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  • 1.
    Daggfeldt, Karl
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Huang, Q M
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    The visible human anatomy of the lumbar erector spinae.2000In: Spine, ISSN 0362-2436, E-ISSN 1528-1159, Vol. 25, no 21, p. 2719-25Article in journal (Refereed)
    Abstract [en]

    STUDY DESIGN: Image data of the male and female cadavers from the Visible Human Project were visualized and quantified. OBJECTIVE: To clarify the anatomy of the lumbar part of the human lumbar erector spinae muscles. SUMMARY OF BACKGROUND DATA: Recent studies have shown discrepancies in the description of the anatomy of the lumbar part of the lumbar erector spinae. The main differences concern whether lumbar fascicles of iliocostalis lumborum exist and whether the lumbar fascicles have direct attachments to the ilium or attach via the erector spinae aponeurosis. With the Visible Human Project from the U.S. National Library of Medicine, a new powerful basis for anatomic investigation has become available. METHODS: Software was produced to visualize sections oriented in any direction and with maximum resolution of the Visible Human male and female. Three-dimensional coordinates of anatomic structures in the image space could be marked in the cross-sectional images. The geometry and the physiologic cross-sectional areas of the erector spinae fascicles of lumbar origin were thus derived. RESULTS AND CONCLUSIONS: The study supports a classification of the lateral fascicles of the lumbar part of the lumbar erector spinae as part of iliocostalis lumborum. In both the male and the female, a large part of the erector spinae fibers of lumbar origin attached to the erector spinae aponeurosis. These results are of importance for biomechanical analysis of force transmission in the lumbar spine.

  • 2. Huang, Q M
    et al.
    Andersson, Eva
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Intramuscular myoelectric activity and selective coactivation of trunk muscles during lateral flexion with and without load.2001In: Spine, ISSN 0362-2436, E-ISSN 1528-1159, Vol. 26, no 13, p. 1465-72Article in journal (Refereed)
    Abstract [en]

    STUDY DESIGN: Myoelectric activity of trunk muscles was measured intramuscularly in six healthy subjects as they maintained static trunk postures at 0 degrees, 15 degrees, and 30 degrees of lateral bending, unloaded or holding a 20-kg load in one hand alongside the body. OBJECTIVE: To determine the position and load dependency of the agonistic and antagonistic myoelectric responses of deep and superficial trunk lateral flexor muscles. SUMMARY OF BACKGROUND DATA: Loading of the trunk in lateral bending is associated with incidences of low back pain. The neuromotor control of muscles surrounding the spine may be decisive for its vulnerability. Earlier documentation of the activation pattern of trunk muscles, particularly those situated deeply, is incomplete. METHODS: Trunk angle was measured between S1-C7 and the vertical with a protractor. Electromyographic activity was recorded unilaterally from eight trunk muscles using intramuscular fine-wire electrodes inserted under the guidance of ultrasound. RESULTS: The electromyographic data showed that all muscles on the side contralateral to the load, except rectus abdominis, had their highest activity while loaded in the position most laterally flexed to the loaded side. The degree of bilateral coactivation was greater for the ventral than for the dorsal muscles. CONCLUSIONS: The myoelectric responses of most lumbar trunk muscles to static lateral flexion were dependent on trunk position and loading. The abdominal muscles demonstrated more coactivation than the other trunk muscles, and thus appeared to contribute more to trunk stabilization in laterally bent and loaded trunk positions.

  • 3. Oddsson, L I
    et al.
    Persson, T
    Cresswell, Andrew G
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Interaction between voluntary and postural motor commands during perturbed lifting.1999In: Spine, ISSN 0362-2436, E-ISSN 1528-1159, Vol. 24, no 6, p. 545-52Article in journal (Refereed)
    Abstract [en]

    STUDY DESIGN: An experimental study was conducted to evaluate the effect of an unexpected postural perturbation during a lifting task. OBJECTIVES: To investigate electromyographic responses in the erector spinae to a postural perturbation, simulating slipping, during an ongoing voluntary lifting movement. It was hypothesized that specific combinations of voluntary movement and postural perturbation present a situation in which injury caused by a rapid switch between conflicting motor commands can occur. SUMMARY OF BACKGROUND DATA: Studies of postural perturbations have mainly focused on behavior during static tasks such as quiet, upright standing. To date, there are no published studies of the effect of a perturbation during an ongoing voluntary lifting movement. METHODS: Subjects standing on a movable platform were exposed to random perturbations while lifting a 20-kg load. Muscle activity was recorded from flexor and extensor muscles of the trunk and hip. Trunk flexion angle in the sagittal plane was recorded with a video system. RESULTS: Perturbations forward were followed by an increased activity in erector spinae superimposed on the background activation present during the lift, indicating that both the voluntary and postural motor programs caused an activation of erector spinae. During backward perturbation, however, there was a sudden cessation of erector spinae activity followed by an extended period of rapid electromyographic amplitude fluctuations while the trunk was flexing, indicating an eccentric contraction of the erector spinae. CONCLUSIONS: This erratic behavior with large electromyographic amplitude fluctuations in the erector spinae after a backward slip during lifting may indicate a rapid switch between voluntary and postural motor programs that require conflicting functions of the back muscles. This may cause rapid force changes in load-carrying tissue, particularly in those surrounding the spine, thus increasing the risk of slip-and-fall-related back injuries.

  • 4. Tveit, P
    et al.
    Daggfeldt, Karl
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Hetland, S
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Erector spinae lever arm length variations with changes in spinal curvature.1994In: Spine, ISSN 0362-2436, E-ISSN 1528-1159, Vol. 19, no 2, p. 199-204Article in journal (Refereed)
    Abstract [en]

    Magnetic resonance imaging was used to study the effect of different curvatures in the lumbar spine on lever arm lengths of the erector spinae musculature. Eleven subjects were instructed to simulate static lifts while lying supine in a magnetic resonance camera with the lumbar spine either in kyphosis or lordosis. A sagittal image of the spine was obtained to analyze the lumbosacral angle and to guide the imaging of transverse sections through each disc (L1/L2 to L5/S1). Images were analyzed for lever arm lengths of the erector spinae muscle (ES) and the erector spinae aponeurosis (ESA), the latter functioning as a tendon for superiorly positioned ES muscle portions. The lumbosacral angle (between superior surfaces of S1 and L4) averaged 44 degrees in the lordosed, 26 degrees in the kyphosed and 41 degrees in a neutral supine position. In lordosis, the lever arm lengths were significantly longer than in kyphosis for all levels, averaging 60-63 mm (ES) and 82-86 mm (ESA). The corresponding values for kyphosis were 49-57 mm (ES) and 67-77 mm (ESA), respectively. Thus, there was a considerable effect (10-24%) of lumbar curvature on lever arm lengths for the back extensor muscles. The change in leverage will affect the need for extensor muscle force and thus the magnitude of compression in the lumbar spine in loading situations such as lifting.

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