possible while exerting the maximum efforts until exhaustion. Analysis of variance, the MANOVA procedure with a repeated measure design, was performed among the selected parameters of the first, middle and last three repetition cycles. The selected parameters are the trunk motor output and movement patterns; the total angular excursion, range of motion, maximum and average torque and angular velocity of the trunk. All the selected parameters were significantly reduced in the sagittal plane. Subjects displayed significantly less motor control and greater range of motion in the coronal and transverse planes in performing the primary task of flexion and extension. The reduction in the functional capacity of the primary muscles performing the required task is compensated by secondary muscle groups and the spinal structure is loaded in a more injury prone pattern, as identified by finite element models. In addition it is suggested that the fatigued muscles would be less able to compensate any perturbation in the load or position of the trunk. The repetitive loading results in a weakening of the viscoelastic passive elements of the spineless structure. The loss of ability to protect these weakened passive elements makes the spine susceptible to industrial and recreational injuries.

Adult↗

PubMed1995

Cardiovascular stress in isokinetic trunk strength test.

STUDY DESIGN: In this experimental study, the participants served as their own controls. OBJECTIVE: To estimate cardiovascular stress in isokinetic trunk extension-flexion strength test. SUMMARY OF BACKGROUND DATA: Thirty-one women with low back or neck pain who participated in the physical reconditioning program were the study participants. METHODS: Trunk extension and flexion strength was measured at three angular velocities with heart rate recording and standard graded submaximal bicycle ergometer test. Power output at the maximal age-predicted heart rate level was estimated separately by trunk extension-flexion and bicycle ergometer tests. RESULTS: Torque decreased and heart rate and power increased with angular velocity (P < 0.0001). Power and heart rate values at the highest angular velocity of 120 degrees s-1 in isokinetic trunk strength testing were comparable to those measured during bicycle ergometer test at the submaximal level. In trunk strength testing 13 subjects exceeded the power and 23 subjects exceeded the heart rate they achieved in the bicycle ergometer test. Power output at the maximal age-predicted heart rate level estimated by isokinetic trunk strength test and bicycle ergometer test had a clear correlation 0.76 (confidence interval 95% 0.55-0.88). CONCLUSIONS: The cardiovascular capacity is an important factor-limiting performance in isokinetic trunk strength testing, particularly at high velocities. Patients with suspected heart problems need special attention. Heart rate recording may help estimate degree of effort.

Adult↗

PubMed1998

Trunk muscle co-contraction increases during fatiguing, isometric, lateral bend exertions. Possible implications for spine stability.

STUDY DESIGN: Surface electromyographic activities were recorded from bilateral trunk muscles as test participants maintained a 50% maximum, voluntary, isometric, lateral bend contraction to volitional exhaustion. OBJECTIVES: To challenge the trunk with a prolonged lateral bend task and observe the responses of the agonist and antagonist muscles to the resulting fatigue. SUMMARY OF BACKGROUND DATA: Lateral bend exertions of the trunk have been identified as a risk factor for injury to spine tissues. However, little is known about the response of spine muscles to fatigue and the subsequent implications for spine stability, joint loading, and tissue injury. Surface electromyography provides a window on muscle loading and progressive fatigue. METHODS: Eleven male participants performed a set of maximum lateral bend exertions at the start of the trial, then maintained an upright standing posture while resisting 50% of the maximum moment until volitional exhaustion, then performed another set of maximum contractions. All contractions were isometric. Measurements were made, throughout each contraction, of the lateral bend moment and abdominal and trunk extensor electromyographic activities at six bilateral surface electromyography sites. Electromyographic amplitude and mean power frequency were calculated with 500-millisecond segments recorded serially every 800 milliseconds. Mean values were calculated with data from the first and last 5% of the trial durations. Statistics determined if fatigue had a significant effect on maximum moment and the electromyographic statistics for each muscle site. RESULTS: Fatigue resulted in a significant decrease in maximum lateral bend moment and increase in moment variability. Decreases in mean power frequency, indicating fatigue, were observed in three agonists (the trunk extensors) and one antagonist muscle. Unfatigued agonist electromyographic amplitudes correlated well with the mechanical advantage of muscles to generate lateral bend moments. Unfatigued antagonist activities were low except for the thoracic erector spinae. The agonists and antagonists demonstrated average increases of 17% and 8%, respectively, when pooled across muscles. Much of this change was predicted to have been associated with increases in co-contracting muscle forces. CONCLUSIONS: The trunk responded to a prolonged, lateral bend contraction by increasing co-contraction as agonist trunk muscles fatigued. It was proposed that the fatigue compromised neural coordination and that the co-contraction served to maintain spine stability.

Adult↗