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Correlation between electromyographic spectral changes and subjective assessment of lumbar muscle fatigue in subjects without pain from the lower back
Journal of Manipulativeand Physiological Therapeutics Volume 23 • Number 5 • June 2000
373
Journal Abstracts
hand as an important diagnostic and prognostic symptom for the assessment and treatment of carpal tunnel syndrome.
during walking. The magnitude of joint motions, muscular activation, and joint loading provide further insight into the tissue demands during gait and demonstrate that slow walking produced more 'static' lumbar spine loading and motion patterns activity that may present difficulty for some low Callaghan JP, Patla AE, McGill SM. Low back three-dimensional back injured. While, faster walking appears to be a cyclic joint forces, kinematics, and kinetics during walking. Clin Biomech activity that is only mildly demanding in terms of tissue 1999;14:203-16. loading, rendering it a low risk of injury for most individuABSTRACT: als. Reprinted from Clinical Biomechanics, Volume 14, Objective: The purpose of this study was to examine the Callaghan JP, Patla AE, McGill SM, Low back threethree-dimension low back loads, spinal motions, and trunk dimensional joint forces, kinematics, and kinetics during muscular activity during gait. Specific objectives involved walking, 203-16, 1999, with permisson from Elsevier assessment of the effects of walking speed, and arm swing on Science Ltd. spinal loads, lumbar spine motion, and muscular activation. Design: An in vivo modeling experiment using five male participants. Thirty walking trials were performed by each CuppT, Oeffinger D, Tylkowski C,Augsburger S. Age-related participant yielding five repeats of each condition (3 walk- kinetic changes in normal pediatrics. J Pediatr Orthop 1999;19:475-8. ing cadences x 2 arm swing conditions). Background: Walking is often prescribed as a rehabilitation ABSTRACT: Summary: Kinetic data have become an important adjunct task for individuals with low back injuries. However, there are to kinematic and electromyography data in the interpretation few studies which have examined the joint loading, spinal moof gait data and in the clinical decision making for children tions, and muscular activity present when walking. Additionwith pathologic gait patterns. A normative database is essenally, the majority of studies examining spine loading during tial for comparison with the patterns of walking in children gait have used an inverse dynamics model, commencing at the with gait abnormalities. Gait analyses of 23 able-bodied cranial aspect of the body, approach which does not include children (ages 4-10 yea~s) were compared with those of five the impulsive phases of gait (i.e. heel strikes and toe offs). able-bodied adults. The patterns and amplitudes of the norMethods: Low back joint forces (bone on bone) and mal able-bodied children's kinetics showed five significant moments were determined using an anatomically complex differences from those of the adults: a) diminished hipthree-dimensional model (detailing 54 muscles and the pasabduction moment, b) diminished plantar-flexion moment, sive structures acting at the low back) during three walking c) diminished A2 power generation, d) diminished kneecadences and with free arm swing or restricted arm swing. extensor moment, and 3) pattern of knee-power data. The In order to assess the influence of the transient factors such data indicated a progression toward the adult normals as heel contact on the joint forces a bottom up (from the feet to the lumbar spine) rigid link segment analyses approach because differences were more significant in the youngest group (4- to 5-year-olds) than in the older groups (6- to 7was used as one input to the three-dimensional anatomic model. Lumbar spine motion and trunk muscle activation and 8- to 10-year-olds). levels were also recorded to assist in partitioning forces amongst the active and passive tissues of the low back. Results: Net joint anterior-posterior shear loading was the Dedering A, N6meth G, Harms-Ringdahl K. Correlationbetween electromyographic spectral changes and subjective assessment of lumbar only variable significantly affected by walking cadence (fast muscle fatigue in subjects without pain from the lower back. Clin Biomeeh versus slow P <0.0003). No variable was significantly 1999;14:103-11. affected by the arm swing condition. Trends demonstrated an increase in all variables with increased walking cadence. ABSTRACT: Objective: The purpose of this study was to correlate Similarly, most variables, with the exception of axial twist and lateral bend lumbar spine motion and lateral joint shear, objective measurements of muscle fatigue in the lower back demonstrated increasing trends caused by the restriction of to the subject's own assessment of fatigue. Design: Muscle fatigue in the lower back was assessed in normal arm swing. Conclusions: Tissue loading during walking appears to be healthy subjects using electromyography (EMG), endurance below levels caused by many specific rehabilitation tasks, time and the Borg scale. Background: Muscle fatigue, measured with EMG and suggesting that walking is a wise choice for general back endurance time, in the lower back, is significant for patients exercise and rehabilitation programs. Slow walking with restricted arm swing produced more 'static' lumbar spine with pain in the lower back. Methods: Fifty healthy subjects partieipated.~ EMG was loading and motion patterns, which could be detrimental f o r detected from the lumbar extensor muscles during,a modicertain injuries and tissues. Fast walking produced a more fied Serensen's test, an isometric contraction for the back cyclic loading pattern. extensors until exhaustion. During the test, subjects rated Relevance: This work provides a detailed analysis of low their subjective fatigue on a Borg CR-10 scale, back joint loading, lumbar motion, and muscular activation
374
Journal of Manipulative and Physiological Therapeutics Volume 23 ° Number 5 • June 2000
Journal Abstracts
Results: Borg scale ratings correlated with endurance time (0.68) and EMG median- and mean power frequency slopes (0.41-0.50). At a Borg rating of 3, median- and mean power frequency and endurance time were reduced by 30%. At a Borg rating of 5, median- and mean power frequency and endurance time were reduced by 50%. At a Borg rating of 7, median- and mean power frequency and endurance time were reduced by 60-70%. Conclusions: Significant correlation between the Borg scale, EMG and endurance time suggests a close relationship between subjective and objective assessment of muscle fatigue. Relevance: The close relationship between EMG, endurance time and the Borg scale, is proposed to be useful in clinical testing. A sub-maximal time performance until a Borg rating of 5 (strong fatigue) is reached could be preferred to limit the factor of motivation in a testing situation. Reprinted from Clinical Biomechanics, Volume 14, Dedering/~, N6meth G, Harms-Ringdahl K, Correlation between electromyographic spectral changes and subjective assessment of lumbar muscle fatigue in subjects without pain from the lower back, 103-11, 1999, with permisson from Elsevier Science Ltd.
de Looze MP, Groen H, Horemans H, Kingma I, van Die~n JH. Abdominal musclescontribute in a minorway to peak spinal compression in lifting. J Biomech 1999;32:655-62.
ABSTRACT: In lifting, the abdominal muscles are thought to be activated to stabilize the spine. As a detrimental effect, they contribute to spinal compression. The existing literature is not conclusive about the biological relevance of this effect. From biological, mechanical and anatomical considerations it was hypothesized that the relative abdominal contribution to compression would be minor in the beginning of the lift, that the relative and absolute abdominal contribution to compression would rise throughout the lift, and that the obliques would contribute to a larger extent than the rectus abdominis. To investigate these hypotheses, 10 subjects lifted 0.5, 10.5 and 22.5 kg. EMG levels obtained from the rectus abdominis and the obliques were converted into force using normalized EMG, muscle potential and area values, and modulating factors for muscle length and contraction velocity. An anatomical model was applied to compute the abdominal effects on spinal compression in three consecutive phases within a lift. If expressed relative to the total spinal compression, the abdominai contribution for the three weight conditions was 7.1% (SD, 1.7), 10.4% (4.7) and 12.5% (4.4) in the beginning and 21,0% (5.8), 19.0% (5.3) and 22.2% (6.6) in the end phase. Thus, the relative abdominal contribution to compression was minor in the beginning and increased towards the end. The absolute abdominal contribution was constant throughout the lift. The contributions could be retraced to the obliques rather than the rectus, while during the lift a shift in activation from the obfiquus externus to internus was observed. Reprinted from the Journal of Biomechanics, Volume
32, de Looze ME Groen H, Horemans H, Kingma I, van DieEn JH, Abdominal muscles contribute in a minor way to peak spinal compression in lifting, 655-62, 1999, with permisson from Elsevier Science Ltd.
EngstromT, Hanse JJ, Kadefors R. Musculoskeletalsymptomsdue to technical preconditions in longcycle time work in an automobileassembly plant: a study of prevalenceand relation to psychologicalfactors and physical exposure.Appl Ergon 1999;30:443-53. ABSTRACT: The aim was to evaluate the prevailing ergonomic conditions in a parallelized flow, long cycle time, assembly system. The evaluation focused on physical exposure, psychosocial factors and work-related musculoskeletal symptoms. A random sample of 67 assembly operators was included in a cross-sectional study mainly based on questionnaires. Hand/ wrist symptoms were common and related to work exposure with hand-held powered tools. In general, the self-reported physical exposure showed only a few significant associations with musculoskeletal symptoms. This may in part be explained by the ergonomic conditions generally being good, with a relatively low duration of 'combined' extreme work postures. Significant associations were found between the psychosocial work environment and musculoskeletal symptoms. Reprinted from Applied Ergonomics, Volume 30, Engstrom T, Hanse J J, Kadefors R, Musculoskeletal symptoms due to technical preconditions in long cycle time work in an automobile assembly plant: a study of prevalence and relation to psychological factors and physical exposure, 44353, 1999, with permission from Elsevier Science Ltd.
Gu M, Leung Lai T. Determinationof power and sample size in the design of clinical trials with failure-timeendpoints and interim analyses. Control Clin Trials 1999;20:423-38.
ABSTRACT: An important but difficult task in the design of a clinical trial to compare time to failure between two treatment groups is determination of the number of patients required to achieve a specified power of the test. Because patients typically enter the trial serially and are followed until they fail or withdraw from the study or until the study is terminated, the power of the test depends on the accrual pattern, the noncompliance rate, and the withdrawal rate in addition to the actual survival distributions of the two groups. Incorporating interim analyses and the possibility of early stopping into the trial increases its complexity, and although normal approximations have been developed for computing the significance level of the test when the log-rank or other rank statistics are used, there are no reliable analytic approximations for evaluating the power of the test. This article presents methods, based on Monte Carlo simulations and recent advances in group sequential testing with time-to-event responses, to choose appropriate test statistics, compute power and sample size at specified alternatives, cheek the adequacy of commonly used"
373
Journal Abstracts
hand as an important diagnostic and prognostic symptom for the assessment and treatment of carpal tunnel syndrome.
during walking. The magnitude of joint motions, muscular activation, and joint loading provide further insight into the tissue demands during gait and demonstrate that slow walking produced more 'static' lumbar spine loading and motion patterns activity that may present difficulty for some low Callaghan JP, Patla AE, McGill SM. Low back three-dimensional back injured. While, faster walking appears to be a cyclic joint forces, kinematics, and kinetics during walking. Clin Biomech activity that is only mildly demanding in terms of tissue 1999;14:203-16. loading, rendering it a low risk of injury for most individuABSTRACT: als. Reprinted from Clinical Biomechanics, Volume 14, Objective: The purpose of this study was to examine the Callaghan JP, Patla AE, McGill SM, Low back threethree-dimension low back loads, spinal motions, and trunk dimensional joint forces, kinematics, and kinetics during muscular activity during gait. Specific objectives involved walking, 203-16, 1999, with permisson from Elsevier assessment of the effects of walking speed, and arm swing on Science Ltd. spinal loads, lumbar spine motion, and muscular activation. Design: An in vivo modeling experiment using five male participants. Thirty walking trials were performed by each CuppT, Oeffinger D, Tylkowski C,Augsburger S. Age-related participant yielding five repeats of each condition (3 walk- kinetic changes in normal pediatrics. J Pediatr Orthop 1999;19:475-8. ing cadences x 2 arm swing conditions). Background: Walking is often prescribed as a rehabilitation ABSTRACT: Summary: Kinetic data have become an important adjunct task for individuals with low back injuries. However, there are to kinematic and electromyography data in the interpretation few studies which have examined the joint loading, spinal moof gait data and in the clinical decision making for children tions, and muscular activity present when walking. Additionwith pathologic gait patterns. A normative database is essenally, the majority of studies examining spine loading during tial for comparison with the patterns of walking in children gait have used an inverse dynamics model, commencing at the with gait abnormalities. Gait analyses of 23 able-bodied cranial aspect of the body, approach which does not include children (ages 4-10 yea~s) were compared with those of five the impulsive phases of gait (i.e. heel strikes and toe offs). able-bodied adults. The patterns and amplitudes of the norMethods: Low back joint forces (bone on bone) and mal able-bodied children's kinetics showed five significant moments were determined using an anatomically complex differences from those of the adults: a) diminished hipthree-dimensional model (detailing 54 muscles and the pasabduction moment, b) diminished plantar-flexion moment, sive structures acting at the low back) during three walking c) diminished A2 power generation, d) diminished kneecadences and with free arm swing or restricted arm swing. extensor moment, and 3) pattern of knee-power data. The In order to assess the influence of the transient factors such data indicated a progression toward the adult normals as heel contact on the joint forces a bottom up (from the feet to the lumbar spine) rigid link segment analyses approach because differences were more significant in the youngest group (4- to 5-year-olds) than in the older groups (6- to 7was used as one input to the three-dimensional anatomic model. Lumbar spine motion and trunk muscle activation and 8- to 10-year-olds). levels were also recorded to assist in partitioning forces amongst the active and passive tissues of the low back. Results: Net joint anterior-posterior shear loading was the Dedering A, N6meth G, Harms-Ringdahl K. Correlationbetween electromyographic spectral changes and subjective assessment of lumbar only variable significantly affected by walking cadence (fast muscle fatigue in subjects without pain from the lower back. Clin Biomeeh versus slow P <0.0003). No variable was significantly 1999;14:103-11. affected by the arm swing condition. Trends demonstrated an increase in all variables with increased walking cadence. ABSTRACT: Objective: The purpose of this study was to correlate Similarly, most variables, with the exception of axial twist and lateral bend lumbar spine motion and lateral joint shear, objective measurements of muscle fatigue in the lower back demonstrated increasing trends caused by the restriction of to the subject's own assessment of fatigue. Design: Muscle fatigue in the lower back was assessed in normal arm swing. Conclusions: Tissue loading during walking appears to be healthy subjects using electromyography (EMG), endurance below levels caused by many specific rehabilitation tasks, time and the Borg scale. Background: Muscle fatigue, measured with EMG and suggesting that walking is a wise choice for general back endurance time, in the lower back, is significant for patients exercise and rehabilitation programs. Slow walking with restricted arm swing produced more 'static' lumbar spine with pain in the lower back. Methods: Fifty healthy subjects partieipated.~ EMG was loading and motion patterns, which could be detrimental f o r detected from the lumbar extensor muscles during,a modicertain injuries and tissues. Fast walking produced a more fied Serensen's test, an isometric contraction for the back cyclic loading pattern. extensors until exhaustion. During the test, subjects rated Relevance: This work provides a detailed analysis of low their subjective fatigue on a Borg CR-10 scale, back joint loading, lumbar motion, and muscular activation
374
Journal of Manipulative and Physiological Therapeutics Volume 23 ° Number 5 • June 2000
Journal Abstracts
Results: Borg scale ratings correlated with endurance time (0.68) and EMG median- and mean power frequency slopes (0.41-0.50). At a Borg rating of 3, median- and mean power frequency and endurance time were reduced by 30%. At a Borg rating of 5, median- and mean power frequency and endurance time were reduced by 50%. At a Borg rating of 7, median- and mean power frequency and endurance time were reduced by 60-70%. Conclusions: Significant correlation between the Borg scale, EMG and endurance time suggests a close relationship between subjective and objective assessment of muscle fatigue. Relevance: The close relationship between EMG, endurance time and the Borg scale, is proposed to be useful in clinical testing. A sub-maximal time performance until a Borg rating of 5 (strong fatigue) is reached could be preferred to limit the factor of motivation in a testing situation. Reprinted from Clinical Biomechanics, Volume 14, Dedering/~, N6meth G, Harms-Ringdahl K, Correlation between electromyographic spectral changes and subjective assessment of lumbar muscle fatigue in subjects without pain from the lower back, 103-11, 1999, with permisson from Elsevier Science Ltd.
de Looze MP, Groen H, Horemans H, Kingma I, van Die~n JH. Abdominal musclescontribute in a minorway to peak spinal compression in lifting. J Biomech 1999;32:655-62.
ABSTRACT: In lifting, the abdominal muscles are thought to be activated to stabilize the spine. As a detrimental effect, they contribute to spinal compression. The existing literature is not conclusive about the biological relevance of this effect. From biological, mechanical and anatomical considerations it was hypothesized that the relative abdominal contribution to compression would be minor in the beginning of the lift, that the relative and absolute abdominal contribution to compression would rise throughout the lift, and that the obliques would contribute to a larger extent than the rectus abdominis. To investigate these hypotheses, 10 subjects lifted 0.5, 10.5 and 22.5 kg. EMG levels obtained from the rectus abdominis and the obliques were converted into force using normalized EMG, muscle potential and area values, and modulating factors for muscle length and contraction velocity. An anatomical model was applied to compute the abdominal effects on spinal compression in three consecutive phases within a lift. If expressed relative to the total spinal compression, the abdominai contribution for the three weight conditions was 7.1% (SD, 1.7), 10.4% (4.7) and 12.5% (4.4) in the beginning and 21,0% (5.8), 19.0% (5.3) and 22.2% (6.6) in the end phase. Thus, the relative abdominal contribution to compression was minor in the beginning and increased towards the end. The absolute abdominal contribution was constant throughout the lift. The contributions could be retraced to the obliques rather than the rectus, while during the lift a shift in activation from the obfiquus externus to internus was observed. Reprinted from the Journal of Biomechanics, Volume
32, de Looze ME Groen H, Horemans H, Kingma I, van DieEn JH, Abdominal muscles contribute in a minor way to peak spinal compression in lifting, 655-62, 1999, with permisson from Elsevier Science Ltd.
EngstromT, Hanse JJ, Kadefors R. Musculoskeletalsymptomsdue to technical preconditions in longcycle time work in an automobileassembly plant: a study of prevalenceand relation to psychologicalfactors and physical exposure.Appl Ergon 1999;30:443-53. ABSTRACT: The aim was to evaluate the prevailing ergonomic conditions in a parallelized flow, long cycle time, assembly system. The evaluation focused on physical exposure, psychosocial factors and work-related musculoskeletal symptoms. A random sample of 67 assembly operators was included in a cross-sectional study mainly based on questionnaires. Hand/ wrist symptoms were common and related to work exposure with hand-held powered tools. In general, the self-reported physical exposure showed only a few significant associations with musculoskeletal symptoms. This may in part be explained by the ergonomic conditions generally being good, with a relatively low duration of 'combined' extreme work postures. Significant associations were found between the psychosocial work environment and musculoskeletal symptoms. Reprinted from Applied Ergonomics, Volume 30, Engstrom T, Hanse J J, Kadefors R, Musculoskeletal symptoms due to technical preconditions in long cycle time work in an automobile assembly plant: a study of prevalence and relation to psychological factors and physical exposure, 44353, 1999, with permission from Elsevier Science Ltd.
Gu M, Leung Lai T. Determinationof power and sample size in the design of clinical trials with failure-timeendpoints and interim analyses. Control Clin Trials 1999;20:423-38.
ABSTRACT: An important but difficult task in the design of a clinical trial to compare time to failure between two treatment groups is determination of the number of patients required to achieve a specified power of the test. Because patients typically enter the trial serially and are followed until they fail or withdraw from the study or until the study is terminated, the power of the test depends on the accrual pattern, the noncompliance rate, and the withdrawal rate in addition to the actual survival distributions of the two groups. Incorporating interim analyses and the possibility of early stopping into the trial increases its complexity, and although normal approximations have been developed for computing the significance level of the test when the log-rank or other rank statistics are used, there are no reliable analytic approximations for evaluating the power of the test. This article presents methods, based on Monte Carlo simulations and recent advances in group sequential testing with time-to-event responses, to choose appropriate test statistics, compute power and sample size at specified alternatives, cheek the adequacy of commonly used"