Erector Spinae Lever Arm Length Variations with Changes in Spinal Curvature

Tveit, Per; Daggfeldt, Karl; Hetland, Stein; Thorstensson, Alf

doi:10.1097/00007632-199401001-00015

Cited by 102 publications

(41 citation statements)

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“…While local muscles were modeled as straight lines between their respective insertion points, realistic muscle paths were considered for global extensor muscles by wrapping them over all T12-S1 vertebrae whenever in the course of lifts their distance to associated vertebral bodies reduced more than 10% of their initial distances. This allowed for a maximum of~10% reduction in muscle lever arms at different levels during flexion which was chosen in accordance with published data in the literature [50,62,99]. The wrapping of global muscles occurred at all levels under larger flexion angles and resulted in curved paths with realistic lever arms at different levels.…”

Section: Methodological Issuesmentioning

confidence: 94%

“…Moderate flexion has been recommended by model [6,91,92] as well as experimental studies [2] to reduce risk of failure under high compressive forces. As the lumbar posture alters from a lordotic one to a kyphotic one, the effectiveness of erector spinae muscles in supporting the net moment (due to smaller lever arms [50,62,99] and the anterior shear force (due to changes in line of action [68]) decreases while the passive contribution of both extensor muscles and the ligamentous spine increases [6,8,62].…”

Section: Introductionmentioning

confidence: 99%

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Analysis of squat and stoop dynamic liftings: muscle forces and internal spinal loads

2006

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Despite the well-recognized role of lifting in back injuries, the relative biomechanical merits of squat versus stoop lifting remain controversial. In vivo kinematics measurements and model studies are combined to estimate trunk muscle forces and internal spinal loads under dynamic squat and stoop lifts with and without load in hands. Measurements were performed on healthy subjects to collect segmental rotations during lifts needed as input data in subsequent model studies. The model accounted for nonlinear properties of the ligamentous spine, wrapping of thoracic extensor muscles to take curved paths in flexion and trunk dynamic characteristics (inertia and damping) while subject to measured kinematics and gravity/ external loads. A dynamic kinematics-driven approach was employed accounting for the spinal synergy by simultaneous consideration of passive structures and muscle forces under given posture and loads. Results satisfied kinematics and dynamic equilibrium conditions at all levels and directions. Net moments, muscle forces at different levels, passive (muscle or ligamentous) forces and internal compression/shear forces were larger in stoop lifts than in squat ones. These were due to significantly larger thorax, lumbar and pelvis rotations in stoop lifts. For the relatively slow lifting tasks performed in this study with the lowering and lifting phases each lasting~2 s, the effect of inertia and damping was not, in general, important. Moreover, posterior shift in the position of the external load in stoop lift reaching the same lever arm with respect to the S1 as that in squat lift did not influence the conclusion of this study on the merits of squat lifts over stoop ones. Results, for the tasks considered, advocate squat lifting over stoop lifting as the technique of choice in reducing net moments, muscle forces and internal spinal loads (i.e., moment, compression and shear force).

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Section: Methodological Issuesmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Analysis of squat and stoop dynamic liftings: muscle forces and internal spinal loads

2006

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“…In an effort to compensate for this fixed sagittal imbalance, the patient flexes the knees and attempts to hyperextend the cervical spine and any remaining mobile vertebral segments in the thoracic and lumbar spine. Biomechanical studies have demonstrated that increased paraspinal muscular forces are required to maintain an erect posture when there is loss of normal lumbar or cervical lordosis, which may contribute to the fatigue-related etiology of the symptoms 37,38 . Furthermore, attempts to compensate and maintain a horizontal gaze may result in increased strain, pain, and degenerative changes within the cervical spine or unfused lower lumbar discs, which may require operative treatment.…”

Section: Clinical Presentationmentioning

confidence: 99%

Prevention and Management of Iatrogenic Flatback Deformity

Potter

Lenke

Kuklo³

2004

The Journal of Bone and Joint Surgery-American Volume

147

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“…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) .…”

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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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Erector Spinae Lever Arm Length Variations with Changes in Spinal Curvature

Cited by 102 publications

References 0 publications

Analysis of squat and stoop dynamic liftings: muscle forces and internal spinal loads

Analysis of squat and stoop dynamic liftings: muscle forces and internal spinal loads

Prevention and Management of Iatrogenic Flatback Deformity

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

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