Trunk Muscle Balance and Muscular Force

Jg, Reid; Costigan, PA

doi:10.1097/00007632-198710000-00013

Cited by 55 publications

(16 citation statements)

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“…This is consistent with the findings of Reid and Costigan (1987) who found the females exhibited smaller sagittal moment-arm to trunk depth ratios than males, with the trunk depth measured at the L 5 level. Thus, these gender differences in muscle vector location indicates that the loading directions may be different depending on the direction of the exertion (e.g., flexion for the rectus abdominis or twisting or extension for the internal obliques), or as increases in coactivity occur, which would influence the loading on the spine .…”

Section: Muscle Vector Locationssupporting

confidence: 92%

A Spine Loading Model of Women in the Military

Marras¹

1998

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Public reporting burdeni for hio. C ollecton a Inf~ormation is eamated to a.venae .1. ho ur pe.r , ro iie ncluding the tIme for reviewn ie.ctoa esa•• _mfon e .aan dat .'ce.. galtherin and. maintainig, the dta need ,an completing a~nd reviewg th cOllectio of inforlmation. Seni -comment. reoalrdiIg Na burde ab~znllmatel omr anyl other~ofte~l collection of information including mugeationa for reducing thiseburden. ABSTRACT (Maximum 200The risk of low-back disorders (LBD) may be particularly great for women in the military, influencing training effectiveness, costs, and military readiness. The goal of this research is to quantify musculoskeletal loads on the spine of women performing military manual materials handling (MMH) tasks. This will permit assessment of LBD risk factors for military women, and the potential to evaluate tasks and training methods for female military personnel.Our efforts are progressing in general accordance with the proposal and tinmeline. Magnetic Resonance Images (MRI) have been employed to measure the muscle cross-sectional areas, moment-arms in the coronal and sagittal plane, and muscle vector angles in both healthy females and males. Muscle force-velocity and length-strength relationships have been determined with biomechanical model performance determined, with a few more subjected needed to be collected to solidify the promising results. Validation of the biomechanical model using the relationships determined from muscle geometry and force-velocity and length-strength relationships, as well as comparison of spinal loading between males and females performing the same MMH tasks is almost complete. Validation efforts indicate that the female-specific biomechanical model performs very well in predicting spinal loading on the female spine.After the third year of this research effort, we are progressing well and are confident that an accurate biomechanical model can be developed for the evaluation of spinal loading of women performing military MMH tasks. (Jones et al., 1988), it is apparent that the risk of work related low back disorders (LBD) may be particularly great for women in the military. Heavy manual materials handling (MMH) that would challenge the injury tolerance of most industrial workers' spines has been shown to be the most physically demanding task in 90% of all military job specialties (Sharp and Vogel, 1992). As these military occupational specialties (MOSs) are becoming increasingly available to women, the risk of LBD to women will have greater consequences as they fill these roles, particularly when considering a downsizing military. Thus, there is a need to reliably assess the risk of military task related LBD to women, and to identify potential features or training that might mitigate that risk. SUBJECT TERMSThe goal of this research is to extend the capability of predicting musculoskeletal loads on the trunk and spine to women performing realistic MMH tasks. Current models of musculoskeletal loading on the spine are based upon male biomechanics, and must be enhance...

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Section: Muscle Vector Locationssupporting

confidence: 92%

A Spine Loading Model of Women in the Military

Marras¹

1998

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“…From the resulting images, we manually measured both the right and left sides of the moment arm length and cross-sectional area of the muscles of the erector spinae and rectus abdominis based on the method of Reid et al 5) . The moment arm length was defined as the anterior-posterior distance between the center of the muscle and that of the vertebral body.…”

Section: Methodsmentioning

confidence: 99%

“…Many studies have tried to obtain precise values for these parameters [2][3][4][5][6][7][8][9][10][11][12] . Some of them analyzed the relationships between these parameters and physical data such as height and weight 4,7,9,12) .…”

mentioning

confidence: 99%

Estimation of Trunk Muscle Parameters for a Biomechanical Model by Age, Height and Weight

Seo

Lee

Kusaka

2003

Journal of Occupational Health

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Estimation of Trunk Muscle Parameters for a Biomechanical Model by Age, Height and Weight: Akihiko Seo, et al. Department of Intelligent Systems, Graduate School of Engineering, Tokyo Metropolitan Institute of Technology—To establish more accurate equations for estimating the moment arm length and cross‐sectional area of the erector spinae and rectus abdominis muscles, the effects of height, weight and age on those muscles were analyzed by using a high‐order polynomial equation. Data on the moment arm length and cross‐sectional area at L3/ 4 were obtained from MRI images of 152 males and 98 females. The statistical model used in this study has any combination of up to third‐order independent variables for age, height and weight. The effective independent variables were selected by the forward step method of multiple regression analyses. The results of multiple regression analyses showed that the polynomial equations for the moment arm length of erector spinae in both genders, and that for the rectus abdominis in males, contained all three variables of age, height and weight. That for the moment arm length of female rectus abdominis contained the variables of weight and age. The multiple correlation coefficients of the erector spinae and rectus abdominis were 0.355 and 0.650 for males, 0.364 and 0.411 for females, respectively. The equations for the cross‐sectional area of the erector spinae in both genders, as well as that for male rectus abdominis contained only one variable (weight). The multiple correlation coefficients of the cross‐sectional area of the erector spinae were 0.576 for males and 0.469 for females. The cross‐sectional area of the female rectus abdominis had no effective variables.

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“…Strength is less in asymmetric postures [37] and eccentric (lengthening) and isometric contractions produce higher levels of strength than concentric (shortening) contractions [60,70]. Patients who develop acute LBP will produce a lower force than they were capable of before the pain developed.…”

Section: Introductionmentioning

confidence: 99%

Is there a rational basis for post-surgical lifting restrictions? 1. Current understanding

et al. 1999

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IntroductionAfter surgery it is a common practice to prescribe lifting restrictions. These seem to be based on a premise that the spine is weaker and thus subject to re-injury when there has been some disruption of the functional spinal motion unit (FSU) due to surgery. Re-injury is not, however, often reported in the literature. More often a failure of fusion is reported [3, 6, 12, 23, 27,72,79].Recurrent low back pain (LBP) or other impairments may exist after back surgery in up to 50% of operated patients [61]. Robert et al. [71] studied the outcome after operation for lumbar herniated nucleus pulposus (HNP). The median duration of postoperative work incapacity was 3.5 months. Seventy-eight percent of the patients resumed full-time work in their previous job, and 75% were pain free. Predictive factors for a good outcome were a preoperative work incapacity of less than 4 weeks and, for men, no daily lifting of heavy weights.Although most surgeons employ some kind of postoperative lifting restrictions, there is not much scientific literature upon which to base those limitations. If the empirical basis for limitations were correct, one would expect a consensus on the limitations (i.e., there would be a tendency for physicians to agree on the correct restrictions).Lifting restrictions are not a trivial issue. A restriction may prevent return to work if the employer is unable, or Abstract Lifting restrictions postoperatively are quite common, but there appears to be little scientific basis for them. Lifting restrictions are inhibitory in terms of return to work and may be a factor in chronicity. The mean functional spinal motion unit stiffness changes with in vitro or computer-simulated discectomies, facetectomies and laminectomies were reviewed from the literature. We modified the NIOSH lifting equation to include another multiplier related to stiffness change post surgery. The new recommended lifts were computed for different lifting conditions seen in industry. The reduction of rotational stiffness ranged from 21% to 41% for a discectomy, 1% to 59% for a facetectomy and 4% to 16% for a partial laminectomy. The recommended lifts based on our modified equation were adjusted accordingly. There is no rational basis for current lifting restrictions. The risk to the spine is a function of many other variables as well as weight (i.e., distance of weight from body). The adjusted NIOSH guidelines provide a reasonable way to estimate weight restrictions and accommodations such as lifting aids. Such restrictions should be as liberal as possible so as to facilitate, not prevent, return to work. Patients need more advice regarding lifting activities and clinicians should be more knowledgeable about the working conditions and constraints of a given workplace to effectively match the solution to the patient's condition.Key words Lifting · Surgery · Return to work · Low back pain · NIOSH ORIGINAL ARTICLE Eur Spine J (1999) 8 : 170-178

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Trunk Muscle Balance and Muscular Force

Cited by 55 publications

References 0 publications

A Spine Loading Model of Women in the Military

A Spine Loading Model of Women in the Military

Estimation of Trunk Muscle Parameters for a Biomechanical Model by Age, Height and Weight

Is there a rational basis for post-surgical lifting restrictions? 1. Current understanding

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